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["필드선택","검색값"]
["권호","39권2호","☜ 필드선택 - 검색값 입력 후 Enter (첫 글자 대소문자 구분)"]
[]
["시트","권호","제목","토픽","초록","키워드","저자","DOI"]

{"sheet":"2021년","index":1,"n_rows":37,"n_cols":7,"rows_kept":37,"cut":false,"hidden":false,"merged":[]}
["권호","제목","토픽","초록","키워드","저자","DOI"]
["37권1호\npp.1-10","SLA을 이용한 소수성 표면 제작\n(Fabrication of Hydrophobic Surfaces with Stereolithography)","Bio-Tribology/Biomimetics ","This paper presents the experimental results of hydrophobic surfaces developed using a stereolithography-based additive-manufacturing technique. The additive manufacturing technique can be used to manufacture objects with complex geometries from computer-aided design data. Several additive manufacturing methods, such as selective laser sintering, fused deposition modeling, stereolithography apparatus (SLA), and inkjet-based system, have been developed. The SLA is a form of three-dimensional printing technology used to create prototypes, patterns, and production parts in successive layers through photochemical processes. Light causes chemical monomers and oligomers to cross-link together to form objects composed of polymers. Moreover, this method is economical for fabricating surfaces with high output resolution and quality. Here, we fabricate various surfaces using different shapes using an SLA. The surfaces with micro-patterns are fabricated for 10 cases, including the biomimetic surface. The fabricated surfaces with various micro-patterns are evaluated for hydrophobicity performance based on the static contact angle. The contact angle is measured three times for each case, and the averaged value is used. The results indicate that the arrangements in a staggered structure have a larger contact angle than those in a line when the same micro-pattern is applied. Moreover, the mimetic surfaces exhibit more hydrophobic characteristics than those of artificial micro-patterns. ","additive manufacturing(적층 제조), contact angle(접촉각), hydrophobic surface(소수성 표면)","홍성호†\n동국대학교 창의융합공학부 기계시스템공학전공","https://doi.org/10.9725/kts.2021.37.1.1"]
["37권1호\npp.11-17","온도, 속도, 그리고 하중 변화에 따른 볼 베어링용 그리스의 수명평가\n(Life Evaluation of Grease for Ball Bearings Accordingto Temperature, Speed, and Load Changes)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Ball bearing is a device that supports and transmits a load acting on a rotating shaft, and it is a type of rolling bearings that uses the rolling friction of the balls by inserting balls between the inner ring and the outer ring. Grease, which is prepared by mixing a thickener with a base oil, is a lubricant commonly used in bearings and has the advantage of a simple structure and easy handling. Bearings are increasingly being used in high value-added products such as semiconductors, aviation, and robots in the era of the 4th industrial revolution. Accordingly, there is an increasing demand for bearing grease. The selection of grease is an important factor in the bearing design. Therefore, a study must be conducted on the grease life evaluation to select an appropriate grease according to operating conditions such as a high temperature, high rotational speed, and high load. In this study, we evaluate the life of ball-bearing grease according to various operating conditions, namely, temperature, speed, and load changes. For this, we develop and theoretically verify a grease life test machine for ball bearings. We conduct a life test of grease according to various operating conditions of bearings and predict the grease life with a 10% and 50% failure probability using the Weibull analysis. In addition, we analyze the oxide characteristics of the grease over time using the Fourier transform infrared spectroscopy and the deterioration characteristics of the grease using the carbonyl index.","grease life evaluation(그리스의 수명평가), ball bearing(볼 베어링), grease life test machine(그리스 수명시험기), weibull(와이불), FT-IR(적외선 분광분석)","손정훈1ㆍ김세웅2ㆍ최병호3ㆍ이승표4†\n1㈜일진베어링 기술연구소 고분자재료연구팀 책임연구원, 2㈜일진글로벌 기술연구소 고분자재료연구팀 팀장, 3고려대학교 기계공학과 교수, 4(주)일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2021.37.1.7"]
["37권1호\npp.18-26","열 경계 조건이 다른 틸팅패드저널베어링의 성능\n(Performance of Tilting Pad Journal Bearings with DifferentThermal Boundary Conditions)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study shows the effect of the thermal boundary condition around the tilting pad journal bearing on the static and dynamic characteristics of the bearing through a high-precision numerical model. In many cases, it is very difficult to predict or measure the exact thermal boundary conditions around bearings at the operating site of a turbomachine, not even in a laboratory. The purpose of this study is not to predict the thermal boundary conditions around the bearing, but to find out how the performance of the bearing changes under different thermal boundary conditions. Lubricating oil, bearing pads and shafts were modeled in three dimensions using the finite element method, and the heat transfer between these three elements and the resulting thermal deformation were considered. The Generalized Reynolds equation and three-dimensional energy equation that can take into account the viscosity change in the direction of the film thickness are connected and analyzed by the relationship between viscosity and temperature. The numerical model was written in in-house code using MATLAB, and a parallel processing algorithm was used to improve the analysis speed. Constant temperature and convection temperature conditions are used as the thermal boundary conditions. Notably, the conditions around the bearing pad, rather than the temperature boundary conditions around the shaft, have a greater influence on the performance changes of the bearing.","thermal boundary condition(열경계조건), tilting pad journal bearing(틸팅패드 저널베어링), generalized reynolds equation(일반화된 레이놀즈방정식), energy equation(에너지방정식), heat transfer(열전달)","서준호1ㆍ황철호2†\n1부산대학교 기계공학부 조교수, 2한남대학교 기계공학과 교수","https://doi.org/10.9725/kts.2021.37.1.14"]
["37권1호\npp.27-33","초음파나노표면개질기술로 제작된 마이크로 그루브가미끄럼 마찰 특성에 주는 영향\n(Effect of Micro-grooves Manufactured via UltrasonicNanocrystalline Surface Modification on Sliding Friction)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","The surface texture produced via surface texturing is an important approach for controlling the tribological behavior of friction behavior of mechanical devices. The purpose of this study is to investigate the effect of grooves generated via ultrasonic nanocrystal surface modification (UNSM) technology on the tribological performance of AISI 4150 steel against stainless steel 316L. In the study, tribological tests are performed under two different regimes, namely mixed and hydrodynamic lubrication, by varying the applied normal load and reciprocating speed during the tests. According to the test results, the friction coefficient decreases as static load (10 N, 30 N, and 50 N) of UNSM technology increases in the mixed lubrication regime. Conversely, the friction coefficient increases as the static load (10 N, 30 N, and 50 N) of UNSM technology increases in the hydrodynamic lubrication regime. Hence, the results indicate that micro-grooves generate hydrodynamic pressure in the outlet, which increases the oil film thickness between the two mating surfaces. This potentially leads to a reduction in friction in the mixed lubrication regime due to the prevention of contact of asperities and debris. However, the results indicate an adverse effect in the hydrodynamic lubrication regime. In this regard, additional experiments should be performed to investigate the effect of grooves generated by UNSM technology at varying conditions on the friction behavior of AISI 4150 steel, which in turn can be controlled by the generated pressure and oil film thickness at the contact interface.","groove(그루브), sliding friction(미끄럼 마찰), UNSM(초음파나노표면개질)","노준석1ㆍ아마노프 아웨즈한2†\n1선문대학교 대학원 융합과학기술학과 석사과정생, 2선문대학교 기계공학과/융합과학기술학과 부교수","https://doi.org/10.9725/kts.2021.37.1.25"]
["37권1호\npp.34-38","스러스트 래버린스 실을 배면에 갖는 원심형 임펠러의 축력 해석\n(Analysis of the Axial Thrust Force of a Centrifugal Impeller with a Thrust Labyrinth Seal at its Backside)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study describes the effects of a thrust labyrinth seal applied to the backside of a centrifugal impeller on the axial thrust force for high speed turbomachinery. The bulk flow model using Neumann’s equation calculates the seal cavity pressures and leakage flow rate of the thrust labyrinth seal based on three configurations: teeth-on-rotor (TOR), teeth-on-stator (TOS), and interlocking labyrinth seal (ILS). Prediction results show that the ILS is superior to the TOR and TOS in terms of leakage flow rate. A mathematical model of a centrifugal impeller with a thrust labyrinth seal on its backside calculates the force components corresponding to the impeller inlet, shroud, impeller backside outer, backside seal, and backside inner pressures. A summation of the force components renders the total axial thrust force acting on the centrifugal impeller. The Newton-Raphson numerical scheme iteratively calculates the pressures and leakage flow rate through the impeller wall gap. The prediction results reveal that the leakage flow rate and total axial thrust force increase with rotor speed, and the ILS significantly decreases the leakage flow rate, whereas it slightly increases the axial thrust force when compared to TOR and TOS. Increasing the seal clearance causes an increase in the leakage flow rate and a slight decrease in the axial thrust force with the ILS.","labyrinth seal(래버린스 실), leakage flow rate(누설 유량), pressure drop(압력 강하), axial thrust force(축력), centrifugal impeller(원심형 임펠러)","박준혁1ㆍ김태호2†\n1국민대학교 대학원 기계설계학과 석사과정생, 2국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2021.37.1.31"]
["37권2호\npp.41-47","유전상수 센서를 이용한 유압 작동유의 분석을 위한 실험장비 개발\n(Development of Experimental Device for Analysis of Hydraulic Oil Characteristics with Dielectric Constant Sensors)","Condition Monitoring & Maintenance System (System Reliability)","An experimental device was developed for analysis of hydraulic oil characteristics with dielectric constant sensors. Online analysis is the most effective method of the three methods used for analyzing lubricant oils. This is because it can monitor the machine condition effectively using oil sensors in real time without requiring excellent analysis skill and eliminates human errors. Determining the oil quality usually requires complex laboratory equipment for measuring factors such as density, viscosity, base number, acid number, water content, additive, and wear debris. However, the electric constant is another indicator of oil quality that can be measured on-site. The electric constant is the ratio of the capacitance of a capacitor using that material as a dielectric, compared with a similar capacitor that has a vacuum as its dielectric. The electric constant affects the factors such as the base oil, additive, temperature, electric field frequency, water content, and contaminants. In this study, the tendency of the electric constant is investigated with a variation of temperature, water content, and dust weight. The experimental device can control working temperature and mix the contaminants with oil. A machine condition monitoring program developed to analyze hydraulic oil is described. This program provides graph and digital values with variation of time. Moreover, it includes an alarm system for when the oil condition is bad.","dielectric constant(유전상수), hydraulic oil(유압 작동유), machine condition monitoring(기계상태진단)","홍성호†\n동국대학교 창의융합공학부 기계시스템공학전공 조교수","https://doi.org/10.9725/kts.2021.37.2.41"]
["37권2호\npp.48-53","풍력발전용 피치 드라이브 시스템의 복합 유성기어류에 대한 피로 강도해석\n(Fatigue Strength Analysis of Complex Planetary Gear Trainof the Pitch Drive System for Wind Turbines)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ,Others","Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.","wind turbine(풍력 발전기), pitch drive(피치 드라이브), planetary gear train(유성기어 트레인), gear bending stress(기어 굽힘 응력), gear compressive stress(기어 면압 응력)","김광민1ㆍ배명호2ㆍ조연상3†\n1우림기계 기술개발센터 이사, 2창원문성대학교 항공정비학부 교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2021.37.2.48"]
["37권2호\npp.54-61","WC위 TiAlN 코팅층에 미치는 Sand Blasting 처리의 영향\n(Effects of Sand Blasting on TiAlN Coating on WC Hard Metal Alloy Tip)","Tribology in Design & Manufacturing (Metalworking / Machining) ","The effect of the sand blasting before TiAlN coating in the manufacture of WC hard metal alloy tips have been studied. For four different tips, according to the status of processing of the sand blasting and the coating, residual stress measurement by X-ray diffraction and several tests for mechanical properties have been conducted. The results suggest that there was no difference in static mechanical properties, such as hardness, surface roughness and elastic modulus, between two coatings. Furthermore, compressive residual stress was generated equally on their surfaces. Additionally, the compressive residual stress in substrate WC was found to increase greatly when subjected to sand blasting treatment. However, the compressive residual stress decrease after coating regardless of sand blasting treatment. Nevertheless, it is confirmed that the compressive residual stress generated in the coating after sand blasting is less than that in the non-sandblasting coating. This was attributed to the plastic deformation occurring in the WC substrate during coating after sand blasting. In contrast to the scratch test results, sand blasting was assumed to have a negative effect on the adhesion between the coating and substrate. This is because there is a high possibility of microcracks due to plastic deformation in the WC substrate under the coating after sand blasting.","residual stress(잔류응력), sand blasting(샌드 블라스팅), WC(텅스텐카바이드), TiAlN coating(TiAlN 코팅), plastic deformation(소성변형)","이한영†\n계명대학교 신소재공학과 교수","https://doi.org/10.9725/kts.2021.37.2.54"]
["37권2호\npp.62-70","Ni-25at.%Al 금속간화합물의 연소합성반응에 미치는사전 Annealing 처리의 영향\n(Effects of Pre-Annealing Treatment on the Combustion Synthesis of Ni3Al Intermetallics Coating)","Tribology in Design & Manufacturing (Metalworking / Machining) ","The problem with intermetallics coating using the heat of molten casting is that the heat generated\uffffﾠ\uffffﾠ\nduring combustion synthesis dissolves the coating and the substrate metal. This study investigates whether pre-annealing before synthesis can control the reaction heat, with the aim of Ni3Al coating on the casting surface. Therefore, the effects of the annealing temperature and time on the combustion synthesis behavior of the powder compact of Ni-25at%Al after annealing were investigated. As results, the reaction heat when synthesized decreased as the annealing temperature was high and the annealing time was longer. This was attributed to the fact that Al was diffused to Ni particles during low temperature annealing and intermediate Ni-Al compounds were formed during high temperature annealing. After combustion synthesis, however, it was found that their microstructures were almost identical except for the amount of intermediate intermetallics. Furthermore, an annealing temperature above 450oC, at which intermediate compounds begin to form, is needed to prevent the dissolving problem during synthesizing. The intermetallics synthesized after annealing at higher temperature and prolonger annealing time showed a good wear resistance. This might be because much intermediate intermetallics of high hardness were remained in the microstructure.","reaction heat(반응열), heat of molten casting(용탕열), coating(코팅), pre-annealing(사전어닐링),\ncombustion synthesis(연소합성)","이한영1†ㆍ모남규2\n1계명대학교 신소재공학과 교수, 2계명대학교 대학원 재료공학과 석사졸업생","https://doi.org/10.9725/kts.2021.37.2.62"]
["37권2호\npp.71-76","액체-고체 접촉대전을 위한 PET 기판 기반 ODA/PDMS딥 코팅 제조 및 평가\n(Synthesis and Evaluation of Superhydrophobic ODA/PDMSDip Coating on PET for Liquid-Solid Contact Electrification)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","As opposed to using fossil fuels, we need to use eco-friendly resources such as sunlight, raindrops and wind to produce electricity and combat environmental pollution. A triboelectric nanogenerator (TENG) is a device that converts mechanical energy into electricity by inducing repetitive contact and separation of two dissimilar materials. During the contact and separation processes, electron flow occurs owing to a change in electric potential of the contacting surface caused by contact electrification and electrostatic induction mechanisms. A solid-solid contact TENG is widely known, but it is possible to generate electricity via liquid-solid contact. Therefore, by designing a hydrophobic TENG, we can gather electricity from raindrop energy in a feasible manner. To fabricate the superhydrophobic surface of TENGs, we employ a dip coating technique to synthesize an octadecylamine (ODA)- and polydimethylsiloxane (PDMS)-based coating on polyethylene terephthalate (PET). The synthesized coating exhibits superhydrophobicity with a contact angle greater than 150° and generates a current of 2.2 μA/L while water droplets fall onto it continuously. Hence, we prepare a box-type TENG, with the ODA/PDMS coating deposited on the inside, and place a 1.5 mL water droplet into it. Resultantly, we confirm that the induced vibration causes continuous impacts between the ODA/PDMS coating and the water, generating approximately 100 pA for each impact.","wettability(젖음성), superhydrophobicity(초소수성), contact angle(접촉각), dip coating(딥 코팅), triboelectric nanogeneroator(마찰전기 나노발전기)","박선영1ㆍ강현규2ㆍ변도영3ㆍ조대현4†\n1성균관대학교 기계공학부 공학연구원, 2성균관대학교 기계공학부 학사과정, 3성균관대학교 기계공학부 교수, 4경상국립대학교 메카트로닉스공학부 조교수","https://doi.org/10.9725/kts.2021.37.2.71"]
["37권2호\npp.77-80","나노스케일 마찰거동에서 스프링 상수가 마찰에 미치는 영향에 대한 분자동역학 연구\n(Study on Influence of Spring Constant on Frictional Behaviorat the Nanoscale through Molecular Dynamics Simulation)","Modeling & Simulation in Tribology","In this study, we investigated the effect of the spring constant on frictional behavior at a nanoscale through molecular dynamics simulation. A small cube-shaped tip was modeled and placed on a flat substrate. We did not apply the normal force to the tip but applied adhesive force between the tip and the substrate. The tip was horizontally pulled by a virtual spring to generate relative motion against the substrate. The controlled spring constant of the virtual spring ranged from 0.3 to 70 N/m to reveal its effect on frictional behavior. During the sliding simulation, we monitored the frictional force and the position of the tip. As the spring constant decreased from 70 to 0.3 N/m, the frictional force increased from 0.1 to 0.25 nN. A logarithmic relationship between the frictional force and spring constant was established. The stick–slip instability and potential energy slope increased with a decreasing spring constant. Based on the results, an increase in the spring constant reduces the probability of trapping in the local minima on the potential energy surface. Thus, the energy loss of escaping the potential well is minimized as the spring constant increases.","spring constant(스프링 상수), friction(마찰), molecular simulation(분자 시뮬레이션), stick-slip(스틱슬립)","강원빈1ㆍ김현준2,3†\n1경북대학교 미래과학기술융합학과 석사과정생, 2경북대학교 정밀기계공학과 부교수, 3경북대학교 미래과학기술융합학과 부교수","https://doi.org/10.9725/kts.2021.37.2.77"]
["37권3호\npp.83-90","표면개질 기술에 의한 Cu 기반 바이메탈의 인장강도,스크래치 저항성 및 트라이볼로지 성능 향상\n(Improvement in Tensile Strength, Scratch Resistance and Tribological Performance of Cu-based Bimetals by Surface Modification Technology)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","In this study, an ultrasonic nanocrystal surface modification (UNSM) was used to improve the mechanical properties, scratch resistance and tribological performance of Cu-based bimetals, which are usually used to manufacture sliding bearings and bushings for internal combustion engines (ICEs). Two different Cu-based bimetals, namely CuPb10Sn10 and CuSn10Bi7, were sintered onto a low carbon steel substrate. The mechanical properties and dry tribological performance using a tensile tester and micro-tribo tester were evaluated, respectively. The scratch resistance was assessed using a micro-scratch tester at an incremental load. The tensile test results showed that the yield strength (YS) and ultimate tensile strength (UTS) of both Cu-based bimetals increased after UNSM. Furthermore, the scratch and tribological tests results revealed that the scratch resistance and tribological performance of both Cu-based bimetals were improved by the application of UNSM. These improvements were mainly attributed to the eliminated pores, increased hardness and reduced roughness after UNSM. CuSn10Bi7 demonstrated better mechanical properties, scratch resistance and tribological performance than CuPb10Sn10. It was found that the presence of Bi in CuSn10Bi7 formed a Cu11Bi7 intermetallic phase, which is harder than Cu3Sn. Hence, CuSn10Bi7 demonstrated higher strength and wear resistance than CuPb10Sn10. In addition, a CuSn10Bi7 formed both SnO2 and Bi2O3 that prevented adhesion and improved the tribological performance. It can be expected that under dry tribological conditions, ICEs can utilize UNSM bearings and bushings made of CuSn10Bi7 instead of CuPb10Sn10 under oil-lubricated conditions.","bimetal(바이메탈), porosity(기공), tensile strength(인장강도), sliding friction(미끄럼마찰), sliding wear(미끄럼마모), surface modification(표면개질)","카림바예프 루슬란1ㆍ아마노프 아웨즈한2\n1선문대학교 대학원 융합과학기술학과 박사과정생, 2선문대학교 기계공학과/융합과학기술학과 부교수","https://doi.org/10.9725/kts.2021.37.3.83"]
["37권3호\npp.91-98","정압 베어링을 적용한 수소 액화 공정용 터보 팽창기 개발\n(Development of Turbo Expanders with Hydrostatic Bearingsfor Hydrogen Liquefaction Plants)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents a hydrostatic bearing design and rotordynamic analysis of a turbo expander for a hydrogen liquefaction plant. Th~e turbo expander includes the turbine and compressor wheel assembled to a shaft supported by two hydrostatic radial and thrust bearings. The rated speed is 75,000 rpm and the rated power is 6 kW. For the bearing operation, we use pressurized air at 8.5 bar as the lubricant that is supplied to the bearing through the orifice restrictor. We calculate the bearing stiffness and flow rate for various gauge pressure ratios and select the orifice diameter providing the maximum bearing stiffness. Additionally, we conduct a rotordynamic analysis based on the calculated bearing stiffness and damping considering design parameters of the turbo expander. The predicted Cambell diagram indicates that there are two critical speeds under the rated speed and there exists a sufficient separation margin for the rated speed. In addition, the predicted rotor vibration is under 1 μm at the rated speed. We conduct the operating test of the turbo expander in the test rig. For the operation, we supply pressurized air to the turbine and monitor the shaft vibration during the test. The test results show that there are two critical speeds under the rated speed, and the shaft vibration is controlled under 2.5 μm.","hydrostatic bearing(정압베어링), turbo expander(터보팽창기), orifice(오리피스), hydrogen liquefaction(수소액화)","이동현1†ㆍ김병옥1ㆍ박무룡2ㆍ임형수2\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 에너지변환기계연구실 책임연구원","https://doi.org/10.9725/kts.2021.37.3.91"]
["37권3호\npp.99-105","Stability Characteristics of Supercritical High-Pressure Turbines Depending on the Designs of Tilting Pad Journal Bearings","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","In this study, for a high-pressure turbine (HPT) of 800 MW class supercritical thermal-power plant, considering aerodynamic cross-coupling, we performed a rotordynamic logarithmic decrement (LogDec) stability analysis with various tilting pad journal bearing (TPJB) designs, which several steam turbine OEMs (original equipment manufacturers) currently apply in their supercritical and ultra-supercritical HPTs. We considered the following TPJB designs: 6-Pad load on pad (LOP)/load between pad (LBP), 5-Pad LOP/LBP, Hybrid 3-Pad LOP (lower 3-Pad tilting and upper 1-Pad fixed), and 5-Pad LBPs with the design variables of offset and preload. We used the API Level-I method for a LogDec stability analysis. Following results are summarized only in a standpoint of LogDec stability. The Hybrid 3-Pad LOP TPJBs most excellently outperform all the other TPJBs over nearly a full range of cross-coupled stiffness. In a high range of cross-coupled stiffness, both the 6-Pad LOP and 5-Pad LOP TPJBs may be recommended as a practical conservative bearing design approach for enhancing a rotordynamic stability of the HPT. As expected, in a high range of cross-coupled stiffness, the 6-Pad LBP TPJBs exhibit a better performance than the 5-Pad LBP TPJBs. However, contrary to one’s expectation, notably, the 5-Pad LOP TPJBs exhibit a slightly better performance than the 6-Pad LOP TPJBs. Furthermore, we do not recommend any TPJB design efforts of either increasing a pad offset from 0.5 or a pad preload from 0 for the HPT in a standpoint of stability.","cross-coupled stiffness, LogDec stability, supercritical high-pressure turbine, tilting pad journal bearing.","An Sung Lee1† and Sun-Yong Jang2\n1Principal Researcher, Dept. of System Dynamics Research, Division of Mechanical Systems Safety Research,Korea Institute of Machinery & Materials, 2Director, R&D Center, Daedong Metal Industry Co.","https://doi.org/10.9725/kts.2021.37.3.99"]
["37권3호\npp.106-111","액체금속(GaInSn)윤활하에서 DLC(ta-C) 코팅된 레이저표면 텍스쳐링 딤플패턴의 미끄럼 마찰특성평가\n(Evaluation of Sliding Friction Properties of Laser Surface Texturing Dimple Pattern with DLC Coating under GaInSn Liquid Metal Lubricant)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","There are several studies on reducing the friction that occurs on the relative sliding contact surface of moving parts under extreme environments. In particular, a solid lubricated bearing is studied to solve the tribological problem with friction reduction and durability parts using solid lubricants (lead or silver) in a vacuum atmosphere. Galinstan is mainly used as a liquid metal lubricant, but it is inevitable to have limited tribological applications owing to its high coefficient of friction. Many researchers work on surface texturing for surface modification and precision processing methods. To increase durability and low friction, DLC coating with hydrophobicity is applied on the contact surface texture. Therefore, using an untextured specimen, a dimple specimen, and a DLC-coated dimple specimen under liquid metal lubrication, this paper presents the following experimental sliding friction characteristics in the sliding friction test. 1) The average coefficient of friction of the DLC-coated dimple specimen and dimple specimen are lower compared to that of a non-patterned specimen. 2) In the DLC-coated dimple specimens, the average coefficient of friction changes according to the change in the dimple density. 3) DLC-coated dimple specimens with a density of 12.5 have the lowest average coefficient of friction under 41.6 N of normal load and 143.3 RPM.","dimple pattern(딤플 패턴), DLC(diamond like carbon), laser surface texturing(레이저 표면 텍스쳐링), liquid metal lubricant(액체 금속 윤활), sliding friction(미끄럼 마찰)","권규빈1ㆍ장영준2ㆍ채영훈3†\n1경북대학교 금속신소재공학과 학부생, 2한국재료연구원 책임연구원, 3경북대학교 공학설계연구소 연구교수","https://doi.org/10.9725/kts.2021.37.3.106"]
["37권3호\npp.112-116","충돌 해석 시 마찰 모델 적용을 위한 기초 마찰 시험 연구\n(Feasibility Study of Friction Characteristics for Impact Analysis)","Modeling & Simulation in Tribology","Appropriate friction model usage is important for impact analysis because the relative motions between parts that are in contact for very short durations can vary greatly depending on the friction model. Vehicle seat components that have significant effects on impact analysis are also considered. This paper presents an experimental investigation of various material contact pairs to obtain the friction parameters of the Benson exponential friction model for impact simulation. The Coulomb friction model has limitations for impact analysis because of singularity at zero velocity. Metal/nonmetal materials are prepared, and friction tests are conducted for various sliding speeds, loads, and lubrication conditions. The obtained data are used in the friction model to implement finite element analysis. The parameters of the friction model are obtained by the curve-fitting method. The experimental results show that the friction coefficient with metal/nonmetal contact pairs is stable regardless of the working conditions. The friction model used in this study can also be applied for finite element analysis of the crash conditions, where the friction changes abruptly at the contact interface; the obtained friction parameters are also expected to be more accurate with more precise tests under different working conditions. These results can help improve the accuracy of the finite element analysis.","friction(마찰), friction model(마찰모델), lubrication(윤활), friction decay constant(마찰 감쇄 계수)","이광희1ㆍ이철희2†\n1인하대학교 대학원 기계공학과 박사과정생, 2인하대학교 기계공학과 교수","https://doi.org/10.9725/kts.2021.37.3.112"]
["37권4호\npp.117-124","에어 포일 스러스트 베어링의 탑포일 경사면 형상이유동특성에 미치는 영향에 대한 수치해석 연구\n(The Effects of Inclined Foil Shape on Flow Characteristicsin Air Foil Thrust Bearing Using CFD)","Modeling & Simulation in Tribology","In this study, we perform a 3D CFD conjugate analysis according to the shape of the foil ramp of the air foil thrust bearing, analyze the flow characteristics inside the bearing, and compare the results corresponding to the two shapes. Air has a lower viscosity than lubricating oil. Therefore, the thrust runner of the bearing must rotate at high speed to support the load. The gap between thrust runner and foil is significantly smaller than that of the oil bearing. Hence, it is crucial to analyze the complex flow characteristics inside the bearing to predict the complex flow inside the bearing and performance of the bearing. In addition, flow characteristics may appear differently depending on the ramp shape of the bearing foil, which may affect bearing performance. In this study, we numerically analyze the main flow path of air flowing into the bearing and the secondary flow path used for cooling the bearing using the commercial CFD software ANSYS CFX and compare the flow characteristics for straight and curved foil ramp shapes. Notably, there is a difference in the speed of the flowing air according to the shape of the ramp, which affects the bearing performance.","air foil thrust bearing(에어 포일 스러스트 베어링), computational fluid dynamics(전산유체역학), hydrodynamic lubrication(유체윤활), load capacity(하중지지능력), leakage rate(누설 유량)","백건웅1ㆍ주원구2†ㆍ문형욱3ㆍ황성현4ㆍ정성윤3ㆍ박정구5\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 기계공학과 교수, 3한화파워시스템 연구원, 4한화파워시스템 책임연구원, 5한화파워시스템 수석연구원","https://doi.org/10.9725/kts.2021.37.4.117"]
["37권4호\npp.125-128","육방정질화붕소 나노플레이크/폴리이미드 복합체를 이용한마찰전기 나노발전기 평가\n(Evaluation of h-BN Nanoflakes/Polyimide Compositesfor a Triboelectric Nanogenerator)","Eco/Green Tribology (Renewable / Alternative Energies)","A means of enhancing the performance of triboelectric nanogenerators (TENGs) is increasing the differences in work functions between contacting materials. Hexagonal boron nitride (h-BN) exhibits excellent mechanical properties and high chemical stability as well as a high work function. As a result, engineers in the field of energy harvesting have envisioned using h-BN in the electrification layer in TENGs. For the industrial application of h-BN in TENGs, large-scale production is necessary, and h-BN is generally exfoliated and dispersed in various solvents. In this study, we evaluate the performance of a TENG with h-BN nanoflakes in the polyimide (PI) layer. To synthesize a PI composite containing h-BN nanoflakes, h-BN powders are exfoliated and dispersed in poly(amic acid) (PAA), which is the precursor of PI. Then, h-BN dispersion is spin-coated onto the PI film and cured for 2 h under 300oC. This composite material can then be used for the electrification layer in TENGs. Below the electrification layer, an aluminum foil is placed and used as an electrode. When the contact and separation processes with polyethylene terephthalate are repeated, the fabricated TENG shows a maximum power density of 190.8 W/m2. This study shows that h-BN is a promising material for enhancing the performance of the electrification layer in TENGs.","hexagonal boron nitride(육방정 질화붕소), polyimide(폴리이미드), triboelectric nanogenerator(마찰전기 나노발전기)","박선영1ㆍ변도영2ㆍ조대현3†\n1성균관대학교 기계공학부 공학연구원, 2성균관대학교 기계공학부 교수, 3경상국립대학교 메카트로닉스공학부 조교수","https://doi.org/10.9725/kts.2021.37.4.125"]
["37권4호\npp.129-135","포켓의 깊이가 공기 베어링 스테이지의 햄머링 현상에 미치는 영향\n(Effect of the Pocket Depth on the Hammering Behaviorof an Air Bearing Stage)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","An air-bearing stage uses externally pressurized air as the lubricant between the stage and the rail. The supporting force generated by the supplied air makes the stage rise and move smoothly with extremely low friction. Mechanical contacts rarely happen, the bearing surfaces do not produce wear particles, and dust is not generated. It also has the advantage of having low energy loss and high precision. Because of its advantages, an air-bearing stage is used in several types of machines that require high precision. In this article, the effect of the pocket depth on the hammering phenomena of the air bearing is studied. An analysis program is developed to calculate the dynamic behavior of the stage by solving the Reynolds equation between the stage and the guideway and the equations of motion on the stage. The acceleration, constant movement, and deceleration are applied to the stage. The stage is modeled as a five-degree-of-freedom system. In the course of the dynamic behavior, the hammering phenomena occur under some special conditions. The deeper the pocket, the more unstable the behavior of the stage, and air hammering occurs when it exceeds a certain depth. In addition, the higher the supply pressure, the more unstable the behavior of the stage. However, hammering occurs even with a shallow pocket depth. Other conditions that affect the hammering phenomena are calculated and discussed.","air bearing stage(공기베어링 스테이지), clearance(틈새), hammering(햄머링), pocket depth(포켓 깊이)","이춘무1ㆍ김규하2ㆍ박상준3ㆍ황규진4ㆍ박상신5†\n1㈜트리엔 대표이사, 2(주)트리엔 연구소장, 3영남대학교 대학원 기계공학과 석사졸업생, 4영남대학교 대학원 기계공학과 석사과정생, 5영남대학교 기계공학부 교수","https://doi.org/10.9725/kts.2021.37.4.129"]
["37권4호\npp.136-143","체결력을 고려한 내부 및 외부연결형 임플란트의반복 하중에 대한 풀림 연구\n(Loosening behavior of Internal and External Connection Dental Implants under Cyclic Loads Considering Pre-fastening Force)","Contact Mechanics & Friction ","This paper presents the loosening behavior that occurs after the application of an external load to internal and external connection types of dental implants using the finite element method. We use fastening force between an abutment and a fixture to clamp the dental implant system; however, loosening and breakage may occur owing to cyclic external loads. In this study, we considered the initial fastening condition in the pre-load analysis and then investigated the change in stress and contact surface status when applying external loads. After the application of the initial fastening load, we verified that the internal connection-type model exhibited a relatively lower stress distribution than that of the external connection-type one. Moreover, we found that the former model showed a lower stress concentration after the application of the external load. In addition, after the application of this load, we found that the higher the shear load acting on the implant system, the higher the possibility of loosening. The study results showed the change in stress distribution and contact surface according to the connection type of the dental implants and the phenomenon of loosening by cyclic loads. We expect that the results of this study will be useful for the study of reliability and design of dental implant systems.","dental implant(치과용 임플란트), abutment-implant connection(지대주 연결 방식), FEM(유한요소법), srew loosening(나사 풀림), fastening force(체결력), cyclic load(반복 하중)","이용우1ㆍ장용훈2†\n1신한대학교 기계자동차융합공학과 조교수, 2연세대학교 기계공학부 교수","https://doi.org/10.9725/kts.2021.37.4.136"]
["37권4호\npp.144-150","유한요소해석에 의한 코팅면의 브리넬 경도 평가:제2보 - 모재와 코팅두께의 영향\n(Evaluation of Brinell Hardness of Coated Surfaceby Finite Element Analysis:Part 2 - Influence of Substrate and Coating Thickness)","Contact Mechanics & Friction, Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","The most cost-effective method of reducing abrasive wear in mechanical parts is increasing their hardness with thin hard coatings. In practice, the composite hardness of the coated substrate is more important than that of the substrate or coating. After full unloading of the load applied to an indenter, its indentation hardness evaluated based on the dent created on the test piece was almost dependent on plastic deformation of the substrate. Following the first part of this study, which proposes a new Brinell hardness test method for a coated surface, the remainder of the study is focused on practical application of the method. Indentation analyses of a rigid sphere and elastic-perfect plastic materials were performed using finite element analysis software. The maximum principal stress and plastic strain distributions as well as the dent shapes according to the substrate yield stress and coating thickness were compared. The substrate yield stress had a significant effect on the dent size, which in turn determines the Brinell hardness. In particular, plastic deformation of the substrate produced dents regardless of the state of the coating layer. The hardness increase by coating behaved differently depending on the substrate yield stress, coating thickness, and indentation load. These results are expected to be useful when evaluating the composite hardness values of various coated friction surfaces.","Brinell hardness(브리넬 경도), coating(코팅), indentation analysis(압입해석), finite element analysis(유한요소해석), yield stress(항복응력)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2021.37.4.144"]
["37권5호\npp.151-163","그래핀의 나노스케일 마찰 및 표면 특성에 대한 연구동향\n(Research Trends in the Nanoscale Friction and SurfaceCharacteristics of Graphene)","Micro/Nano-Tribology","Since the discovery of single-layer graphene, exploiting graphene’s excellent physical/chemical properties in tribology systems has been a topic of interest in academia over the last few decades. There is no doubt that understanding the underlying friction mechanism of graphite should precede this. Even now, new properties of graphene are being reported in academia, and based on this, studies exploring the origins of graphene’s surface properties and friction characteristics in a wide range of scales are also being performed. From the perspective of lubrication engineering, graphene research can be largely divided into studies that 1) reveal its basic friction mechanism at the nanoscale and 2) explore its application in macroscale sliding systems. At the nanoscale, the basic friction mechanism of graphene is mainly due to its atomic thickness. In this paper, the various research on the nanoscale friction and surface characteristics of graphene is reviewed. Graphene surface properties, such as wettability and surface energy and the basic friction mechanisms of graphene attributed to adhesion, electron-phonon scattering, bending stiffness, and the underlying substrate, are summarized. Further, we provide the research outcomes on the superlubricity of graphene. Finally, the potential application and challenges of the superlubricity of graphene are highlighted. Through this, we intend to provide summarized information to researchers interested in the tribological properties of graphene and help set the direction of future research.","graphene(그래핀), friction(마찰), surface characteristics(표면 특성), superlubricity(초윤활성)","윤민아1,2ㆍ김광섭3,4†ㆍ조대현5‡\n1한국과학기술연합대학원대학교 나노메카트로닉스학과 박사과정생, 2한국기계연구원 나노융합장비연구부 학생연구원, 3한국과학기술연합대학원대학교 나노메카트로닉스학과 교수, 4한국기계연구원 나노융합장비연구부 책임연구원, 5경상국립대학교 메카트로닉스공학부 부교수","https://doi.org/10.9725/kts.2021.37.5.151"]
["37권5호\npp.164-171","초음파 센서의 1차 정합층 두께에 따른 가스탱크 미세누설 수신특성\n(Gas Tank Microleakage Reception Characteristics According to Thickness of the First Matching Layer of Ultrasonic Sensor)","Automotive Tribology","Ultrasonic sensors show various reception characteristics based on the density of the measurement medium; hence, they are used in various fields to benefit from the characteristics of ultrasonic signals. In this study, the reception characteristics according to the thickness of the first matching layer are compared and analyzed for application to gas tank microleak detection. Accordingly, three types of sensors are manufactured with varying thicknesses of the first matching layer, namely 4.8 mm, 5.1 mm, and 5.5 mm; further, a direct measurement method is used wherein the sensor is attached to the inside of the chamber. Experiments are conducted to observe the phase change due to microleakage, which is the most linear in the sensor with the 4.8 mm thick first matching layer. This is assumed to be the result of stable signal transmission and reception with little phase deviations over time because the first matching layer is closest to the ultrasonic wavelength. The other sensors show nonlinear results with increasing thickness of the first matching layer. Through this study, it is found that appropriately selecting the thickness of the first matching layer of the ultrasonic sensor can greatly influence sensor reliability.","gas density(가스 밀도), gas fuel(가스 연료), gas storage(가스 저장소), microleakge(미세 누설), ultrasonic sensor(초음파 센서)","서원준1ㆍ손성진2ㆍ임석연3†\n1충남대학교 대학원 기계공학과 박사과정생, 2충남대학교 대학원 융복합시스템공학과 석사과정생, 3충남대학교 기계 · 재료공학교육과 부교수","https://doi.org/10.9725/kts.2021.37.5.164"]
["37권5호\npp.172-178","고압 인젝터의 동적 거동을 고려한 최적 틈새 조합에 관한 연구\n(Selection of Optimum Clearance Considering the Dynamic Behavior of a High-pressure Injector)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","An injector is a mechanical device present inside the engine. Its main function is to supply an appropriate volume of fuel into the combustion chamber, which is directly related to the overall engine efficiency of a car. During the operation of an injector, a magnetic force lifts the parts of the injector from closed position to open position which generates a horizontal force on the needle. The horizontal force acts on a different position from that of the center of mass of the needle. Therefore, this causes eccentricity in the needle and the generation of a tilting motion during the lifting operation which can result in wear. However, appropriate selection of clearances for these parts can prevent wear. In this study, lubrication analysis is conducted to determine the optimum clearance of parts with sliding motion inside the injector. The height functions are derived considering the dynamic behavior and relative velocity of the parts. Using the derived height function, the pressure profiles are calculated for the lubricated surfaces from the Reynolds' equation. Subsequently, the fluid reaction forces are calculated. The equations of motions are applied to the fluid reaction forces and external forces are solved to calculate the minimum film thickness between each part with variation in the clearances. Finally, the optimum clearances are determined. The effect of the clearances on the behavior of the moving parts is presented and discussed.","clearance(틈새), dynamic behavior(동적 거동), height function(높이 함수), high pressure injector(고압 인젝터)","류대원1ㆍ김동준2ㆍ박상신3†ㆍ류봉우4\n1영남대학교 대학원 기계공학과 석사졸업생, 2영남대학교 대학원 기계공학과 석사과정생, 3영남대학교 기계공학부 교수, 4 ㈜현대케피코 책임연구원","https://doi.org/10.9725/kts.2021.37.5.172"]
["37권5호\npp.179-188","Diamond-like Carbon Tribological Endurance usingan Energetic Approach","Contact Mechanics & Friction ,Wear Phenomena & Mechanisms ,Tribo-Testing / Measurement & Instruments ","Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 μm thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc1), and the other (Nc2) indicating the friction failure which is situated where the CoF reaches a threshold value of μth = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc1, Nc2). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.","friction, DLC coatings, fretting wear, Archard energy density factor, tribology","Fathia Alkelae1 and Tea-Sung Jun2†\n1Postdoctoral Research Associate, Dept. of Mechanical Engineering, Incheon National University, 2Associate Professor, Dept. of Mechanical Engineering, Incheon National University","https://doi.org/10.9725/kts.2021.37.5.179"]
["37권5호\npp.189-194","전기화학 에칭 공정을 이용한 스테인리스 스틸 메쉬의방수 특성 연구\n(A Study on Water-Proof Characteristics of a Stainless Steel Mesh by Electrochemical Etching Process)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ,Micro/Nano-Tribology ","A straightforward, yet effective surface modification method of stainless steel mesh and its interesting anti-wetting characteristics are reported in this study. The stainless steel mesh is electrochemically etched, and the specimen has both micro and nano-scale structures on its surface. This process transforms the two types of mesh specimens known as the regular and dense specimens into hydrophobic specimens without applying any hydrophobic chemical coating process. The fundamental wettability of the modified mesh is analyzed through a dedicatedly designed experiment to investigate the waterproof characteristics, for instance, the penetration threshold. The waterproof characteristics are evaluated in a manner that the modified mesh resists as high as approximately 2.7 times the pressure compared with the bare mesh, i.e., the non-modified mesh. The results show that the penetration threshold depends primarily on the advancing contact angles, and the penetration stop behaviors are affected by the contact angle hysteresis on the surfaces. The findings further confirm that the inexpensive waterproof meshes created using the proposed straightforward electrochemical etching process are effective and can be adapted along with appropriate designs for various practical applications, such as underwater devices, passive valves, and transducers. In general, , additional chemical coatings are applied using hydrophobic materials on the surfaces for the applications that require water-repelling capabilities. Although these chemical coatings can often cause aging, the process proposed in this study is not only cost-effective, but also durable implying that it does not lose its waterproof properties over time.","mesh structure(메쉬 구조물), surface modification(표면 개질), hydrophobic surface(소수성 표면), liquid penetration characteristic(액체 침투 특성), micro/nanostructure(마이크로/나노구조)","이찬1ㆍ김지민2ㆍ김형모3†\n1한국원자력연구원 핵연료안전연구부 선임연구원, 2한국교원대학교 기술교육과 조교수, 3경상국립대학교 기계공학부 조교수","https://doi.org/10.9725/kts.2021.37.5.189"]
["37권5호\npp.195-202","고체표면에 응축된 물 분자의 윤활특성에 대한분자시뮬레이션 연구\n(Lubrication Characteristics of Condensed Water Moleculesat Solid Surface through Molecular Simulation)","Modeling & Simulation in Tribology ","This paper presents a numerical analysis of the lubrication characteristics of condensed water molecules on a solid surface by conducting molecular dynamics simulations. We examine two models consisting of a simple hexahedral substrate with and without water molecules to reveal the lubrication mechanism of mono-layered water molecules. We perform a sliding simulation by contacting and translating a single asperity on the substrate under various normal loads. During the simulation, we measure the friction coefficient and atomic stress. When water molecules were interleaved between solid surfaces, atomic stress exerted on individual atom and friction coefficient were smaller than those of model without water molecule. Particularly, at a low load, the efficacy of water molecules in the reduction of atomic stress and friction is remarkable. Conversely, at high loads, water molecules rarely lubricate solid surfaces and fail to effectively distribute the contact stress. We found a critical condition in which the lubrication regime changes and beyond the condition, significant plastic deformation was created. Consequently, we deduce that water molecules can distribute and reduce contact stress within a certain condition. The reduced contact stress prevents plastic deformation of the substrate and thus diminishes the mechanical interlocking between the asperity and the substrate.","condensation(응축), water molecule(물 분자), lubrication(윤활), molecular simulation(분자 시뮬레이션), plastic deformation(소성변형)","김현준1,2†\n1경북대학교 정밀기계공학과 부교수, 2경북대학교 미래과학기술융합학과 부교수","https://doi.org/10.9725/kts.2021.37.5.195"]
["37권6호\npp.203-207","윤활유 물성 측정을 위한 유전상수 센서 개발\n(Development of Dielectric Constant Sensor for Measurementof Lubricant Properties)","Condition Monitoring & Maintenance System (System Reliability)","This study presents the development of dielectric constant sensors to measure lubricant properties. The lubricant oil sensor is used to measure oil properties and machine conditions. Various condition monitoring methods are applied to diagnose machine conditions. Machine condition monitoring using oil sensors has advantage over other machine condition monitoring methods. The fault conditions can be noticed at the early stages by the detection of wear particles using oil sensors. Therefore, it provides an early warning in the failure procedure. A variety of oil sensors are applied to check the machine condition. Among all oil sensors, only one sensor can measure the tendency of several properties such as acidity and water content. A dielectric constant sensor is also used to measure various oil properties; therefore, it is very useful. The dielectric constant is the ratio of the capacitance of a capacitor using that material as a dielectric to that of a similar capacitor using vacuum as its dielectric. The dielectric constant has an effect on water content, contaminants, base oil, additive, and so forth. In this study, the dielectric constant sensor is fabricated using MEMS process. In the fabrication process, the shape, gap of the electrode array, and thickness of the insulation material are considered to improve the sensitivity of the sensor.","dielectric constant(유전상수), lubricant(윤활유), machine condition monitoring(기계상태진단), oil property(윤활유 물성), oil sensor(윤활유 센서)","홍성호1†ㆍ강문식2\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2이너센서 대표","https://doi.org/10.9725/kts.2021.37.6.203"]
["37권6호\npp.208-212","전해 이온화와 자외선광을 이용한 사파이어 화학기계적 연마의 재료제거 효율 향상에 관한 기초 연구\n(Basic Study on the Improvement of Material Removal Efficiency of Sapphire CMP Using Electrolytic Ionization and Ultraviolet Light)","Chemical Mechanical Polishing","Chemical mechanical polishing (CMP) is a key technology used for the global planarization of thin films in semiconductor production and smoothing the surface of substrate materials. CMP is a type of hybrid process using a material removal mechanism that forms a chemically reacted layer on the surface of a material owing to chemical elements included in a slurry and mechanically removes the chemically reacted layer using abrasive particles. Sapphire is known as a material that requires considerable time to remove materials through CMP owing to its high hardness and chemical stability. This study introduces a technology using electrolytic ionization and ultraviolet (UV) light in sapphire CMP and compares it with the existing CMP method from the perspective of the material removal rate (MRR). The technology proposed in the study experimentally confirms that the MRR of sapphire CMP can be increased by approximately 29.9, which is judged as a result of the generation of hydroxyl radicals (·OH) in the slurry. In the future, studies from various perspectives, such as the material removal mechanism and surface chemical reaction analysis of CMP technology using electrolytic ionization and UV, are required, and a tribological approach is also required to understand the mechanical removal of chemically reacted layers.","sapphire(사파이어), chemical mechanical polishing(화학기계적 연마), ultraviolet(자외선), electrolytic ionization(전해 이온화), material removal rate(재료제거율)","박성현1ㆍ이현섭2†\n1동명대학교 대학원 기계시스템공학과 석사과정생, 2동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2021.37.6.208"]
["37권6호\npp.213-223","전기화학-기계적 평탄화에 관한 연구 동향 분석\n(Analysis of Research Trends on Electrochemical-Mechanical Planarization)","Chemical Mechanical Polishing","Electrochemical mechanical planarization (ECMP) was developed to overcome the shortcomings of conventional chemical mechanical planarization (CMP). Because ECMP technology utilizes electrochemical reactions, it can have a higher efficiency than CMP even under low pressure conditions. Therefore, there is an advantage in that it is possible to reduce dicing and erosions, which are physical defects in semiconductor CMP. This paper summarizes the papers on ECMP published from 2003 to 2021 and analyzes research trends in ECMP technology. First, the material removal mechanisms and the configuration of the ECMP machine are dealt with, and then ECMP research trends are reviewed. For ECMP research trends, electrolyte, processing variables and pads, tribology, modeling, and application studies are investigated. In the past, research on ECMP was focused on basic research for the development of electrolytes, but it has recently developed into research on tribology and process variables and on new processing systems and applications. However, there is still a need to increase the processing efficiency, and to this end, the development of a hybrid ECMP processing method using another energy source is required. In addition, ECMP systems that can respond to the developing metal 3D printing technology must be researched, and ECMP equipment technology using CNC and robot technology must be developed.","Chemical mechanical planarization(화학기계적 평탄화), Electrochemical mechanical planarization(전기화학-기계적 평탄화), Research trend(연구 동향)","이현섭1†ㆍ김지훈2ㆍ박성민2ㆍ추동엽2\n1동아대학교 기계공학과 부교수, 2동아대학교 기계공학과 학부생","https://doi.org/10.9725/kts.2021.37.6.213"]
["37권6호\npp.224-231","자동차 전장 커넥터 방수시일 단면의 최적설계\n(Optimization Design of a Waterproof Seal Cross-Sectionof Automotive Electrical Connectors)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","Recently, the waterproofing performance of high-voltage connectors in automotive vehicles has attracted increased interest. In this study, an optimal cross-sectional shape was derived to obtain uniform contact pressure and strain by considering stress relaxation problems caused by initial tension when mounting a seal. A high strain of 52.1 was distributed in the round region, owing to excessive initial tension. The finite element method (FEM) analysis indicated that the strain corresponding to the optimal initial tensile was 11. We adopted six design factors to optimize the seal cross-section and three factors as the main design factors. An orthogonal arrangement table was prepared using Minitab. FEM analyses of 16 study models were conducted to determine the optimized model. The contact pressure of the optimization model is the most evenly distributed while satisfying the waterproof performance of 0.47 MPa. Compared to the initial model, the difference in strain decreases from 35.5% to 19.6%. Finally, the derived cross-sectional shape can reduce the strain of the round region by 33.8% and the differences in the contact pressure at the upper and lower surfaces by 42% and 76%, respectively.","connector seal(커넥터 시일), contact pressure(접촉압력), finite element analysis(유한요소해석), optimal design(최적설계), waterproof performance(방수성능)","강규태1ㆍ이채은1ㆍ김호경2†\n1서울과학기술대학교 일반대학원 자동차공학과 석사과정생, 2서울과학기술대학교 기계자동차공학과 교수","https://doi.org/10.9725/kts.2021.37.6.224"]
["37권6호\npp.232-239","가짜 고급휘발유 판정을 위한 성분 분석\n(Analysis of Components to Determine Illegal Premium Gasoline)","Automotive Tribology","Petroleum is the most consumed energy source in Korea with a usage rate of 38.7% among the available primary energy sources. The price of liquid petroleum products in Korea includes taxes such as transportation·environment·energy tax. Thus, illegal production and distribution of liquid petroleum is widespread because of its huge price difference from that of the normal product and its tax-free nature. Generally, the illegal petroleum product is produced by mixing liquid petroleum with other similar petroleum alternatives. The two kinds of gasoline, common gasoline and premium gasoline, are being distributed in Korea. The premium gasoline is often adulterated with cheaper common gasoline that lowers the octane number of gasoline. It is possible to distinguish them with their color difference, green and yellow for different grade gasoline. However, when small volume of common gasoline is added to premium gasoline, it is difficult to determine whether premium gasoline contained common grade or not. In this study, we inspect gasoline, which is illegally produced by mixing common gasoline to premium gasoline. When the ratio of mixing common gasoline is increased, premium gasoline shows decreasing absorbance at 600 nm and 650 nm under UV-Vis spectrometer. Moreover, the detected intensity (mV·s) of green dye in high performance liquid chromatography (HPLC) was decreased by common gasoline under 0.99 correlation value. The more the common gasoline is mixed, the more olefin and naphthene are detected by gas chromatography. In addition, trimethyl pentane as octane improver, paraffin and toluene are decreased by common gasoline mixing. The findings of this study suggests that illegal petroleum can be identified by analysis of components and simulated samples.","illegal gasoline(가짜휘발유), premium gasoline(고급휘발유), common gasoline(보통휘발유), dye(염료), octane number(옥탄가)","임영관1†ㆍ강병석2ㆍ이보오미2ㆍ박소휘3ㆍ박장민4ㆍ고영훈5ㆍ김승태6ㆍ강대혁7\n1한국석유관리원 수도권북부본부 팀장, 2한국석유관리원 수도권북부본부 대리, 3한국석유관리원 수도권북부본부 사원, 4한국석유관리원 시험처 대리, 5한국석유관리원 시험처 사원, 6한국석유관리원 영남본부 대리, 7한국석유관리원 수도권북부본부 본부장","https://doi.org/10.9725/kts.2021.37.6.232"]
["37권6호\npp.240-245","유한요소해석에 의한 코팅면의 브리넬 경도 평가:제3보 - 다층 코팅에 적용\n(Evaluation of Brinell Hardness of Coated Surface Using FiniteElement Analysis: Part 3 - Application to Multilayer Coatings)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Ceramic coatings with high hardness and excellent chemical stability have been successfully applied to various machine elements, tools, and implants. However, in the case of monolayer coating on soft substrates, a high-stress concentration at the interface between the coating and the substrate causes delamination of the coating layer. Recently, to overcome this problem, multilayer coatings with a metal layer with a low modulus of elasticity added between the ceramic and the substrate have been widely applied. This study presents the third part of a recent study and focuses on the effect of the number of coating layers on the Brinell hardness of multilayered coating with TiN/Ti, following the two previous studies on a new Brinell hardness test method for a coated surface and on the influence of substrate and coating thickness. Indentation analyses are performed using finite element analysis software, von Mises stress and equivalent plastic strain distributions, load-displacement curves, and residual indentation shapes are presented. The number of TiN/Ti layers considerably affect the stress distributions and indentation shapes. Moreover, the greater the number of TiN/Ti layers, the higher is the Brinell hardness. The stress and plastic strain distributions confirm that the multilayer coatings improve the wear resistance. The results are expected to be used to design and evaluate various coating systems, and additional study is required.","Brinell hardness(브리넬 경도), indentation analysis(압입해석), finite element analysis(유한요소해석), multilayer coating(다층 코팅)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2021.37.6.240"]
["37권6호\npp.246-252","오일 등급에 따른 트라이볼로지 특성의 관한 실험적 고찰\n(Experimental Study of Tribological Properties According to Oil Grade)","Lubrication (Lubricants & Additives)","Among the engine components of an internal combustion engine, the valve train is a series of systems that supply intake gas to the combustion chamber and operate intake and exhaust valves that discharge exhaust gas. If excessive wear occurs in the valve train system, the suction and exhaust valves do not open and close on time, which leads to abnormal combustion and exhaust gas. In this study, we conduct experiments and analyses on friction and wear characteristics of the valve train system. Moreover, we experimentally study the correlation between the pinball and pinball cap on engine oil lubrication, friction experiment, wear amount analysis, and surface analysis. Specifically, we experiment using Ball on reciprocating tribo-tester and apply commercial engine oil sold on the market engine oil. We construct the experimental conditions for each new oil and oil. Accordingly, the completed specimen was subjected to a confocal microscope to check the wear volume, observe the surface of the specimen, and confirm the elemental components using a scanning microscope (SEM) and an energy dispersion X-ray spectrometer (EDS). Through this experiment, we analyze the friction and wear characteristics of valve train components according to engine oil grade, and the obtained data serve as an effective engine oil management method.","valve train(밸브 트레인), friction(마찰),wear(마모), oil grade(오일 등급), tribo-film(트라이보필름)","이종호1ㆍ서국진2ㆍ황윤후2ㆍ한재호2ㆍ김대은3†\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 대학원 기계공학과 박사과정생, 3연세대학교 기계공학과 정교수","https://doi.org/10.9725/kts.2021.37.6.246"]
["37권6호\npp.253-260","금속관 내부의 음압유량 향상을 위한 기하학적 디자인및 SLIPS 윤활\n(Geometrical Design and SLIPS Lubrication for Enhancement of Negative-pressure-driven Internal Flow Rate in Metal Pipes)","Lubrication (Lubricants & Additives), Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification), Micro/Nano-Tribology","Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.","metal pipe(금속관), surface lubrication(표면 윤활), computational fluid dynamics(전산 유체 역학), cannula(캐뉼라)","김동근1*ㆍ장창환1*ㆍ김성재1*ㆍ김대겸2†ㆍ김산하3‡\n1한국과학기술원 기계공학과 석사과정생, 2한국과학기술원 기계공학과 부교수, 3한국과학기술원 기계공학과 조교수","https://doi.org/10.9725/kts.2021.37.6.253"]
["37권6호\npp.261-272","고속 전동기용 무급유 포일 저널 베어링 구조체의 하중지지 및 진동 특성 규명\n(Identification of Load Carrying and Vibration Characteristicsof Oil-Free Foil Journal Bearing Structures for High Speed Motors)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This study investigates the structural characteristics of oil-free, gas beam foil journal bearings (GBFJBs) for use in high speed motors. Mathematical modeling was carried out, and reaction force modeling for static load was performed to predict the structural characteristics of the GBFJB. Mathematical modeling and reaction force modeling for static load are performed to predict the structural characteristics of GBFJBs. The reaction force of the test bearing against static loads was measured during experiments and compared with the predicted results. The measured experimental data reveal the nonlinear stiffness characteristics of the GBFJB against varying displacement and agree well with the predictions. Dynamic load tests using an exciter allow to identify the vibration characteristics of the GBFJB. Test results show that the vibration displacement, dynamic force, and acceleration measured on the test bearing are most dominant at the applied dynamic load (synchronization) frequency. Futhermore, the test results show that the hysteresis area recorded during the dynamic tests increases with the excitation amplitude and frequency, and that the beam stick phenomena occurr at high excitation frequencies. The single degree of freedom (DOF) vibration model aids to identify the stiffness and damping coefficient of the GBFJB, which decrease as the excitation frequency increases.","high speed motor(고속 전동기), beam foil(빔포일), gas foil bearing(가스 포일 베어링), rotordynamics(회전체동역학), structural characteristics(구조 특성)","백두산1ㆍ황성호2ㆍ김태호3†\n1국민대학교 대학원 기계설계학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2021.37.6.261"]

{"sheet":"2022년","index":2,"n_rows":41,"n_cols":7,"rows_kept":41,"cut":false,"hidden":false,"merged":[]}
["권호","제목","토픽","초록","키워드","저자","DOI"]
["38권1호\npp.1-7","패드 마모 균일성 향상을 위한 CMP 컨디셔닝 시스템설계 변수 연구\n(Design Variables of Chemical-Mechanical Polishing Conditioning System to Improve Pad Wear Uniformity)","Chemical Mechanical Polishing","Chemical-mechanical polishing (CMP) process is a semiconductor process that planarizes a wafer surface using mechanical friction between a polishing pad and a substrate surface during a specific chemical reaction. During the CMP process, polishing pad conditioning is applied to prevent the rapid degradation of the polishing quality caused by polishing pad glazing through repeated material removal processes. However, during the conditioning process, uneven wear on the polishing pad is inevitable because the disk on which diamond particles are electrodeposited is used. Therefore, the abrasion of the polishing pad should be considered not only for the variables during the conditioning process but also when designing the CMP conditioning system. In this study, three design variables of the conditioning system were analyzed, and the effect on the pad wear profile during conditioning was investigated. The three design variables considered in this study were the length of the conditioner arm, diameter of the conditioner disk, and distance between centers. The Taguchi method was used for the experimental design. The effect of the three design variables on pad wear and uniformity was assessed, and new variables used in conditioning system design were proposed.","Chemical mechanical planarization(화학적 기계 평탄화), Pad conditioning(패드 컨디셔닝), Design variables(설계 변수), Conditioning simulation(컨디셔닝 시뮬레이션), Pad wear profile(패드 마모 프로파일)","박병훈1ㆍ박범영2ㆍ전언찬3ㆍ이현섭4†\n1동아대학교 대학원 기계공학과 박사과정생, 2부산대학교 대학원 기계공학부 박사, 3동아대학교 기계공학과 특임교수, 4동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.1.1"]
["38권1호\npp.8-14","컴프레서 부품의 DLC코팅 적용에 따른 트라이볼로지적 특성 연구\n(Tribological Characteristics of DLC-Coated Part in Compressor)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Amorphous carbon (a-C) has excellent wear resistance and, therefore is used as a coating to protect numerous mechanical components to prolong their lifetimes. Among the a-C coatings, diamond-like carbon (DLC) and DLC-containing silicon (Si-DLC) receive extensive attention owing to their enhanced wear resistance and low frictional characteristics. In this study, the friction and wear characteristics of DLC and Si-DLC coatings are analyzed. For comparative analysis, DLC-coated and Si-DLC-coated vanes are utilized with the counterpart of a roller for the friction tests. Since the lubricated mechanical components are generally vulnerable to wear when a lubricant film does not form properly, friction tests are conducted under boundary lubrication conditions to promote wear. A cylinder-on-cylinder type tribometer is used to perform the friction tests with various normal load conditions. After the friction test, a 3D laser confocal microscope is used for quantifying the wear volume to calculate the wear rate of each specimen. Consequently, the DLC-coated specimen shows a lower coefficient of friction (COF) and wear rate than the specimen without the coating, while the Si-DLC coating shows a higher COF than the bare specimen. The results of this study are expected to contribute to improving the efficiency and reliability of compressors.","Coating hardness(코팅 경도), Compressor(압축기), DLC coating(DLC 코팅), Surface topography(표면 형상), Vane(베인)","윤주용1ㆍ서국진2ㆍ한재호2ㆍ전지환3ㆍ송지영3ㆍ고영덕4ㆍ남자현3ㆍ김선교4ㆍ김대은5†\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 대학원 기계공학과 박사과정생, 3삼성전자 생활가전사업부 책임연구원, 4삼성전자 생활가전사업부 수석연구원, 5†연세대학교 기계공학과 교수","https://doi.org/10.9725/kts.2022.38.1.8"]
["38권1호\npp.15-21","다이아몬드 강화 Cr 기반 소재의 정량적 마모 특성 평가\n(Quantitative Assessment of Wear Characteristics of Cr-based Coating Reinforced with Diamond)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials)","Diamond reinforced Cr-based coating has been proposed as wear-resistant materials. In this study, the friction and wear characteristics of diamond reinforced Cr-based coating are experimentally assessed. The experiments are performed using a pin-on-reciprocating plate tribo-tester under various normal forces with boundary lubrication. The stainless-steel ball is used as a counter material. Prior to the experiments, mechanical properties such as elastic modulus and hardness are determined using nanoscale instrumented indentation. The hardness of the specimen is further determined using a Vickers hardness tester. The specimens before and after the experiments are carefully observed using a confocal microscope to understand the wear characteristics. In addition, the wear volume and wear rate of the specimens are determined based on the confocal microscope data. The results show that the friction coefficients are 0.096–0.100 under 20–40 N normal forces. Furthermore, the wear rates of the diamond reinforced Cr-based coating and the stainless steel ball under 20–40 N normal forces are found to be 12.8 × 10-8 mm3/(Nm)–15.5 × 10-8 mm3/(Nm) and 1.9 × 10-8 mm3/(Nm)–3.9 × 10-8 mm3/(Nm), respectively. However, the effect of the normal force on wear rates is not clearly observed, which may be associated with the flattening of the ball. The results of the study may be useful for the tribological applicability of diamond reinforced Cr-based coating as wear-resistant materials.","Diamond reinforced Cr-based coating(다이아몬드 강화 Cr 기반 코팅), Friction(마찰), Wear rate(마모율)","후인 옥-팟1ㆍ부 아 린2ㆍ정구현3†\n1울산대학교 대학원 기계공학과 박사과정생, 2울산대학교 대학원 기계공학과 석사졸업생, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.1.15"]
["38권1호\npp.22-26","1.7톤급 소형 굴착기용 주행 감속기의 복합 유성기어류에대한 강도 평가\n(Strength Evaluation of Complex Planetary Gear Train ofTraveling Reducer for 1.7-Ton Grade Small Excavator)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","A 1.7-ton grade small excavator is a construction equipment that can perform various functions in limited spaces where heavy equipment cannot enter easily. Owing to the recent acceleration of urbanization, it has been used increasingly in drainage and gas pipes, as well as for road repair works in urban areas. The power train of a traveling reducer for a 1.7-ton grade small excavator utilizes a complex planetary gear system. Complex planetary gears are vital to the power train of a traveling reducer as it mitigates the fatigue strength problem. In the present study, the specifications of a complex planetary gear train are calculated; furthermore, the gear bending and compressive stresses of the complex planetary gears are analyzed to achieve an optimal design of the latter in terms of cost and reliability. In this study, the actual gear bending and compressive stresses of a planetary gear system are analyzed using a self-developed gear design program based on the Lewes and Hertz equation. Subsequently, the calculated specifications of the complex planetary gears are verified by evaluating the results with the data of allowable bending and compressive stress based on curves of stress vs. number of cycles of the gears.","Excavator(굴착기), Travelling reducer(주행 감속기), Complex planetary gear train(복합 유성기어 트레인), Gear bending stress(기어 굽힘 응력), Gear compressive stress(기어 면압 응력)","남석주1ㆍ배명호2ㆍ조연상3†\n1(주)델릭스 대표이사, 2창원문성대학교 항공정비학부 교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2022.38.1.22"]
["38권1호\npp.27-31","3D 프린팅 기법을 이용한 하모닉 드라이브(Harmonic Drive) 설계 및 응용 분석\n(Design of a Novel 3D Printed Harmonic Drive and Analysis of its Application)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Harmonic drives have attracted increasing attention with the development of materials, parts, and related equipment. Harmonic drives exhibit high deceleration, high accuracy, and light weight. The stiffness of flexible splines according to the radial load is studied using a commercial FEM program to design the structure of the flexible spline and finite element to improve the weight and price competitiveness of harmonic drives. In addition, several studies have measured and compared friction coefficients based on 3D printed tread patterns. However, owing to the characteristics of plastic materials, a decrease in stiffness in the radial direction is inevitable. To prevent a decrease in stiffness in the radial direction, we designed and manufactured flex splines with a wrinkle shape. Through structural analysis, the reaction force and stiffness in the radial direction were determined. In addition, the maximum angle of the mound was derived by theoretical calculations, and the performance of the harmonic drive was compared with the results obtained in the mound experiment. Structural analysis shows that the shape of wrinkles decreased the stress and reaction force and increased the safety factor in comparison with that of the circular shape. During performance verification through continuous experiments, the developed harmonic drive showed continuous performance similar to that of an actual tank model. It is expected that the flex spline with a compliant spring and wrinkle shape will prevent a decrease in the radial stiffness.","Harmonic drive(하모닉 드라이브), Flex spline(플렉스 스플라인), Compliant spring(컴플라이언트 스프링), Wrinkle shape(주름 형상), Static analysis(정적 해석)","김상현1ㆍ변창섭2ㆍ이철희3†\n1인하대학교 건설기계공학과 석사과정생, 2인하대학교 기계공학과 학부생, 3인하대학교 기계공학과 교수","https://doi.org/10.9725/kts.2022.38.1.27"]
["38권2호\npp.33-40","정압베어링을 적용한 터보팽창기의 회전체 동역학 해석 및 구동시험\n(Rotordynamic Analysis and Operation Test of Turbo Expander with Hydrostatic Bearing)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 μm, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.","Hydrostatic bearing(정압베어링), Turbo expander(터보팽창기), Orifice(오리피스), Hydrogen liquefaction(수소액화)","이동현1†ㆍ김병옥1ㆍ정준하2ㆍ임형수3\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 시스템다이나믹스연구실 선임연구원, 3한국기계연구원 에너지변환기계연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.2.33"]
["38권2호\npp.41-52","전력분야의 바이오 기반 친환경 전기 절연유 적용에 관한 개발 동향 분석\n(Analysis of Development Trends on Bio-based Environmental Transformers Oils in Power Sector)","Eco/Green Tribology (Renewable / Alternative Energies) ","Mineral electrical insulating oil, which is widely used in transformers, exhibits excellent cooling performance and transformer efficiency. However, given that it is composed of petroleum-based components, it is weak in terms of biodegradability. This causes environmental problems in case of leakage and a low flash point, which is a factor that would cause great damage in the event of a fire in a substation. In this context, the use of eco-friendly electric insulating oil composed of bio-based vegetable oil and synthetic ester, which has excellent biodegradability and flame retardancy performance, has recently been expanded to the field of electric power, and various research and development (R&D) studies are in progress. According to different research results, vegetable oil and synthetic ester manufacturing technology, thermal stability, oxidation stability, property change, and quality control, which are characteristics of eco-friendly electrical insulating oils, are major factors affecting the maintenance of insulating oil properties. In addition, power companies have established and operated quality control standards according to the use of eco-friendly electrical insulating oil as they expand the exploitatoin of renewable energy in electricity production. In particular, deterioration and oxidation characteristics were jointly identified in R&D as an important influencing factor according to the content of saturated and unsaturated fatty acids present in vegetable oils and synthetic esters in power transformer applications.","Vegetable oil(식물성 오일), Synthetic ester(합성 에스테르), Transformer(절연유), Biodegradable oil(생분해성 오일), Thermal stability(열안정성), Oxidation stability(산화안정성)","김재곤1†ㆍ민영제2ㆍ김목연3ㆍ곽병섭4ㆍ박현주5\n1한국석유관리원 미래기술연구소 팀장, 2한국석유관리원 미래기술연구소 선임연구원, 3한국석유관리원 미래기술연구소 책임연구원, 4한전 전력연구원 일반연구원, 5한전 전력연구원 책임연구원","https://doi.org/10.9725/kts.2022.38.2.41"]
["38권2호\npp.53-62","무급유 포일 베어링으로 지지되는 소형 전동 압축기의회전체동역학 성능 측정 및 예측\n(Measurements and Predictions of Rotodynamic Performance ofa Motor-Driven Small Turbocompressor Supportedon Oil-Free Foil Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study presents experimental measurements of the rotordynamic performance of a motor-driven small turbocompressor supported by gas beam foil journal bearings (GBFJBs) and compares the test results with the predictions of a computational model. The experiments confirmed that the rotational synchronous frequency component dominates the behavior of the overall rotor vibrations, whereas the nonsynchronous components are insignificant, indicating the rotor-bearing system remains stable up to 100 krpm. The undamped natural frequency and imbalanced response of the rotor-bearing system are predicted when integrating the finite element model of the rotor-bearing system with the predictions of the bearing dynamic coefficients. The results are in good agreement with the experimental results. In addition, base excitation test results show that the small turbocompressor can endure large external forces and demonstrate limited rotor amplitudes. A simple single degree-of-freedom rotor model using the nonlinear stiffness of the GBFJBs can effectively predict the test results.","High speed motor(고속 전동기), Beam foil(빔포일), Gas foil bearing(가스 포일 베어링), Rotordynamics(회전체동역학), Base excitation(바닥 가진)","백두산1ㆍ황성호2ㆍ김태호3†ㆍ이종성4ㆍ김태영5\n1국민대학교 대학원 기계설계학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3국민대학교 기계공학부 교수, 4한온시스템 연료전지부품팀 전임연구원, 5현대자동차 연료전지운전장치설계팀 책임연구원","https://doi.org/10.9725/kts.2022.38.2.53"]
["38권2호\npp.63-69","스월 브레이크가 장착된 래버린스 씰의 동특성 해석\n(Rotordynamic Analysis of Labyrinth Seal with Swirl Brake)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","In this research, the rotordynamic characteristics of the labyrinth seal with and without swirl brake were predicted using the computational fluid dynamic (CFD) model. Based on previous studies, a simple swirl brake consisting of square vanes without stagger angle is designed and placed in front of the seal inlet. The rotating frame of reference is utilized to consider the whirling motion of the rotor in the steady-state analysis since the whirling motion is transient behavior in nature. CFD analysis was performed in the range of -1 to 1 pre-swirl ratio for a given seal and swirl brake design and operating conditions. The CFD analysis result shows that the swirl brake effectively reduces the pre-swirl since the circumferential fluid velocity of labyrinth seal with swirl brake was lower than that without swirl brake. The cross-coupled stiffness coefficient, which is greatly affected by the circumferential fluid velocity, increased with an increasing pre-swirl ratio in a seal without a swirl brake but showed a low value in a seal with a swirl brake. The change in the damping coefficient was relatively small. The effective damping coefficient of the labyrinth seal with swirl brake was generally constant and showed a higher value than the labyrinth seal without swirl brake.","Labyrinth seal(래버린스 씰), Swirl brake(스월 브레이크), Pre-swirl(프리스월), Rotordynamic coefficient(동특성 계수), Effective damping coefficient(유효감쇠계수)","이정인1ㆍ서준호2†\n1부산대학교 대학원 기계시스템설계전공 석박사통합과정생, 2부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2022.38.2.63"]
["38권2호\npp.70-72","구동 모듈 감속기 윤활 특성에 관한 연구\n(Research on the Lubrication Characteristics of Driving Modules)","Eco/Green Tribology (Renewable / Alternative Energies) ","In this study, we report on a power system developed as a decelerator for a driving module in an electric vehicle. The system is to be mounted in a limited space. The research focus was on development of miniaturization, light weight, and high power density. In particular, we aimed to minimize the layout of existing external components as integrated or built-in, and to maximize the power density by applying optimal cooling technology to increased requirements for developing modular power systems applicable to various OEM models. South Korean automakers ranked fourth in global electric-vehicle sales in 2020, but domestic sales are relatively slow. Despite government's expansion in subsidies for eco-friendly cars, consumers are delaying purchases after 2021 considering the cost-effectiveness of electric vehicles. In major European markets, the demand for electric vehicles exceeded the demand for diesel cars, and sales of hybrid cars, which used to represent eco-friendly cars, are slowing down as Toyota, started selling electric vehicles. In this study, the internal lubrication characteristics of a decelerator installed in an electric vehicle were analyzed in terms of the deceleration time while driving. By selecting the proper oil and oil viscosity, it was confirmed that there is no problem in lubricating the bearings and gears of the decelerator.","Driving module(구동 모듈)","김은겸1ㆍ김현찬2ㆍ박준영3†\n1삼보모터스 책임연구원, 2삼보모터스 수석연구원, 3삼보모터스 연구소장","https://doi.org/10.9725/kts.2022.38.2.70"]
["38권3호\npp.73-83","직각 쐐기와 응착접촉 하는 반무한 평판 내 전위: 제1부 - 보정 함수 유도\n(Dislocation in Semi-infinite Half Plane Subject to Adhesive Complete Contact with Square Wedge: Part I - Derivationof Corrective Functions)","Contact Mechanics & Friction","This paper is concerned with an analysis of a surface edge crack emanated from a sharp contact edge. For a geometrical model, a square wedge is in contact with a half plane whose materials are identical, and a surface perpendicular crack initiated from the contact edge exists in the half plane. To analyze this crack problem, it is necessary to evaluate the stress field on the crack line which are induced by the contact tractions and pseudo-dislocations that simulate the crack, using the Bueckner principle. In this Part I, the stress filed in the half plane due to the contact is re-summarized using an asymptotic analysis method, which has been published before by the author. Further focus is given to the stress field in the half plane due to a pseudo-edge dislocation, which will provide a stress solution due to a crack (i.e. a continuous distribution of edge dislocations) later, using the Burgers vector. Essential result of the present work is the corrective functions which modify the stress field of an infinite domain to apply for the present one which has free surfaces, and thus the infiniteness is no longer preserved. Numerical methods and coordinate normalization are used, which was developed for an edge crack problem, using the Gauss-Jacobi integration formula. The convergence of the corrective functions are investigated here. Features of the corrective functions and their application to a crack problem will be given in Part II.","Adhesive complete contact(응착 완전접촉), Perpendicular crack(수직 균열), Dislocation density function method(전위밀도함수법), Corrective function(보정 함수), Stress intensity factor(응력확대계수)","김형규1,2†\n1한국원자력연구원 핵연료안전연구부 책임연구원, 2과학기술연합대학원대학교 원자력 및 방사선안전전공 교수","https://doi.org/10.9725/kts.2022.38.3.73"]
["38권3호\npp.84-92","직각 쐐기와 응착접촉 하는 반무한 평판 내 전위: 제2부 - 보정 함수의 근사 및 응용\n(Dislocation in Semi-infinite Half Plane Subject to Adhesive Complete Contact with Square Wedge: Part II - Approximation and Application of Corrective Functions)","Contact Mechanics & Friction","In Part I, developed was a method to obtain the stress field due to an edge dislocation that locates in an elastic half plane beneath the contact edge of an elastically similar square wedge. Essential result was the corrective functions which incorporate a traction free condition of the free surfaces. In the sequel to Part I, features of the corrective functions, Fkij,(k = x, y;i,j = x,y) are investigated in this Part II at first. It is found that Fxxx() = Fyxy() where = y/η and η being the location of an edge dislocation on the y axis. When compared with the corrective functions derived for the case of an edge dislocation at x = ξ, analogy is found when the indices of y and x are exchanged with each other as can be readily expected. The corrective functions are curve fitted by using the scatter data generated using a numerical technique. The algebraic form for the curve fitting is designed\nas Fkij() = where λI = 0.5445, the eigenvalue of the adhesive complete contact problem\nintroduced in Part I. To investigate the exponent of Fkij, i.e.(1 − λI) and p, Log|Fkij|()-Log|()| is plotted and investigated. All the coefficients and powers in the algebraic form of the corrective functions are obtained using Mathematica. Method of analyzing a surface perpendicular crack emanated from the complete contact edge is explained as an application of the curve-fitted corrective functions.","Dislocation density function method(전위밀도함수법), Corrective function(보정 함수), Crack problem(균열 문제), Numerical approximation(수치적 근사)","김형규1,2†\n1한국원자력연구원 핵연료안전연구부 책임연구원, 2과학기술연합대학원대학교 원자력 및 방사선안전전공 교수","https://doi.org/10.9725/kts.2022.38.3.84"]
["38권3호\npp.93-100","마이크로 스탬프를 이용한 Micro-LED 개별 전사 및 리플로우 공정에 관한 연구\n(A Study on Selective Transfer and Reflow Process of Micro-LED using Micro Stamp)","Micro/Nano-Tribology","Micro-light emitting diode (micro-LED) displays offer numerous advantages such as high brightness, fast response, and low power consumption. Hence, they are spotlighted as the next-generation display. However, defective LEDs may be created due to non-uniform contact loads or LED alignment errors. Therefore, a repair process involving the replacement of defective LEDs with favorable ones is necessitated. The general repair process involves the removal of defective micro-LEDs, interconnection material transfer, as well as new micro-LED transfer and bonding. However, micro-LEDs are difficult to repair since their size decreases to a few tens of micron in width and less than 10 μm in thickness. The conventional nozzle-type dispenser for fluxes and the conventional vacuum chuck for LEDs are not applicable to the micro-LED repair process. In this study, transfer conditions are determined using a micro stamp for repairing micro-LEDs. Results show that the aging time should be set to within 60 min, based on measuring the aging time of the flux. Additionally, the micro-LEDs are subjected to a compression test, and the result shows that they should be transferred under 18.4 MPa. Finally, the I-V curves of micro-LEDs processed by the laser and hot plate reflows are measured to compare the electrical properties of the micro-LEDs based on the reflow methods. It was confirmed that the micro-LEDs processed by the laser reflow show similar electrical performance with that processed by the hot plate reflow. The results can provide guidance for the repair of micro-LEDs using micro stamps.","Micro-LED(마이크로 엘이디), Micro stamp(마이크로 스탬프), Repair process(수리 공정), Selective transfer process(선택적 전사 공정), Laser reflow(레이저 리플로우)","한승1,3ㆍ윤민아2,3ㆍ김 찬4ㆍ김재현5,6ㆍ김광섭5,6†\n1과학기술연합대학원대학교 나노메카트로닉스학과 석사과정생, 2과학기술연합대학원대학교 융합기계시스템 박사과정생, 3한국기계연구원 나노융합장비연구부 학생연구원, 4한국기계연구원 나노융합장비연구부 박사후 연구원, 5과학기술연합대학원대학교 융합기계시스템 교수, 6한국기계연구원 나노융합장비연구부 책임연구원","https://doi.org/10.9725/kts.2022.38.3.93"]
["38권3호\npp.101-108","자장여과아크소스의 자장필터 꺾임 각도와 아크방전전류에따라 증착된 ta-C 코팅의 마모 거동 연구\n(A Study on the Wear Behavior of Tetrahedral Amorphous Carbon Coatings Based on Bending Angles of the Filtered Cathodic Vacuum Arc with Different Arc Discharge Currents)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","The structure and properties of tetrahedral amorphous carbon (ta-C) coatings depend on the main process parameters and bending angles of the magnetic field filter used in the filtered cathodic vacuum arc (FCVA). During the process, it is possible to effectively control the plasma flux of carbon ions incident on the substrate by controlling the arc discharge current, thereby influencing the mechanical properties of the coating film. Furthermore, we can control the size and amount of large particles mixed during carbon film formation while conforming with the bending angle of the mechanical filter mounted on the FCVA; therefore, it also influences the mechanical properties. In this study, we consider tribological characteristics for filtered bending angles of 45° and 90° as a function of arc discharge currents of 60 and 100 A, respectively. Experiment results indicate that the frictional behavior of the ta-C coating film is independent of the bending angle of the filter. However, its sliding wear behavior significantly changes according to the bending angle of the FCVA filter, unlike the effect of the discharge current. Further, upon changing the bending angle from 45° to 90°, abrasive wear gets accelerated, thereby changing the size and mixing amount of macro particles inside the coating film.","Filtered cathodic vacuum arc(자장여과아크플라즈마), Arc discharge current(아크방전전류), Hardness(경도), Surface roughness(표면거칠기), Wear(마모), Macro particle(거대입자)","김원석1,3ㆍ김송길2ㆍ장영준3†ㆍ김종국3‡\n1부산대학교 대학원 기계공학부 석사과정생, 2부산대학교 기계공학부 부교수, 3한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.3.101"]
["38권3호\npp.109-114","마이크로 버블 발생장치와 결합된 오일 플러싱 장치 개발\n(Development of Oil Flushing System with Microbubble Generator)","Condition Monitoring & Maintenance System (System Reliability)","This paper reports the development of an oil flushing system combined with a microbubble generator. Oil flushing plays a crucial role in regulating the lubricant’s performance during the lubricant replacement process. Moreover, harmful contaminants, such as sludge, wear particles, and rust, from piping systems or lubrication system can be removed by oil flushing. Oil flushing aims to increase the system’s efficiency using a dedicated flushing oil, increasing of the supply pressure and generating a vortex. In addition, it helps the mechanical system or equipment achieve peak performance and reduces the potential for premature failure. However, the contaminant-removal applications of existing oil flushing system are limited. In this research, we aim to improve the performance of oil flushing system by incorporating a microbubble generator, which uses the venture effect to generate microbubbles and mixes them with lubricant. The microbubbles in the blended lubricant remove contaminants from the lubrication system more effectively. Structural mechanics and fluid dynamics are analyzed through fluid-structure interaction (FSI) analysis, and the numerical analysis results are used for the designing the system. The magnitude of the maximum stress is investigated based on the pressure results obtained by the CFD analysis; through the CFD analysis, the mixing ratio of air (bubble) and lubricant is evaluated using the volume of fluid (VOF) model according to the working conditions.","Fluid-structure interaction analysis(유동-구조 연성 해석), Lubricant(윤활유), Microbubble generator(마이크로 버블 발생기), Oil flushing(오일 플러싱)","홍성호1†ㆍ이경희2ㆍ정남화3\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2삼영필텍 대표, 3삼영필텍 전무","https://doi.org/10.9725/kts.2022.38.3.109"]
["38권3호\npp.115-119","Influence of Grease Consistency on the Wear of Gear Surfaces","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This paper selected three kinds of grease with the same type but different consistency for the experiment. The purpose of the experiment is tested the effect of different consistency of grease on the wear of the gear surface. Different torque test groups were selected in the test, and the lubrication effect of different greases was tested in the test groups with the same torque. After each set of tests, the wear of the gear surfaces was observed and recorded. The data recorded in the experiment included the area of the wear area on the gear surface, the type of wear and the volume of wear. After the test, the gear surface roughness was measured. By calculating the wear volume, the effects of different concentrations of grease on the gear surface wear were compared. The experimental results show that under different stress conditions, the consistency of the grease has a great influence on the lubricating effect of the gear surface and the gear wear. Under the condition with low speed and high torque, different grease consistency affect the gear surface wear, the high consistency grease can reduce the wear of the gear surface, so that the gear can get better lubrication effect during the work.","Consistency, Gear, Grease, Pitting, Surface wear","Chen-Xiao Li1, Haneum Park2 and Chul-Hee Lee3†\n1Ph.D. Student, Graduate School, Dept. of Mechanical Engineering, Inha University, 2Researcher, R&D Team, CALS Corporation, 3Professor, Dept. of Mechanical Engineering, Inha University","https://doi.org/10.9725/kts.2022.38.3.115"]
["38권4호\npp.121-127","통합형 오일 정제 시스템의 개발\n(Development of an Integrated Oil Purification System)","Condition Monitoring & Maintenance System (System Reliability)","This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a microbubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60oC, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.","Lubricant(윤활유), Oil filter(오일 필터), Oil flushing(오일 플러싱), Oil purification(오일 정제), Vacuum chamber(진공 챔버)","홍성호1†ㆍ이경희2ㆍ정남화3\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2삼영필텍 대표, 3삼영필텍 전무","https://doi.org/10.9725/kts.2022.38.4.121"]
["38권4호\npp.128-135","가속내구시험 마모영역 판별에 대한 이미지 분석 연구\n(A Study on Image Analysis for Determination of Wear Areain Accelerated Durability Test)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements), Tribology Applications (Industrial Case Studies)","In the product development process, the reliability of the product can be secured through durability tests. However, since the durability test method is expensive and time consuming, a method to save time and money by utilizing virtual product development (VPD) is required. However, research on the accuracy of the results of virtual product development is required. In this paper, an accelerated durability test was designed and conducted using a planetary gear decelerator. And an analysis model under the same conditions was created and simulated. To correlate the results of the experiment with the results of the analytical model, created a model that can discriminate the wear region using one of the data mining methods, the k-means algorithm method and HSV (Hue, Saturation, Value). The wear area is compared by counting the number of pixels defined as wear through a discrimination model. A similar ratio was calculated by comparing the pixel ratio of the area determined as wear in the entire area. It showed a similar ratio of about 70%, and it is necessary to improve the discrimination method.","Accelerated durability test(가속내구시험), CAE(컴퓨터 응용해석), Wear area(마모 영역), Planetary gear(유성기어), Virtual product development(가상제품개발)","천민우1ㆍ이철희2†\n1인하대학교 대학원 기계공학과 박사과정생, 2인하대학교 기계공학과 정교수","https://doi.org/10.9725/kts.2022.38.4.128"]
["38권4호\npp.136-142","공정 개선에 따른 사고저항성 CrAl 코팅 피복관의 내마모성 향상\n(Improved Coating Process for Enhanced Wear Resistance of CrAl Coated Claddings for Accident Tolerant Fuel)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ,Wear Phenomena & Mechanisms","This paper investigates the enhanced wear performance of a CrAl coated accident tolerant fuel (ATF) cladding. In the wake of the Fukushima accident, extensive research on ATF with respect to improving the oxidation resistance of cladding materials is ongoing. Since coated Zr claddings can be applied without major changes to the criteria for reactor core design, many researchers are studying coatings for claddings. To improve the quality of the CrAl coating layer, optimization of the manufacturing process is imperative. This study employs arc ion plating to obtain improved CrAl coated claddings using CrAl binary alloy targets through an improved coating method. Surface roughness and adhesion are improved, and droplets are reduced. Furthermore, the coated layer has a dense and fine microstructure. In scratch tests, all the tested CrAl coated claddings exhibit a superior resistance compared to the Zr cladding. In a fretting wear test, the wear volume of the CrAl coated claddings is smaller compared to the Zr cladding. Furthermore, the coated cladding manufactured through the improved process exhibits better wear resistance than other CrAl coated claddings. Based on these results, we suggest that fine microstructure is attributed to a mechanically and microstructurally robust CrAl coating layer, which enhances wear resistance.","Fretting wear(프레팅 마모), Accident tolerant fuel cladding/ATF cladding(사고저항성핵연료 피복관), Arc Ion Process(아크 이온 플레이팅), CrAl coating(CrAl 코팅), Scratch test(스크래치 시험)","김성은1†ㆍ이영호 2ㆍ김대호2ㆍ김현길2\n1한국원자력연구원 핵연료안전연구부 박사후 연구원, 2한국원자력연구원 핵연료안전연구부 책임연구원","https://doi.org/10.9725/kts.2022.38.4.136"]
["38권4호\npp.143-151","건설기계의 오일진단 관련 특허 분석\n(Analysis of Patents Related to Oil Diagnosis of Construction Equipment)","Condition Monitoring & Maintenance System (System Reliability)","This study analyzes patents related to oil diagnosis of construction equipment. Oil diagnosis is extremely important for maintaining construction equipment properly. Through the evaluation of existing patents, a patent strategy for the future construction equipment market is presented. The related patents are classified and selected in several steps. Finally, 16 valid patents are selected and analyzed in detail. In the classification process, patents are classified by country, year, and company. A market analysis shows that the top 10 companies have a market share of more than 50. In addition to patents related to the oil analysis of construction equipment, patents related to automobile oil analysis and development of oil sensors are investigated to identify the contents of patents in other fields that can be applied to oil diagnosis technology for construction equipment. Moreover, not only the contents of research articles of two Korean construction companies, but also the research trends in the literature in this field are used in the analysis. The related patents of the two Korean companies are few. Companies with a high market share, including Caterpillar, hold many patents, and patents for diagnosis algorithms using such technologies as artificial intelligence and artificial neural networks, along with oil sensor-based condition monitoring technology, are gradually expanding.","Construction equipment(건설기계), Lubricant(윤활유), Oil diagnosis(오일진단), Patent(특허)","홍성호1†ㆍ장범석2\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2동국대학교 창의융합공학부 기계시스템공학전공 학부생","https://doi.org/10.9725/kts.2022.38.4.143"]
["38권4호\npp.152-161","인공신경망을 활용한 CMP 컨디셔닝 시스템 설계 변수에 따른 컨디셔닝 밀도의 불균일도 분석\n(Nonuniformity of Conditioning Density According to CMP Conditioning System Design Variables Using Artificial Neural Network)","Chemical Mechanical Polishing","Chemical mechanical planarization (CMP) is a technology that planarizes the surfaces of semiconductor devices using chemical reaction and mechanical material removal, and it is an essential process in manufacturing highly integrated semiconductors. In the CMP process, a conditioning process using a diamond conditioner is applied to remove by-products generated during processing and ensure the surface roughness of the CMP pad. In previous studies, prediction of pad wear by CMP conditioning has depended on numerical analysis studies based on mathematical simulation. In this study, using an artificial neural network, the ratio of conditioner coverage to the distance between centers in the conditioning system is input, and the average conditioning density, standard deviation, nonuniformity (NU), and conditioning density distribution are trained as targets. The result of training seems to predict the target data well, although the average conditioning density, standard deviation, and NU in the contact area of wafer and pad and all areas of the pad have some errors. In addition, in the case of NU, the prediction calculated from the training results of the average conditioning density and standard deviation can reduce the error of training compared with the results predicted through training. The results of training on the conditioning density profile generally follow the target data well, confirming that the shape of the conditioning density profile can be predicted.","Chemical mechanical planarization(화학적기계적 평탄화), Pad conditioning(패드 컨디셔닝), Design ariables(설계 변수), Conditioning simulation(컨디셔닝 시뮬레이션), Artificial neural network(인공신경망)","박병훈1ㆍ이현섭2†\n1동아대학교 대학원 기계공학과 박사과정생, 2동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.4.152"]
["38권4호\npp.162-169","CoCrW와 CoCrMo 합금의 트라이볼로지 특성 평가\n(Assessment of Tribological Characteristics of CoCrW and CoCrMo Alloys)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials)","Cobalt–chromium (CoCr)-based alloys have been used for wear applications because of their excellent mechanical properties and wear resistance. With growing concern over environmental problems, CoCr alloys are expected to be used for various tribological applications in degraded lubrication states. To expand the applicability of the materials, data should be accumulated across a broad spectrum of experimental parameters. In this work, the friction and wear characteristics of cobalt–chromium–tungsten (CoCrW) and cobalt–chromium–molybdenum (CoCrMo) alloys are investigated experimentally. The tests are conducted using a pin-on-reciprocating-plate tribo-tester in dry lubrication. CoCrW and CoCrMo are used as pin and plate materials to investigate the effect of the counter material. The results show that the friction coefficients between CoCrW and CoCrMo generally range from 0.4 to 0.5. The friction coefficient between the CoCrW pin and plate is found to be slightly small. However, the total wear between the CoCrW pin and plate is found to be the largest. In contrast, the total wear between the CoCrW pin and plate is relatively small. Furthermore, CoCrW may cause a faster wear progression of CoCrMo, especially for the case in which CoCrMo is used as the pin material. The results of this work provide a better understanding of the tribological properties of CoCrW and CoCrMo alloys. In addition, this work provides a practical guideline for the use of CoCrW and CoCrMo from the tribological design viewpoint.","CoCrMo alloy(CoCrMo 합금), CoCrW alloy(CoCrW 합금), Friction(마찰), Wear rate(마모율)","권동균1ㆍ오세진2ㆍ정구현3†\n1울산대학교 기계공학부 학사과정생, 2울산대학교 기계공학부 석사과정생, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.4.162"]
["38권4호\npp.170-178","SUJ2 베어링 강의 트라이볼로지 특성에 대한 초음파나노표면개질 (UNSM) 및 원더프로세스크래프트 (WPC) 처리 효과 연구\n(A Study on the Effects of Ultrasonic Nanocrystal SurfaceModification (UNSM) and Wonder Process Craft (WPC)Treatments on Tribological Properties of SUJ2 Bearing Steel)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Mechanical surface treatment is an excellent approach widely used to modulate and improve the performance and service life of bearings, gears, and frictional joints. The main purpose of this study is to investigate and compare the effect of ultrasonic nanocrystal surface modification (UNSM) and wonder process craft (WPC) on the surface and tribological properties of SUJ2 bearing steel. The surface roughness and hardness of the untreated and treated (UNSM- and WPC-treated) specimens were measured and compared. Their tribological properties were evaluated using a micro-tribometer under grease-lubricated and dry conditions against itself. Surface hardness measurement results revealed that both the UNSM- and WPC-treated specimens had a higher hardness than that of the untreated specimen. The surface roughness of the untreated specimen was reduced after UNSM and WPC treatments. Abrasive wear mode was observed on the surface of the specimens worn under grease-lubricated conditions, while adhesive wear mode was found on the surface of the specimens worn in dry conditions. According to the tribological test results, the friction coefficient and wear rate of the untreated specimens were reduced by the application of both the UNSM and WPC treatments under grease-lubricated and dry conditions.","SUJ2 bearing steel(SUJ2 베어링 강), Sliding friction(미끄럼 마찰), Sliding wear behavior(미끄럼 마모거동), UNSM(초음파나노표면개질), WPC(원더프로세스크래프트)","아마노프 아웨즈한1†ㆍ카림바예프 루슬란2ㆍ조인호3ㆍ김응주4\n1선문대학교 기계공학과/융합과학기술학과 부교수, 2선문대학교 대학원 융합과학기술학과 박사과정생, 3(주)디자인메카 대표이사, 4(주)포휴먼사이언스 대표이사","https://doi.org/10.9725/kts.2022.38.4.170"]
["38권5호\npp.179-184","21톤급 휠 굴착기용 트랜스미션의 기어 트레인에 대한 강도 해석\n(Strength Analysis of Complex Gear Train for Transmission of 21-Ton Grade Wheel Excavator)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","The power train of transmission for 21-ton grade wheel excavator makes use of a complex gear train composed of a planetary and helical gear system to drive the wheel excavator by transmitting power to the axle. The complex gear train with a shift mode is an important part of the transmission because of strength problems in an extreme environment. To calculate the specifications of the complex gear train and analyze the gear bending and compressive stresses of the complex gear train, this study analyzes gear bending and compressive stresses accurately for the optimal design of the complex gear train with respect to cost and reliability. In this article, the gear bending and compressive stresses of the complex gear train are calculated using the Lewes and Hertz equation. Evaluating the results with the data of the allowable bending and compressive stress from the stress and number of cycles curves of the gears verified the calculated specifications of the complex gear train. A computer structure analysis is performed with the 3D model of the planetary and helical gears to analyze the structure strength of the complex gear train. The results demonstrate that the durability and strength of the complex gear train are safe, because the safety factors of the bending and compressive stresses are more than 1.0.","Wheel excavator(휠 굴착기), Transmission(변속기), Complex gear Train(복합 기어 트레인), Gear bending stress(기어 굽힘 응력), Gear compressive stress(기어 면압 응력), Computer structure analysis(컴퓨터 구조 해석)","이준희1ㆍ배명호2ㆍ조연상3†\n1(주)디아이씨 기술연구소 부장, 2창원문성대학교 항공정비학부 교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2022.38.5.179"]
["38권5호\npp.185-190","히트파이프 모세관 성능 개선을 위한 스크린-메쉬 윅의 표면 개질\n(Surface Modification of Screen-Mesh Wicks to Improve Capillary Performance for Heat Pipes)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.","Capillary performance(모세관 성능), Capillary rise height(모세관 상승 높이), Micro(마이크로 구조), Screen-mesh wick(스크린-메쉬 윅), Surface modification(표면 개질)","정지윤1ㆍ임혜원1ㆍ김혜원1ㆍ이상민2ㆍ김형모3†\n1경상국립대학교 기계공학부 학부연구생, 2동의대학교 기계자동차로봇부품공학부 조교수, 3경상국립대학교 기계공학부 조교수","https://doi.org/10.9725/kts.2022.38.5.185"]
["38권5호\npp.191-198","사각형 딤플로 Surface Texturing한 경사진 Slider 베어링의 윤활해석\n(Lubrication Analysis of Surface-Textured Inclined Slider Bearing with Rectangular Dimples)","Lubrication (Lubricants & Additives) ,Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","With the world's fast expanding energy usage comes a slew of new issues. Because one-third of energy is lost in overcoming friction, tremendous effort is being directed into minimizing friction. Surface texturing is the latest surface treatment technology that uses grooves and dimples on the friction surface of the machine to significantly reduce friction and improve wear resistance. Despite the fact that many studies on this issue have been conducted, most of them focused on parallel surfaces, with relatively few cases of converging films, as in most sliding bearings. This study investigated the lubrication performance of surface-textured inclined slider bearings. We analyzed the continuity and Navier–Stokes equations using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and velocity distributions and the lubrication performance according to the number and orientation of rectangular dimples. Partial texturing somewhat improves the lubrication performance of inclined slider bearings. The number of dimples with the maximum load-carrying capacity (LCC) and minimum friction is determined. When the major axis of the dimple is arranged in the sliding direction, the LCC and friction reduction are maximized. However, full texturing significantly reduces the LCC of the slider bearing and increases the flow rate. The results have the potential to improve the lubrication performance of various sliding bearings, but further research is required.","Slider bearing(슬라이더 베어링), Surface texturing(표면조직가공), Hydrodynamic lubrication(유체윤활), Computational fluid dynamics(CFD, 전산유체역학), Numerical analysis(수치해석)","박태조1†ㆍ장인규2\n1경상국립대학교 기계공학부 교수·공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2022.38.5.191"]
["38권5호\npp.199-204","물 분자막의 두께와 윤활특성의 상관관계에 대한 분자시뮬레이션 연구\n(Molecular Simulation Study on Influence of Water Film Thickness on Lubrication Characteristics)","Modeling & Simulation in Tribology ","This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.","Contact area(접촉면적), Film thickness(유막 두께), Lubrication(윤활), Molecular simulation(분자 시뮬레이션), Water molecule(물분자)","김현준1,2†ㆍ허세곤3\n1경북대학교 정밀기계공학과 부교수, 2경북대학교 미래과학기술융합학과 부교수, 3한국기계연구원 3D프린팅장비연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.5.199"]
["38권5호\npp.205-212","고속 전동기용 2 패드 빔 타입 가스 포일 저널 베어링의 회전체동역학 성능 측정\n(Rotordynamic Performance Measurements of a Two-PadBeam-Type Gas Foil Journal Bearing for High Speed Motors)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents experimental measurements of the structural characteristics of a two-pad beam-type gas foil journal bearing and its rotordynamic performance for a high-speed motor-driven turbocompressor. The test bearing had two top foils and two beam foils, each with an arc length of ~180°. Each beam foil was etched to obtain 40 beams with six geometries of different lengths and widths. The insertion of beam foils into the bearing housing produces equivalent beam heights. The structural tests of the bearing with a non-rotating journal revealed a smaller bearing clearance and larger structural stiffness for the load-on-pad configuration than for the load-between-pads configuration. Rotordynamic performance measurements during driving tests up to 100 krpm demonstrated synchronous vibrations and subsynchronous vibrations with large amplitudes. The test was repeated after inserting the shim between the top foil and beam foil to reduce the bearing radial clearance. The reduced bearing clearance resulted in a reduction in the peak amplitude of the synchronous vibrations and an increase in the speed at which the peak amplitude occurred. In addition, the onset speed and amplitude of the subsynchronous vibrations were dramatically increased and diminished, respectively. The rotor coast-down tests at 100 krpm show that the reduction in the bearing clearance extends the time to rotor stop, thus implying an improvement in hydrodynamic pressure generation and a reduction in bearing frictional torque.","High speed motor(고속 전동기), Bam foil(빔 포일), Gas foil bearing(가스 포일 베어링), Rotordynamics(회전체동역학), Bearing clearance(베어링 간극)","정권종1ㆍ황성호2ㆍ백두산3ㆍ김태영4ㆍ김태호5†\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3현대모비스 연료전지시스템개발셀 연구원, 4현대자동차 연료전지운전장치설계팀 책임연구원, 5국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.5.205"]
["38권5호\npp.213-221","경사 그루브를 갖는 평판 실의 압력 강하 및 누설 성능\n(Pressure Drop and Leakage Performances of Flat Seals with Inclined Grooves)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.","Seal(실), Leakage flow rate(누설 유량), Pressure drop(압력 강하), Groove(그루브), Pressure ratio(압력비)","정진우1ㆍ정권종1ㆍ황성호2ㆍ김태호3†ㆍ김어진4\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3국민대학교 기계공학부 교수, 4두산에너빌리티 주임연구원","https://doi.org/10.9725/kts.2022.38.5.213"]
["38권5호\npp.222-226","압축기 부품소재 표면 적용을 위한 탄소 기반 고체 윤활막의 마찰 및 마모 특성 평가\n(Evaluation of Friction and Wear Characteristics of Carbon-based Solid Lubricant Films for Surface Application of Compressor Parts)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Between diaphragms made of stainless steel (SUS), which is the main component of a hydrogen gas compressor, micro-slip occurs owing to repeated bending, resulting in scratches on the surface. The surface scratch of the compressor part is a problem with airtightness, which reduces the efficiency of the compressor; in severe cases, damage is a possibility. In this study, the changes in friction and wear characteristics due to the surface polishing of SUS and carbon-based solid lubricant films (graphene and CNT) were analyzed. Bare SUS, polished SUS, graphene film, and CNT film specimens were prepared. The surface roughness of the SUS was significantly reduced by surface polishing but increased by carbon-based solid lubricating films. In contrast, the friction coefficient maintained a similar value after surface polishing but was significantly reduced by the carbon-based solid lubricant films. In particular, the graphene film exhibited the lowest initial friction coefficient, while the CNT film exhibited the lowest overall average friction coefficient. Regarding the wear rate, polished SUS exhibited the lowest value, but the surface condition of the wear track showed that the carbon-based solid lubricating films were relatively less damaged. Although the wear rate measured was largely attributed to the solid lubricating film peeling off, the SUS surface under the film was considered protected.","Carbon nanotube(탄소나노튜브), Friction/wear(마찰/마모), Graphene(그래핀), Solid lubricant(고체 윤활제), Surface polishing(표면 연마)","이성준1ㆍ김창래2†\n1조선대학교 대학원 기계공학과 박사과정생, 2조선대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.5.222"]
["38권6호\npp.227-234","선박엔진 부품의 성능 향상을 위한 초기 마모 및 윤활 해석 연구\n(Simulation of the Initial Wear and Lubrication Performance of Marine Engine Components)","Tribology in Transportation (Railway / Road) ","Recently, the demand for improving energy efficiency has rapidly increased because of the growing concerns over environmental issues. In this work, the tribo-test and simulation for the initial wear and lubrication performance were performed for the piston pin in the small end system of the connecting rod of a marine engine, to obtain useful data for improving the efficiency of marine engine systems. In addition, a diamond-like carbon (DLC) coating was applied to the piston pin to explore feasibility of eliminating the bush used in the system. The initial wear and lubrication characteristics between the uncoated piston pin and bush were compared with that between the DLC-coated piston pin and connecting rod in the tribo-test. The simulation for the wear and lubrication performance according to the wear progression was conducted based on the data obtained from the test. The wear characteristics were quantitatively assessed by the wear depth and wear volume, and the lubrication performance was characterized with the change of pressure and minimum oil film thickness with respect to the crank angle. It was found that the DLC-coated piston pin may provide better initial wear characteristics and lubrication performance. The results of this work may provide fundamental information for marine engines with improved efficiency.","DLC coating(DLC 코팅), Friction(마찰), Piston pin(피스톤 핀), Wear(마모)","차수빈1ㆍ이 향2ㆍ정구현3†\n1울산대학교 대학원 기계공학부 석사과정생, 2현대중공업㈜ 엔진기계사업본부 엔진기계연구소 책임연구원, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.6.227"]
["38권6호\npp.235-240","Frictional Anisotropy of CVD Bi-Layer Graphene Correlated with Surface Corrugated Structures","Micro/Nano-Tribology","Atomically-thin 2D nanomaterials can be easily deformed and have surface corrugations which can influence the frictional characteristics of the 2D nanomaterials. Chemical vapor deposition (CVD) graphene can be grown in a wafer scale, which is suitable as a large-area surface coating film. The CVD growth involves cooling process to room temperature, and the thermal expansion coefficients mismatch between graphene and the metallic substrate induces a compressive strain in graphene, resulting in the surface corrugations such as wrinkles and atomic ripples. Such corrugations can induce the friction anisotropy of graphene, and therefore, accurate imaging of the surface corrugation is significant for better understanding about the friction anisotropy of CVD graphene. In this work, the combinatorial analysis using friction force microscopy (FFM) and transverse shear microscopy (TSM) was implemented to unveil the friction anisotropy of CVD bi-layer graphene. The periodic friction anisotropy of the wrinkles was measured following a sinusoidal curve depending on the angles between the wrinkles and the scanning tip, and the two domains were observed to have the different friction signals due to the different directions of the atomic ripples, which was confirmed by the high-resolution FFM and TSM imaging. In addition, we revealed that the atomic ripples can be easily suppressed by ironing the surface during AFM scans with an appropriate normal force. This work demonstrates that the friction anisotropy of CVD bi-layer graphene is well-correlated with the corrugated structures and the local friction anisotropy induced by the atomic ripples can be controllably removed by simple AFM scans.","CVD graphene, Frictional anisotropy, Friction force microscopy(FFM), Transverse shear microscopy(TSM)","Seonha Park1, Mingi Choi2, , Seokjun Kim3 and Songkil Kim4†\n1M. S. Student, Graduate School, School of Mechanical Engineering, Pusan National University, 2Ph.D. Student, Graduate School, School of Mechanical Engineering, Pusan National University, 3Student Researcher, School of Mechanical Engineering, Pusan National University, 4Associate Professor, School of Mechanical Engineering, Pusan National University","https://doi.org/10.9725/kts.2022.38.6.235"]
["38권6호\npp.241-246","극저온이 22MnB5강의 냉간 스탬핑 마모에 미치는 영향\n(Effects of Cryogenic Temperature on Wear Behavior of 22MnB5 Under Cold Stamping)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials) ,Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ,Wear Phenomena & Mechanisms ","This paper presents the effects of cryogenic temperature on the wear behavior of 22MnB5 blank under cold stamping. After immersing the blank in liquid nitrogen (LN2) for 10 min, a strip drawing test was performed within 10 s. The hardness was measured using the Rockwell hardness test, which increased from 165 HV at 20oC to 192 HV at cryogenic temperature. The strip drawing test with 22MnB5 blank and SKD61 tool steel shows that for the different wear mechanisms on the tool surface with respect to temperature; adhesive wear is dominant at 20oC, but abrasive wear is the main mechanism at cryogenic temperature. As the friction test is repeated, sticking gradually increases on the tool surface at 20oC, whereas the scratch increases at cryogenic temperature. For the friction behavior, the friction coefficient rapidly increases when adhesive wear occurs, and it occurs more frequently at 20oC. The results for nanoindentation near the worn blank surface indicate a difference of 1.3 GPa at 20oC and 0.8 GPa at cryogenic temperature compared to the existing hardness, indicating increased deformation by friction at 20oC. This occurs because thermally activated energy available to move the dislocation decreases with decreasing temperature.","Cold stamping(냉간 스탬핑), Cryogenic(극저온), Adhesive wear(접착 마모), Abrasive wear(연마 마모)","지민기1ㆍ노연주2ㆍ강현학3ㆍ전태성4†\n1인천대학교 기계공학과 박사과정생, 2인천대학교 기계공학과 석사과정생, 3인천대학교 기계공학과 학부생, 4인천대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.6.241"]
["38권6호\npp.247-254","자외선 광을 활용하는 화학기계적 연마에 관한 연구 동향\n(Research Trends on Chemical Mechanical Polishing Using Ultraviolet Light)","Chemical Mechanical Polishing","Chemical mechanical polishing (CMP) is a hybrid surface-polishing process that utilizes both mechanical and chemical energy. However, the recently emerging semiconductor substrate and thin film materials are challenging to process using the existing CMP. Therefore, previous researchers have conducted studies to increase the material removal rate (MRR) of CMP. Most materials studied to improve MRR have high hardness and chemical stability. Methods for enhancing the material removal efficiency of CMP include additional provision of electric, thermal, light, mechanical, and chemical energies. This study aims to introduce research trends on CMP using ultraviolet (UV) light to these methods to improve the material removal efficiency of CMP. This method, photocatalysis-assisted chemical mechanical polishing (PCMP), utilizes photocatalytic oxidation using UV light. In this study, the target materials of the PCMP application include SiC, GaN, GaAs, and Ru. This study explains the photocatalytic reaction, which is the basic principle of PCMP, and reviews studies on PCMP according to materials. Additionally, the researchers classified the PCMP system used in existing studies and presented the course for further investigation of PCMP. This study aims to aid in understanding PCMP and set the direction of future research. Lastly, since there have not been many studies on the tribology characteristics in PCMP, research on this is expected to be required.","Chemical mechanical polishing(화학-기계적 연마), Ultraviolet(UV) light(자외선 광), Photocatalyst(광촉매), Research trend(연구 동향)","이현섭†\n동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.6.247"]
["38권6호\npp.255-260","의료용 폴리머 소재를 활용한 3D 프린팅 인공치아용 사면체 비정질 카본 코팅 기술 연구\n(A Study on the Tetrahedral Amorphous Carbon (ta-C) Coating on Medical Polymer Materials for 3D Printing Artificial Teeth)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","This research presents tetrahedral amorphous (ta-C) coating on the artificial tooth for improving the durability and functionality (esthtics, foreign body of tooth) by filtered cathodic vacuum arc (FCVA). A differentiated coating method is required for a ta-C coating on polymer owing to the low melting point of the polymer, inter-facial adhesion, low friction, and non-conductivity. Herein, ta-C coating is applied below 50oC, and the potential difference of the carbon plasma drawn to the substrate was controlled by applying a positive duct bias voltage without using a substrate bias voltage. Consequently, the ta-C coating with a thickness of 70nm using the duct bias condition of 20V with the highest plasma intensity satisfies the esthetics of the artificial tooth and had a 5B level of inter-facial adhesion. In addition, the composite hardness of ta-C/polymer is 380 MPa, and correlations with esthetics, sp3 bonding, and mechanical properties. The friction coefficient (CoF) of the ta-C coating in a water-lubricated environment is 0.07, showing a six-fold reduction in CoF compared with that of a polymer.","3D Printing(3D 프린팅), Medical polymer resin(의료용 폴리머 레진), Artificial teeth(인공치아), ta-C(사면체 비정질 카본), Composite hardness(복합 경도)","장영준1ㆍ김종국1ㆍ신창희2ㆍ유성미3†\n1한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원, 2제이머티리얼즈 부설연구소 상무, 3광주보건대학교 간호학과 교수","https://doi.org/10.9725/kts.2022.38.6.255"]
["38권6호\npp.261-266","그리스 윤활하에서 레이저 표면 텍스쳐링된 그루브 빗살무늬 패턴의 사잇각에 따른 미끄럼 마찰특성 평가\n(Dependence of Sliding Friction Properties on the Angle of Laser Surface Texturing for a Grooved Crosshatch Pattern Under Grease Lubrication)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","Notably, laser surface patterning facilitates tribological applications under lubricated sliding contacts. Consequently, a special pattern that can reduce the coefficient of friction under contact is considered necessary for improved machine efficiency. However, inappropriate pattern designs produce higher friction coefficients and cannot reduce friction. In this study, we use cast iron pins as specimens to investigate their friction and wear characteristics. Moreover, we experimentally investigate the correlation between the friction reduction effect and the design of groove crosshatch patterns fabricated with various angles and widths. We conduct a friction test using a pin-on-disc type tribometer under grease lubrication to study the friction reduction effect of the specimens, and we observe that the average coefficient of friction changes with the crosshatch angle and width. The experiment reveals that grooved crosshatch specimens with a crosshatch angle of 135°maximize friction reduction. The coefficient of friction of the groove specimens with a width of 120 μm is lower than that of the specimens with a width of 200?. The friction reduction effect of the width of the groove is attributed to the density of the groove pattern. Thus, grooved crosshatch patterns can be designed to maximize friction reduction, and the friction property of a grooved crosshatch pattern is found to be related to its width and angle.","Groove crosshatch pattern(그루브 빗살무늬 패턴), Laser surface texturing(레이저 표면 텍스쳐링), Grease(그리스), Sliding friction(미끄럼 마찰)","공민선1ㆍ채영훈2†\n1경북대학교 금속신소재공학과 학부생, 2경북대학교 기계연구소 연구교수","https://doi.org/10.9725/kts.2022.38.6.261"]
["38권6호\npp.267-273","사각형 그루브로 Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석: 제1보 − 유막온도경계조건의 영향\n(THD Lubrication Analysis of a Surface-Textured Parallel Thrust Bearing with Rectangular Grooves:Part 1 − Effect of Film-Temperature Boundary Condition)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Surface texturing is the latest technology for processing grooves or dimples on the friction surface of a machine. When appropriately applied, it can reduce friction and significantly increase durability. Despite many studies over the past 20 years, most are isothermal (ISO) analyses in which the viscosity of the lubricant is constant. In practice, the viscosity changes significantly owing to the heat generated by the viscous shear of the lubricant and film-temperature boundary condition (FTBC). Although many thermohydrodynamic (THD) analyses have been performed on various sliding bearings, only few results for surface-textured bearings have been reported. This study investigates the effects of the FTBC and groove number on the THD lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves. The continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations are numerically analyzed using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and temperature distributions, variations of load-carrying capacity (LCC), and friction force with four FTBCs. The FTBCs greatly influence the lubrication characteristics of surface-textured parallel thrust bearings. A groove number that maximizes the LCC exists, which depends on the FTBC. ISO analysis overestimates the LCC but underestimates friction reduction. Additional analysis of various temperature boundary conditions is required for practical applications.","Computational fluid dynamics(CFD / 전산유체역학), Film-temperature boundary condition(유막 온도경계조건), Parallel thrust bearing(평행 스러스트 베어링), Surface texturing(표면 텍스쳐링), Thermohydrodynamic lubrication(THD / 열유체 윤활)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2022.38.6.267"]
["38권6호\npp.274-280","다구찌 강건 설계를 통한 반도체 Probe상 Ti 도핑된 DLC(ta-C:Ti) 코팅 막의 전도성 및 기계적 물성 연구\n(Conductive and Mechanical Properties Study of Ti-doped DLC (ta-C:Ti) Film on Semiconductor Probe through Taguchi Bobust Design)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","There is a problem that semiconductor probe pin has a short lifespan. In order to solve this problem, Ti having excellent conductivity was doped to tetrahedral amorphous carbon (ta-C) having excellent hardness and abrasion resistance. This experiment was planned through the Taguchi robust design to determine the effect of the control factor of the ta-C:Ti coating film. The effect and contribution of control factors such as Unbalanced Magnetron Sputter(UBM) discharge current, arc discharge current, temperature, and bias voltage on ta-C:Ti characteristics were analyzed from the perspective of electrical and mechanical characteristics. The UBM discharge current was set to 4, 6, and 8 A. The main control factor of thickness and resistance is the UBM discharge current, and the thickness increased and the resistance decreased as the current increased. The decrease in resistance is due to the increase in the Ti content of the ta-C:Ti coating film. The arc discharge current was set to 60, 80, and 100 A. The main control factor of hardness and wear is the arc discharge current, and as the current rises, the hardness increases and the wear area decreases. This is due to the increased ta-C content of the ta-C:Ti coating film. Since resistance and wear are important for Probe Pin, the optimal level is set from the perspective of resistance and wear and a confirmation experiment is conducted.","Taguchi robust design(다구찌 강건 설계), ta-C:Ti(Ti 도핑 ta-C), Conductive(전도성), Hardness(경도), wear(마모)","김도영1ㆍ신준기2ㆍ장영준3ㆍ김종국3†\n1한국기술교육대학교 에너지신소재화학공학부 학부생, 2부산대학교 바이오산업기계공학과 학부생, 3한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.6.274"]
["38권6호\npp.281-286","Critical Shoulder Height of Raceway in Ball Bearing Considering Elastohydrodynamic Lubrication","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","In this study, the effects of Elasto-hydrodynamic lubrication pressure on the critical shoulder height of raceway in an angular contact ball bearing were investigated. Both 3D contact analyses using an influence function and the EHL analysis were conducted for the contact geometry between the ball and raceways. The pressure distributions by 3D contact analysis and EHL analysis for an example bearing were compared. The effect of ellipse truncation on the minimum film thickness also investigated from EHL analysis. The critical shoulder height in the dry contact and the EHL state were compared for various applied loads. It is shown that when the ellipse truncation occurs, the pressure spike for the EHL conjunction is higher than that for the dry contact, and its location moves more inward of the contact center. The steep pressure gradients would increase the flow rate, so in order to maintain flow continuity a significant reduction in film thickness and an abrupt rise in pressure occurs in the edge of shoulder. Significant reduction of the minimum film thickness occurs near the edge of shoulder. The critical shoulder heights in the EHL state are calculated as higher values compared with in the dry contact. This results shows that the determination of critical shoulder height by the EHL analysis is more proper.","Ball bearing, Shoulder height, EHL(Elastohydrodynamic lubrication), Minimum film thickness","Kyeongsoo Kim1 and Taewan Kim2†\n1Ph.D. Student, Special Ship Advanced Technology Center, Research Institute of Medium & Small Shipbuilding, 2Professor, Dept. of Mechanical Engineering, Pukyong National University","https://doi.org/10.9725/kts.2022.38.6.281"]
["38권6호\npp.287-290","압축수 방식 사출장치 내부 과도압력파 모의를 위한 간이 식\n(Simplified Formula for Simulating Overpressure Waves in Compressed-Water-Type Launching Device)","Marine Tribology ","Compressed-water-type launching devices convert the force from compressed water into force-launching underwater structures, such as torpedos and autonomous underwater vehicles. In particular, the overpressure wave in the launching tube is a critical design factor for the launching device. This paper presents a simplified formula for simulating overpressure waves in the launching tube of a compressed-water-type launching device. Scaled model experiments were performed to obtain actual measurement data of overpressure waves in a launching tube with varying piston speeds to examine the practical applicability of the simplified formula. The main factor of the simplified formula was estimated using an optimization technique. The time history of the overpressure waves was satisfactorily simulated using the estimated factor values and showed consistency with the measurement data. In addition, the trend of change by the piston speed of the estimated factors was reviewed, and the practical applicability was demonstrated. A systematic study of the factors influencing the overpressure waves in launching tubes will be possible using experimental data for more various conditions and the proposed simplified formula.","Compressed-water-type launching device(압축수방식 사출장치), Overpressure wave(과도압력파), Simplified formula(간이 식), Scaled model experiment(축소모형 실험)","김국현†\n동명대학교 조선해양공학과 교수","https://doi.org/10.9725/kts.2022.38.6.287"]

{"sheet":"2023년","index":3,"n_rows":14,"n_cols":7,"rows_kept":14,"cut":false,"hidden":false,"merged":[]}
["권호","제목","토픽","초록","키워드","저자","DOI"]
["39권1호\npp.1-7","화학공정용 전동기에 사용된 3D 프린팅 플라스틱 볼베어링의 내화학성 평가 및 현장적용 연구\n(Chemical Resistance and Field Trial of 3D-Printed Plastic Ball Bearing Used in Electric Motors for Chemical Processes)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Fluid pumps in chemical processes are typically driven by electric motors. Even if the motor is separated from the pump with seals, wear resulting from friction and misalignment can lead to leakage of chemical fluid, causing corrosion in the bearing supporting the motor, and, eventually, failure of the motor. It is thus a standard procedure to replace bearings at regular intervals. In this article, we propose 3D-printed plastic ball bearings for use as an alternative to commercial stainless-steel ball bearings. The plastic bearings are easy to manufacture, require less time to replace, and are chemically resistant. To validate the applicability of the plastic bearings, we first conducted chemical resistance tests. Bearings were immersed in 30 caustic acid and 30 nitric acid for 30 min and 24 h, respectively. The test results showed no corrosive damage to the bearings. A test rig was set up to compare the performance of the plastic bearings with that of the commercially equivalent deep-groove ball bearings. Loading test results showed that the plastic bearings performed as well as the commercial bearing in terms of vibration level and load-handling capability. Finally, a plastic bearing was subjected to a clean-in-place process for three months. It actually outperformed the commercial bearing in terms of chemical resistance. Thus, 3D-printed plastic bearings are a viable alternative to stainless-steel ball bearings.","3D printing(3D 프린팅), Plastic bearing(플라스틱 베어링), Chemical process(화학공정), Chemical resistance(내화학성), Field applicability(현장 적용성)","권영준1ㆍ노명규2†\n1충남대학교 대학원 메카트로닉스공학과 석사과정생, 2충남대학교 메카트로닉스공학과 교수","https://doi.org/10.9725/kts.2023.39.1.1"]
["39권1호\npp.8-12","Thermal wetting 현상이 탄소나노튜브-금속박막 계면의응착력에 미치는 영향에 관한 분자 시뮬레이션 연구\n(A Molecular Simulation on the Adhesion Control of Metal Thin Film-Carbon Nanotube Interface based on Thermal Wetting)","Modeling & Simulation in Tribology","This study presents a molecular simulation of adhesion control between carbon nanotube (CNT) and Ag thin film deposited on silicon substrate. Rough and flat Ag thin film models were prepared to investigate the effect of surface roughness on adhesion force. Heat treatment was applied to the models to modify the adhesion characteristics of the Ag/CNT interface based on thermal wetting. Simulation results showed that the heat treatment altered the Ag thin film morphology by thermal wetting, causing an increase in contact area of Ag/CNT interface and the adhesion force for both the flat and rough models changed. Despite the increase in contact area, the adhesion force of flat Ag/CNT interface decreased after the heat treatment because of plastic deformation of the Ag thin film. The result suggests that internal stress of the CNT induced by the substrate deformation contributes in reduction of adhesion. Contrarily, heat treatment to the rough model increases adhesion force because of the expanded contact area. The contact area is speculated to be more influential to the adhesion force rather than the internal stress of the CNT on the rough Ag thin film, because the CNT on the rough model contains internal stress regardless of the heat treatment. Therefore, as demonstrated by simulation results, the heat treatment can prevent delamination or wear of CNT coating on a rough metallic substrate by thermal wetting phenomena.","Adhesion(점착), Contact area(접촉 면적), Heat treatment(열처리), Molecular simulation(분자 시뮬레이션), Surface roughness(표면 거칠기)","이상훈1ㆍ김현준2,3†\n1경북대학교 대학원 미래과학기술융합학과 석사과정생, 2경북대학교 미래과학기술융합학과 부교수, 3경북대학교 정밀기계공학과 부교수","https://doi.org/10.9725/kts.2022.39.1.8"]
["39권1호\npp.13-20","Enhancement of Wear Resistance of CoCrNiAlTi Plasma Sprayed Coatings Using Titanium Carbide","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Large drill bits may face high hardness ore and high working pressure when working. To optimize the use effect of large drill bits and prolong the use time, it is necessary to add a layer of pressure-resistant, wear-resistant, and low-friction coating on the surface of the drill bit. In this study, CoCrNiAlTi high-entropy alloy coatings and CoCrNiAlTi (70 wt%)-TiC (30 wt%) composite coatings are successfully prepared on Q235 steel by plasma spraying. The CoCrNiAlTi (70 wt%)-TiC (30 wt%) coating consists of FCC solid solution and a small amount of TiC phase. The effect of TiC on the composition phase, microhardness, and elastic modulus of HEA coating is studied by X-ray diffractometer (XRD) and microhardness tester. The effect of TiC on the friction and wear properties of HEA coatings is investigated using a wear tester. By improving the process parameters, the metallurgical bonding between the coating and the substrate is well combined, and a coating without pores and cracks is obtained. The experimental results confirm that the microhardness, elastic modulus, and wear resistance of CoCrNiAlTi-TiC composite coating are better, and the friction coefficient is lower.","High-entropy alloy, Coating, Composite, Plasma spray, Wear","De-Yong Li1 and Chul-Hee Lee2†\n1Master student, Dept. of Mechanical Engineering, Inha University, 2Professor, Dept. of Mechanical Engineering, Inha University","https://doi.org/10.9725/kts.2023.39.1.13"]
["39권1호\npp.21-27","사각형 그루브로 Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석: 제2보 - 그루브 깊이의 영향\n(THD Lubrication Analysis of a Surface-Textured Parallel Thrust Bearing with Rectangular Grooves: Part 2 - Effect of Groove Depth)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","Surface texturing is widely applied to friction surfaces of various machine elements. Most of the theoretical studies have focused on isothermal (ISO) analyses which consider constant lubricant viscosity. However, there have been limited studies on the effect of oil temperature increase owing to viscous shear. Following the first part of the present study that investigated the effects of film-temperature boundary condition (FTBC) and groove number on the thermohydrodynamic (THD) lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves, this study focuses on the effect of groove depths. Current study numerically analyzes the continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations using a commercial computational fluid dynamics (CFD) software, FLUENT. The results of variation in temperature, velocity, and pressure distributions as well as load-carrying capacity (LCC) and friction force indicate that groove depth and FTBC significantly influence the temperature distribution and pressure generation. The LCC is maximum near the groove depth at which the vortex starts, smaller than the ISO result. For intense grooves, the LCC of THD may be larger than that from ISO. The frictional force decreases as the groove becomes deeper, and decreases more significantly in the case of THD. The study shows that groove depth significantly influences the THD lubrication characteristics of surface-textured parallel thrust bearings.","Computational fluid dynamics(CFD/전산유체역학), Film-temperature boundary condition(유막온도경계조건), Parallel thrust bearing(평행 스러스트 베어링), Thermohydrodynamic lubrication(THD)(열유체 윤활), Surface texturing(표면 텍스쳐링)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2023.39.1.21"]
["39권1호\npp.28-34","다공질 공기 베어링을 적용한 반도체 웨이퍼 연마용 스핀들 개발\n(Development of Wafer Grinding Spindle with Porous Air Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Because of their cleanliness, low friction, and high stiffness, aerostatic bearings are used in numerous applications. Aerostic bearings that use porous materials as means of flow restriction have higher stiffness than other types of bearings and have been successfully applied as guide bearings, which have high motion accuracy requirements. However, the performances of porous bearings exhibit strong nonlinearity and can vary considerably depending on design parameters. Therefore, accurate prediction of the performance characteristics of porous bearings is necessary or their successful application. This study presents a porous bearing design and performance analysis for a spindle used in wafer polishing. The Reynolds and Darcy flow equations are solved to calculate the pressures in the lubrication film and porous busing, respectively. To verify the validity of the proposed analytical model, the calculated pressure distribution in the designed bearing is compared with that derived from previous research. Additional parametric studies are performed to determine the optimal design parameters. Analytical results show that optimal design parameters that obtain the maximum stiffness can be derived. In addition, the results show that cross-coupled stiffness increases with rotating speed. Thus, issues related to stability should be investigated at the design stage.","Aerostatic bearing(공기 베어링), Porous bearing(다공질 베어링), Spindle(스핀들)","이동현1†ㆍ김병옥1ㆍ전병찬2ㆍ허균철3ㆍ김기수4\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 시스템다이나믹스연구실 선임기술원, 3한국기계연구원 시스템다이나믹스연구실 선임연구원, 4카스윈㈜ 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.1.28"]
["39권2호\npp.35-42","시간에 따른 회전 및 하중을 고려한 강체 동역학 해석에기반한 베어링 성능 평가\n(Bearing Performance Evaluation Based on Rigid Body Dynamic Analysis Considering Rotation and Loads Over Time)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Bearing is a mechanical component that supports loads and transmits rotation. As the application of high-value-added products such as semiconductors, aviation, and robots have recently become diverse and more precise, an accurate bearing performance prediction and evaluation technology is required. Bearing performance evaluation can be divided into evaluations based on bearing theory and on numerical analysis. An evaluation based on numerical analysis is a technique that has been highlighted because the problems that remained unsolved owing to time problems can be solved through recent developments in computers. However, current studies have the disadvantage of not considering the essential changes over time and bearing rotation. In this study, bearing performance evaluation based on rigid body dynamic analysis considering rotation and load over time is performed. Rigid body dynamic analysis is performed for deep groove ball bearing to calculate the load applied by the ball. The reliability of the analysis is verified by comparing it with the results calculated using bearing theory. In addition, rigid body dynamic analysis is performed for automotive wheel bearings to calculate the contact angle and load applied by the ball for cases where axial load and radial load are applied, respectively. The effect of rotation and load over time is evaluated from these results.","Bearing(베어링), Dynamic analysis(동역학 해석), Rotation(회전), Rigid body(강체), Numerical analysis(수치해석)","이승표†\n㈜일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.2.35"]
["39권2호\npp.43-48","Lubricating Effect of Water-soluble Hexagonal Boron Nitride Nanolubricants on AISI 304 Steel Sliding Pair","Lubrication (Lubricants & Additives) ,Wear Phenomena & Mechanisms ","In this study, we investigate the tribological behavior of AISI 304 stainless steel pairs under deionized water and hexagonal boron nitride (h-BN) water dispersion lubrication. The specimen friction and wear properties are evaluated using a reciprocating ball-on-flat tribometer. The coefficient of friction remains nearly constant throughout the test under both lubricant conditions. The wear depth of the specimens under h-BN lubrication is smaller than that under deionized water lubrication, indicating the inhibition behavior of h-BN nanolubricants on direct metal–metal contacts. Optical micrographs and stylus profilometer measurements are performed to evaluate the severity of damage caused by the sliding motion and to determine the wear morphology of the specimens, respectively. The results show that h-BN nanolubricants does not have a significant effect on the friction behavior but demonstrates reduced wear owing to their trapping effect between the sliding interfaces. Moreover, scanning electron microscopy and energy-dispersive X-ray spectroscopy images of the specimens were acquired to confirm the trapping effect of h-BN between the sliding interfaces. The results also suggest that the trapped lubricants can distribute the contact pressure, reducing the wear damage caused by the metal–metal contact at the interface. In conclusion, h-BN nanolubricants have potential as an anti-wear additive for lubrication applications. Further investigation is needed to provide direct evidence of the trapping effect of h-BN nanoparticles between the sliding interfaces. These findings could lead to the development of more efficient and effective lubricants for various industrial applications.","Reciprocating sliding, Aqueous additive, Nanolubricant, AISI 304 steel","Gowtham Balasubramaniam1 and Dae-Hyun Cho2,3†\n1Ph.D. Student, Department of Computer Mechatronics Engineering, Gyeongsang National University, 2Associate Professor, Department of Mechatronics Enigneering, Gyeongsang National University, 3Associate Professor, Department of Energy System Engineering, Gyeongsang National University","https://doi.org/10.9725/kts.2023.39.2.43"]
["39권2호\npp.49-55","메탄올 첨가에 따른 Ni 기반 합금의 트라이볼로지 특성 변화에 대한 실험적 연구\n(Experimental Assessment of the Methanol Addition Effect on the Tribological Characteristics of Ni-based Alloy)","Wear Phenomena & Mechanisms","Currently, the demand for green technologies toward a sustainable future is rapidly increasing due to growing concern over environmental issues. Methanol is biodegradable and can provide clean combustion to reduce sulfur oxide and nitrogen oxide emissions, and therefore it is a candidate fuel for marine engines. However, the effect of methanol on tribological characteristic degradation should be addressed for methanol-fueled engines. In this study, the methanol addition effects on tribological characteristic degradation is experimentally assessed using a pin-on-disk tribo-tester. Ni-based alloy is used as a target material due to its broad applicability as an engine component material. For a lubricant, engine oil with and without methanol are used. The tests are conducted for up to 10,000 cycles under boundary lubrication while the change in friction force is monitored. Additionally, the wear rate is determined based on laser scanning confocal microscope data. An additional test in which methanol is added at regular intervals is performed with an aim to directly observe its effect on friction. Overall, the friction coefficient increases slightly with increasing methanol concentration. Furthermore, the wear rate of the pin and disk increase significantly with methanol addition. The results also indicate that the friction increases instantaneously with methanol addition at the contacting interface. These findings may be useful for better understanding the methanol effect on the tribological characteristics of Ni-based alloys for methanol-fueled engines with improved performance.","Friction(마찰), Methanol(메탄올), Ni-based alloy(Ni 기반 합금), Wear rate(마모율)","최준민1*ㆍ박상문1*ㆍ김영준1ㆍ김성훈1ㆍ김혜민1ㆍ박정언1ㆍ유정원1ㆍ이명규1ㆍ이현우1ㆍ정구현2†\n1울산대학교 기계공학부 학사과정생, 2울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.49"]
["39권2호\npp.56-60","경사 돌기 표면의 젖음 특성 평가\n(Hydrophobicity Evaluation of Oblique Micro-asperities Structures)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","In this study, we evaluate the anisotropic flow of droplets according to the directionality of asperities. We manufacture a mold with an inclined hole by adjusting the jig angle using a high-power diode laser. Using the manufactured mold, we prepare specimens for wettability studies by the micro molding technique. We fabricate twelve kinds of surfaces with micro-asperities inclined at 0°, 15°, 30°, and 45° for asperity pitches of 100 μm, 200 μm, and 300 μm. We evaluate the static and dynamic behaviors of the droplets as a function of the asperities pitch and inclination angles. The anisotropic effect increases as the pitch increases between asperities, and the anisotropic flow characteristics increase as the inclination angle of the asperities increases. On the surface with hole pitches of 100 μm and 200 μm, the contact angle of the droplet shows high hydrophobicity at approximately 160°, but on the surface with the 300-μm hole pitch, the contact angle is approximately 110°, indicating that the hydrophobic effect rapidly reduces. Additionally, when the inclination angle of the asperities is approximately 30°, the left and right contact angle deviations of the droplet are the lowest, showing that the roll-off angle is relatively low.","Hydrophobic surface(소수성 표면), Anisotropic flow(이방성 흐름), Asperity(돌기)","백승익1ㆍ김태완2†\n1부경대학교 대학원 지능로봇공학과 석사과정생, 2부경대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.56"]
["39권2호\npp.61-71","누설유량과 회전체동역학적 성능을 고려한 래버린스 씰 설계\n(Labyrinth Seal Design Considering Leakage Flow Rate and Rotordynamic Performance)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study proposes a procedure for designing a labyrinth seal that meets both leakage flow rate and rotordynamic performance criteria (effective damping, amplification factor, separation margin, logarithmic decrement, and vibration amplitude). The seal is modeled using a one control volume (1CV) bulk flow approach to predict the leakage flow rate and rotordynamic coefficients. The rotating shaft is modeled with the finite element (FE) method and is assumed to be supported by two linearized bearings. Geometry, material and operating conditions of the rotating shaft, and the supporting characteristics of the bearings were fixed. A single labyrinth seal is placed at the center of the rotor, and the linearized dynamic coefficients predicted by the seal numerical model are inserted as linear springs and dampers at the seal position. Seal designs that satisfy both leakage and rotordynamic performance are searched by modifying five seal design parameters using the multi-grid method. The five design parameters include pre-swirl ratio, number of teeth, tooth pitch, tooth height and tooth tip width. In total, 12500 seal models are examined and the optimal seal design is selected. Finally, normalization was performed to select the optimal labyrinth seal designs that satisfy the system performance requirements.","Labyrinth seal(래버린스 씰), Dynamic coefficient(동특성 계수), Leakage flow(누설유량), Bulkflow model(벌크플로우 모델), FE model(유한요소 모델)","문민주1ㆍ이정인2ㆍ서준호3†\n1부산대학교 대학원 기계공학부 기계시스템설계전공 석사과정생, 2부산대학교 대학원 기계공학부 기계시스템설계전공 박사과정생, 3부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2023.39.2.61"]
["39권2호\npp.72-75","SiO2/TiO2 혼합입자 슬러리 SiC CMP의 재료제거율 모델링\n(Material Removal Rate Modeling of SiO2/TiO2 Mixed-Abrasive Slurry CMP for SiC)","Chemical Mechanical Polishing ","Silicon carbide (SiC) is used as a substrate material for power semiconductors; however, SiC chemical mechanical polishing (CMP) requires considerable time owing to its chemical stability and high hardness. Therefore, researchers are attempting to increase the material removal rate (MRR) of SiC CMP using various methods. Mixed-abrasive CMP (MAS CMP) is one method of increasing the material removal efficiency of CMP by mixing two or more particles. The aim of this research is to study the mathematical modeling of the MRR of MAS CMP of SiC with SiO2 and TiO2 particles. With a total particle concentration of 32 wt, using 80-nm SiO2particles and 25-nm TiO2 particles maximizes the MRR at 8 wt of the TiO2 particle concentration. In the case of 5 nm TiO2 particles, the MRR tends to increase with an increase in TiO2 concentration. In the case of particle size 10-25 nm TiO2, as the particle concentration increases, the MRR increases to a certain level and then decreases again. TiO2 particles of 25 nm or more continuously decreased MRR as the particle concentration increased. In the model proposed in this study, the MRR of MAS CMP of SiC increases linearly with changes in pressure and relative speed, which shows the same result as the Preston's equation. These results can contribute to the future design of MAS; however, the model needs to be verified and improved in future experiments.","Chemical mechanical polishing(CMP), Mixed-abrasive slurry(MAS), Silicon dioxide(SiO2), Titanium oxide(TiO2), Silicon carbide(SiC)","이현섭†\n동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2023.39.2.72"]
["39권2호\npp.76-80","냉각 유량이 가스 포일 스러스트 베어링의 성능에 미치는 영향\n(Effects of Cooling Flow Rate on Gas Foil Thrust Bearing Performance)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.","Cooling flow rate(냉각 유량), Drag torque(마찰 토크), Friction coefficient(마찰 계수), Gas foil thrust bearing(가스 포일 스러스트 베어링)","황성호1ㆍ김대연2ㆍ김태호3†\n1국민대학교 기계공학부 박사후연구원, 2LG이노텍 Actuator 선행개발팀 사원, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.76"]
["39권2호\npp.81-85","표면 거칠기가 가스 포일 스러스트 베어링의 성능에 미치는 영향\n(Effects of Surface Roughness on the Performance of a Gas Foil Thrust Bearing)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study presents an experimental investigation of the effects of surface roughness on gas foil thrust bearing (GFTB) performance. A high-speed motor with the maximum speed of 80 krpm rotates a thrust runner and a pneumatic cylinder applies static loads to the test GFTB. When the motor speed increases and reaches a specific speed at which a hydrodynamic film pressure generated within the gap between the thrust runner and test GFTB is enough to support the applied static load, the thrust runner lifts off from the test GFTB and the friction mechanism changes from the boundary lubrication to the hydrodynamic lubrication. The experiment shows a series of lift-off test and load-carrying capacity test for two thrust runners with different surface roughnesses. For a constant static load of 15 N, thrust runner A with its lower surface roughness exhibits a higher start-up torque but lower lift-off torque than thrust runner B with a higher surface roughness. The load capacity test at a rotor speed of 60 krpm reveals that runner A results in a higher maximum load capacity than runner B. Runner A also shows a lower drag torque, friction coefficient, and bearing temperature than runner B at constant static loads. The results imply that maintaining a consistent surface roughness for a thrust runner may improve its static GFTB performance.","Gas foil thrust bearing(가스 포일 스러스트 베어링), Surface roughness(표면 조도), Load capacity(하중지지력), Friction coefficient(마찰 계수)","황성호1ㆍ김대연2ㆍ김태호3†\n1국민대학교 기계공학부 박사후연구원, 2LG이노텍 Actuator 선행개발팀 사원, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.81"]