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다리스렝 스르멩닥와(Shirmendagva Darisuren),아마노프 아웨즈한(Auezhan Amanov),김준형(Jun-Hyong Kim),이승철(Seung-Chul Lee),최갑수(Gab-Su Choi),편영식(Young-Sik Pyun) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.6
This study proposes a sustainable bearing remanufacturing process using the ultrasonic nanocrystal surface modification (UNSM) technique. The UNSM technique is a newly developed and sophisticated surface modification technique that can increase the mechanical properties and improve the friction and wear performance of materials. Taking advantage of the bearing manufacturing process is the most significant way of optimizing the life of a bearing. The proper maintenance and usage of repaired bearings can increase their life to be equal to or greater than that of new bearings. This paper discusses the restoration of certain mechanical properties of worn, damaged, and discarded bearings, and suggests a remanufacturing process for used bearings, which can impart them with a lifespan equivalent to that of new bearings. The most damaged part of the discarded bearings is the raceway, which is the site of accumulated fatigue. The existing polishing or barrel finishing processes can recover the accumulated fatigue only partially. Rolling contact fatigue tests performed on UNSMtreated new and used specimens polished after 4×10<SUP>6</SUP> cycles reveal that UNSM-treated new specimens exhibit the longest fatigue life compared to other specimens. This study verifies the proposed complete fatigue recovery process, which can increase the fatigue life of used bearings to a level greater than that of new bearings.
초음파나노표면개질기술로 제작된 마이크로 그루브가 미끄럼 마찰 특성에 주는 영향
노준석(Junsuek Ro),아마노프 아웨즈한(Auezhan Amanov) 한국트라이볼로지학회 2021 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.37 No.1
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.
Selective Laser Melting 방식으로 적층가공된 Ti-6Al-4V 합금의 내마모성 특성에 미치는 고온 UNSM 처리 영향에 대한 연구
산성충호(Choongho Sanseong),노준석(Jun-Suek Ro),편영식(Young-Sik Pyoun),아마노프 아웨즈한(Auezhan Amanov) 한국트라이볼로지학회 2020 한국윤활학회지(윤활학회지) Vol.36 No.1
In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) treatment at room and high temperatures (RT and HT of 400oC) on friction and wear behavior of Ti-6Al-4V alloy prepared by selective laser melting (SLM) were investigated. The objective of this study is to improve the mechanical properties and frictional behavior of Ti-6Al-4V alloy by UNSM treatment. Dry friction and wear tests were conducted using a ball-on-disk method at RT with a bearing steel as the counter ball. Due to the high HT and UNSM treatment, the surface hardness tended to increase and surface roughness tended to reduce. X-ray diffraction (XRD) analysis showed that nanocrystallization structure and compressive residual stress were formed at the surface layer after UNSM treatment at both RT and HT. After UNSM treatment, it was observed that the wear rate was reduced by about 6% for the specimen treated at RT and a 28% reduction for the specimen treated at HT in comparison with the untreated one. Based on scanning electron microscope (SEM) images showed that the damage caused by fatigue wear occurred in the wear track of the heattreated specimen, and it is believed to be the cause of the highest wear rate. Mechanical properties and wear resistance of Ti-6Al-4V alloy were improved and prospect of industrial application was confirmed. Further research is still required to improve the characteristics of SLM Ti-6Al-4V alloy to the level of wrought Ti-6Al-4V alloy.