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Experimental Study on Effect Ultrasonic in Incremental Forming Process
Darisuren Shirmendagva,Seimi Choi,J.P.B.A Sembiring,Choongho Sanseong,Junsuek Ro,A. Amanov,Y.S. Pyun 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.5
The spring-back effect during Incremental forming still becomes a concern because affects the dimensional accuracy of the finished part. To resolve it, ultrasonic vibration was introduced to incremental forming process. The addition ultrasonic during incremental forming was reported reducing the spring-back effect, decreasing the force for forming and increasing tool life due to reduced friction. In this experimental study, the comparison between conventional incremental forming. Ultrasonic Assisted incremental forming and Ultrasonic incremental forming was done. The results showed there is no significant difference between the conventional incremental forming process and ultrasonic incremental forming in terms or dimensional accuracy and surface finish. Therefore, the elimination of rotation spindle could be done which possibly reduce cost of device and operation.
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.
대형 상용차용 인젝터 볼 밸브의 수명 복원 기초 기술 개발
다리스렝 스르멩닥와(Shirmendagva Darisuren),편영식(Youngsik Pyun),김준형(Junhyong Kim),카유모브 라빌(Ravil Kayumov) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
Significant wear occurs in the ball valve of heavy duty diesel injectors. This wear is due to the continuous contact stress. For this reason injector must be periodically changed. Although used injectors can be reused, used ball valves must be replaced by new set. The other option until now was ball valve seat polishing to remove cracks around the valve orifice, which does not provide full recovery. In this research, as a part of development of the basic method of injector parts restoration, UNSM technology was applied to the ball valve seat to remove cracks, enhance surface properties and restore valve’s life. Ball-on-Disk wear tests were carried out on untreated and treated specimens. Results are compared. The possibility of used injector parts restoration process is established and explained.
초음파나노표면개질기술을 이용한 저널베어링 마찰 및 피로특성 연구
최갑수(Gab-Su Choi),다리스렝 스르멩닥와(Shirmendagva Darisuren),이승철(Seung-Chul Lee),김준형(Jun-Hyong Kim),아마노프 아웨즈한(Auezhan Amanov),편영식(Young-Sik Pyun) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.1
In this study, we apply an ultrasonic nanocrystal surface modification (UNSM) technique to radial journal bearings (JBs) and disks made of SUJ2 and SCM440, respectively. We investigate frictional properties of untreated and UNSM-treated specimens using a ball-on-disk tester. We construct the Stribeck curve at the boundary, under mixed and full hydrodynamic lubrication conditions for the specimens using friction data obtained from JB tests. The friction at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM-treated specimens is reduced, which improves the service life of JBs. The major effects of this reduction in the three lubrication regimes can be explained in the terms of improved mechanical properties and the presence of micro dimples. Moreover, we estimate the friction and fatigue properties of SCM440 specimens using a ball-on-disk specimen under dry and oil-lubricated conditions. Friction test results reveal that the UNSM-treated specimens show lower friction coefficient than the untreated specimens under both dry and oil-lubricated conditions. We evaluate the fatigue properties of SCM440 specimens by calculating the Hertzian stress with respect to the failure cycles. Fatigue tests results also reveal that the UNSM-treated specimens possess a longer fatigue life than the untreated specimens. The improved properties are effective in increasing the energy efficiency of bearings.