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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.
J.P.B.A Sembiring,Seimi Choi,Choongho Sanseong,Junsuek Ro,A. Amanov,Y.S. Pyun 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.5
The existing ultrasonic assisted grinding used for machining hard and brittle material still has some drawbacks, such as low material removal rate rapid tool wear and low quality of surface finish. To resolve those problem, a retrofit idea of existing concept is propose. In this paper, an idea to retrofit the existing ultrasonic assisted grinding machining center is proposed by changing the spindle design, tool tip and the modification of ultrasonic transducer. The consideration behind design changing and modification of existing concept will be discussed. Due to the design changing and modification, the capability of high speed rotational machining and the elliptical tool motion of 2D Vibration Assisted Machining (VAM) are expected to be obtained. Due to the elliptical tool motion, it is expected that the cutting force can be reduced, extension of tool life, capability to cut the brittle material in ductile regime and improvement surface finish can be obtained.
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.