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윤활영역에서 멀티크기 Laser Surface Texturing 효과
김종형(Jong-Hyoung Kim),최시근(Si Geun Choi),다윗제네베세구(Dawit Zenebe Segu),정용섭(Yong-Sub Jung),김석삼(Seock-Sam Kim) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.1
Laser Surface Texturing(LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on a surface by a material ablation process, which can improve such as load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication and the results compared with that of the non-textured surface. Through an increase in sliding speed, the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performances than the non-textured surface due to the hydrodynamic lubrication effect.
DLC 코팅된 60E1(UIC60) 강의 건조 마찰에서의 미끄럼 마찰 거동
김종형(Jong-Hyoung Kim),정재일(Jae-Il Jeong),김재원(Jae-Won Kim),김태규(Tae-Gyu Kim),Chau Kian Hao,Willey Y. H. Liew,김석삼(Seock-Sam Kim) 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.2
본 논문은 철도 레일용으로 사용되는 60E1 강 표면에 RF-PECVD 방법으로 Si-doped DLC 코팅과 non-doped DLC 코팅을 제작하여 ball-on-disk형 마찰시험기로 실험을 수행하고 DLC 코팅층의 경도와 마찰 특성을 평가하였다. 시험 결과, Si-doped DLC 코팅층의 경도가 non-doped DLC 코팅층보다 높게 나타났으며 마찰 계수는 낮게 나타났다. SEM 사진의 미시적 마찰면의 관찰 결과, non-doped DLC면에는 표면균열과 응착에 의한 마찰면이 관찰되었고, Si-doped DLC의 마찰면은 응착 유동에 의한 응착과 이착이 주된 마찰 메카니즘이었다. In this study, the nano-hardness and frictional behavior of non-doped DLC (diamond-like carbon) and Sidoped DLC coated 60E1 steel deposited by RF-PECVD method were investigated. The results showed that Si-doped DLC exhibited higher nano-hardness and lower friction coefficient than the non-doped DLC from ball-on-disk type tribometer. By using SEM (scanning electron microscope), SEM images showed friction mechanism of the base material was adhesion and that of DLC showed adhesion and brittle fracture. owever, Si-doped DLC showed adhesion friction and transfer layer of DLC to counterpart.
Fatigue Characteristics of Bearing Steel in Giga Cycles
장주호(Ju-Ho Jang),서창민(Chang-min Suh),김종형(Jong-Hyoung Kim),김상천(Sang-Chun Kim),이태성(Tae-Sung Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Fatigue tests were carried out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine using the three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this study. S-N curves obtained from the fatigue tests of the B and C specimens tend to come down again in the super-long life range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface defects such as scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes.