마이크로 크기를 가지는 빗살무늬 그루우브 패턴의 빗살각도변화에 대한 실험적 마찰특성

김석삼(Seock-Sam Kim),채영훈(Youn-Ghun Chae) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.3

Micro-scale surface pattern has an benefit of tribological application under lubricated sliding contact. Therefore, a special pattern, that has to reduce the coulomb friction under contact, is considered to be necessary for improved efficiency of machines. The current study investigated the friction property of angle effect for micro-scale grooved crosshatch pattern on bearing steel surface using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of hatched-angle on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction.

마모기구에 관한 최근 연구 동향

김석삼(Seock-Sam Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4

부품의 접촉구동부 접촉표면의 상대운동으로 야기되는 마모현상은 부품의 기능과 성능에 지대한 영향을 끼친다. 최근에는 부품이 더욱 극소화되어감에 따라 마모현상은 부품의 신뢰성과 수명과 직결되는 중요한 과제가 된 것이다. 마모기구에 관한 연구는 오래 전부터 연구되어 온 것으로 접촉표면의 상대운동에 따른 미소파괴현상으로 정의되며 응착마모, 연삭마모, 피로마모, 부식마모, 미동마모 등으로 분류되고 있다. 본 논문에서는 저자가 그 동안 수행해오고 있는 마모기구에 대해서 소개하고자 한다.

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.

Hertz 접촉하중하에서의 복수표면균열의 상호간섭

김상우,김석삼,Kim, Sang-Woo,Kim, Seock-Sam 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.10

Analysis model containing two inclined surface cracks on semi-infinite elastic body is established and analyzed on the basis of linear fracture mechanics to examine mutual interference of two surface cracks. Muskhelishvili's complex stress functions are introduced and a set of singular integral equations is obtained for a dislocation density function. The stress intensity factors at crack tip are obtained by using the Gerasoulis'method. When two surface cracks are parallel and have the same length, the values of $K_1$and $\Delta K_11$(variation of $K_11$) for crack 1 and crack 2 decrease by the mutual interference of two surface cracks as the distance between the two surface cracks shortens. The effect of mutual interference is remarkable in high friction coefficient. In case that two surface cracks are parallel, the values of $K_1$and $\Delta K_11$for crack 2 decrease as the length ratio ot crack 2 to crack 1 becomes small. As the crack inclination angle rises, the value of $K_1$ and the mutual interference of $K_1$for crack 2 increase and the value of$\Delta K_11$ for crack 1 becomes smaller than that for crack 2.

미끄럼 접촉시 이종세라믹 간의 트라이볼로지적 특성

김법민(Bupmin Kim),김석삼(Seock-sam Kim),신동우(Dongwoo Shin),윤상보(Sang-bo Yoon) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.39 No.-

현재 구조용 세라믹에 대한 연구는 여러 가지 작동 조건에 의해 도출된 마멸 데이터를 정량적으로 제시하고 이들의 마멸기구의 변화가 일어나는 사용 조건의 시점을 파악하였다. 이 전의 연구들은 주로 동질 재료까지 마찰 마멸 실험으로 제한되었다. 그러나 상대 운동하는 세라믹 재료들의 특성 상기계적, 화학적 물성차이에 의해 마멸 기구와 트라이볼로지적 거동(마찰계수, 마멸율)등이 다르게 나타날 확률이 높다. 이에, 본 연구에서는 볼 온 디스크 마멸 실험을 통해 여러 가지 작동환경에 따라 서로 상대 운동하는 세라믹의 재료를 달리하며 실험 하며 다른 세라믹 재료간의 트라이볼로지적 특성을 고찰하였다. 지르코니아 시편에 대해 지르코니아, 알루미나, 실리콘카바이드 3종의 상대재를 사용하여 속도와 하중조건을 변화하여 마멸실험을 수행한 결과, 지르코니아-실리콘카바이드 조합의 실험에서 저마찰 저마멸 트성이 나타났다. Currently, the study on structural ceramic helps to suggest the precise data of friction and wear in accordance with the various conditions in operations. Also, the study helps to predict effective operating conditions by monitoring the occurrence of wear transition. The studies in the past were mainly concentrated in using identical materials. However, it is highly likely to have unqualified data from the differences of mechanical and chemical properties between ceramic materials. Thus, in this study, through conducting the ball-on-disk type wear testing, the different ceramic materials has been used to consider tribological characteristics between different ceramic materials. We conducted the wear test by using three kinds of specimen which are zirconia, alumina and silicon carbide against zirconia. We have changed the sliding velocity and the loading conditions in this test and found out that there is row friction coefficient and wear rate in the combination of zirconia and silicon carbide.

$Al_2O_3/NiCr$ 코팅의 미끄럼 마멸 특성

채영훈,박병희,김석삼,Chae, Young-Hun,Park, Byung-Hee,Kim, Seock-Sam 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7

The sliding wear behavior of $Al_2O_3/NiCr$ coating deposited on steel(SM45C) was investigated under lubrication. The parameters of sliding wear are normal loads, coating thickness. As a result, the wear resistance of $Al_2O_3/NiCr$ coating was remarkably greater than that of $Al_2O_3$ coating. The optimized coating thickness was found to be $300{\mu}m$ to ensure good anti-wear. The bond coating played important role in decreasing residual stress. The residual stress had much influence on wear mechanism. These results were correlated with the stress state of coating and the microstructure of coating.

마찰열을 고려한 미끄럼 접촉시 내부 복수 수평균열 전파해석

이진영(Jin-Young Lee),김석삼(Seock-Sam Kim),채영훈(Young-Hun Chae) 한국트라이볼로지학회 2002 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.18 No.3

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.

플라즈마 코팅한 주조용 알루미늄합금의 마찰 및 마멸특성

채영훈,임정일,박준목,김석삼,Chae, Young-Hun,Ren, Jing-Ri,Park, Jun-Mock,Kim, Seock-Sam 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.5

The wear characteristics and wear mechanisms of plasma sprayed Al/sub 2/ O/sub 3/-40%TiO/sub 2/ and Cr/sub 2/O/sub 3/ deposited on casting aluminum alloy(AC4C) were investigated. Specimens were processed for various coating thicknesses. Ball on disk type wear tester was used for wear test. The scratch test on plasma sprayed coating surface showed that critical load to break the coating layer was greater than 40 N. The critical load increase with the increase of coating thickness of specimens. The friction coefficient of Cr/sub 2/O/sub 3/ coating layer was less than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. The wear resistance of Cr/sub 2/O/sub 3/ coating layer was greater than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. Microscopic observation of worn surfaces was made by SEM. SEM observation showed that the main mechanism of wear for Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer was abrasive wear under 50 N. For the case of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer, as the surface cracks perpendicular to sliding direction propagated, the wear debris was generated in wear track. However, the main mechanism of wear for Cr/sub 2/O/sub 3/ coating layer was brittle fracture under 150 N.

마찰제어를 위한 Surface texturing 의 Micro-scale dimple 밀도영향

채영훈(Young-hun Chae),김석삼(Seock-sam Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

Surface texturing of tribological application is another attractive technology of friction reducing. Also, reduction of friction is therefore considered to be a necessary requirement for improved efficiency of machine. In this paper attempts to investigate the effect of density for micro-scale dimple pattern on bearing steel flat mated with pin-on-disk. We demonstrated the lubrication mechanism for a Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. It is found that friction coefficient is depended on the density of surface pattern. It was thus verified that micro-scale dimple could affect the friction reduction.Lubrication condition regime has an influence on the friction coefficient induced the density of micro dimple.