Surface Texturing by Micro ECM for Friction Reduction

Byun, Jung-Won,Shin, Hong-Shik,Kwon, Min-Ho,Kim, Bo-Hyun,Chu, Chong-Nam 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.5

Surface texturing with micro-dimples is a known method for friction reduction under lubricated sliding contact, and various machining techniques have been researched and developed in order to fabricate micro-dimple patterns. However, previous fabrication methods possess several problems, such as causing thermal damage on the workpiece or limiting the available workpiece geometry. In micro ECM, micro features can be machined without any resulting thermal or mechanical damage. From this perspective, micro ECM has certain advantages over surface texturing. Also, micro ECM is applicable to non-planar work pieces. In this research study, micro ECM with microsecond pulses was applied in order to fabricate a micro-dimple pattern. The machining characteristics were investigated in fabricating micro dimples on AISI 440C specimen. On the basis of the experimental results, a ${\phi}300{\mu}m$ dimple pattern was successively produced on the AISI 440C specimen. Afriction test on the textured specimen was performed and compared with a non-textured specimen. The enhancement of frictional performance was successfully demonstrated experimentally.

Fabrication of Micro-Dimpled Surfaces through Micro Ball End Milling

Eldon Graham,Chaneel I. Park,Simon S. Park 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

Industry and researchers have begun to shift their focus towards more sustainable and eco-friendly manufacturing processes in recent years. They have recognized the vital role of functional micro surfaces for a wide range of advanced applications to address this issue. By physically altering the surface structure of a material in micrometric scale, tribological, optical, fluidic properties and many other surface characteristics can be altered. Several researchers have reported that micro surface patterns can reduce friction between lubricated sliding surfaces, which in turn alleviate energy consumption and increase service life of components. Micro ball end milling is another viable technique for creating patterned surfaces, especially for metallic parts. By tilting the spindle and tool at an inclined angle, the spindle speed and feed rate can be adjusted so that the flutes of the cutter create periodic patterns in a workpiece surface. Machining is an efficient and versatile manufacturing technique, making the micro dimple machining technique an ideal method to fabricate dimpled surfaces. In this study, the fabricated surfaces are evaluated at a tribological level to illustrate their effectiveness at reducing friction. The development of efficient methods to produce micro patterns onto large surface areas can promote a sustainable future for a variety of novel products. The development of efficient surface pattern algorithms for generating different dimple geometries is also a focus; and, trends in cutting forces are identified by changing different machining parameters. Depth of cut and dimple shape, spacing and arrangement are crucial parameters, all of which factor into the performance of a functional surface. The results of this study strongly indicate micro dimple machining as an environmentally sustainable method of producing functional surfaces for advanced technological applications.

Photolithography 를 이용한 micro-dimple 크기에 따른 미끄럼 마찰거동

채영훈(Y. H. Chae),김석삼(S. S. Kim) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

The aim of this paper is to investigate the effect of micro-dimple size on reduction friction and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

미세 딤플 가공 표면의 수력학적 윤활특성에 대한 수치해석

홍사훈(Sa Hoon Hong),이재응(Jaeung Lee),조민행(Min Haeng Cho),이성혁(Seong Hyuk Lee) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.4

This study deals with the numerical investigation on two-dimensional lubrication characteristics of micro-dimple shapes fabricated on solid surfaces by using the commercial CFD code (Fluent V.6.3) to examine the influence of micro dimple depth and width on the reduction in friction under the sliding plate condition. In addition, single and multiple dimple arrays are simulated, all for a fixed area fraction of dimple on the surface. As a result, it is found that the existence of micro-dimpled surface makes it possible to substantially reduce the friction forces exerted on the surfaces, and such an optimum dimple depth would be present because the dimple depth larger than the optimum value did no longer affect the reduction in shear stresses, indicating that the reduction of friction is likely to be associated with inner flows of lubricant inside dimples. Moreover, it is observed that at the fixed area fraction, the friction reduction increases with the increase of dimple diameter.

Effect of burrs on the friction performance of hierarchical micro-dimple textured AISI 1045 steel

박건철,Saood Ali,Rendi Kurniawan,Tae Jo Ko 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.12

One of the common problems associated with surface texturing is the presence of burrs/bulges around a micro-dimple surface. This study experimentally investigates the effect of micro-dimples with burrs on the friction properties of the textured surfaces. Textured surfaces were generated using a two-modulation 3D elliptical vibration texturing method on an AISI 1045 cylindrical steel specimen. Tribological tests were conducted with a block-on-ring configuration at a constant load of 50 N under transition state between mixed lubrication and hydrodynamic lubrication regime. The results indicate that the increase in texture density adversely affects the friction properties of the micro-dimples with burrs. This is attributed to the higher metal-to-metal contact between the sliding surfaces owing to the presence of burrs. Smaller micro-dimples with specific height of burrs (3.7 ± 1.093 μm) show reduced friction characteristics, especially in the high-sliding-speed regions. The results suggest that the small micro-dimples with low texture density were effective in reducing the friction of the textured surfaces with the specific height of burrs around the micro-dimples. Additionally, oxidation wear was discovered in the non-textured surface after frictional tests.

마이크로 딤플 패턴에 따른 마찰특성에 관한 연구

황남성 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.3

The purpose of this study is to investigate friction characteristics according to micro-dimple patterns. The surface texturing of micro-dimple patterns was tested to examine the friction of pin-on-disk using flat-on-flat contact geometry. The patterns of both dimple circle and groove pattern were adopted to carry out the effect of those ones. In the low loads, such as 13.8N and 27.7N, the friction coefficients of groove pattern were lower than those of dimple circle pattern. In many other comparisons of normal loads, the groove pattern had lower friction forces, which showed the effect of surface texturing. The relationship between sliding time and friction forces showed that the increase of friction forces of groove pattern were relatively lower than those of dimple pattern. In conclusion, the dimple patterns of dimple-circle pattern and groove pattern strongly contributed to reducing the friction between contacting materials.

Laser Texturing한 평행 스러스트 베어링의 윤활특성 : 제1보 - 딤플깊이의 영향

박태조(Tae-Jo Park),황윤건(Yun-Geon Hwang) 한국트라이볼로지학회 2009 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.25 No.5

Laser surface texturing (LST) methods are applied recently to generate micro-dimples in machine components having parallel sliding surfaces such as thrust bearings, mechanical face seals and piston rings, etc. And it is experimentally reported by several researchers that the micro-dimpled bearing surfaces can reduce friction force. Until now, however, theoretical results for various dimple parameters are not fully presented. In this paper, a commercial computational fluid dynamics (CFD) code, FLUENT is used to investigate the effect of dimple depth on the lubrication characteristics of parallel thrust bearing. The results show that the pressure, velocity and density distributions within dimples are highly affected by dimple depths and cavitation conditions. Adoption of micro-dimple on the bearing surface can reduce the friction force highly and its levels are affected by dimple depth. The numerical methods and results can be use in design of optimum dimple characteristics to improve thrust bearing performance.

Micro-texturing한 미끄럼 베어링의 윤활해석

박태조(Taejo Park),김민정(Minjeong Kim),정요한(Yohan Jeong) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4

Friction reduction is essential to improve efficiency and reliability of all machines. It is recently reported that the micro-textured machine components such as thrust bearings, mechanical face seals and piston rings can reduce the friction force drastically. The results are mainly experimentally reported, however, precise theoretical results are not enough. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is used to investigate the lubrication characteristics of two types of sliding bearing having 3-dimensional micro-dimple. The results show that the pressure distributions and bearing load capacities are highly affected by dimple location and film shapes. And reduction of friction force acting on micro-dimpled sliding bearing surface are obtained regardless of sliding bearing types. Therefore the numerical results can be use in optimum sliding bearings.

Micro-scale surface texturing을 기반으로 한 저마찰효과에 대한 기초연구

채영훈(Younghun Chae),김석삼(SeockSam Kim) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.39 No.-

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 using photolithography 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 considerably under mixed and hydrodynamic lubrication conditions from based on friction map. Lubrication condition regime has an influence on the friction coefficient induced the density of micro dimple.

Cutting Force Model in Micro-Dimple Pattern Process using Two-Frequency Elliptical Vibration Texturing (TFEVT) Method

Rendi Kurniawan,고태조 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1

We herein propose a cutting force model in a micro-dimple pattern process using the two-frequency elliptical vibration texturing (TFEVT) method. The TFEVT method decreases the cutting force compared to the conventional texturing (CT) method owing to the intermittent cutting behavior. The cutting force model in the TFEVT method is formulated, in which the shear angle is assumed as a transient and the transient area of cut of the micro-dimple is determined. The transient area of cut of the micro-dimple can be determined by obtaining the starting and ending time of cutting, while the shear angle can be determined by Cerniway’s hypothesis. Finally, the cutting force model was compared with the experimental cutting force value. The comparison results show that the cutting force simulation is in agreement with the experimental cutting force value. The experimental results also show that the cutting force in the TFEVT method is lower than that in the CT method.