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이중 주파수 타원형 진동 궤적법 기반 마이크로 딤플의 마찰계수 및 습윤성 분석
박건철(Gun Chul Park),고태조(Tae Jo Ko),쿠르니아완 렌디(Rendi Kurniawan),아리 사우드(Saood Ali) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.5
Surface texturing of micro-dimples has been used in many manufacturing industries to reduce friction between two sliding contacted surfaces. Surface texturing decreases the frictional force owing to minimizing of the sliding contact area. In this paper, micro-dimples have been fabricated on an Al6061-T6 surface using a two-frequency elliptical vibration texturing (TFEVT) method. A high-frequency of 18 kHz and low-frequency of 250 Hz were applied to an elliptically-vibrated tool holder. The Stribeck curve was plotted to analyze the friction coefficient trends. Furthermore, the representative wetting index, such as the water contact angle (WCA), was measured by considering the friction coefficient. WCA is associated with micro-dimple density and associated parameters. Consequently, the dimpled surfaces with a low friction coefficient exhibited a relatively high WCA in the feed direction. According to the Stribeck curve, the dimpled surfaces demonstrate superior friction performance for mixed-film lubrication compared to the non-textured surface.
박건철(Gun Chul Park),고태조(Tae Jo Ko),쿠르니아완 렌디(Rendi Kurniawan),아리 사우드(Saood Ali) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.2
Surface texturing is a promising route to reduce the friction forces between two surfaces in sliding contact. To this end, the fabrication of micro dimples is one of the most widely used surface texturing methods. According to published results, textured surfaces with elliptical micro dimples offer the best friction performance. Therefore, we fabricated elliptical micro dimples on carbon steel (SM45C) by using dual frequency vibration assisted machining. High and low frequencies of 16.3 ㎑ and 230 ㎐ were applied to the 3D resonant elliptical vibrator. The 3D resonant elliptical vibrator with a triangular cubic boron nitride insert was assembled on a computer numerically controlled turning lathe. Oval micro dimples of various profiles were manufactured on carbon steel. In terms of the profile of the elliptical micro dimples, the experimental results indicated that the average micro dimple width and depth were 112 ㎛ and 7.7 ㎛. These dimensions are closely related to the cutting conditions and can be easily controlled.