Title: An experimental investigation on effective friction coefficient in elliptical ultrasonic assisted grinding of monocrystal sapphire

Authors: Zhiqiang Liang; Xibin Wang; Yongbo Wu; Lijing Xie; Li Jiao; Wenxiang Zhao

Addresses: Key Laboratory of Fundamental Science for Advanced Machining, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China ' Key Laboratory of Fundamental Science for Advanced Machining, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China ' Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, 84-4 Tsuchiya-ebinokuchi, Yurihonjo, Akita 015-0055, Japan ' Key Laboratory of Fundamental Science for Advanced Machining, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China ' Key Laboratory of Fundamental Science for Advanced Machining, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China ' Key Laboratory of Fundamental Science for Advanced Machining, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China

Abstract: In this study, in order to investigate the effective friction coefficient in elliptical ultrasonic assisted grinding (EUAG) of sapphire, the single abrasive grain scratching experiments are performed to simulate the grinding process by setting up the elliptical ultrasonic vibrator attached with the sapphire substrate on a multi-axis CNC grinder. The single grain diamond tool slides on the elliptically vibrated surface at a serial of pressures, and the grinding forces are measured. The friction coefficients under different pressure and vibration amplitude are obtained by calculating the ratio of tangential grinding force to normal grinding force, i.e., F_f / F_n. Comparing friction coefficients in both scratching with and without vibration, there is a critical pressure F_pc at a range of pressure. As the pressure is less than F_pc, the friction coefficient in EUAG is smaller than that in conventional grinding (CG), and once the increasing pressure is more than F_pc, that is much higher than that in CG. When the pressure is slight, ploughing occurs and no chips are generated, and actually at low pressure, the ratio F_t / F_n can be close to the effective friction coefficient in EUAG. Thus, the experimental results at low pressure indicate that the effective friction coefficient in EUAG is less than that in CG, and is decreasing with the increasing vibration amplitude.

Keywords: elliptical UAG; ultrasonic assisted grinding; EUAG; friction coefficient; grinding forces; monocrystal sapphire; CNC grinding; vibration amplitude.

DOI: 10.1504/IJNM.2013.057589

International Journal of Nanomanufacturing, 2013 Vol.9 No.5/6, pp.477 - 485

Received: 15 Sep 2012
Accepted: 26 Feb 2013
Published online: 31 Mar 2014 *

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