Experimental and numerical investigations on size effect of friction in meso-/micro-forming without lubricant

The main purpose of this paper is to investigate the variation mechanism of tribological size effect in meso-/micro-forming processes. The effects of specimen size on friction behavior in meso-/micro-forming were investigated through the pure copper upsetting experiments without lubricant. It reveals that the friction coefficient on contact surface is getting smaller with the decreasing of specimen size. Then, the influence mechanisms of specimen size on friction behavior were studied by the combination of experimental and numerical methods. It indicates that as the specimen size decreases, the reducing friction coefficient is caused by the decreasing of normal pressure on contact surface in meso-/micro-forming processes without lubricant. The investigation results are very useful for predicting friction behavior in meso-/micro-forming processes without lubricant.