表面形貌变形对塑性成形滑动接触界面摩擦的影响

为了更好地理解塑性成形滑动接触界面的摩擦行为,构建了一种新型的摩擦试验装置,运用表面纹理化技术制备了两类表面形貌的1050铝材试件,在不同的接触压力和滑动速度条件下进行一系列拉伸摩擦试验.对试验前后试件三维表面形貌进行了测量;提取真实接触面积比、封闭空体面积比和开放空体面积比等三维表面参数,来描述试件表面形貌的变化.试验发现:摩擦系数随名义接触压力和滑动速度增加而逐渐减小;试件初始表面形貌对摩擦有明显的影响;试件表面形貌和参数随接触条件出现了规律性变化.基于机械流变模型的分析表明:随着试件表面形貌变形,不同的机理决定界面摩擦行为,摩擦系数对名义接触压力和滑动速度的依赖性可分别归因于微观塑性流体动压润滑效应和入口区流体动压牵引效应.

Influence of Surface Topography Deformation on Friction at Sliding Contact Interface in Metal Forming

In order to obtain a better understanding of the frictional behavior at sliding contact interface in metal forming, a novel friction test apparatus was built up. A series of strip drawing friction tests using aluminum 1050 sheet specimens with two types of texturing topographies were conducted at different contact pressures and sliding speeds. The three dimensional surface topographies of specimens before and after tests were measured. Such three dimensional surface parameters as real contact area ratio, closed void area ratio and open void area ratio, were used to describe the variations of surface topography of specimens. Experimental results show that the friction coefficient decreases with increasing nominal contact pressure and sliding speed. The initial surface topography of the specimens has a definite influence on the friction behavior. The three dimensional surface topographies and parameters of the specimens vary regularly with contact conditions. Based on mechani- cal-rheological model, it is found that depending on the surface topography deformation, different mechanisms determine the friction behavior. The dependence of the friction coefficient on nominal contact pressure and sliding speed can be attributed to micro-plasto-hydrodynamic lubrication and hydrodynamic entrainment in the inlet at the interface respectively.