在考虑粗糙实体弹塑性变形、热力耦合、微凸体间相互作用和摩擦热流耦合等影响下,运用有限元法数值模拟具有三维分形特性的粗糙面与刚性平面间滑动摩擦过程,分析了粗糙实体接触凸点塑性变形随深度变化情况。发现:在速度的突变和闪点温度形成时,摩擦接触表层等效塑性应变增大明显;在这一摩擦表层,过不同接触点的纵向剖面塑性应变沿深度分布不同:有的是接触表面塑性变形最大,有的是在接触微凸体表面下某一深度塑性变形最严重,而接触凸点表面的塑性应变稍小些。这与相关文献用SEM研究干摩擦后金属摩擦表层变形照片后发现的结果一致。滑动摩擦过程中,金属粗糙摩擦接触表层塑性变形的不断累积,将会导致材料表层中的夹杂或微观缺陷周围萌生微孔和裂纹源。
A thermo-mechanical coupling model for a rigid flat plane and an elastic-plastic rough surface based on three-dimensional fractal theory is established. The model considers the elasto-plastic deformation of the rough solid, the interaction between asperities, and the heat flux coupling between the sliding surfaces. By using the finite element method, the frictional sliding process of the rough surface and the flat plane is simulated. The plastic deformation varied with depth on the contact asperity of the rough solid are analyzed. The numerical results from the analysis and simulation show that the equivalent plastic strain on the frictional contact surface layer increases obviously when the relative sliding velocity changes suddenly and the instantaneous flash temperature emerges. On this frictional contact surface layer, through the different contact asperity, the distribution of the plastic deformation varied with the depth is different. The maximum equivalent plastic strain may be located on the contact surface or in some depth under the contact surface. These results are validated by experimental observation results available in the literature. The experimental results are obtained by studying the surface layer deformation photograph of the metal after the dry friction. The plastic deformation on the frictional contact surface layer accumulates during the frictional sliding, which will result in the micro-hole and the crack source around the micro-defects on the contact surface layer.