Development of wear-mode transition model based on analysis of contact mechanics of rough surfaces

本项目的目的是对Burwell-Strang的假设进行实验验证，该假说是由屈服区域从粗糙峰水平过渡到表观接触面积水平引起的。为了实现这一目标，我们尝试了以下几种方法：1.研制了一种利用商用金属显微镜观察粗糙面附近变形的测试装置。在本试验中，我们测量了硬体楔体与平坦软面之间的压痕和拖拽后在软面一侧形成的网格的变形。2.用滑移线场理论对模型的数值计算结果与有限元计算结果进行了比较，两者吻合较好。利用有限元计算结果对模型进行了改进。为了预测粗糙表面和光滑表面之间的接触压力，我们还研制了一种基于全反射法的接触显微镜。在该装置中，除了法向载荷外，我们还可以滑动接触面积。作为初步研究，我们观察了在法向载荷作用下，抛光后的随机粗糙表面上真实接触点的生长和增加。实验结果表明，该装置能较好地估算过渡压力，验证了理论的正确性。我们将研究法向应力和剪应力对实际接触点变化的影响。我们还将尝试发展我们的理论，可以在广泛的条件下预测磨损转变压力。

The Objective of this project is the experimental verification of Burwell-Strang's hypothesis, that is "abrupt increase of ware rate is caused by transition of yield area from asperity summit level to apparent contact area level".To achieve the objective, we tried these approaches :1.We developed a test apparatus for observation of deformation near an asperity using commercial metal microscope. In this test, we measured deformation of mesh previously made on side of softer surface after indentation and dragging between wedge of hard body and flat soft surface.2.We got good agreement between numerical results of our model used by slip line field theory and those of finite element method. We refined our model using results of FEM. We also calculated distribution of real contact spots under normal and shear stress.3.We also developed a contact microscope using total reflection method, in order to predict the transition pressure of contact between rough surface and smooth surface. In this apparatus, we can slide contact area in addition to normal load. For preliminary study, we observed growth and increase of real contact spots on blast finished random rough surface under normal load. The results indicated that apparatus could estimate transition pressure and verify our theory.We are going to study the effect of normal and shear stress on change of real contact spot. We will also try to develop our theory that can predict wear transition pressure under extensive condition.