The mode transition from mild to severe wear - observation of the realistic contact area under shear stress -

Burwell和Strang于1952年提出了一种从轻微磨损到严重磨损的模式转变概念，并尝试从各向同性和高斯面来估算载荷状态从轻到重的门槛，并通过直接观测进行验证。简而言之，阈值条件表示为名义接触区域完全被屈服区域覆盖的临界压力。利用随机粗糙面接触理论和Johnson的弹塑性压痕模型，结合Chang-Etsion分析，计算了该临界压力。粗糙粗糙的单个顶点被认为是一个球体，它们的半径都是相同的。分析了滑移对粗糙表面接触的影响。应用滑移线场理论，将接触视为二维，假设粗糙面与平面之间的接触，设计了能同时施加法向载荷和剪切载荷的微滑动机构，以观察真实的接触点。对于纳米级的执行器，一开始就计划进行压电扫描，但很难减小其接触处的剪切变形，观察在电机驱动的滑块驱动下400 mm的末端因磨损而产生的粘着状态。在实验中，同时测量了法向力和切向力。讨论了机械特性(法向压力、剪应力、杨氏模数、硬度和表面剪切强度)、几何特性(表面粗糙度和形状)对磨损模式的影响。计划在不久的将来直接观测实际接触面积，即接触的凹凸体的形状、数量和面积。

The threshold of load condition from light to heavy that Burwell and Strang proposed in 1952 as a concept of the mode transition from mild to severe wear, are tried to be estimated considering isotropic and Gaussian surface, and verification by direct observation. In brief, the threshold condition is expressed as the critical pressure at which the nominal contact area is wholly covered with the yielding area. This critical pressure has been calculated using stochastic rough surface contact theory and Johnson's Elastic Plastic Indentation model with Chang-Etsion's analysis. Individual summit of rough asperity has been assumed to be a sphericity and all of them to have the same radius. Analysis has been developed the effect of slip on rough surface contact. The contact is regarded as 2D and is assumed as that between rough surface and plane to apply the slip line field theory.Micro-sliding mechanism are designed for the system which is able to give the normal load and shearing load to observe the realistic contact points. At the beginning the piezo-scanning stage would be planned for nano-scaled actuator, but it is difficult to decrease the shear deformation at their contact, observe the status of adhesion due to wear of the end of the 400 mm traveling by motor actuated slider.In the experiments, normal force and tangential force are measured simultaneously. The effects of mechanical characteristics (normal pressure, shear stress, the Young's modulus, hardness and shear strength of surfaces) , geometric characteristics (surface roughness and shape) are investigated in the discussion of the wear mode. The direct observation of the realistic contact area, which mean the shape, number and area of contacted asperity is planed in the near future.