多层介质粗糙表面热弹塑性接触问题研究

【作者】 佟瑞庭；

【导师】 刘更；

【作者基本信息】 西北工业大学 ， 机械设计及理论， 2007， 硕士

【摘要】 应用有限元方法对二维多粗糙峰涂层表面的弹塑性接触力学行为进行了系统的分析。对不同涂层材料弹性模量、不同屈服极限、不同涂层厚度及不同表面形貌的粗糙表面与刚性平面的弹塑性接触问题进行了模拟，分析了这几种因素对接触压力、接触面积、表面轮廓变形及接触体应力场分布的影响。 考虑恒定的热传递和热弹塑性变形引起的粗糙峰变形，对多层介质粗糙表面热弹塑性接触模型进行分析。针对不同涂层材料，研究了接触压力、接触面积、平均间隙之间的关系，涂层厚度对表面接触压力分布、温升的影响，以及材料属性、涂层厚度、摩擦系数和热输入对应力分布和温升分布的影响。发现软涂层的应用，降低了粗糙峰温度峰值。另一方面，硬涂层的高压力峰和低传热性，导致粗糙峰的最高温度非常高，而且涂层厚度越大，压力峰值和温度峰值越高。硬涂层材料的最大von Mises应力发生在涂层表面，基体材料发生在涂层．基体界面处。之后，讨论了应用硬涂层材料减小基体材料塑性区域时硬涂层的合理厚度。 建立了可考虑屈服应力温度相关的粗糙表面热弹塑性接触模型。研究了摩擦力和不同热输入情况下圆柱体与弹塑性平面的接触力学特性。研究表明，在考虑剪切摩擦力作用后，弹塑性接触压力分布不再关于接触区域中轴线对称而出现了“塌陷”现象。忽略温度相关效应将高估最大接触压力而低估相应外载荷下产生的接触面积。由于材料屈服应力随温度升高而降低，忽略温度相关效应的影响将高估材料的强度性能。求解了考虑屈服应力温度相关的粗糙表面热弹塑性接触问题，探讨了摩擦热效应对表面温升、接触压力和接触体应力分布的影响。发现考虑屈服应力温度相关效应后，相同接触压力作用下，粗糙表面接触的平均间隙相对较小。相同载荷作用下，最高表面温升略低于不考虑温度相关效应的表面温升。 提出了考虑热膨胀系数温度相关效应的热弹塑性接触模型。通过刚性圆柱体与半无限大平面的热弹塑性接触研究了热膨胀系数温度相关效应对接触体应力分布及温升分布的影响。考虑热膨胀系数温度相关效应后，接触体的平均应力水平相对较高，且等应力线向左右两端扩展，热膨胀系数温度相关效应对接触体温升分布影响较小。 最后，总结了全文，指出今后的研究方向。更多还原

【Abstract】 A two-dimensional elasto-plastic contact model of multi-asperities with coating by using the finite element method is presented. Two profiles of multi-asperities which have different topographies with the same root mean square roughness are used. The influences of surface topography, Young’ modulus, yield strength of coating materials and coating thickness on contact pressure, contact area, profile deformation and von Mises stress distributions of the contacting bodies are investigated.A thermal elasto-plastic asperity contact model is investigated, which takes into account the steady-state heat transfer and the asperity distortion due to thermal elasto-plastic deformations. A hard coating and a soft coating are applied to study the correlations between contact area and contact pressure, average gap and contact pressure, coating thickness and contours of the contact stress distribution et al. The effects of material properties, the coating thickness, frictional coefficient, and the heat input combinations on the stress distribution and the temperature rise distribution are investigated and discussed. The frictional heat input increases the maximum value of von Mises stress. Application of the soft coating with the high thermal conductivity reduces the asperity temperature peaks. On the other hand the higher pressure peaks and the lower heat conductivity of the hard material make the maximum temperature rise of the hard coating higher. The thicker the hard coating layer, the higher the pressure and temperature peaks. The appropriate thickness of the hard coating is also discussed.A thermal elasto-plastic contact model which can consider the effects of temperature-dependent yield strength is developed to investigate the influences of the steady-state frictional heating on the contact performance of surface asperities and subsurface stress fields between two contacting bodies. The model is verified through the contact analysis of a rigid, isolated cylinder with a thermal elasto-plastic plane. The results show that the contact pressures of elasto-plastic contact with considering the frictional tractions are no longer symmetric. The maximum contact pressure will be overestimated and the contact areas will be underestimated if the effects of temperature-dependent yield strength is ignored. Furthermore, the thermal effects on the contact pressure, real area of contact, and average gap of real rough surface with different frictional heat inputs under the thermal elasto-plastic contact conditions are studied. When the effects is considered, with the same contact pressure, average gaps更多还原