考虑微凸体弹塑性过渡变形机制的结合面法向接触刚度分形模型

Normal Contact Stiffness Fractal Model Considering Asperity Elastic-Plastic Transitional Deformation Mechanism of Joints

基于粗糙表面微凸体变形的连续性和光滑性原理,研究了在法向载荷逐渐增加时的粗糙表面单个微凸体弹塑性过渡变形机制,提出了考虑弹塑性过渡变形机制的结合面微凸体微观接触模型,建立了法向接触载荷和法向接触刚度的数学模型;基于分形几何理论,建立了结合面法向接触刚度的分形模型,并对结合面法向接触刚度进行仿真计算.结果表明:在较小的塑性指数条件下,法向接触载荷与法向接触刚度近似呈线性关系;在较大的塑性指数条件下,法向接触载荷与法向接触刚度呈非线性关系;法向接触刚度随着分形维数和法向接触载荷的增加而增大,随着无量纲分形特征尺度系数的增大而减小;所得结合面法向接触刚度的仿真计算值与铣削加工和磨削加工条件下的实验值较吻合.

Based on the contact mechanics theory, the deformation behavior of a single contacting asperity was studied, a micro contact model was proposed considering elastic-plastic transition deformation mechanism of rough surface joints, and a mathematical model of normal contact load and contact stiffness were established. Besides, the fractal model of mechanical joints normal contact load and contact stiffness were presented based on the fractal geometry theory. The results show that the plasticity index is lesser, the relationship between normal contact load and contact stiffness is approximately linear, and with the plastic index increasing, the relationship between normal contact load and contact stiffness is strongly nonlinear. The normal contact stiffness increases with increasing fractal dimension and normal contact load and de creases with increasing dimensionless fractal scale parameters. Moreover, the joints normal contact stiff- ness whose machining surface were milled and ground were calculated respectively by using the present model. The comparion of test results show that the present model is consistent with the experiment result.