结合面静摩擦因数分形模型的建立与仿真

Fractal model of static friction coefficient of joint interface and its simulation

提出一个确定分形维数和分形粗糙度参数G*的分形函数,并用分形函数逼近结合面的表面粗糙度。根据分形理论和改进后的尺寸分布,推导了静摩擦因数f的解析解。数字仿真结果表明,f随量纲为一的总法向载荷P*增加而增加。当D较小或较大时,f与P*之间存在不同的微凸和微凹弧非线性关系,D=1.2时f与P*的关系基本上是线性的;当D较小时,f随D增加而增加;当D较大时,f随D增加而减小;f随分形粗糙度参数G*增加而减小,随相关系数K增加而增加,随材料特性φ增加而增加。

A fractal function,which is adopted to approximate the surface roughness of joint interface,is proposed for the first time in order to determine the fractal dimension and fractal roughness parameter.The static friction coefficient is one of the most important parameters for predicting the dynamic characteristics on bolted joint interface.Using the fractal theory and modified size distribution,the analytic solution to static friction coefficient is deduced.The numerical simulations indicate that the static friction coefficient increases with increasing dimensionless total normal load.The micro convex nonlinear relation of the static friction coefficient versus dimensionless total normal load is very evident when the fractal dimension becomes smaller;while the micro concave nonlinear relation of the static friction coefficient versus dimensionless total normal load is very evident when the fractal dimension becomes larger.The static friction coefficient increases with increasing fractal dimension when the fractal dimension becomes smaller;while the static friction coefficient decreases with increasing fractal dimension when the fractal dimension becomes larger.The static friction coefficient decreases as the fractal roughness parameter increases;while the static friction coefficient increases as the correlation coefficient or material property increases.