考虑弹塑性阶段的结合面法向接触阻尼分形模型

Fractal Model for Normal Contact Damping of Joint Surface Considering Elastoplastic Phase

结合面法向接触阻尼建模时,只考虑微凸体弹性变形时的弹性能和塑性变形时的损耗能是不完全的,因为微凸体存在弹塑性变形情况。将微凸体弹塑性变形时的法向接触载荷'分离'为弹性载荷和塑性载荷两部分,得到微凸体弹塑性变形时的弹性能和损耗能,建立更加完善、合理的结合面法向接触阻尼模型。将结合面法向接触动力学模型等效为弹簧和黏性阻尼器,建立包括微凸体三种变形状况的结合面法向接触阻尼损耗因子和法向接触阻尼系数的解析模型,并量纲一化处理。仿真结果表明,分形维数D和分形粗糙度G~*是影响结合面法向接触阻尼损耗因子和法向接触阻尼系数的最主要参数。在塑性指数f不变,D小于拐点值(D=1.56)时,法向接触阻尼系数随着G~*的增大而增大;当D超过拐点值时,G~*越大,法向接触阻尼系数减小。当G~*不变,D<1.66时,?越大,法向接触阻尼系数越小;当D>1.66时,法向接触阻尼系数随?的变化很小。利用线轨滑台模态试验验证所建模型的准确与可靠性。

When modeling the normal contact damping of the joint surface,it is incomplete to consider only the elastic energy of the asperity in the perfectly elastic deformation phase and the loss energy in the fully plastic deformation phase,because there is the elastic-plastic deformation phase.The normal contact load of the contacting asperity in the elastoplastic deformation phase is'separated'into the elastic contact load and the plastic contact load,and the elastic and loss energy of the contacting asperity are obtained.The normal contact dynamic model of the joint surface is equivalent to spring and viscous damper,and the analytic model of damping loss factor and normal contact damping of the joint surface is established,and the dimensionless processing is carried out.The results reveal that fractal dimension D and fractal roughness G~*are the important parameters affecting the damping loss factor and the normal contact damping coefficient.When the plastic index f is constant and D is less than the inflection point value(D=1.56),the normal contact damping coefficient increases with the increase of;when D exceeds the inflection point value,it decreases with the increase of G~*.When G~*remains unchanged and D is less than 1.66,the greater the plastic index,the smaller the normal contact damping coefficient;when D is greater than 1.66,the change of the normal contact damping coefficient with f is very small.The accuracy and reliability of the model are verified by the results of experimental modal analysis on line rail sliding table.