A comprehensive method for joint wear prediction in planar mechanical systems with clearances considering complex contact conditions

Abstract

A comprehensive method to predict wear in planar mechanical systems with clearance joints is presented and discussed in this paper. This method consists of a system dynamic analysis and a joint wear prediction. As the size and shape of the clearance are dictated by wear and evolve with the dynamic response of the system, the contact between the journal and bearing could be conformal or non-conformal, which makes the contact conditions in clearance joints quite complicated. Therefore a modified contact force model is employed to evaluate the joint reaction force in this study. As the nonlinear stiffness coefficient is related to the physical and geometrical properties of contact bodies and varies with the deformation, this contact force model is applicable to different contact conditions between the journal and bearing. Furthermore, based on the Archards wear model, the amount of wear can be quantified in the joint. And the geometry is updated to reflect the evolving contact boundary. Then, the wear process and the contact force model are integrated into the motion equations of the system to perform coupled iterative analyses between system dynamic response and joint wear prediction. In addition, a slider-crank mechanism is simulated as an example to demonstrate efficiency of the proposed method and to carry out a parametric study on mechanical systems considering joint wear. The influence of clearance size and driving power are discussed and compared respectively. The index of concordance is introduced to quantify contributions of contact pressure and sliding distance to wear rate under different types of journal motion. This study could help to predict joint wear in mechanical systems with clearances and optimize mechanisms in design.