Application of the Momentum Exchange Approach for Vibration Performance Evaluation of Flexible Mechanisms with Joint Clearance

Clearances are necessary in assemblage of mechanisms to permit the relative motion between the joined bodies. This clearance exists due to machining tolerances, wear, material deformations, and imperfections, and it can deteriorate mechanism performance such as precision and vibration. The influence of joint flexibility on instantaneous natural frequencies of a flexible slider-crank mechanism with a clearance between crank and coupler is studied in this paper. Clearance size is varied to see its effect on instantaneous natural frequencies. Finite element method is used to determine the equations of motion. In order to model the clearance, the momentum exchange approach is chosen and the stiffness of the clearance is modeled as a linear spring incorporated into the assembled stiffness matrix. The simulation results show that an increase in the joint stiffness increases the natural frequency until it converges to an amount. In addition, clearance size does not make a considerable change in the maximum or minimum amount of the instantaneous natural frequencies.