Simulating fatigue damage on planar mechanisms considering wear in revolute joints with clearance

Clearances and wear are present in almost all mechanisms. Their presence leads to degradation of the dynamic behavior of the mechanisms, involving the appearance of vibrations, noise, high forces at the joints, and an increasing fatigue damage. To simulate this problem, a flexible multibody model is proposed to efficiently determine the stresses involved, thus avoiding the high computational costs associated with the finite element method. The model considers the mechanical interactions and material degradation processes that affect the stress state, providing a more accurate estimation of fatigue damage. In this work, a methodology is proposed for estimating fatigue damage in mechanisms with clearance joints without the need of simulating all the cycles actually performed. The proposed methodology is applied to a planar slider-crank mechanism in which the fatigue undergone by the connecting rod is considered. Results show that clearances strongly affect the fatigue damage of the links. Furthermore, the effect of wear changes the linear behaviour of fatigue damage with respect to the number of cycles, generally producing a higher damage, and changing the critical damage zones in some cases.