Research on reliability and dynamic characteristics of planar complex multi-bar mechanism considering clearance and irregular wear effect

• Propose the motion reliability analysis method that uses failure efficiency as the reliability metric and combines it with the Monte Carlo algorithm. • Propose a method for analyzing and quantifying the irregular wear effect of multi-bar mechanism with clearances. • Discuss the influence of crank speed and clearance size on the nonlinear dynamic characteristics of clearance mechanism. • Provide theoretical basis for improving motion reliability, reducing wear depth and restraining nonlinear dynamic behavior caused by clearance in practical application. To study the motion reliability and dynamic characteristics of a planar multi-bar mechanism with clearance, this paper takes the R-2RRP-RRR mechanism with single clearance as the research object, establishes its dynamic model based on the Newton-Euler method, and the effectiveness of the dynamic model is verified through both the numerical computation and multibody dynamics simulation. A method for motion reliability analysis using failure rate as a reliability metric based on Monte Carlo algorithm is proposed, which is simple and highly accurate, and the influence rule of mechanism motion reliability under the interaction of multiple factors is revealed using the proposed method. Based on Archard's model and Lankarani-Nikravesh nonlinear contact force model, a method for analyzing and quantifying irregular wear effects of multi-bar mechanism with clearance is presented, and the influence on the mechanism of crank speed, clearance size, coefficient of friction and coefficient of restitution on irregular wear of mechanism with clearance are investigated systematically. The factors affecting the behavior of the nonlinear characteristics of multi-bar mechanism are studied, and the obtained conclusions provide sound foundation for the life prediction and optimal design of multi-bar mechanism with single clearance as well as multi-clearance in practical application.