Kinematic Reliability Evaluation of Planar Mechanisms with Time-Varying Correlation of Wear in Multiple Joints

The wear in joints is a critical factor influencing the service life of the mechanism. Unlike existing researches that focus on wear prediction of joints, the correlation of wear among multiple joints in a mechanism is investigated in this study. The wear correlation of multiple joints in a mechanism is analyzed firstly. Then, a kinematic reliability evaluation method of planar mechanisms considering the wear correlation of joints is proposed. In the method, the wear depth in joints is modeled by Gamma process to take the stochastic characteristic into account. Vine copula functions and two correlation evolution equations are introduced to capture the time-varying and pairwise correlation of wear in the joints. At last, a numerical procedure is presented based on the Monte Carlo simulation. A four-bar mechanism is used to illustrate the proposed method. The results show that the wear of joints in a mechanism correlates with each other strongly, and the correlation varied with time. The correlation differs with one another in different pairs of joints. Besides, the time-varying correlation of wear has a significant influence on the kinematic reliability of the mechanism.