Modeling and prediction of fatigue life of robotic components in intelligent manufacturing

Wear of actuators is of special interest in intelligent manufacturing since actuators are essential to implement motion in any machines and robots. The fatigue life of an actuator closely relates to many factors including load, lubrication, material properties, surface properties, pressure, and temperature. Therefore, modeling the fatigue life of an actuator has to take into account many variables in solid mechanics, fluid dynamics, contact mechanics, and thermal dynamics simultaneously. Even though numerous works have been published in past 50 years, the practical methods for the predication of fatigue life of actuators are still lacking. In this paper, we are motivated to model and validate the wear and fatigue life of a type of linear actuators, e.g. lead screw actuators. Firstly, the concept of asperity contact is introduced and the Archard's model is adopted to quantify wear under specified working conditions. Secondly, the experiments are designed based on the test protocols by American Society for Testing and Materials (ASTM) where the wear at the ball-on-flat sliding are measured to validate the developed wear model. Thirdly , finite element analysis is applied to determine the stress distribution in the assembly of linear actuators. The analysis results from three sources are then integrated and used to predict fatigue lives of lead-screw actuators.