Numerical Investigation of Adhesive Wear and Static Friction Based on the Ductile Fracture of Junction

Abstract

Adhesion plays a significant role in the friction and wear in the case where the contact surfaces are continuous and smooth such that roughnessbased factors are negligible. Therefore, imposing an external load to overcome the friction is, in essence, a failure process of adhesive junctions. In this work, a finite element model was developed in order to investigate the formation of adhesive wear particles and static friction based on the ductile fracture of junctions. Focusing on the cylindrical contact and the combined contact loading configuration, a modified element deletion method with three empiric fracture criteria was employed and the failed elements satisfying some fracture criterion were used to represent the cracks. Based on the different crack development stages, a qualitative adhesive wear mechanism was summarized. The simulation results indicate that the secondary crack initiated in the pileup of material possibly accounts for the crack kinking, which is the origin of the flakelike wear particle. Friction behaviors under different loading configurations were investigated and a simple comparison for three different fracture models was presented. It was found that all three models show the same trend of friction decreasing with the increase of normal preload. Where the most conservative Bao–Wierzibicki (BW) fracture model predicts higher friction compared to two other fracture models, the Johnson–Cook (JC) model predicts a lower ductile fracture strain, thus the ductility of the material is relatively underestimated.