Study of adhesive wear mechanisms in asperity junctions based on phase field fracture method

Adhesive wear that is mostly induced by adhesion between asperities of rough surfaces in contact is one of the most common forms of wear of materials. However, the adhesive wear mechanisms are still not fully understood. In this work, the phase field fracture method that does not require any assumption on the crack path is used to explore the debris formation mechanism during asperity separation in adhesive wear. It is found that for ideal materials without defects the size of wear particles depends on the contact length. A small contact length leads to fracture at the junction and the formation of small wear particles. On the contrary, a large contact length will cause fracture in the bulk, resulting in large wear particles. Moreover, the angle of crack propagation decreases with increasing base angle of asperity and the ratio of the asperity height to the base edge width. The variation of fracture angle is mainly related to the ratio of asperity height to the base edge width that will influence the angle of the interaction force between asperities in the wear process. For materials with initial hole defect, the formation mechanism of wear particles will be little affected when the hole is rather small or far away from the junction. However, as the hole diameter further increases, the wear particles will change from large particles to small ones. And for materials with initial crack defect, the crack propagation always starts from the initial crack during adhesive wear. Moreover, for adhesive wear of materials with an initial crack at the bottom of asperity, fracture angle in the bulk is significantly positively correlated with the contact length and large wear particles are easy to form. However, during adhesive wear of asperity with the initial crack inside the bulk of asperity, small particles are more likely to form. This work contributes to further understanding of adhesive wear process.