Interference effect on friction behavior of asperities on single crystal copper

By using Green function molecular dynamics method, we systematically study the friction behavior of a single asperity and asperity array over the (1 1 1) surface of single crystal copper. We find that internal plastic behavior (burst of stacking faults, dislocation emission and propagation) is a promising reason for the higher value of static friction coefficient than that of dynamics friction in non-adhesive scratch. For the rough surface, however, the difference between static and dynamic friction coefficients disappear due to the interference between asperities. The interference dramatically increases the friction coefficient by introducing atomic scale plastic features (pile-up atoms, stacking faults, and U-shape dislocation loop).