Nano-sized single-asperity friction behavior: Insight from molecular dynamics simulations

Friction phenomenon plays an essential role in contact pairs, from macroscale to nanoscale friction. Nano-sized friction behavior is different from macroscopic friction behavior due to discreteness of atoms. Taking α-Fe as paradigm material, single-asperity friction molecular dynamics (MD) simulations are conducted. The MD results show that the multi-slip phenomenon exists during the tangential loading process of nano-sized single asperity. Meanwhile, the macroscopic friction coefficient model is not suitable for nano-sized friction, while the macroscopic Kogut-Etsion (KE) contact radius model can approximately describe nano-sized contact radius. Besides, the Mindlin model can hardly describe the initial tangential stiffness under large normal loadings due to the neglect of plastic deformation. Therefore, it is suggested to modify the macroscopic friction models by considering the plastic deformation mechanism and asperity size effect to improve the full-scale description ability.