Molecular Dynamics Simulation of Heat Transfer at Contact Interface of Hot Forming Die

Abstract

During metal hot forming process, the billet and the die interact by contact under high temperature, high pressure and severe sliding. In this paper, an atomistic approach is utilized to study the behaviour of heat transfer at the contact interface of hot forming die and the material. Based on non-equilibrium molecular dynamics and phonon scattering theory, the phonon heat transfer process at the billet/die rough interface at nano-scale is analysed. The effects of interfacial lattice defect concentration and average interfacial temperature on the phonon heat transfer coefficient are examined. It is found that when the lattice defect concentration increases the phonon mismatch at the interface deteriorates and the interfacial thermal resistance increases, which leads to a sharp decrease in phonon heat transfer coefficient. A higher temperature of the contact body and a higher average interface temperature lead to a higher probability of inelastic scattering of phonons at the interface. Moreover, the high frequency phonons at high temperature might be decomposed into two or more low frequency phonons during the energy transmission, which increases the propagation of phonon at the interface; thus the phonon heat transfer coefficient increases accordingly.