Phase field simulation of stick-slip flow incorporating shear melting and wall slip

The origin of stick–slip flow has been attributed to various possible processes such as interlayer slip, interfacial slip, and strain-induced melting based on experiments and molecular dynamics simulations. Although both experimental and molecular scale simulations show evidence for different mechanisms of stick–slip flow, the results are difficult to interpret without the aid of a simple model. In this study, we investigate the origin of stick–slip flow using a phase field model that was originally developed to simulate melting induced stick–slip. Unlike molecular dynamics simulations, the phase field model contains parameters that can be independently varied to help explain the causes of stick–slip motion. We extend this model by including interfacial slip as a possible mechanism for stick–slip flow. Both Navier wall slip and a yield stress wall slip mechanism are incorporated into the phase field model. We determined a state diagram that illustrates three different types of stick–slip behavior. We find that both wall slip and shear induced melting are viable mechanisms for stick–slip flow, but the parameter range where wall slip induced stick–slip flow occurs is very narrow. At a fixed value of the Navier slip length above a certain threshold, as the critical yield stress for wall slip is increased from zero, we see a transition from simple slip flow to wall yield stress induced stick–slip flow, to melting-induced stick–slip flow. If the slip length is less than this threshold value, we see only melting induced stick–slip flow for all values of the critical wall slip yield stress. • Stick–slip flow in a confined channel can be induced by shear melting or wall slip mechanisms. • Phase field simulation utilities a mesoscopic model to study stick–slip flow with minimal computational effort. • The phase field model provides additional insight into the mechanisms of stick–slip flow that is not accessible by purely macroscopic or atomistic modelling. • Different stick–slip phenomena can be analyzed by controlling parameters of the model, such as the wall slip critical yield stress and slip length.