Numerical simulation of flow-induced stresses in mold filling process using a three-dimensional two-phase flow model

Abstract

The flow-induced stresses which arise during the filling stage have significant influences on the mechanical and optical properties of injection-molded products. The prediction of flow-induced stresses in mold-filling process is a challenging problem, which includes viscoelastic polymer melt free surface flow. Thus, this paper presents a three-dimensional (3D) non-isothermal two-phase flow model to quantitative predict the flow-induced stresses in polymer mold-filling process based on the XPP model. In this model, the governing equations for gas and viscoelastic melt are united into a system namely the generalized Navier–Stokes equations. In order to improve the stability of the numerical method in 3D, an enhanced treatment of stress solid boundaries is proposed. The stresses on solid boundaries are calculated using an effective second-order Runge–Kutta method. The model is successfully solved by using the finite volume method, and the melt front is accurately captured by level set method. The validity of the method is verified by two benchmark problems. Then the mold-filling process of a rectangular plate is studied numerically, obtaining the evolutions of flow-induced stresses at different levels along the gap-wise direction, which can not be simulated by 2.5D model. The predicted flow-induced birefringence is in agreement with the experimental result reported in the literature. Furthermore, the effects of injection velocity and some model parameters of XPP model on flow-induced stresses are numerically predicted. The numerical results show that the 3D simulation technology can effectively predict the flow-induced stresses and birefringence in non-isothermal viscoelastic polymer mold-filling process. The results can provide the theory foundation for improving the properties of products in actual production processes.