Numerical simulation of injection mold filling for semi-solid materials

Abstract

Processing of metals and metal matrix composites in the semi-solid state is an emerging new technology and is becoming increasingly popular. This method provides several advantages over the traditional liquid state processing including better control over the viscosity and final microstructure and reduced solidification shrinkage. A two-dimensional simulation of the injection molding filling process for semi-solid materials is presented. The material is modeled as a homogeneous incompressible fluid and the stress tensor is expressed using a shear rate thickening Bingham fluid model. This article shows the filling of a standard tension test specimen from one end. Due to symmetry, only one half of the geometry is modeled. Results are presented for filling rates as functions of the inlet velocity and pressure conditions. The effects of the adjustable parameters of the constitutive relation (yield stress, Bingham exponent, power-law index) are investigated. These results are presented and discussed. The effectiveness of the shear-thickening Bingham fluid model in representing the material behavior is also discussed.