Calculation of residual stresses in injection molded products

Both flow- and thermally-induced residual stresses which arise during the injection molding of amorphous thermoplastic polymers are calculated in the filling and post-filling stage. To achieve this, a compressible version of the Leonov model is employed. Two techniques to calculate flow-induced residual stresses are investigated. First, a direct approach is developed where the pressure problem is formulated using the viscoelastic material model. Second, generalized Newtonian material behavior is assumed in formulating the pressure problem, and the resulting flow kinematics is used to calculate normal stresses employing the compressible Leonov model. The latter technique gives comparable results, while reducing the computational cost significantly.