Prediction of residual flow and thermoviscoelastic stresses in injection molding

A general model for predicting the total residual stresses generated during filling and cooling stages of injection-molded parts has been developed. The model takes into account the phenomena associated with non-isothermal stress relaxation. The main hypothesis in our approach is to use the kinematics of a generalized Newtonian fluid at the end of the filling stage as the initial state for the calculation of residual flow stresses. These stresses are calculated using a single integral rheological model (Wagner model). The calculation of stresses developed during the cooling stage is based on a thermoviscoelastic model with structural relaxation. Illustrative results emphasizing the effect of both the melt temperature and the flow rate during the filling stage are presented.