There are two kinds residual stress of injection molded parts

flow residual stress and thermal residual stress.A numerical simulation model for predicting thermal residual stress which arises during the injection molding of thermoplastic polymer in the cooling stage is developed in this thesis.The temperature field is already calculated while calculating residual stress.The cooling polymer behaves as an isotropic thermorheologically simple solid

and a fully time-dependent algorithm is based on the calculation of the elastic response at each time step.The recurrence formulae for calculating time-dependence stress of two-dimensional integral thermoviscoelastic constitutive equations are established

and then FEM formulae can be derived.The finite element method employed is based on the theory of shell as an assembly of flat elements.This method is well suited for thin injection molded products of a complex shape.A calculation example is given

while considering the effects of cooling efficiency and resin melt temperature.The predicted residual stress by the method used in this thesis agrees with the literature data.