注塑件残余热应力的数值计算

注塑件残余应力主要有流动残余应力和残余热应力 ,文中主要考虑注塑件的残余热应力 .利用文中建立的二维积分型热黏弹本构方程的递推公式 ,推导了单元的有限元求解公式 .数值算例考察了冷却效率、熔体注射温度对注塑件残余应力的影响 ,得到的结论与文献中结论一致 .

NUMERICAL CALCULATION OF THERMAL RESIDUAL STRESS OF INJECTION MOLDED PARTS

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.