注塑成型充填阶段模拟中的黏度模型比较

Comparison of viscosity models for injection filling simulation

阐述了常用的热塑性塑料幂律模型、二阶模流模型、Cross模型和Carreau模型等黏性模型表达式和特点。利用仿真的方法得出不同模型下熔体的填充速度、剪切率、剪切应力与温度这4个参数随时间变化曲线,再利用试验的方法采样得到实测值。把仿真值和实验值相对比,得到不同黏性模型的适用场合。结果表明,幂律模型和Carreau模型描述熔体填充速度时比较准确,在填充初始时描述剪切应力和温度变化率时可应用二阶模流模型、Cross模型或Carreau模型,填充后期采用幂律模型更加准确。该结果为合理选取热塑性塑料注射成型CAE填充模拟时材料的黏性模型提供了依据。

The representation and features of viscosity models for thermal plastics, including power law model, second order Moldflow model, Cross and Carreau models, were described. Simulation was conducted to fit the curves of filling velocity, shear rate, shear stress and temperature versus time. Measured data were obtained via sampling experiment. The application of the viscosity models was discussed by comparisons between the theoretical and measured data. The results show that the power law model and Carreau model can describe the filling velocity more precisely; that the second order Moldflow model, Cross model or the Carreau model can better describe the shear press and the temperature gradient at the initial filling; that the power law model works well in the latter period. The result can serve as referenc for the selection of viscosity models in filling simulation.