气辅共注射成型充填过程数值模拟中的移动界面追踪技术

气辅共注射成型工艺的充填过程中存在多个移动界面。为能对充填过程进行有效的模拟,针对凝固层界面、表层熔体前沿、内层熔体前沿和气体穿透前沿推进的特点,采用不同的方法实现其追踪。模拟结果与实验结果比较表明,该方法简单有效,能够较准确地预测内层熔体前沿的位置,而要更准确地预测气体穿透前沿的位置,还要进一步考虑注气延迟时间和保压冷却阶段气体在熔体中的“二次穿透”。

Technology on tracking the moving interfaces in the numerical simulation of the filling stage of gas-assisted co-injection molding process

There exist several flow fronts during the filling stage of gas-assisted co-injection molding process. In order to simulate the filling stage of GACIM effectively,the advancements of solid/liquid,skin polymer/air,skin/core polymers and core polymer/gas interfaces are tracked by different ways in which the freezing polymer is considered as a flow whose viscosity is 105 times of the melt viscosity and the air and gas are considered as a fictitious fluid that does not contribute to the pressure drop in the mold and their viscosities are 1/1000 of melt viscosity. The simulated distribution of core polymer shows reasonably good coincidence with experimental observation. But the simulated distance of gas penetration is shorter than the experimental result for the consideration of delay time and “the second gas penetration” occurred during the post-filling stage absence. Further investigation of post-filling stage of gas-assisted co-injection molding process is required.