水辅助注塑中高压水穿透过程的数值模拟

对水辅助注塑(WAIM)中高压水的穿透过程进行有限元模拟,研究熔体的充模行为,并分析其拉伸场和剪切场。结果显示,高压水推动熔体充模的过程可分为填充初期、快速填充期和填充末期3个阶段;较明显的拉伸应变速率仅出现在高压水前沿和熔体前沿区域;高压水前沿区域存在分布较宽且较为强烈的剪切速率,而高压水对已穿透区域的熔体几乎没有剪切作用。此外,模拟所得WAIM制品的穿透长度和掏空率与实验结果较吻合。

Numerical simulation of water penetration in water-assisted injection molding

The process of high-pressure water penetration in water-assisted injection molding (WAIM) was simulated based on the volume of fluid method, and the filling behavior of polymer melt as well as the elongation and shear fields were studied and analyzed.The simulated results showed that the process of melt filling propelled by high-pressure water was divided into three stages, namely, initial filling, fast filling, and terminal filling stages.Remarkable elongational rate was only present in the regions near both water and melt fronts.Widely-distributed and high shear rate was present in the region near the water front, whereas water had little shear effect on the melt in the water-penetrated zone.The simulated penetration length and hollow rate of the WAIM part matched well with the experimentally determined ones.