聚合物多层气辅共挤精密成型机制的数值分析

基于传统共挤成型技术，提出一种先进的气辅多层共挤精密成型技术。研究表明，气辅共挤成型技术不仅可实现挤出制品尺寸的精确自动控制，而且还起到明显的节能降耗的效果。通过建立的稳态有限元数值算法，对传统共挤成型和气辅共挤成型的成型过程和离模膨胀过程进行了系统的对比分析研究，并探讨了气辅共挤成型消除整体离模膨胀的机制。结果表明，多层共挤成型芯壳层熔体的离模膨胀是由黏弹性熔体的二次流动引起，主要取决于芯壳层熔体二次流动的方向与强度。熔体二次流动的方向与第二法向应力差的正负号有关，而熔体二次流动的强度则与第二法向应力差大小成正比。气辅共挤成型的气辅口模段可通过气垫膜层的壁面完全滑移作用，有效减小或消除芯壳层熔体的第一和第二法向应力差，使其二次流动消失，从而达到消除口模整体离模膨胀的目的。因此，气辅多层共挤精密成型技术能精确地控制共挤成型的复合产品最终外形和尺寸与挤出口模的形状和尺寸完全相同。此外，研究结果还表明气辅共挤成型的挤出压力相对传统共挤成型可降低约30%以上。

Numerical investigation on the mechanism of polymer multilayer gas assisted co-extrusion precision molding process

Based on the traditional co-extraction,an advanced multilayer gas assisted co-extraction precision molding technology(GACEPMT) was put forward.The research shows that GACEPMT can not only implement the automatic and accurate control of the product dimension,but also save energy.A comparative analysis on molding process and die swelling process of traditional co-extraction and gas assisted co-extrusion was implemented by the stable finite element numerical algorithm established.Based on the above analysis,th...