聚合物挤出成型模流平衡系数修正

挤出模具的合理设计对于获得挤出产品所需的外形和精确的尺寸非常重要。由模流不平衡引起的,伴随着挤出胀大产生的不均匀的几何形变,是挤出模具设计的难点所在。传统的模流平衡系数需要对截面进行子区域划分,但是对于截面形状较为复杂的异型材制品,子区域划分具有较强的不确定性。对传统的聚合物挤出成型的模流平衡系数进行修正,提出更有利于数值计算和理论研究的修正的模流平衡系数,并用数值方法对其进行验证。修正后的模流平衡系数消除了数值分析过程中挤出速度和模具出口截面积对模流平衡判断的影响,在产品形状一定时,模流平衡系数只和材料本构相关,因此可以比较准确地反映模具出口的模流平衡情况。修正后的模流平衡系数主要应用于逆向挤出和优化设计求解口模形状。

Mold-flow Equilibrium Coefficient Correction of Polymer Extrusion

The reasonable design of the extrusion die is essential for the required shape and precise dimensioning of extrusion products.Uneven geometrical deformation as occurring in extrusion swelling,which is caused by the unbalance of mold flow,is one of the difficult points in the design of extrusion die.The traditional mold-flow equilibrium coefficient needs to sub-divide the cross section of flow,which have high uncertainty for complex plastic profiles.Mold-flow equilibrium coefficient for traditional polymer extrusion is modified,and a modified mold-flow equilibrium coefficient which is efficient for numerical calculation and theoretical investigation is proposed,which is validated by numerical simulation.The modified mold-flow equilibrium coefficient has eliminated the influence of the extrusion speed and outlet cross-sectional area in the numerical analysis process.It is only correlated to material constitutive if the shape of the product is certain,therefore can more accurately reflect mold flow balance out of the outlet.The modified mold-flow equilibrium coefficient is mainly used in the reverse extrusion and design optimization for solving the shape of the die.