挤出平缝口模优化设计

挤出平缝口模通常用于加工膜和片材，对产品厚度的一致性有很高要求。本文给出了结合聚合物成型模拟技术、设计灵敏度分析和数值优化技术的口模形状优化设计方法。以最小压力降为目标函数，口模出口处任意点的速率与出口已知速率相对误差的平方和小于容许误差为约束函数，口模形状参数为优化设计变量，给出了目标函数的表达式，推导了日标函数、约束函数对优化设计变量的灵敏度公式。利用灵敏度分析和基于梯度的优化算法即序列二次规划算法(SQP法)求解最优设计参数。通过算例表明，应用该法进行口模优化设计可以减小压力降和口模出口速率变化率。

Optimal design for polymer sheeting dies

Polymer sheeting dies are commonly used for the extrusion of plastic sheets and films. The key of designing sheeting dies is the invariance of distribution to flow rate on the exit. In this paper an optimal design approach for polymer sheeting dies was developed which combines polymer process modeling, design sensitivity analysis and numerical optimization. A nonlinear constrained optimization problem was put forward which minimizes the inlet pressure P_(in) subject to a constraint on the exit velocity variation. Analytical design sensitivities were derived to quantify the relationship between design parameter, cost and constraint functions using direct methods. The analytical design sensitivities are combined with a sequential quadratic programming (SQP) algorithm to systematically traverse the design space towards the optimal values. An example shows that using this method can obtain a uniform velocity profile across the die and minimize pressure drop.