T型口模气辅段长度对挤出胀大的影响

摘要

T-shape die extrusion model was simulated by fluid finite element analysis software polyflow. The melt velocity field and pressure field in the die was studied,and combined with the melt velocity field and pressure field,the effect of gas-assisted length on extrusion swell was emphatically analyzed. The result show that the melt flow velocity in the gas-assisted section of the gas-assisted extrusion is basic consistent . The maximum pressure in gas-assisted extrusion is far less than that in ordinary extrusion, the internal stress of the melt is smaller. When the gas-assisted length is 10~30 mm,the extrusion swell ratios are reduced greatly as the gas-assisted length increasing. When the gas-assisted length is more than 30 mm,the extrusion swell ratios change little and gradually trended to 1 as the gas-assisted length increasing. Therefore,the gas-assisted length should be set according to the need in die design.%用流体有限元分析软件Polyflow对T型口模挤出模型进行模拟，研究了口模内熔体的速度场和压力场，并结合熔体的速度场、压力场，着重分析了气辅段长度对挤出胀大的影响。研究发现，在气辅挤出的气辅段中，熔体的流动速度基本趋于一致；气辅挤出口模内熔体的最大压力远小于普通挤出，熔体内应力更小；当气辅段长度为10～30 mm时，挤出胀大比随气辅段长度的增加大幅度减小，当气辅段长度超过30 mm时，挤出胀大比随气辅段长度增加变化微小且逐渐趋于1。设计口模时，应根据需要设定合理的气辅段长度。