螺杆挤出过程中物料在线流变行为及其数值模拟

In-line Rheological Behaviors and Numerical Simulation of Material in Extrusion Processing

为研究发射药螺杆挤出成型工艺,采用硝化棉(NC)代料二醋酸纤维素(CDA)、通过狭缝流变仪研究了物料在螺杆挤出成型过程中的在线流变行为。结果表明,CDA溶液为一种非牛顿假塑性流体,提高加工温度有利于改善物料的流动性并降低机头压力。同时利用计算机辅助工程软件Polyflow对挤出机机头流道内物料的流变行为进行了数值模拟,选取Power模型,得到流道内物料的压力分布、剪切速率分布和剪切粘度分布,模拟结果与实验数据相近。模拟结果表明,螺杆转速增大,物料的剪切粘度降低,但同时增大了机头压力和压降速率,不利于发射药的质量和加工的安全性。CDA溶液挤出成型过程中在线流变行为及其数值模拟计算的研究,对发射药的连续挤出成型具有重要的指导意义。

The die rheometer is utilized to investigate the in-line rheological behaviors of CDA solution, as the substitute of NC, in extrusion processing. The experimental results demonstrate that CDA solution is a non-Newtonian pseudoplastic fluid, and the increase in processing temperature is in favor of improving the rheological behaviors of CDA solution. The finite element software Polyflow is provided for the numerical simulation of CDA solution in the die to get the distribution of pressure, shear rate and shear viscosity. A power model is applied as the constitutive equation. The data calculated by the numerical simulation is close to the results obtained from the experiment. Polyflow indicates that the higher screw speed not only decreases the viscosity but also increases the pressure and pressure drop rate which is disadvantageous to the quality and processing security of propellants. The experiment and numerical simulation of the in-line rheological behaviors of CDA solution have the guiding significance for the continuous processing of gun propellants.