气辅挤出口模中滑移段长度对压力降和第一法向应力差的影响

Influence of Slip Length of Gas-Assisted Extrusion Die on Pressure Drop and First Normal Stress

采用壁面滑移方程和EVSS/SUPG混合有限元方法,使用PTT流变学基本方程,对粘弹性高分子熔体在不同气体辅助挤出口模内的流动进行了数值模拟研究。考察了口模滑移段长度对压力降和第一法向应力差的影响。研究表明,气辅挤出可以有效减小压力降,并将应力集中的位置由口模出口处转移到气体的注入点。且随着滑移段长度增大,压力降和应力集中的程度得到减小;熔体在100%完全滑移段口模中流动时无流动阻力、压力降和应力集中现象,是一种理想流动状态。

Based on the Generalized Navier＇ s slip law and the mixed finite element methods of EVSS/SUPG （Elastic-Viscous Stress Split elastic/Streamline Upwind Petrov-Galerkin） , using lYFT rheological constitutive equation, a numerical simulation system describing the flowing visco-elastic polymer passes through different gasassisted extrusion （GAE） dies was established. By means of simulation, the effects of slip length on pressure drop and first normal stress were investigated. The result indicates that GAE can reduced the pressure drop and moved the local exit stress concentration to the point of gas injection. It is also observed that first normal stress and pressure drop can be largely decreased with the increase of slip length. Melt is an ideal flow in 100 percent full-slip GAE die when no movement of resistance, the pressure drop and stress concentration.