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应用有限元方法研究了微注射成型中瞬态、可压缩、非牛顿熔体流动的黏弹性对流动前沿及流动平衡的影响。基于Phan-Thien-Tanner模型建立了熔体流动的本构方程,利用Hele-Shaw假设和简化建立了瞬态、可压缩、非牛顿熔体流动的连续性方程、动量方程、能量方程;为了有效地描述微注射成型的尺寸效应,采用了边界滑移和表面张力边界条件。通过分部积分和待定系数法导出了带有边界信息的变分方程和求解应力分量的半解析公式,构造了有限元离散求解及超松驰迭代算法。模拟结果表明:熔体的黏弹性对浇口附近的压力和后续的熔体流动前沿有重要影响;与黏性模型相比,黏弹性模型可以控制模拟压力的快速增长,减少不同型腔之间的充填差异,与短射实验结果也更吻合。
The influence of viscoelasticity on flow front and flow equilibrium of transient, compressible and non-Newtonian melt flow in microinjection molding was studied by finite element method. Based on the Phan-Thien-Tanner model, the constitutive equation of melt flow is established. The continuity, transient and energy equations of transient, compressible and non-Newtonian melt flow are established by the Hele-Shaw assumption and simplification. Describe the dimensional effect of micro injection molding, using the boundary slip and surface tension boundary conditions. The variational equations with boundary information and the semi-analytical formulas for solving the stress components are derived by the method of integral integral and undetermined coefficient method. The discrete finite element method and over-relaxation iterative algorithm are constructed. The simulation results show that the viscoelasticity of the melt has an important influence on the pressure near the gate and on the front of the subsequent melt flow. Compared with the viscous model, the viscoelastic model can control the rapid growth of the simulated pressure and reduce the difference between the different cavities The difference between the filling and short-shot experiment results is more consistent.