充模过程中熔接痕的改进光滑粒子动力学方法模拟与预测

提出了一种黏弹性流体的改进光滑粒子动力学(SPH)方法以试探性地模拟和预测黏弹性FENE-P熔体充模过程中熔接痕的形态演化. 首先基于SPH方法建立了聚合物流动的宏微观耦合模型, 同时提出了黏弹性流体的改进SPH离散格式. 随后, 通过模拟一些基准算例验证了改进的SPH方法模拟聚合物宏微观耦合问题的有效性及收敛性, 以及所提出的黏弹性温度模型的有效性. 最后, 模拟了环型腔内的充模过程, 试探性地展示了充模过程中微观分子的变形过程. 同时采用顺序热流道技术模拟了多浇口C形腔内的充模过程, 并与其他数值结果做比较. 数值结果表明: 对于大制件多浇口充模过程, 顺序热流道技术能够改善甚至消除充模过程中的熔接痕.

Simulation and prediction of the weld-line in the filling process using a corrected smoothed particle hydrodynamics method

A corrected smoothed particle hydrodynamics (SPH) method for viscoelastic fluid is proposed and used to tentatively simulate and predict the behavior of the molecule near the weld line in the filling process of the FENE-P fluid in this paper. And the corrected SPH scheme for the viscoelastic fluid is simultaneously presented. Firstly, a coupled macro-micro model based on the SPH method for the viscoelatic fluid is set up. Then, some benchmarks, such as the flow behavior of the periodic cylinders of FENE-P fluid and the non-isothermal Poiseuille flow based on the Oldroyd-B model which is a simplified model of FENE-P model, are simulated to verify their validity and the convergence of the corrected SPH method of solving the coupled macro-micro problem of the polymer and the discrete SPH temperature model for viscoelastic fluid. Finally, the filling process of the viscoelastic fluid based on the FENE-P model in a ring-shaped mold is simulated, and the behavior of the micro molecules in the filling process is tentatively shown by orientation ellipse. Meanwhile the non-isothermal filling process of the FENE-P fluid is also implemented. The numerical results show clearly the behavior of the molecules in the filling process of the FENE-P fluid, the weld line is indeed observed in the filling process of the FENE-P fluid in the ring-shaped mold, and the non-isothermal filling process can improve the weld line to some extent. In order to further discuss the improvement of the weld line, the filling processes of different cases are simulated in the multiple-gating C-shaped mold by using the pattern of the hot runner and valve gates, and the obtained results are compared with other available data. Moreover, the effect of the delay time needed for the fluid to be injected on the flow is also investigated. The numerical results show that the pattern of the hot runner and valve gates can improve and even remove the weld-line in the filling process of the polymer melt, especially for the big-sized product, and the shorter the delay time is, the faster the flow is, and the bigger the appearance probability of the weld line is.