基于数值模拟的气体辅助注射成型工艺参数优化研究

【作者】 张响；

【导师】 申长雨； 李倩；

【作者基本信息】 郑州大学 ， 材料加工工程， 2004， 硕士

【摘要】 气体辅助注射成型是20世纪70年代在传统注射成型基础上发展起来的一项新的塑料成型工艺。其过程是在向模具型腔内注射一定塑料熔体后，立即或稍后注射高压气体，以使塑料熔体在气体的推动下充满型腔。由于气辅成型引入气体而成为两相流动，增加了更多的工艺参数，如熔体预注射量、延迟时间、气体注射压力等，这些参数间的相互干扰和制约与传统注射成型相比更加明显。采用数值算法实现对气体辅助注射成型过程的模拟和分析，将为有效控制成型过程从而确保成型质量，提供一个以科学分析为基础的实用技术手段，对于提高气辅技术的应用水平具有重要的科学意义和应用价值。 本文针对气辅成型过程数值模拟及其工艺参数优化开展了研究和分析，主要工作包括： 1、从粘性流体力学的基本方程出发，通过对气／熔界面两相流充模过程物理量和几何变量的分析，建立了气辅成型充模过程气—熔两相非等温非稳态流动的控制方程。 2、基于有限元／有限差分／控制体积法，通过引入充填因子给出了求解气—熔两相流动的数值方法并开发出计算程序，实现了气辅充模过程的数值模拟。 3、推导一维圆管流动中熔体前沿等速推进的气体压力控制方程，得到在气体注射阶段使熔体前锋匀速推进的气体压力条件，并通过数值模拟进行了验证。 4、通过自制气辅模具开展了气辅实验研究，考察了不同工艺条件和参数对成型过程的影响，并对数值模拟结果进行了实验验证，取得了定性相符的结果。更多还原

【Abstract】 Gas assisted injection molding (GAIM) is an innovative multi-component injection molding developed on the basis of traditional injection molding in the 1970’s. In GAIM, the mold cavity is partially filled with the polymer melt, followed by the injection of compressed gas. The gas penetrates into the polymer melts and forces them to fill the whole mold cavity. GAIM can realize gas holding and packing, reduce shrinkage and warp-page, get the hollow products in the section, save materials, make mold designing more flexible.However more process parameters, such as melt injection percent in advance, delay time, gas inject pressure in the process, are included in GAIM because two phase flow happens at gas filling time. So how to predict gas penetration and the influence of parameters on GAIM products become the key problem before mould making. In this study, based on the molding filling principle and Theological theories, a mathematical model is established by using generalized Hele-Shaw flow of an inelastic and No-Newtonian fluid under non-isothermal conditions. A hybrid finite element/finite difference numerical scheme is applied to solve pressure field, temperature field, and velocity field etc. Control volume method is used to trace gas/melt interface and melt advancement. Polymer skin fraction and polymer filling fraction are used to describe the melt and gas distribution.The pressure control equation of constant flow front speed is deduced, the relationship between gas pressure and melt front speed was found, and controlequation were verified by numerical simulation.Experiments are investigated to study how various process conditions and parameters influence the process, and comparison results of experiments and numerical simulation verify the program.更多还原