塑料注压成型流动诱导应力演化机理及预测方法研究

To overcome the predicting difficulty of flow-induced stress after injection switching to compression, Bird configuration tensor simulation, infrared spectrometer analysis and birefringence experiments are firstly carried out to explore the relationship between flow-induced stress and molecular orientation, reveal the micro mechanism of stress evolution, and construct the fundamental formulas of rheological parameters such as relaxation time as a function of molecular orientation. Then propose the constitutive equation including shear rate derivative to describe the abrupt increase of compressing force during compression start and end stages so as to master the law of flow-induced evolution. Furthermore, the steady and convergent numerical method for the viscoelastic flow problem in injection-compression molding will be proposed to predict the flow-induced stress through comparing the adaption and computation efficient of streamline up-wind, viscoelastic split and iteration methods. The impact, extension and light transmission tests will be carried out to further investigate the dependence of mechanical, optical properties on flow-induced stresses. Combining numerical simulation and injection-compression molding of typical parts to disclose the relationship between flow-induced stress and mold structures and process conditions, and design the mold structures and process conditions for low stress plastic parts with injection-compression molding. The results of this project will serve as the theoretical basis and analysis tool for the high performance optical parts, for example the integral cockpit canopy of new generation battleplane, molded with injection-compression.

针对注射转压缩后流动诱导应力难以预测问题，开展Bird分子构象张量模拟、红外光谱分析及双折射实验探索流动诱导应力与分子取向的依赖关系，揭示应力演化的微观机理，进而构建松弛时间等流变参数与取向度的函数关系；提出带有剪切速率导数的黏弹本构模型以描述压缩开始和结束阶段压缩力突增现象，掌握注压成型流动诱导应力的演化规律；研究求解黏弹性流动问题流线上风、黏弹分裂、迭代等数值方法对移动边界问题的适应性和计算效率，构造收敛范围大、稳定性好的注压成型流动应力求解方法，预测流动诱导应力。开展冲击、拉伸、光透射等实验进一步探索流动诱导残余应力与力学、光学性能的关系。再结合典型件注压成型实验揭示流动诱导应力与模具结构、加工工艺之间的内在联系，提出低应力制品注压成型的模具结构与加工工艺，为新一代战机整体座舱盖等高端光学制品注压成型加工提供理论支撑和分析工具。

针对注射转压缩后流动诱导应力难以预测问题，开展了压缩流变实验和材料微观结构演化实验，建立了黏弹性流体注射压缩过程的控制方程，提出了计算应力的修正Phan-Thien–Tanner模型，导出了应力随Weissenberg数变化的物质函数；基于任意拉格朗日—欧拉原理构造了包含移动网格信息的物质导数，提出了双重迭代方法求解黏弹性流动的数值算法，并用经典4:1收缩流动问题验证了算法的有效性，为注压成型一体化建模、分析及后续的软件开发奠定了理论和算法基础，扩展了传统注射成型工艺模拟方法。开展了实际制品的注压成型实验，发现了注压成型过程中应力随温度、压力、保压时间等工艺条件的变化规律以及压力在成型周期内的演化趋势，实验结果表明建立的方法较好地预测了压缩开始阶段的应力突增现象（误差<6%），与传统方法相比模拟精度提高1倍以上。.基于项目的理论和算法成果开发了注压成型一体化模拟软件，以此为平台结合大型塑料件成型特征为中国船舶重工集团公司第七一三研究所开发了用于低压注射成型的“注塑模拟分析软件”；结合橡胶轮胎成型特征，为中国化工集团曙光橡胶工业研究设计院有限公司开发了“橡胶轮胎成型仿真软件”；将项目的数值计算技术与流变实验相结合，为合肥华凌股份有限公司开发了“黏性模型参数拟合软件”，获得了总计146万元资金资助。.获得发明专利2项、软件著作权2个，在Journal of Non-Newtonian Fluid Mechanics、中国科学等中外学术期刊发表学术论文10篇，参加学术会议4人次，毕业博士研究生1名，硕士研究生8名。