【作者】 李赞；

【导师】 周华民；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2013， 硕士

【摘要】 注塑成型是最高效的塑料产品成型方法之一，良好的温度调节系统对生产周期和最终产品质量有着重要影响。注塑冷却过程的准确建模与模拟对优化模具冷却系统设计、后续热应力与制品翘曲分析具有重要意义。传统的稳态冷却分析不能满足周期温度波动范围大的注塑工艺模拟要求，本文围绕注塑模三维瞬态分析模型的建立和实现开展了研究。本文首先对注塑过程中换热系统的热平衡和热流进行了分析，对注射成型不同阶段的热物理边界进行了讨论，重点考虑型腔壁面和塑料制件的接触热阻建模，提出了注塑过程中冷却阶段、开模阶段和加热阶段的分析模型和边界处理方法，建立了基于有限元方法的具有多工艺适应性的三维瞬态分析模型。基于ANSYS实现了注塑过程三维瞬态传热分析，并与Moldflow常规模具瞬态温度场结果进行了对比，验证了分析模型的正确性。在此基础上，实现了快速热循环模具（RHCM）的瞬态温度场建模与模拟，分析案例表明，由于RHCM模具材料导热系数大，型腔边缘与中心存在20℃左右温差，文献采用中心截面的二维模型预测的加热时间比三维模型短10%左右，复杂、精密RHCM模具应采用三维分析模型；接触热阻大大降低了热传导效率，冷却时间增长12.8%以上，为提高效率，可从工艺方面考虑减小热阻。开发了注塑过程三维瞬态传热模拟模块，解决了矩阵总装，时间域离散，混合边界处理等问题。由于塑件和模具的温度是不断变化的，对动态变化接触边界提出了在每个时间步长进行映射处理的方法。通过计算模具加热和模具/制品耦合冷却案例，并与ANSYS结果对比，验证了程序计算的准确性。更多还原

【Abstract】 Plastic injection molding is one of the most efficient processing methods for plasticproducts. The temperature regulation system has an important influence on the productioncycle and the product quality. The accurate simulation of the temperature field is of greatimportance for cooling system optimization and the subsequent thermal stress and warpinganalysis. The traditional steady cooling analysis is not suitable for injection process in whichthe temperature oscillates in a big range. This paper researches on modeling and analysis ofthree-dimensional transient heat transfer for injection mold.The paper analyzes the heat balance and heat flow of the heat transfer system forinjection mold, and discusses the thermal boundary conditions of different injection processstages at first. The model of the contact thermal resistance (TCR) between cavity wall andplastic parts of the contact thermal resistance is established, the treatment of the boundaryconditions for the cooling stage, ejection stage and heating stage is presented. Then themodel of the3D transient heat transfer analysis is proposed, which is based on the finiteelement method and suitable for more plastic process.The analysis of3D transient heat transfer for injection molding is realized with ANSYS.Compared with the transient temperature field of a regular mold calculated by Moldflow, theanalysis model is proved to be correct. What’s more, the analysis model of the rapid heatingcycled mold (RHCM) is established. The simulation results show that the temperaturedifference between the edge and the middle area of the cavity wall is about20℃because ofthe relative large thermal conductivity coefficient of the mold. Complicated and precisemold should be analyzed with3D model as the predicted heating time is about10%shorterusing2D model. TCR reduces the efficiency of heat transfer a lot and the cooling time rises12.8%as a result. So it’s recommend that minimizing TCR by changing process parametersis a good way to improve efficiency.The module of the3D transient heat transfer simulation for injection mold ispreliminarily developed. Matrix assembly, dispersion of the time and treatment of the mixedboundaries are realized. As the temperature of the mold and the plastic part changed with the time, we have to map the part temperature to the mold on the contact area at every sub step.Compared with the result calculated with ANSYS, the heat transfer process analyzed by themodule is accurate.更多还原