低压铸造铝合金轮毂模具热变形的数值模拟

Numerical Simulation of Thermal-deformation of Molds for Low Pressure Die-casting Aluminum Alloy Wheel Hubs

目的针对模具高温变形影响低压铸造铝合金轮毂尺寸精度的问题,通过数值模拟和实验相结合的方式,揭示低压铸造过程中模具的变形规律。方法建立了低压铸造过程中描述模具热力学行为的数学模型以及铸造多循环计算方法,进行了轮毂低压铸造实时蓝光扫描验证,通过模拟与实验结果的对比验证,研究了轮毂低压铸造过程中的模具温度、应力及变形规律。结果模拟与实测温度对比结果表明,两者变化趋势基本一致,侧模和下模在开模时刻的最高温度分别为486℃和512℃。侧模的模拟与实测温度峰值的相对误差为2%,下模模拟与实测温度最大相差23℃。变形模拟与实时扫描结果均表明,侧模热变形呈曲率减小趋势,按变形大小划分,侧模型腔表面存在小变形(-0.04-0.16mm)、过渡(0.16-0.48mm)和大变形(0.48-0.89mm)3个变形区域,侧模变形的模拟精度约80%;下模平面沿轮毂轴向下沉0.4mm,变形模拟精度约75%。结论所建立的热变形模拟方法可以较好地计算铝合金铸造模具热变形,阐明铝轮毂低压铸造模具变形规律,为后续模具反变形设计、提高轮毂尺寸精度提供研究基础。

The work aims to reveal the rule of mold deformation during low pressure die casting process with numerical simulation and experiment to solve the effect of high-temperature deformation of the mold on the dimensional accuracy of low pressure die casting(LPDC)aluminum alloy wheel hubs.A numerical model on thermodynamic behavior of the mold during low pressure die casting was established,and a simulation method for casting cycles was proposed.The real-time blue laser in-spection verification of low pressure wheel hub casting was carried out.The mold temperature,stress and deformation rule dur-ing low-pressure wheel hub casting were studied by comparing the simulation and experimental results.The simulated and measured temperature trends were consistent with each other.The maximum temperatures of the lateral mold and the bottom mold at the moment of mold opening were 486℃and 512℃,respectively.The relative error between the simulated and meas-ured peak temperatures for the lateral mold was 2%,and the maximum difference between the simulated and measured tem-peratures for the bottom mold was 23℃.The simulation and inspection results showed that the thermal deformation of lateral mold showed a curvature decreasing trend.There were three deformation regions of small deformation(-0.04-0.16 mm),transi-tion(0.16-0.48 mm)and large deformation(0.48-0.89 mm)on the surface of the cavity of the lateral mold according to the de-formation size.The accuracy of deformation simulation for lateral mold was about 80%.The bottom mold plane was sunk 0.4 mm in the axial direction of the hub,and its simulation accuracy was about 75%.The established thermal-deformation simulation method can well describe deformation of aluminum alloy casting molds.The study shows the deformation rule of molds of LPDC aluminum wheel hubs,providing a research basis for the subsequent inverse design of mold deformation to im-prove dimensional accuracy of wheel hubs.