焊接数值模拟材料新模型的建立及应用

Establishment and application of material models for numerical simulation of welding process

在焊接数值模拟中建立了材料性能依赖于温度及温度过程并考虑加工硬化效应的材料新模型,从而可以更加真实地研究焊接过程中应力应变的变化,并更准确地预测焊后残余应力和应变的分布.热力模拟试验结果表明,从热循环峰值温度至室温的冷却过程中,铝合金5A06材料性能变化遵循一系列不同于加热过程的曲线.考虑加工硬化效应后,焊接热循环过程中不同的屈服应力变化过程,导致了不同的纵向残余应力演变历程.考虑焊接热循环历史对材料性能影响,经历了较高温度焊接热循环以后,焊缝区金属的性能有所降低,焊缝区金属的纵向压缩塑性应变在冷却过程中的恢复程度大于常规模型,最终导致焊缝附近残余拉应力水平低于常规模型.

Temperature and temperature history dependent material model and temperature history dependent work hardening model were established based on the thermal-mechanical experimental results.The results of thermal-mechanical experiments indicated that material properties of aluminum alloy 5A06 during the cooling stage of typical thermal cycles followed one set of curves,which were different from those during the heating stage.The established models were applied in numerical simulation to study the evolution of stress during welding process more actually and predict the distribution of residual stress more accurately.Taking the work hardening effect into consideration,the different evolutions of yield stress led to the different evolutions of longitudinal stress.Yield stress of the material at the weld zone decreased a lot after having experienced weld thermal history and longitudinal compressive plastic strain at the weld zone recovered to some extent during the cooling stage.These are the main cause for the lower peak longitudinal residual tensile stress in history dependent models.