Ti-6Al-4V合金动态本构模型参数敏感性及其优化

Parameter Sensitivity and Optimization for Dynamic Constitutive Relationship of Ti-6Al-4V Alloy

由于未考虑参数敏感性,经典的5参数Johnson-Cook模型在描述Ti-6Al-4V合金的动态力学响应时,会萎缩为少于5参数的模型。此外,该模型未考虑参数的耦合效应,一组参数仅仅需要在特定应变率和温度条件下的一条实验曲线就可以拟合得到,而所得参数在预测其他条件下的实验曲线时会遇到挑战。首先通过拉丁超立方抽样和Spearman秩相关分析理论结合的方法,对经典Johnson-Cook模型进行参数敏感度分析,得出5参数敏感度相当的合理取值范围并将其作为初始搜索区间。然后结合遗传算法对5个材料参数进行全局最优搜索,得到考虑5参数相互耦合变化的优化值。优化后的模型能够较好地预测Ti-6Al-4V合金在低应变率、不同温度下的应力-应变关系。此外,采用上述方法,并将材料参数考虑为温度的函数,预测了高应变率、不同温度下Ti-6Al-4V合金的力学行为,结果与实验值吻合。

Since the parameter sensitivity is not considered, the classical 5-parameter Johnson-Cook model will reduce to less than 5 parameters when describing the dynamic mechanical response of Ti-6Al-4V alloy. Besides, as the classical Johnson-Cook model does not consider the coupling effect between various parameters, and a set of parameters is obtained from only one curve under a specific strain rate and temperature, such parameters will encounter challenges when predicting other experimental curves under different strain rate and temperature conditions. Firstly, the sensitivity of parameters in the classical Johnson-Cook model is calculated by Latin hyper-cube sampling method and Spearman rank correlation analysis theory, then the reasonable range in which the 5 parameters have equivalent sensitivities are obtained. Taking the range as the initial search range, the global optimal search is applied by the genetic algorithm, and optimal 5 parameters are the results considering the coupling effect between parameters. The optimized model predicts the stress-strain relationship of Ti-6Al-4V alloy in low strain rate, different temperature conditions quite well. In addition, when parameters considered as functions of temperature, the behavior under high strain rate and different temperature is also predicted. And the predicted results agree with the experimental data.