基于位错机制钛合金本构关系的目标参数识别及实验验证

Identification of Target Parameters and Experimental Verification for Dislocation-mechanics-based Constitutive Relations of Titanium Alloy

为描述钛合金在不同应变率下的复杂本构行为,基于细观塑性变形机理和位错动力学理论提出了一种钛合金粘塑性本构模型,并描述了模型各参数的物理意义及其与微结构特征量之间的关联性。该本构模型含有12个待定参数,为降低参数识别计算量,提高参数识别效率和精度,提出了一种基于拉丁超立方抽样、Spearman秩相关分析的参数敏感度整体分析方法,并在参数敏感度分析结果和基本遗传算法的基础上,建立了一种基于改进小生境算法、全局最优点判断策略和局域精确搜索技术的改进遗传算法。最后以Ti-6Al-4V钛合金为算例,描述了其在不同应变率、温度下的单轴流变应力塑性应变曲线,数值模拟和已有的实验数据吻合良好。

In order to analyze the complex constitutive behavior of titanium alloy under different strain rates,a new titanium alloy viscoplastic constitutive model was proposed based on the plastic deformation mechanism and the dislocation dynamics theory. The relationship of model parameters and micro structure characteristics,as well as the physical significance were described. As the constitutive model contains 12 undetermined parameters,the identification of parameters would be computationally expensive. An overall analysis method of parameter sensitivity based on the latin hypercube sampling（ LHS） method and spearman rank correlation method was developed,which is effective and accurate enough in identifying parameters. Furthermore,on the fundamental of the analytic result of parameter sensitivity and basic genetic algorithm（ GA）,an advanced genetic algorithm based on the advanced niche genetic algorithm,global peak value determination strategy and local accurate searching techniques was developed. Finally,taking Ti-6Al-4V alloy as example,the single axis flow stress-plastic strain curve of this alloy under different strain rates and temperatures was described,and the results of numeric simulation agree very well with experiments from the existed reference.