(1. 中国工程物理研究院 总体工程研究所，绵阳 621999；
2. 四川大学 建筑与环境学院，成都 610065)
摘 要: 为描述Ti-6Al-4V(TC4)两相钛合金在高应变率、高温载荷条件下的复杂力学行为，基于细观塑性变形机理和位错动力学理论，从细观尺度构建一种两相钛合金粘塑性本构模型，并阐释各本构参数与微结构特征量之间的关联及其表征的物理意义。为确定本构参数并提高参数的识别效率与精度，提出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，建立基于改进小生境算法、可疑峰值点判断策略和局域精确搜索技术的改进遗传算法，得到了TC4两相钛合金的本构参数。采用应力补偿更新算法，通过显式用户子程序接口VUMAT将两相钛合金本构模型嵌入ABAQUS有限元软件中，实现了钛合金在高应变率、高温条件下动态本构行为的数值模拟。对比模拟结果与实验数据发现，所构建的本构模型描述材料高应变率条件下力学行为的准确性优于Johnson-Cook模型的。
关键字: Ti-6Al-4V；本构模型；位错动力学；VUMAT用户子程序
（1. Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621999, China;
2. College of Architecture and Environment, Sichuan University, Chengdu 610065, China）
Abstract:A new physically-based constitutive model of dual-phase Ti-6Al-4V alloy (TC4) was developed based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. The relationships among constitutive parameters and microstructure characteristics, as well as the physical meanings were illustrated. In order to determine the constitutive parameters and improve the efficiency and precision of parameters identification, an overall analysis method of parameter sensitivity based on Latin Hypercube Sampling (LHS) method and spearman rank correlation method was presented. Furthermore, the constitutive parameters of the material were determined by a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and local accurate searching techniques. By adopting a stress compensation updating algorithm, a subroutine VUAMT of the proposed constitutive model of dual-phase titanium alloy was programmed on plat of ABAQUS/Explicit. Then finite element simulation of dynamic responses of TC4 alloy under loading conditions of high strain rate and high temperature was investigated. The comparison results indicate that the proposed model is more suitable and accurately to describe the mechanical behavior of material subjected to high strain rate than Johnson-Cook model.
Key words: Ti-6Al-4V; constitutive model; dislocation dynamics; VUMAT user subroutine
