基于修正Johnson-Cook模型的钛合金热黏塑性动态本构关系及有限元模拟

Thermal-viscoplastic constitutive relation of Ti-6Al-4V alloy and numerical simulation by modified Johnson-Cook modal

为了准确描述钛合金在高应变率、高温载荷下的热粘塑性本构行为,以及因材料内部出现绝热剪切带而导致材料流变应力减小的定量关系,构造功热转换系数β与应变率?(5)之间的函数关系,提出一种基于修正Johnson-Cook模型的钛合金热粘塑性动态本构关系,并通过以最小二乘法为目标函数的局部搜索优化算法,对基于实验数据的本构参数进行快速优化识别。最后利用应力补偿更新算法,通过显式用户子程序VUMAT将热黏塑性本构模型嵌入ABAQUS软件中,得到Ti-6Al-4V钛合金在不同应变率、温度条件下的单轴动态应力-应变曲线。数值模拟结果与实验数据吻合良好,表明该修正模型能准确描述钛合金高应变率下的热黏塑性变形,可适用于各种应变率下钛合金本构行为的描述。

In order to accurately describe the thermo viscoplasticity constitutive behavior of titanium alloy under high strain rate and elevated temperature, a modified Johnson-Cook equation was proposed by constructing function of conversion coefficient about strain rate. And the quantitative relation between decreasing flow stress and adiabatic shear band appeared in the material was analyzed. All the constitutive parameters could be quickly identified by the local search optimization algorithm taking least squares method as the object function. By adopting a stress compensation updating algorithm, a subroutine VUAMT of the proposed constitutive model was programmed on plat of ABAQUS/Explicit. The finite element simulation of dynamic responses of Ti-6A1-4V titanium alloy under different strain rates and temperatures are obtained. The modified Johnson-Cook modal can accurately describe the thermo viscoplasticity dissipation due to good agreement between simulation results and experimental data. The subroutine VUAMT and applicability of constitutive description for titanium alloy under various strain rates were verified.