TC4钛合金动态力学性能及本构模型研究

摘要

为研究 TC4钛合金的动态力学性能及本构模型，利用电子万能试验机、高速液压伺服试验机和分离式Hopkinson 压杆（SHPB）装置，对其进行常温下准静态、中应变率和高应变率动态力学性能试验，得到不同应变率下的应力应变曲线，拟合得到 Johnson-Cook 本构模型，并分析材料中应变率力学特性对本构模型参量的影响。结果表明：TC4钛合金在应变率10－4~103 s －1范围内具有明显的应变率强化效应和一定的应变硬化效应，且应变率强化效应随应变的增大而减小，应变硬化效应随应变率的增大而减小；考虑材料中应变率力学特性可提高本构模型参量的准确性；通过数值方法和试验方法研究 TC4钛合金平板撞击和高速拉伸过程的动态响应，两者结果具有很好的一致性，证明所得本构模型的准确性。%In order to study the dynamic mechanical property and constitutive model of TC4 titanium alloy, dynamic experiments on TC4 titanium alloy under quasi-static,intermediate strain rate and high strain rate were performed by using an electronic universal testing machine,a high velocity hydraulic servo-testing machine and a split Hopkinson press bar (SHPB)at room temperature.The stress-strain curves under different strain rates were obtained,and a Johnson-Cook constitutive model was fitted.The dynamic mechanical property under intermediate strain rate and its effect on the constitutive model were analyzed.The experimental results show that the strain rate strengthening effect and strain hardening effect of TC4 titanium alloy are obvious,when the strain rate is between 10 -4~10 -3 s -1 .The strain rate strengthening effect decreases with the increase of strain,and the strain hardening effect decreases with the increase of strain rate.Moreover,considering the mechanical property under intermediate strain rate can improve the veracity of the rate sensitive parameters in the constitutive model.Good agreement is obtained between the experimental results and the numerical predictions of the dynamic responses in high speed tensile and ball impact processes,which validates the accuracy of the Johnson-Cook constitutive model.