工业纯钛在中低温下的Fields–Backofen和改进型Johnson-Cook方程

Fields–Backofen and a modified Johnson-Cook model for CP-Ti at ambient and intermediate temperature

摘要:

通过单轴拉伸试验研究工业纯钛在283K至573K下应变速率范围为0.00005s_-1~0.005s_-1的流动应力行为。基于Fields–Backofen 方程,确定工业纯钛应变速率敏感性及应变强化指数随温度的定量变化。结果表明：工业纯钛的应变速率敏感性在283K-423K不显著,应变强化指数在353K-573K随温度变化而增加。基于温度变化的修正型Fields–Backofen 方程,建立了能够描述工业纯钛塑性流动应力行为的数学模型。同时,考虑应变、应变速率及温度之间的相互作用,对传统的Johnson-Cook 方程进行改进。与传统的Johnson-Cook 方程相比,改进型的Johnson-Cook 方程与实验结果吻合更好,证明改进型Johnson-Cook 方程预测工业纯钛塑性流动应力的精确性。

Abstract:

The flow stress behavior of commercial pure titanium (CP-Ti) was studied by uniaxial tension tests at temperatures ranging from 283SK to 573SK and strain rates from 0.00005-0.005s_-1. The tensile properties of CP-Ti was investigated to determine the quantitative variation of the strain rate sensitivity and the strain hardening by temperature based on Fields–Backofen (FB) model. The results indicates that the strain rate sensitivity of CP-Ti at 283K-423K is not obvious and strain hardening index increases with temperature at 353K-573K. A mathematical model using an updated FB equation based on temperature changing was established to describe the plastic flow stress behavior of CP-Ti. Meanwhile by considering the coupled effects of strain, strain rate and temperature, a modified Johnson-Cook(JC) model was proposed to predict the flow behavior. Compared with the original JC model, the modified JC model shows more agreement with the experimental stress, which validates the accuracy of the modified model describing the plastic flow stress of CP-Ti.