基于M-K模型的TA15钛合金高温成形极限

In order to investigate the forming limit of TA15 titanium alloy at high temperature and clarify the influence of parameters in the constitutive equation on the forming limit, the constitutive relationship of TA15 titanium alloy in high temperature environment was established considering the high temperature softening phenomenon, and meanwhile, the forming limit of TA15 titanium alloy plate at high temperature was obtained by high temperature forming limit test platform and theoretical predicted through applying the M-K instability theory, respectively. The theoretical results indicate that the major strain under the plane strain state increases from 0.18 to 0.33 when the temperature increases from 800℃ to 880℃. Based on the M-K instability theory and the established high temperature constitutive model, the influence of the parameters in the constitutive equation on the forming limit is analyzed. The results show that, increasing the values of hardening index and the rate sensitivity factor, and decreasing the value of the softening factor can increase the strain hardening rate, and consequently the strain state in the groove region is delayed approaching the plane strain state. Therefore the position of the forming limit curve in strain space is improved. At the same time, the theoretical calculation results show that the influence of the strain rate sensitivity factor on the left side of the forming limit curve is greater than that on the right side, and it is attributed to the fact that the effect of the strain rate sensitivity factor on the strain hardening rate under different strain size is different.