Ti-6Al-4V钛合金型材电热拉弯成形极限仿真方法

FEM of forming limit in electric-thermal stretch bending for Ti-6Al-4V titanium alloy profile

针对电加热拉弯成形工艺,建立了电热拉弯过程顺序耦合的数值模拟方法,实现了电热转台式拉弯成形过程的多工序、多场耦合数值模拟。并选用动力显式热-力耦合分析算法,基于J-C断裂准则,建立了电热拉弯成形极限与断裂预测的三维实体模型。通过Ti-6Al-4V钛合金挤压T型材电热拉弯成形试验与仿真预测结果比较发现:电热拉弯成形过程中,材料的失效主要发生在预拉伸和补拉伸阶段,失效原因为拉伸力过大;电热拉弯成形极限的主要影响因素包括加热温度或电流密度、预拉力、补拉伸过程温度或冷却时间和补拉力;预拉伸和补拉伸极限应力的预测相对误差分别为19.7%和19.1%,验证了模型的有效性。

For the electric-thermal stretch bending of titanium alloy,a numerical simulation method of sequential coupling of electro-thermal stretch bending process was established,and a multi-process and multi-field coupling numerical simulation process of electro-thermal stretch bending with turntable was realized. Then,the dynamic explicit thermal-mechanical coupling analysis algorithm was selected based on J-C fracture criteria,and a 3D model predicting the forming limit and fracture of electro-thermal stretch bending was built. Comparing the experimental result with simulation result of extrusion T-type profile for Ti-6Al-4V titanium alloy,it is found that the failure of material in the electric-thermal stretch bending process is mainly because of the excessive tensile force on the pre-stretching and post-stretching stages. Therefore,the main factors influencing on the forming limit of electric-thermal stretch bending are the heating temperature or current density,the pre-stretching force,the temperature or cooling time of the post-stretching process and the post-stretching force. Furthermore,the predicted relative errors of limit stress for the pre-stretching and post-tensioning are 19. 7% and 19. 1% respectively,and the effectiveness of model is verified.