Chen Xuewen, Yang Zhen, Zhang Bo, Sun Jiawei, Su Zhiyi, Mao Yiran
School of Materials Science and Engineering, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang 471023, China.
Materials (Basel). 2023 Jul 1;16(13):4770. doi: 10.3390/ma16134770.
Ti6AL4V alloy is widely used in the biomedical and energy vehicle industries, among others. Ti6Al4V alloy cannot be fabricated at ambient temperatures; hence, it requires hot forming. However, this method is susceptible to crack defects. The crack defect problem of Ti6AL4V alloy in the hot-forming process cannot be ignored, so we must develop a precise hot-forming damage prediction model. In this study, three high-temperature damage models of Ti6Al4V alloy were developed, considering the temperature and strain rate. These models were derived from the normalized Cockcroft and Latham (NCL), Oyane, and Rice and Tracey (RT) damage models. The damage parameters of the models were identified using a genetic algorithm combined with finite element simulation. The force accumulation error of the Ti6AL4V alloy specimen, which was obtained from a simulated thermal tensile test and an actual test, was used as an optimization target function. Then, the damage parameters were optimized using the genetic algorithm until the target function reached the minimum value. Finally, the optimal damage model parameter was obtained. Through program development, the three high-temperature damage models established in this paper were embedded into Forge NxT 2.1 finite element software. The simulated thermal tensile test of Ti6AL4V alloy was performed at a temperature of 800-1000 °C and a strain rate of 0.01-5 s. The simulated and actual fracture displacements of the tensile specimens were compared. The correlation coefficients (R) were calculated, which were 0.997, 0.951, and 0.912. Of the high-temperature damage models, the normalized Cockcroft and Latham high-temperature damage model had higher accuracy in predicting crack defects of Ti6Al4V alloy during the hot-forming process. Finally, a fracture strain graph and a high-temperature damage graph of Ti6Al4V alloy were constructed. The Ti6Al4V alloy damage evolution and thermal formability were analyzed in relation to the temperature and strain rate.
Ti6AL4V合金广泛应用于生物医学和能源汽车等行业。Ti6Al4V合金无法在环境温度下制造，因此需要热成型。然而，这种方法容易出现裂纹缺陷。Ti6AL4V合金在热成型过程中的裂纹缺陷问题不容忽视，所以我们必须开发一个精确的热成型损伤预测模型。在本研究中，考虑温度和应变速率，开发了Ti6Al4V合金的三种高温损伤模型。这些模型源自归一化的考克罗夫特和拉瑟姆（NCL）、大根模型以及赖斯和特雷西（RT）损伤模型。模型的损伤参数通过遗传算法结合有限元模拟来识别。将模拟热拉伸试验和实际试验得到的Ti6AL4V合金试样的力累积误差用作优化目标函数。然后，使用遗传算法对损伤参数进行优化，直到目标函数达到最小值。最后，获得了最优损伤模型参数。通过程序开发，将本文建立的三种高温损伤模型嵌入到Forge NxT 2.1有限元软件中。对Ti6AL4V合金在800 - 1000°C温度和0.01 - 5 s应变速率下进行了模拟热拉伸试验。比较了拉伸试样的模拟和实际断裂位移。计算了相关系数（R），分别为0.997、0.951和0.912。在高温损伤模型中，归一化的考克罗夫特和拉瑟姆高温损伤模型在预测Ti6Al4V合金热成型过程中的裂纹缺陷方面具有更高的准确性。最后，构建了Ti6Al4V合金的断裂应变图和高温损伤图。分析了Ti6Al4V合金损伤演变和热成型性与温度和应变速率的关系。
