Abstract A methodology for incorporating a ductile fracture criterion into an improved Marciniak–Kuczynski model, which extends the original works to include planar anisotropy using the Barlat89 yield criterion, is proposed to predict the forming limit diagram of AA7075. This is the most promising alloy to be introduced in the automotive industry, resulting in even greater weight reduction when compared with other alloys. Due to its poor formability at room temperature, this study is conducted at 480 °C, an elevated temperature adopted in a thermal multi-step process to form some complex parts. The integrated model is numerically solved using the Newton–Raphson method. Various ductile fracture criteria are estimated to identify the optimal theoretical model. The material constants are determined from uniaxial and equibiaxial tensile tests. To verify the model, a semispherical thickness reduction cruciform specimen is designed to achieve a fracture at the center. Further, thermal biaxial tensile testing technology, an in-plane and non-contact loading method, is adopted. Comparisons with the experimental results show that the integrated model with Oyane’s criterion achieves the optimal performance.

中文翻译：

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使用集成模型对 7075 铝合金板在高温下的成形极限预测

摘要 提出了一种将韧性断裂准则纳入改进的 Marciniak-Kuczynski 模型的方法，该模型将原始工作扩展到使用 Barlat89 屈服准则包括平面各向异性，以预测 AA7075 的成形极限图。这是最有希望引入汽车行业的合金，与其他合金相比，可实现更大的重量减轻。由于其在室温下的可成形性较差，因此本研究在 480 °C 下进行，该温度是多步骤热成型工艺中采用的高温，以形成一些复杂零件。使用 Newton-Raphson 方法对集成模型进行数值求解。估计各种韧性断裂标准以确定最佳理论模型。材料常数由单轴和等双轴拉伸试验确定。为了验证模型，设计了一个半球形减薄十字形试样，以在中心实现断裂。此外，还采用了热双轴拉伸试验技术，即面内非接触加载方法。与实验结果的比较表明，具有 Oyane 准则的集成模型达到了最佳性能。