Many experiments indicated the remarkable dependence of the strength and failure behavior of anisotropic ductile metals on the loading direction and on the stress state. These influences have to be taken into account in accurate material models and in the numerical simulation of complex loading processes predicting the safety and lifetime of aerospace structures. Therefore, the present paper discusses the effect of loading direction and stress state on the damage and failure behavior of the anisotropic aluminum alloy EN AW-2017A. Experiments and corresponding numerical analysis with the newly developed, biaxially loaded X0 specimen have been performed and the influence of different load ratios is examined. The formation of strain fields in critical parts of the X0 specimen is monitored by digital image correlation. Different failure modes are visualized by scanning electron microscopy of fracture surfaces. Stress states are predicted by finite element calculations and they are used to explain damage and fracture processes at the micro-level. The experimental–numerical analysis shows that the loading direction and the stress state remarkably affect the evolution of the width and orientation of localized strain fields as well as the formation of damage processes and fracture modes. As a consequence, characterization of anisotropic metals is highly recommended to be based on an enhanced experimental program with biaxial tests including different load ratios and loading directions.

中文翻译：

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各向异性铝合金 EN AW-2017A 与应力状态相关的损伤和失效行为的双轴实验和数值分析

许多实验表明，各向异性韧性金属的强度和破坏行为对加载方向和应力状态具有显着的依赖性。在精确的材料模型和预测航空航天结构安全性和寿命的复杂加载过程的数值模拟中，必须考虑这些影响。因此，本文讨论了加载方向和应力状态对各向异性铝合金 EN AW-2017A 损伤和失效行为的影响。对新开发的双轴加载 X0 试样进行了实验和相应的数值分析，并检查了不同载荷比的影响。X0 试样关键部位应变场的形成通过数字图像相关性进行监测。通过断裂表面的扫描电子显微镜观察不同的失效模式。应力状态通过有限元计算进行预测，并用于解释微观层面的损伤和断裂过程。实验数值分析表明，加载方向和应力状态显着影响局部应变场的宽度和方向的演变以及损伤过程和断裂模式的形成。因此，强烈建议基于增强的实验程序对各向异性金属的表征进行双轴试验，包括不同的载荷比和载荷方向。应力状态通过有限元计算进行预测，并用于解释微观层面的损伤和断裂过程。实验数值分析表明，加载方向和应力状态显着影响局部应变场的宽度和方向的演变以及损伤过程和断裂模式的形成。因此，强烈建议基于增强的实验程序对各向异性金属的表征进行双轴试验，包括不同的载荷比和载荷方向。应力状态通过有限元计算进行预测，并用于解释微观层面的损伤和断裂过程。实验数值分析表明，加载方向和应力状态显着影响局部应变场的宽度和方向的演变以及损伤过程和断裂模式的形成。因此，强烈建议基于增强的实验程序对各向异性金属的表征进行双轴试验，包括不同的载荷比和载荷方向。