Abstract The present work summarizes the experimental campaign and computational effort performed on Zircaloy-4 material commonly used in nuclear applications. The Zircaloy-4 exhibits a mild strength differential response under compression as compared with tension. Because of the well-known twinning-slip mechanism usually activated in compression after yielding in HCP metals, distortional hardening is required to define plastic flow throughout fracture. A general asymmetric yield function with the first invariant to the Cauchy stress tensor and the third invariant to the deviator stress tensor are considered to model the pressure-sensitive response and the Strength Differential (SD) effect in HCP polycrystal materials. The proposed macroscopic yield function provides results that are in good agreement with experiments. The onset of fracture and subsequent crack propagation in upsetting tests is also investigated. The results show that failure is not only controlled by material properties but also by friction between contact surfaces of specimens and experimental setup. In addition, the concept of a fixed cutoff value for negative stress triaxiality ( η = - 1 / 3 ) condition is analyzed. It turns out that the specimen fails differently of what is observed experimentally when a constant cutoff value is set. However, a cutoff stress triaxiality function, yields a more realistic fracture pattern consistent with tests.

中文翻译：

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Zircaloy-4 在更宽应力状态下的机械响应：从单轴拉伸到单轴压缩

摘要 目前的工作总结了在核应用中常用的 Zircaloy-4 材料上进行的实验活动和计算工作。与拉伸相比，Zircaloy-4 在压缩下表现出温和的强度差异响应。由于众所周知的孪生滑移机制通常在 HCP 金属屈服后在压缩中激活，因此需要变形硬化来定义整个断裂过程中的塑性流动。考虑了柯西应力张量的第一个不变量和偏应力张量的第三个不变量的一般非对称屈服函数来模拟 HCP 多晶材料中的压敏响应和强度微分 (SD) 效应。建议的宏观屈服函数提供的结果与实验非常吻合。还研究了镦锻试验中断裂的开始和随后的裂纹扩展。结果表明，失效不仅受材料特性的控制，还受试样接触面和实验装置之间的摩擦力的控制。此外，还分析了负应力三轴性( η = - 1 / 3 ) 条件的固定截止值的概念。事实证明，当设置恒定的截止值时，试样的失效与实验观察到的不同。然而，截止应力三轴度函数会产生与测试一致的更真实的断裂模式。分析了负应力三轴性 (η = - 1 / 3 ) 条件的固定截止值的概念。事实证明，当设置恒定的截止值时，试样的失效与实验观察到的不同。然而，截止应力三轴度函数会产生与测试一致的更真实的断裂模式。分析了负应力三轴性 (η = - 1 / 3 ) 条件的固定截止值的概念。事实证明，当设置恒定的截止值时，试样的失效与实验观察到的不同。然而，截止应力三轴度函数会产生与测试一致的更真实的断裂模式。