Constitutive modeling for the anisotropic uniaxial ratcheting behavior of Zircaloy-4 alloy at room temperature

A series of monotonic tensile, compressive and uniaxial ratcheting tests are conducted at room temperature on Zircaloy-4 (Zr-4) tubes to investigate the mechanical behaviors under various loading conditions. The experimental results show that the ratcheting strain is sensitive to mean stress, stress amplitude and mean stress direction. It is found that the material features anisotropy both in monotonic tests and uniaxial ratcheting tests with different mean stress directions. The difference of mechanical properties under tensile and compressive loading, especially the yield stress, is believed to contribute to the anisotropic ratcheting behavior of the material. In order to describe the anisotropic nature of the uniaxial ratcheting behavior of Zr-4, an anisotropic Ohno-Wang (OW) constitutive model introducing an initial back stress is developed. The results predicted show reasonable agreement with the experimental data.