Tension-compression asymmetry of creep and unilateral creep damage in aluminum for isothermal and nonisothermal processes

A constitutive model is proposed to describe the damage development in alum inum alloys under creep conditions for both isothermal and nonisothermal pr ocesses. Special emphasis is laid on four specific phenomena: tension-compr ession asymmetry of creep, damage induced anisotropy, unilateral creep dama ge and damage deactivation. Within the framework of the phenomenological ap proach in the Continuum Damage Mechanics, the nonlinear tensor constitutive equation for creep deformation and damage evolution equation are proposed to account for different orientation of microcracks in aluminum alloys unde r tensile and compressive loading types, after a determination of the mater ial parameters in the obtained constitutive equation and damage growth equa tion, the proposed model is applied to the describing creep behavior of the aluminum alloy under uniaxial nonproportional and multiaxial nonproportion al loading for both isothermal and nonisothermal processes.