A thermodynamically consistent creep constitutive model considering damage mechanisms

This paper derives a physically-based creep-damage and life prediction model through the basic laws of thermodynamics. The model divides creep damage into two parts: one corresponding to high temperature and low stress, related to cavity nucleation and cavity growth, and the other corresponding to high temperature and high stress, related to dislocation movement. The creep strain rate consists of two components: diffusion creep, which is assumed to occur in all stress ranges, and dislocation-related creep, which activates when the external stress exceeds a certain threshold. The proposed model characterizes damage by the degradation of creep free energy. It accurately describes creep behavior over a wide stress range, including the transition phenomena observed in creep strain rate curves and creep life curves. This provides a constitutive reference for simulating long-term creep damage and life based on short-term creep data.