Creep fracture entropy: A thermomechanical damage-based failure index

Abstract

This paper presents an analytical framework for thermodynamical modeling of creep damage and fracture in materials through the lens of entropy production. Building on the second law of thermodynamics and principles of irreversible processes, the study establishes a unified coupling between a phenomenological damage law and continuum damage mechanics. The model links creep deformation to internal entropy generation and introduces a process-dependent damage exponent to ensure physically consistent and mathematically robust damage evolution. A key contribution is to introduce Creep Fracture Entropy (CFE)—a novel, material-specific thermodynamic index that serves as a reliable predictor of creep failure. By deriving time-dependent expressions for strain, strain rate, and entropy production, the model captures the full progression of creep behavior, without requiring empirical stage segmentation. The model is validated against a range of experimental data from various alloys, manifesting strong agreement with the observed strain and entropy trends. Notably, the calculated CFE values remain confined within a narrow range for each material, highlighting their intrinsic nature of constancy and reliability as fracture indicators. The thermodynamic formulation presented here enhances predictive accuracy for creep life assessment, emphasizing entropy as a pivotal damage variable in irreversible thermodynamics.