This paper reviews classical wear models and entropy-based degradation approaches used for predicting failure in tribological systems. Various wear models, thermodynamic frameworks, and applications of the Degradation Entropy Generation (DEG) theorem are discussed. Friction, which is the primary source of heat generation in tribological contacts, is responsible for material degradation through a variety of irreversible processes. While classical wear approaches have been widely used for wear prediction and life estimation, they often fail to account for the underlying thermodynamic mechanisms associated with degradation. Entropy-based methodologies provide a physically meaningful framework by incorporating energy dissipation and irreversible thermodynamic effects into failure prediction.

This review critically examines classical wear models, thermodynamic degradation theories, entropy-based damage models, rolling contact fatigue approaches, and condition-monitoring applications for bearings and rotating machinery. Comparative analyses between classical and entropy-based methods are presented together with relevant mathematical formulations. In addition, current challenges, limitations, and future research opportunities associated with entropy-based degradation modelling are discussed. Comparative assessments of wear prediction methodologies and failure prediction approaches are also provided to highlight the potential of entropy-based techniques for next-generation tribological health monitoring and reliability assessment.

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