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Thermodynamic Modeling of Void Evolution, Fatigue, and Tribo-Wear

Cemal Basaran, University at Buffalo

Lakshamana Rao, Indian Institute of Technology Madras

Angelo Maligno, University of Derbey

Sergei Sherbekov, Belarus State University

Jude Osara, University of Twente

Historically degradation of materials, void evolution, fatigue, damage and tribological wear has been modeled using empirical evolution functions. Traditional empirical equations, (or potentials) use stress, or strain or dissipated energy as a variable.  Recent developments have proven that using Boltzmann entropy formulation directly as a metric can eliminate the need for an empirical evolution function and associated parameters.  Even if entropy is used as a variable in an empirical evolution equation, [without Boltzmann formulation] it has been shown that Fatigue Fracture Entropy value of the material at failure is independent of geometry of sample tested, strain rate, loading frequency and loading path. Most of these new techniques use laws of thermodynamics not by writing thermodynamically consistent mechanics equations [ as in traditional approach] but actually, integrating them directly with the laws of Newton. As a result, derivative of displacement with respect to entropy is not zero and there is an additional linearly independent fifth axis, called Thermodynamic State Index axis, as in the Unified Mechanics Theory.