Entropy production during the fatigue process can serve as a measure of degradation. We postulate that the thermodynamic entropy of metals undergoing repeated cyclic load reaching the point of fracture is a constant, independent of geometry, load and frequency. That is, the necessary and sufficient condition for the final fracture of a metal undergoing fatigue load corresponds to a constant irreversible entropy gain. To examine validity, we present the results of an extensive set of both experimental tests and analytical predictions that involve bending, torsion and tension-compression of aluminium 6061-T6 and stainless steel 304 specimens. The concept of tallying up the entropy generation has application in determining the fatigue life of components undergoing cyclic bending, torsion and tension-compression.

The Stribeck curve plays an important role in identifying boundary, mixed, elastohydrodynamic, and hydrodynamic lubrication regimes. Recent advances in elastohydrodynamic lubrication together with rough surface interaction have made it possible to develop a methodology for predicting the trend of the Stribeck curve. In this paper, we report the results of a series of experiments performed on a journal bearing together with a theoretical prediction of the Stribeck-type behavior. Various loads and oil temperatures are considered. The comparison between the experimental results with a mixed elastohydrodynamic lubrication model for line contacts is indicative of good agreement.

An extensive survey of the papers pertaining to the thermodynamic approach to tribosystems, particularly using the concept of entropy as a natural time base, is presented with a summary of the important contributions of leading researchers.

The Floberg–Jakobsson–Olsson cavitation theory is implemented using a mass-conservative algorithm to accurately predict the behavior of cavitation in flat surfaces enhanced with dimples. The multigrid method is used to accelerate the convergence speed. Comparison is made on different cavitation theories. The results reveal that the load-carrying capacity of dimple-enhanced surfaces is limited under the simulated conditions.

The science base that underlies modelling and analysis of machine reliability has remained substantially unchanged for decades. Therefore, it is not surprising that a significant gap exists between available machinery technology and science to capture degradation dynamics for prediction of failure. Further, there is a lack of a systematic technique for the development of accelerated failure testing of machinery components. This article develops a thermodynamic characterization of degradation dynamics, which employs entropy, a measure of thermodynamic disorder, as the fundamental measure of degradation; this relates entropy generation to irreversible degradation and shows that components of material degradation can be related to the production of corresponding thermodynamic entropy by the irreversible dissipative processes that characterize the degradation. A theorem that relates entropy generation to irreversible degradation, via generalized thermodynamic forces and degradation forces, is constructed. This theorem provides the basis of a structured method for formulating degradation models consistent with the laws of thermodynamics. Applications of the theorem to problems involving sliding wear and fretting wear, caused by effects of friction and associated with tribological components, are presented.