Thermodynamic characterization of fretting-induced material degradation using degradation entropy generation framework

Abstract

A thermodynamic approach is proposed to characterize fretting-induced material degradation, leveraging a degradation coefficient (B) derived from the principles of irreversible thermodynamics. This coefficient establishes a linear relation between entropy generation and material degradation due to wear. Results are validated by considering the experimental data from five published fretting studies—spanning a range of materials (compacted graphite cast iron, Ti–6Al–4V, Inconel 690, FeCrAl, and sintered tempered steel), operating conditions (load, displacement, temperature), and different slip regimes. Across all studies, the B coefficient demonstrated greater sensitivity and consistency than the traditional wear rate constant (K), particularly in identifying transitions between wear mechanisms and assessing the severity of wear. For consistent wear modes, B remained stable and constant; however, sharp increases in B reflected shifts to more aggressive wear regimes. This unified framework enhances predictive capabilities and offers a robust degradation metric for diverse tribological applications.