Abstract
A generalization of the Degradation-Entropy Generation (DEG) theorem to multi-disciplinary multi-physics system-process analysis via a combination with pre-existing system models is presented in this article. Existing models and the DEG methodology are reviewed, and a method for evaluating degradation coefficients Bi is proposed. These coefficients characterize the system’s transformation based on active dissipative mechanisms, including temperature effects. The consistency of entropy generation in characterizing degradation is then inherited by these often-empirical system models, thereby rendering them more robust and applicable to similar systems without the need for numerous tests and measurements for model corrections. The approach applies to all systems and can quickly analyze and predict a system’s performance and degradation, even in the absence of experimental data (using known properties and material constants). Demonstrated applications herein include mechanically loaded systems (frictional wear, grease shearing, fatigue loading), electrochemical energy systems, thermal processes, and others.
Highlights
The consistency of entropy generation in characterizing irreversibilities in systems and processes continues to attract degradation/failure experimentalists from various fields
Using several experimental verifications including solder joints and composites, the authors demonstrated high model-to-experiment correlation. This series of works led to the formulation of the unified mechanics theory [8] which combines a thermodynamic state index with otherwise steady-state physical laws to render them more consistent with experimental observations
Bryant et al proposed a structured approach for applying the Degradation-Entropy Generation (DEG) theorem to degradation analysis: identify and measure the degradation measure w and active process energies pi; evaluate entropy generation Si0 = Si0 caused by the pi ; relate degradation measure to entropy generation terms to obtain transformation coefficients
Summary
The consistency of entropy generation in characterizing irreversibilities in systems and processes continues to attract degradation/failure experimentalists from various fields. Using several experimental verifications including solder joints and composites, the authors demonstrated high model-to-experiment correlation This series of works led to the formulation of the unified mechanics theory [8] which combines a thermodynamic state index with otherwise steady-state physical laws to render them more consistent with experimental observations. Combining thermodynamic laws with damage mechanics, Sosnosvskiy and Sherbakov [9,10] introduced the tribo-fatigue entropy to measure local damage accumulation in a mechanical system Their approach, termed mechanothermodynamics, includes damage distribution in a volume, correlating well with measurements. In the Appendix A, a short summary of relevant foundational irreversible thermodynamics concepts is presented, with several references provided for further reading
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