A thermodynamic approach to nonlinear ultrasonics for material state awareness and prognosis

TL;DR

This paper introduces a thermodynamic framework using internal variables and a pseudo-elastic energy function to model nonlinear ultrasonics for damage detection and prognosis in materials, capturing energy storage and dissipation during damage.

Contribution

It presents a novel thermodynamic approach with a pseudo-elastic energy function to model nonlinear ultrasonic damage sensing and prognosis, incorporating damage progression during fatigue and creep.

Findings

Modeling of nonlinear ultrasonic response during damage accumulation

Evolution of nonlinearity parameter with damage and plastic strain

Application to stress relaxation and creep-like degradation scenarios

Abstract

We develop a thermodynamic framework for modeling nonlinear ultrasonic damage sensing and prognosis in materials undergoing progressive damage. The framework is based on the internal variable approach and relies on the construction of a pseudo-elastic strain energy function that captures the energetics associated with the damage progression. The pseudo-elastic strain energy function is composed of two energy functions - one that describes how a material stores energy in an elastic fashion and the other describes how material dissipates energy or stores it in an inelastic fashion. Experimental motivation for the choice of the above two functionals is discussed and some specific choices pertaining to damage progression during fatigue and creep are presented. The thermodynamic framework is employed to model the nonlinear response of material undergoing stress relaxation and creep-like degradation. For each of the above cases, evolution of the nonlinearity parameter with damage as well as with macroscopic measurables like accumulated plastic strain are obtained.