On low-cycle fatigue of austenitic steel. Part I: Changes of Poisson's ratio and elastic anisotropy

Abstract

Microstructural changes under low-cycle fatigue of a metastable austenitic steel are monitored by a combination of the acoustic parameters: Poisson's ratio (more precisely, its change) as indicator of the “diffused” damage and anisotropy change as indicator of changes of texture. Three stages of the Poisson's ratio evolution are identified; they serve as markers of the process of material degradation. A criterion of fracture in terms of a critical combination of the changes of the mentioned parameters is proposed and tested. The challenge of separating the effects of damage accumulation and of the martensitic transformation on elasticity parameters is addressed by combining acoustic monitoring with the eddy current data.