Changes of subsurface properties due to fatigue determined by sin² Ψ-method and harmonic analysis of eddy current signals

Monitoring residual stress relaxation due to mechanical loading has the capability to retrieve a component’s load history. So far, these changes are determined by X-ray diffraction using the sin²Ψ-method going along with high effort regarding specimen preparation, measurement time and costs. The presented paper evaluates harmonic analysis of eddy current measurements as an alternative technology to determine alterations of a component’s subsurface due to fatigue. Transferring this approach to a wide range of machined components and mass production bears the potential to gain access to large databases of service life information, representing an important enabling technology for cyber-physical systems.