Mechanical Stress Identification Method in Anisotropic Ferromagnetic Materials Using Eddy Current Testing

Abstract

This work presents an identification method for multi-axial stresses in steel pipelines. The proposed electromagnetic non-destructive technique evaluates the impedance variation of an eddy current sensor. The method applies to ferromagnetic materials, including anisotropic ones. It is a model based approach using a finite element model that incorporates the magneto-elastic behaviour of the material and simulates the variation of the eddy current sensor impedance with stress. Four parameters are needed to describe the material behaviour. Although the magnetic parameters used in the numerical model are identified from anhysteretic measurements, the results of the identification method correlates with experiments performed on samples extracted along two orthogonal directions of a pipeline.