Analysis of the universality of the residual stress evaluation method based on residual magnetic field measurements

The paper presents an analysis of the universality of the algorithm for the evaluation of residual stress of the first order using the gradients of the residual magnetic field (RMF) components. The impact of the component geometry on quantitative relationships between residual stress and the RMF component gradients are studied. Two kinds of flat samples with a different geometries (type A and B) are analysed. For different degrees of plastic strain, on the surface of the samples, the distributions of the RMF components are measured. The finite element method is used to model residual stress in the samples. The quantitative relationships between the RMF component gradients and equivalent residual (von Mises) stress are developed based on the measurements of samples with type A notch geometry. These relationships are verified by using them to evaluate residual stress in type B samples with a different geometry. It is found that the quantitative evaluation of residual stress in components which is based on the RMF gradients requires at every instance the development of a transition function for the specific geometry, material and orientation of the component in the magnetic field of the Earth.