Test procedure for stress damage of ferromagnetic materials based on metal magnetic memory effects

Abstract

Abstract The metal magnetic memory effect is highly sensitive to stress. This experimental investigation of the magnetic memory signal characteristic of a ferromagnetic material at different stress-strain states has been performed using X80 steel specimens. The magnetic signals were measured in accordance with these procedures at twice the elastic deformation and once the elastic deformation to fracture under the tensile load. The results indicate that magnetic memory signals linearly decrease with increasing tensile load in the elastic state and the reverse in the plastic stage. The intensity clearly increases when damage occurs which can be taken as evidence for damage caused by stress. The test was performed on an actual pipeline with a crack created by a special device. The effect of metal magnetic memory for the evaluation of damage caused by stress has thus been verified by this engineering procedure.