Researches on Stress Concentration and Fatigue Damage for Ferromagnetic Specimen by Permeability Testing Technology

The permeability testing technology are new testing and evaluating method, which based on the electromagnetic induction principle, can realize the test and evaluate high sensitively of stress concentration and fatigue damage for ferromagnetic specimen. Taking Q235 and 45 steel for examples, the relationships of the detection signal and the tensile stress, residual stress, fatigue damage are studied from experiments. The results indicate that permeability testing technology can be used effectively to measure the stress state of specimen and the maximum stress suffered before. According to the residual stress signal after suffer tensile, the maximum stress to be suffered before can be determined with high sensitively. It shows that detection sensitivity of the fatigue damage is less than that of stress concentration. The detection sensitivity of fatigue damage for Q235 steel is greater than that of steel 45 steel. The results indicate that the permeability testing technology has a broad application prospect.