Abstract
The present study investigates plasticity-induced martensitic transformation around a part-through crack in an austenitic stainless steel SUS304 fatigued at room temperature in air. Distributions of the volume fraction of α' martensitic phase around a semi-elliptical fatigue crack were measured with ferrite scope. The results were compared with the distributions of vertical magnetic flux density B_z above and below the crack measured by in a specimen magnetized by a strong electromagnet. It was revealed that the B_z distributions reflected the distributions of α' volume fraction ξ_α' around a fatigue crack: i.e., the distance between the points where B_z reached the maximum and the minimum values B_<zmax> and B_<zmin> had linear correlations with surface crack length 2a. The B_<zmax> and the B_<zmin> values also showed linear relations with maximum stress intensity factors at the surface tips K_<amax> and at the depth position K_<bmax>. These results imply that not only 2a but also K_<amax> and K_<bmax> values can be estimated in an electromagnetic non-destructive way.
