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 α' phase volume fraction ξ_<α'> 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 the crack in the specimen magnetized by a strong electromagnet. It was revealed that the B_z distributions reflected the α' phase distributions around the 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 2α. The B_<zmax> and the B_<zmin> values also showed linear relations with maximum stress intensity factors at the surface tip K_<amax> and at the depth position K_<bmax>. Each relation, i.e., 2α vs. 2l, B_<zmax> vs. K_<amax>, etc. can be represented by a single straight line regardless of R-ratio.
