Pages 43-44
The present study investigates plasticity-induced martensitic transformation around a part-through crack in an austenitic stainless steel SUS304 fatigued at room temperature. Distributions of α' phase volume fraction ζ_<α'> around a semi-elliptic fatigue crack were measured with ferrite scope. The results were compared with the distributions of magnetic flux density B_z above the crack in a specimen magnetized by a strong magnet. 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 2a. The B_<zmax> and the B_<zmax> values also showed linear relations with maximum stress intensity factors at the surface tip 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.
