抄録
The present study has attempted to simulate the distribution of α'martensite and vertical magnetic flux density B_z around the plastic wake of a growing crack in an austenitic stainless steel SUS304 in which stress-induced martensitic phase transformation is to occur at room temperature. FEM calculations of martensitic phase transformation have been made on a center-cracked plate specimen of SUS 304 stainless steel subjected to monotonically increasing tension load at room temperature. The resultant contour maps of α'martensite around fatigue cracks agree well with those measured by ferrite scope, showing that the distribution of α'martensite changes according to the applied maximum stress intensity factor K_<max> value. FEM calculations also have been made on the vertical component of leakage magnetic flux density above fatigue cracks by using a composite permanent magnet model. The α'transformation region around a fatigue crack is modeled as a composite of permanent magnets having different B-H properties varying with to α'content. The resultant distributions of leakage magnetic flux density above fatigue cracks obtained by FEM agree well with those obtained experimentally.
