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概要

The present study investigates plasticity-induced martensitic transformation around fatigue cracks in single V-groove butt-welded SUS304 plates at room temperature in air. Distributions of a' phase volume fraction Va around fatigue cracks were measured with ferrit e scope. The results were compared with the distributions of vertical magnetic flux density B, above fatigue cracks in welded specimens magnetized by a strong electromagnet. It was revealed that the B, distributions reflected the spatial distributions of pre-exist ing ferrite phase and plasticity-induced martensite phase around the weldment and fatigue cracks: i.e., the distance between the points where By reached the maximum and the minimum values Bzmax and Bzmin had linear correlations with real crack length 2a. The Bzmax and the Bzmin values also showed linear relations with applied maxi-mum stress intensity factor value Kmax. These results imply that the measurement of the vertical magnetic flux density above fatigue cracks located near weldments can estimate 2a and Kmax values.

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