マルテンサイト変態を利用したSUS304鋼溶接材中の貫通疲労き裂の非破壊評価(OS9-5 電磁超音波法及び電磁気的方法,OS9 材料損傷・劣化過程の非破壊診断技術)

概要

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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 α' phase volume fraction V_α' around fatigue cracks were measured with ferrite scope. The results were compared with the distributions of vertical magnetic flux density B_z above fatigue cracks in welded specimens magnetized by a strong electromagnet. It was revealed that the B_z distributions reflected the spatial distributions of pre-existing ferrite phase and plasticity-induced martensite phase around the weldment and fatigue cracks: i.e., the distance between the points where B_z reached the maximum and the minimum values Bzmax and B_<zmin> had linear correlations with real crack length 2a. The B_<zmax> and the B_<zmax> values also showed linear relations with applied maximum stress intensity factor value K_<max>. These results imply that the measurement of the vertical magnetic flux density above fatigue cracks located near weldments can estimate 2a and K_<max> values.
社団法人日本機械学会の論文
2004-07-20