延性き裂発生条件に及ぼす強度的不均質および動的負荷の影響

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It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of geometrical heterogeneity and strength mis-matching, which can elevate plastic constraint due to heterogeneous plasstic straining, and loading rate on critical condition to initiate ductile crack using two-parameters. Then, the crack initiation testing were conducted under static and dynamic loading using round bar specimens with circumferential notch and strength mis-matching. To evaluate the stress/strain state in the specimens especially under dynamic loading, thermal elastic-plastic dynamic FE-analysis considering the temperature rise was used. The result showed that equivalent plastic strain to initiate ductile crack expressed as a function of stress triaxiality obtained from the homogeneous specimens with circumferential notch under static loading could be a material constant independent of strength mis-matching and loading rate. And it was demonstrated that by using this two-parameters criterion, the critical crack initiation of specimens with strength mis-matching under static or dynamic loading, such as critical load or critical displacement, could be predicted from thermal elastic-plastic FE-analyses.
社団法人日本船舶海洋工学会の論文

延性き裂発生条件に及ぼす強度的不均質および動的負荷の影響

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