Stress triaxiality in crack tip regions of bend specimens with different crack-depth and fracture criterion at initiation

Abstract For three-point-bend specimens with different crack-depth in 50D steel, the principal reasons, leading to the losing of J-dominance and the crack-depth-dependence of Ji, were discovered by FEM calculations and experiments. The failure initiation locus of Ji, vs the stress triaxiality were obtained. A new elastic-plastic fracture criterion at initiation, J vi = J i f( σ m \ gs ) , was established and proven to be a materials constant independent of crack-depth (stress triaxiality).

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