Issue34

K. Nambu et alii, Frattura ed Integrità Strutturale, 34 (2015) 271-279: DOI: 10.3221/IGF-ESIS.34.29 277 Figure 9: Relation between Δ K and da/dn at each points. Figure 10: Relation between Δ K eff and da/dn at each points. A STUDY ON THE CRACK PROPAGATION BEHAVIOR OF CARBURIZED LAYER hen, the following conclusions were obtained from the result of fracture-surface observation. The crack progress process of VC material was classified into four stages from the crack progress behavior and the fracture-surface photograph. About each stage, the destructive configuration by the crack progress in VC material was shown. Facture surface in Fig. 11, schematic diagram is shown in Fig. 12. Each area is defined as follows. Figure 11: Change of fracture surface morphology with crack propagation.  Stage A: In this stage, the influence of a crack closure effect is not shown by brittleness, but a quick crack progress speed is shown. Also in a fracture surface, an intergranular fracture is mainly shown, and some transgranular fracture follows.  Stage B: The influence of the compressive residual stress by a carburizing layer and a processing induction martensitic transformation is an area which appears most, a crack progress speed falls and the local minimum is shown. Although T