Issue34

K. Nambu et alii, Frattura ed Integrità Strutturale, 34 (2015) 271-279: DOI: 10.3221/IGF-ESIS.34.29 274 The depth-of-cut direction hardness distribution of each processing material is shown in Fig. 5. As shown in a figure, VC material showed the maximum hardness of HV800 on the surface, and went up about 2.6 times as compared with HV400 of QT material. Moreover, an effective hardening depth is 1.2 mm from the surface. Figure 3: Retained austenite distribution from surface Figure 4: Residual stress distribution from surface Figure 5: Vickers hardness distribution from surface R ELATIONSHIP OF CRACK GROWTH RATE DA / DN AND STRESS INTENSITY FACTOR WIDTH ΔK he relationship of crack progress speed da / dN and stress intensity factor width Δ K in the case of the conditions of P max =7000 is shown in Fig. 6. In the case of surface modification processing material, the progress behaviors of a surface crack and an internal crack differ, and it is thinkable that a crack entering edge curves greatly. About this, by report of Egami et al [10], if the rate of internal crack pallet-length b to surface-crack length a is set to m , the following expressions of relations will be materialized among both. b = ma - c (1) T