PSI - Issue 7

Kentaro Wada et al. / Procedia Structural Integrity 7 (2017) 391–398 K. Wada et al./ Structural Integrity Procedia 00 (2017) 000–000

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3.2. Crack closure behavior The results of the crack closure measurements of the non-propagating crack at R = −10 are shown in Fig. 6. Crack closing stress, σ cl , was about 80 MPa, from which Δ K eff th was determined to be 1.6 MPa m 1/2 . This value was nearly equivalent to that of a small crack in carbon steels (141 ≤ HV ≤ 305 ), which was approximately 2 MPa m 1/2 , as reported by Kondo et al. (2003).

Fig. 5: FCG rate at R = −10 as a function of the surface crack length, 2 a .

Fig. 6: Crack-closing behavior after fatigue tests.