Issue 47

Yu. G. Matvienko et alii, Frattura ed Integrità Strutturale, 47 (2019) 303-320; DOI: 10.3221/IGF-ESIS.47.23 312 a b Figure 6 : SIF values as a function of total crack length for specimens of T5-H1 (a) and T5-H2 (b) group. a b Figure 7 : T-stress values as a function of total crack length for specimens of T5-H1 (a) and T5-H2 (b) group. Fracture mechanics parameters versus loading cycle number To quantify the influence of stress ratio R on fatigue life of cold expanded holes, the fracture mechanics parameters for cracks of the fixed length should be plotted against of the loading cycle number. The average values of CMOD, SIF and T- stress, presented in Tab. 3 and Tab. 4 for specimens of T5-H1 and T5-H2 type, respectively, are used to reach this purpose. Experimentally obtained values correspond to remote tensile stress  = 80 MPa for specimens of both groups. Dependencies of CMOD, SIF and T-stress values against of the loading cycle number for cracks of the fixed length are shown in Figs. 8-10. The loading cycle number in these figures is presented as a lifetime percentage.