Issue 37

K. Yanase et alii, Frattura ed Integrità Strutturale, 37 (2016) 101-107; DOI: 10.3221/IGF-ESIS.37.14 103 holes associated with Mode I fatigue crack growth in the principal stress direction (i.e., 45 degrees from the specimen axis), as shown in Fig. 3. Figure 2: One-hole defect (a) before and (b) after fatigue testing at shear stress amplitude,  a = 320 MPa and number of cycles, N = 2.8  10 7 cycles. Figure 3: Mode I fatigue crack growth from a two-hole defect under torsional loading at shear stress amplitude,  a = 290 MPa. 10 0 10 1 10 2 10 ‐13 10 ‐12 10 ‐11 10 ‐10 10 ‐9 10 ‐8 10 ‐7 Stress intensity factor range  K I  (MPa  m) Crack growth rate da/dN (m/cycle) * For torsional loading, the crack is assumed as a semicircular crack Fitting curve Torsion Tension‐Compression Figure 4: FCGR curves for Mode I crack under torsional loading and tension-compression loading [9]. Specimen axis Specimen axis