Mean stress effects on Low-Cycle Fatigue behaviour of Inconel 718 alloy

Uniaxial and biaxial fatigue test results related to Inconel 718 specimens are analysed by using the critical plane-based multiaxial fatigue criterion by Carpinteri et al., formulated in terms of strain, in conjunction with a model similar to that by Smith-Watson-Topper (SWT). More precisely, both smooth solid specimens and thin-walled tubular specimens subjected to proportional and non-proportional loading consisting of tension, torsion, and combined tension and torsion loading under strain control are examined, for strain ratio equal to 0 or -1. Fatigue life is then analytically computed through the above procedure and compared with the experimental one, in terms of number of loading cycles needed to form a surface crack whose length is equal to 1 mm.