Issue 33

Y. Wang et alii, Frattura ed Integrità Strutturale, 33 (2015) 345-356; DOI: 10.3221/IGF-ESIS.33.38 354 The predicted versus experimental fatigue lifetime diagram for 1050 QT steel and 304L steel under discriminating axial- torsion stain paths with random and incremental changes in straining direction is reported in Fig. 5. As it can be seen from Fig. 5, all the data are within scatter bands of 3 from predictions. Fig. 6 shows the predicted versus experimental fatigue lifetime diagram for pure titanium and titanium alloy BT9 under step loading and block loading composed of different combinations of axial, torsion and 90°out-of-phase axial-torsion strain paths. As it can be seen from Fig. 6, 90% of the data are within a scatter band of 3. Figure 5 : Comparison of observed and predicted fatigue lives by the MMCCM for 1045 QT steel and 304L steel. Figure 6 : Comparison of observed and predicted fatigue lives by the MMCCM fo pure titanium and titanium alloy BT9. C ONCLUSIONS (1) The MMCCM originally proposed by Susmel et al. [18] for multiaxial constant amplitude loading was reformulated to estimate fatigue lifetime of components subjected to VA multiaxial fatigue loading. Satisfactory fatigue life predictions were obtained by using the MMCCM, when coupled with the Rain-Flow cycle counting method and Palmgren-Miner