Issue 38

M. de Freitas et alii, Frattura ed Integrità Strutturale, 38 (2016) 121-127; DOI: 10.3221/IGF-ESIS.38.16 127 Figure 4 : Comparison between the observed lives N obsv and the lives N ESWT or N F predicted by critical-plane methods, according to the dominance of normal or shear applied loads. C ONCLUSIONS n this work, it was shown that both critical-plane and SSF approaches have the potential to predict multiaxial fatigue lives, at least for in-phase proportional loadings. Findley’s model neglects tensile damage, while the ESWT model neglects shear damage, which explains why their performance was not very good for all considered load histories. In its current form, the SSF method does not include mean/maximum stress effects, therefore experiments with zero mean loads were chosen to evaluate its performance. The SSF method resulted in a better fit of the experimental data, however it requires more calibration tests (to fit its 5 th -degree polynomial) than the critical plane approach. R EFERENCES [1] Castro, J.T.P., Meggiolaro, M.A., Fatigue Design Techniques (in 3 volumes), CreateSpace, Scotts Valley, CA, USA (2016). [2] Socie, D., Marquis G., Multiaxial Fatigue, SAE International, Warrendale, PA, USA (2000). [3] Findley, W.N., A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending, J. Eng. Industry, 81 (1959) 301-306. [4] Fatemi, A., Socie, D., A critical plane approach to multiaxial damage including out-of-phase loading, Fatigue Fract. Eng. Mater. Struct., 11 (1988) 149-166. [5] Smith, R.N. Watson, P., Topper, T.H., A stress-strain parameter for the fatigue of metals, J. Mater., 5 (1970) 767-778. [6] Anes,V., Reis, L. Li, B., Fonte, M., de Freitas, M., New approach for analysis of complex multiaxial loading paths, Int. J. Fatigue, 62 (2014) 21-33. [7] de Freitas, M., Reis, L., Li, B., Comparative study on biaxial low-cycle fatigue behaviour of three structural steels, Fatigue Fract. Eng. Mater. Struct., 29 (2006) 992-999. I