Issue 41

Carpinteri A. et alii, Frattura ed Integrità Strutturale, 41 (2017) 40-44; DOI: 10.3221/IGF-ESIS.41.06 44 0 1 100 ZERO ORDER MOMENTS RATIO,  0 ,r 0.0 0.5 1.0 1.5 2.0 DAMAGE RATIO, E [ D ] / E ref [ D ] 8 0.00 0.25 0.50 r 16 0.75 1.00 Figure 5 : Comparison between [ ] E D and [ ] ref E D : partially overlapped spectra. It can be observed that, in general, fatigue damage rate is slightly lower than that of the reference sinusoidal loading. Only in the case of bending and torsion loads of the same variance, a fatigue damage rate up to about 60% higher than that of the reference loading case is recorded for completely uncorrelated signals ( 16 0 r  ). C ONCLUSIONS n the present paper a frequency-domain multiaxial fatigue criterion based on the critical plane approach, suitable for fatigue life estimations in the presence of proportional and non-proportional random loading, has been discussed. In order to validate the above criterion, numerical simulations have herein been performed by employing a wide group of combined bending and torsion signals. The narrow-band spectrum of each signal has been assumed to be represented by a PSD function with rectangular shape. Different values of correlation degree, variance and spectral content have been examined. Among the cases being simulated, the most damaging one is identified in the loading combination of bending and torsion having same variance but being completely uncorrelated (correlation coefficient equal to zero). R EFERENCES [1] Niesłony, A., Macha, Spectral Method in Multiaxial Random Fatigue, Springer-Verlag, Berlin Heidelberg, (2007). [2] Carpinteri, A., Handbook of Fatigue Crack Propagation in Metallic Structures, Elsevier, Amsterdam, 1-2 (1994). [3] Carpinteri, A., Spagnoli, A., Vantadori, S., Reformulation in the frequency domain of a critical plane-based multiaxial fatigue criterion. Int. J. Fatigue, 67 (2014) 55–61. [4] Carpinteri, A., Spagnoli, A., Ronchei, C., Scorza, D., Vantadori, S. Critical Plane Criterion for Fatigue Life Calculation: Time and Frequency Domain Formulations. Procedia Eng., 101 (2015), 518–523. [5] Carpinteri, A., Spagnoli, A., Ronchei, C., Vantadori, S., Time and frequency domain models for multiaxial fatigue life estimation under random loading. Frat. ed Integrita Strutt., 9 (2015), 376–381. [6] Carpinteri, A., Fortese, G., Ronchei, C., Scorza, D., Spagnoli, A., Vantadori, S., Fatigue life evaluation of metallic structures under multiaxial random loading. Int. J. Fatigue, 90 (2016), 191–199. [7] Carpinteri, A., Fortese, G., Ronchei, C., Scorza, D., Vantadori, S. Spectral fatigue life estimation for non-proportional multiaxial random loading. Theor. Appl. Fract. Mech., 83 (2016) 67-72. [8] Cristofori, A., Benasciutti, D., Tovo, R. A stress invariant based spectral method to estimate fatigue life under multiaxial random loading. Int. J. Fatigue, 33 (2011), 887–899. I