Issue 41

M.V.C Sá et alii, Frattura ed Integrità Strutturale, 41 (2017) 90-97; DOI: 10.3221/IGF-ESIS.41.13 96 Figure 5: Observed versus estimated lives based on the use of the L  – N f and L  – N f . C ONCLUSIONS n this work a set of experimental fatigue data was produced for plain and notched specimens of Al7050-T7451 under uniaxial and multiaxial proportional loading conditions. A methodology available in the literature, which combines a multiaxial critical plane criterion with a critical distance approach was used to estimate the life for the multiaxial tests. Two curves of critical distance against life obtained under uniaxial and torsional loading were considered in order to determine the material point positon from the notch root where the multiaxial model should be computed. The results showed that neither the distance given by the L  – N f diagram nor the one given by L  – N f curve combined with the MWCM model was capable to estimate lives within a reasonable degree of accuracy. While the methodology provided significant conservative life estimates for all data analysed when the distance from the notch root was taken from the L  – N f curve, non-conservative predictions up to a factor of four were obtained when such a distance was taken from the L  – N f diagram. The authors believe that a and equivalent critical distance that could take into account the sensitiveness of the stress gradient produced by the shear and by the normal stress modes could enhance the life estimates. Other multiaxial fatigue criteria should also be investigated and more data, preferably under non-proportional loading, should be used to corroborate the analysis. Future work by the authors will tackle these issues. A CKNOWLEDGEMENTS he authors would like to acknowledge the financial support of ATE II, ATE III, TAESA, TBE, EATE, BRASNORTE, AETE, TME, FINATEC, and CNPq (309748/2013-5). R EFERENCES [1] Gao, Y. K., Improvement of fatigue property in 7050–T7451 aluminum alloy by laser peening and shot peening. Materials Science and Engineering: A, 528(10) (2011) 3823-3828. 10 4 10 5 10 6 10 7 Observed Fatigue Life, N f (Cycles) 10 4 10 5 10 6 10 7 Estimated Fatigue Life, N f (Cycles) Predictions based on L x N and MWCM Predictions based on L x N and MWCM Perfect Correlation Interval Limits - two bandwidths Interval Limits - Four bandwidths I T