Issue 30

V. Chaves et alii, Frattura ed Integrità Strutturale, 30 (2014) 273-281; DOI: 10.3221/IGF-ESIS.30.34 280 Test Cycles Stage I direction, α (º) Experimental Chaves Matake Carpinteri Axial 119185 4.0 17.0 45.0 11.1 248683 3.5 17.0 45.0 11.1 116413 10.5 17.0 45.0 11.1 145850 12.0 17.0 45.0 11.1 Biaxial 490262 19.5 5.5 22.5 11.4 0.5σ = τ 230944 17.5 5.5 22.5 11.4 Biaxial 424304 31.5 14.7 13.3 20.6 σ = τ 140828 32.0 14.7 13.3 20.6 254124 32.0 14.7 13.3 20.6 204955 32.0 14.7 13.3 20.6 Biaxial 460657 37.0 21.0 7.0 26.9 2σ = τ 460663 40.0 21.0 7.0 26.9 376298 38.5 21.0 7.0 26.9 398576 37.0 21.0 7.0 26.9 278760 36.0 21.0 7.0 26.9 259028 38.0 21.0 7.0 26.9 Torsion 337940 38.0 28.0 0.0 33.9 623200 43.0 28.0 0.0 33.9 134300 34.0 28.0 0.0 33.9 332011 41.0 28.0 0.0 33.9 Table 1 : Experimental and predicted Stage I crack directions for AISI 304L steel. In-phase tests (R=-1) S UMMARY AND CONCLUSIONS ISI 304L stainless steel cylindrical specimens were subjected to biaxial loading fatigue tests in order to construct the S – N curves for the material. The in-phase biaxial loading curve was better fitted by an elliptical quadrant than by an elliptical arc. Photographs of the cracks on the outer surface of broken specimens taken with a light microscope were used to measure the angle at the crack initiation zone (Stage I), which was found to be close to the direction of Mode I. A comparison of the measured angle with predicted values obtained by using the models of Chaves et al., Matake and McDiarmid, and Carpinteri and Spagnoli, revealed that the last provided the best results in this respect. A CKNOWLEDGEMENTS he authors would like to thank the Spanish Ministry of Education for its financial support through grant DPI2011-27019. A T