Issue 41

J.V. Sahadi et alii, Frattura ed Integrità Strutturale, 41 (2017) 106-113; DOI: 10.3221/IGF-ESIS.41.15 113 C ONCLUSIONS urther investigation of the biaxial fatigue behaviour of Waspaloy concluded that even more advanced formulations, as the strain based critical plane approaches assessed here, give poor correlations for the equi-biaxial loading cases. The lack of torsional fatigue data, and the estimation of some of these parameter for the implementation of the Fatemi-Socie formulation, resulted in poor correlation with most test cases. Furthermore, the FS parameter presented an overly conservative behaviour with great scatter of results. In contrast, the SWT parameter presented better correlation with the biaxial fatigue data. Predictions obtained with it lied mostly within or near the bounds of twice and half of the fatigue life. Finally, regarding the evaluation of critical planes, the FS parameter predicted failure nucleating on planes at 45º and 135º of the vertical axis, and the SWT predicted failures on planes at 0º and 180º. A CKNOWLEDGMENTS he authors are grateful for the support of Rolls-Royce plc and the Brazilian National Council of Technological and Scientific Development (CNPq), grant number 207297/2015-0. A portion of this work was part of a Collaborative R&T Project SILOET supported by the Technology Strategy Board. R EFERENCES [1] Bonnand, V., et al. Investigation of multiaxial fatigue in the context of turboengine disc applications. International Journal of Fatigue, 33(8) (2011) 1006-1016. [2] Kalluri, S., Bonacuse, P. J., In-phase and out-of-phase axial-torsional fatigue behavior of haynes 188 superalloy at 760 C. Advances in multiaxial fatigue. ASTM International, (1993). [3] Found, M. S., Upul, S. F., Miller, K. J., Requirements of a new multiaxial fatigue testing facility. Multiaxial fatigue. ASTM International, (1985). [4] Andrews, J. M. H., Ellison, E. G., A testing rig for cycling at high biaxial strains. Journal of Strain Analysis, 8(3) (1973) 168-175. [5] Makinde, A., Thibodeau, L., Neale, K. W., Development of an apparatus for biaxial testing using cruciform specimens. Experimental mechanics, 32(2) (1992) 138-144. [6] Boehler, J. P., Demmerle, S., Koss, S., A new direct biaxial testing machine for anisotropic materials. Experimental mechanics, 34(1) (1994) 1-9. [7] Hannon, A., Tiernan, P., A review of planar biaxial tensile test systems for sheet metal. Journal of materials processing technology, 198(1) (2008) 1-13. [8] Sahadi, J. V., et al., Comparison of multiaxial fatigue parameters using biaxial tests of Waspaloy. International Journal of Fatigue (2017). [9] Crossland, B., Effect of large hydrostatic pressures on the torsional fatigue strength of an alloy steel. Proc. Int. Conf. on Fatigue of Metals. Vol. 138. Institution of Mechanical Engineers London, (1956). [10] Findley, W. N., A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending. No. 6. Engineering Materials Research Laboratory, Division of Engineering, Brown University, (1958). [11] Matake, T., An explanation on fatigue limit under combined stress. Bulletin of JSME 20.141 (1977) 257-263. [12] Socie, D. F., Marquis, G. B., Multiaxial Fatigue. Warrendale, Pa: Society of Automotive Engineers, (2000). [13] Brown, M. W., Miller, K. J., A theory for fatigue failure under multiaxial stress-strain conditions. Proceedings of the Institution of Mechanical Engineers, 187(1) (1973) 745-755. [14] Kurath, P., Multiaxial fatigue life predictions under the influence of mean-stresses. Urbana, 51 (1988) 61801. [15] Smith, K. N., Topper, T. H., Watson, P., A stress-strain function for the fatigue of metals(Stress-strain function for metal fatigue including mean stress effect), Journal of materials, 5 (1970) 767-778. [16] Socie, D. F., Multiaxial fatigue damage models. Transactions of the ASME. Journal of Engineering Materials and Technology, 109(4) (1987) 293-298. [17] Lopez-Crespo, P., et al. Study of crack orientation and fatigue life prediction in biaxial fatigue with critical plane models. Engineering Fracture Mechanics, 136 (2015) 115-130. T