Fatigue Failure Analysis in AISI 304 Stainless Wind Turbine Shafts

Wind turbines are equipment of great importance for generating clean energy in countries and regions with abundant winds. However, complex loadings fluctuations to which they are subject can cause premature failure of these equipment due to the material fatigue process. This work evaluates fatigue failures in small AISI 304 stainless steel turbine shafts. Fractographic analysis techniques, chemical analyzes using energy dispersive spectrometry (EDS), and hardness tests were used to verify the origin of the failures, characterize the properties of the components and the material. The nucleation of cracks on the shafts' surface was observed due to a combined effect of variable stresses, geometric stress concentrating details, and surface wear, leading to the crack's propagation until the catastrophic failure. Beach marks were identified in the macrographic examination, characterizing the probable failure due to fatigue. The sensitization phenomenon was also observed.





References:
[1] J. C. Marín, A. Barroso, F. París, J. Cañas, Study of fatigue damage in wind turbine blades, Eng. Fail. Anal. 16 (2009) 656–668. https://doi.org/10.1016/j.engfailanal.2008.02.005.
[2] M. H. Evans, A.D. Richardson, L. Wang, R.J.K. Wood, Serial sectioning investigation of butterfly and white etching crack (WEC) formation in wind turbine gearbox bearings, Wear. 302 (2013) 1573–1582. https://doi.org/10.1016/j.wear.2012.12.031.
[3] Z. Zhang, Z. Yin, T. Han, A.C.C. Tan, Fracture analysis of wind turbine main shaft, Eng. Fail. Anal. 34 (2013) 129–139. https://doi.org/10.1016/j.engfailanal.2013.07.014.
[4] ASTM E3:11, Standard Guide for Preparation of Metallographic Specimens, 2017.
[5] M. Handbook, Metals Handbook: Fractography and Atlas of Fractographs, First Edit, American Society for Metals, 1974.
[6] E. J. Giordani, V. A. Guimarães, T. B. Pinto, I. Ferreira, Study of the nucleation mechanisms of fatigue cracks and fatigue-corrosion of ASTM F 138 stainless steel used as biomaterial, Brazilian Congress of Materials Science and Engineering – CBECIMAT, 2550-2557, Natal, RN, Brazil, 2002.
[7] F. L. Fachini, Deoxidation study of CF8M stainless steel (AISI 316) in a conventional induction furnace, with variable additions of CaSi and CaSiMn, Master's Dissertation in Mechanical Engineering – Superior Institute Tupy, 51p. Joinville, SC, Brazil, 2009.
[8] A. J. Sedriks, Corrosion of Stainless Steels, Second Edi, New York, USA, 1996