Recent Advances in Modelling and Experimental Evaluation of PlasticityInduced Fatigue Crack Closure A. Kotousov1,∗, J. Vidler1, J. Hughes1, A. Khanna2, C. Wallbrink3 1 School of Mechanical Engineering, The University of Adelaide, Adelaide, SA 5005 Australia 2 The University of Queensland, St Lucia, QLD 4072, Australia 3 Aerospace Division, Defence Science and Technology Group, Melbourne, VIC 3207 Australia ∗ andrei.kotousov@adelaide.edu.au Keywords: crack closure, fatigue life evaluation, variable amplitude loading. Loading cycles of variable amplitude are typical in aerospace, wind turbine, transport, pipeline and many other industrial applications. The evaluation of fatigue life of structural components working under variable amplitude loading is very challenging. There is a broad consensus amongst the international fracture community regarding the significant problems and deficiencies of the existing fatigue life evaluation procedures [1]. At the core of any of advanced fatigue life evaluation methods and computer programs is a crack tip load opening (and closure) model that aims to simulate the crack closure phenomena [2]. Crack closure implies that a fatigue crack remains closed for some portion of a tensile load cycle due to the formation of a plastic wake behind the crack tip, which can significantly reduce the fatigue crack driving force. This paper discusses the latest advances on analytical modelling and experimental evaluation of fatigue crack opening loads under variable amplitude loading conditions. In particular, we present the exact solution obtained by the distributed dislocation technique for a finite fatigue crack propagating under constant amplitude of cyclic stresses as well as a new experimental method [3, 4], which is capable to evaluate cycle-by-cycle crack tip opening load values for large numbers of fatigue cycles. Further, we discuss the applications of these new developments to development and validation of more adequate fatigue life evaluation procedures. References [1] Khanna, A., Kotousov, A. (2020). The potential for structural simulation to augment full scale fatigue testing: A review. Progress in Aerospace Sciences, 121, 100641. [2] Codrington, J. and Kotousov, A. (2009). A crack closure model of fatigue crack growth in plates of finite thickness under small-scale yielding conditions. Mechanics of Materials, 41, 165-173. [3] Wallbrink, C., Hughes, J. M., Kotousov, A. (2023). Application of an advanced piezoelectric strain sensor for crack closure measurement. Int. J. of Fatigue, 167, 107286. [4] Wallbrink, C., Hughes, J. M., Kotousov, A. (2023). Experimental investigation of crack opening loads in an aircraft load spectrum. Int. J. of Fatigue, 171, 107560. 107
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