PLASTICITY-INDUCED FATIGUE CRACK CLOSURE IN HIGH-STRENGTH STEELS: REALITY OR ARTIFACT?

Jesús Toribio  Viktor Kharin       

Anales de la Mecánica de la Fractura, nº 25 . 2008 . Pág. -
Ver (.pdf): 7-19

Resumen: Finite-deformation elastoplastic analyses of cracks subjected to mode I cyclic loadings at various load ranges and ratios, as well as with an overload, are presented focusing the evolutions of the near tip deformations. The results manifest the ambiguity of common justifications concerning fatigue crack closure (FCC) as the universal and intrinsic governing factor of fatigue crack growth. The Laird-Smith conceptual mechanism of cyclic crack advance by means of material transfer from the crack tip towards its flanks is visualised, but no crack closure is detected, and its supposed origin in the filling-in a crack with material stretched out of crack plane behind the tip is discarded. Nevertheless, the rate of cyclic crack growth (numerically computed) reproduces the key experimental trends of fatigue cracking concerning the roles of ?K and overload. In addition, calculated compliance curves always manifest nonlinearity, also despite of the absence of closure, which raises serious doubts about their reliability as a method to detect and evaluate crack closure

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Department of Materials Engineering, University of Salamanca, E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain.
Department of Materials Engineering, University of Salamanca, E.P.S., Campus Viriato, Avda. Requejo 33, 49022 Zamora, Spain.