Abstract
This article deals with the locally multiaxial fatigue behaviour of high strength steel. To this end, the influence of the cracking path deflections (at the micro level) on the plasticity-induced fatigue crack growth is analyzed. With regard to this, a modelling by means of the finite element method was performed for a given stress intensity factor in the Paris regime, considering the existence of micro-roughness in the crack path (local micro-deflections with distinct micro-angles as a function of the microstructure of the material). The numerical results allow one to obtain the fatigue crack propagation rate and compare it with that for the same material in the absence of micro-roughness (with no micro-crack deflections, i.e., uniaxial fatigue behaviour).
Highlights
Fatigue cracks exhibit surface micro-roughness caused by material microstructure, e.g., pearlitic steel shows continuous deflections in the fatigue crack path [1]
A modelling by means of the finite element method was performed for a given stress intensity factor in the Paris regime, considering the existence of micro-roughness in the crack path
The non-linear crack configuration should be taken into account in the matter of crack-morphological aspects in fracture mechanics [2], since variations in crack deflection features influence considerably the fatigue crack propagation rates and threshold stress intensity factor range [3]
Summary
Fatigue cracks exhibit surface micro-roughness caused by material microstructure, e.g., pearlitic steel shows continuous deflections in the fatigue crack path [1]. With regard to plastic crack advance, the Laird-Smith mechanism of propagation by cyclic blunting and re-sharpening, which transfers material from the crack tip towards its flanks, is visualized in [4]. With this sort of modeling procedure, the rate per cycle reproduced common trends of the fatigue cracking dependence on loading range and overload [5]. In the matter of plasticity-induced fatigue crack closure, a strong controversy still does exist, with researchers raising doubts about its mere existence [4,5], and others obtaining it as a numerical result [7], the total length of closed crack at minimum load in plane strain is shown to be a small fraction of the total crack length [8]
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