On numerical analysis of damage evolution in cyclic elastic‐plastic crack growth problems

Abstract

Structures subjected to severe cyclic loading may fail due to low cycle fatigue. During the latter part of the fatigue life the crack growth rate may increase due to crack growth from static failure modes. This was investigated numerically by Skallerud and Zhang (Int. J. Solids Struct. 34, 3141–3161, 1997) for a butt‐welded plate with a circular crack growing from the centre of the weld. The weld material was slightly overmatching, and for simplicity, base material properties were employed in the finite element model. The predicted crack growth rate was significantly underpredicted in the early part of crack growth. In the present investigation, more detailed material modelling was used, and some metallurgical aspects were addressed. The fatigue part of the crack growth was determined by using the computed cyclic J‐integral, and the static mode crack growth from ductile tearing is determined from computations accounting for void nucleation/growth/coalescence by means of a modified Gurson–Tvergaard model.

Effect of cyclic plastic strain on fatigue crack growth

“…Despite this shortcoming, efforts in this area have been reported, e.g. [21,[33][34][35][36]. In order to support the application of the approach, approximation formulas for the cyclic DJ-integral have already been derived together with the first proposal of this concept [14,15,37,38], initially without considering crack closure.…”

A new cyclic J-integral for low-cycle fatigue crack growth

“…Since the cyclic plastic zone is large compared to specimen dimensions during low-cycle fatigue (LCF), the control parameter for characterizing crack growth will be much more complex. In the past a few years, a number of investigators have attempted to describe the rules of LCF crack propagation by the exponential equation with the cyclic J-integral, ΔJ [2][3][4][5][6][7][8][9][10][11][12] . Due to the fact that the cyclic stress-strain responses related with load processes aren't linear during LCF, in which J min and J max denoting respectively the J-integral for the minimum and maximum loading of fatigue are both related to history of loading, so the value of cyclic J-integral can't be simply evaluated by the difference between J max and J min .…”