Abstract
This article deals with the computational modelling of the fatigue crack aspect ratio evolution in embedded, surface, and corner cracks located in finite-thickness plates under tensile fatigue. The approach is based on the Paris law for fatigue propagation and an expression for the stress intensity factor (SIF) provided by Newman and Raju. Numerical results indicate that the crack path develops in such a manner that all flaws tend to reach similar aspect ratios, i.e., a preferential crack path does exist along which there is a one-to-one relationship between the aspect ratio and the relative crack depth (a sort of master curve in the matter of fatigue crack path evolution). Such a reference curve corresponds to that of a very superficial initial flaw with almost circular shape. The convergence (quicker or slower approach between fatigue crack paths starting from different initial defects) is higher for surface flaws than for corner cracks, and quicker for the latter than for embedded discontinuities. Corner defects increase their size faster than surface cracks, and the latter do the same quicker than the embedded ones.
Highlights
The stress intensity factor (SIF) in cracked plates of finite thickness is very useful in fracture mechanics and damage tolerance approaches
The convergence is higher for surface flaws than for corner cracks, and quicker for the latter than for embedded discontinuities
In the case of corner cracks, the highest values of the SIF occurred at the free surface along the width direction for cracks in which the depth is higher than the other dimension and at the free surface along the thickness direction for cracks in which the depth is lower than the other dimension [7]
Summary
The stress intensity factor (SIF) in cracked plates of finite thickness is very useful in fracture mechanics and damage tolerance approaches. In plates with a surface crack under tension loading, the maximum SIF is reached at the crack center when the aspect ratio is lower than 0.6 and at the border when it is higher [5]. The maximum SIF is achieved near the free surface [6]. In the case of corner cracks, the highest values of the SIF occurred at the free surface along the width direction for cracks in which the depth is higher than the other dimension and at the free surface along the thickness direction for cracks in which the depth is lower than the other dimension [7]. The crack front evolution for semielliptical cracks in plates was numerically analyzed [8,9,10,11,12,13]
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