This paper reviews the capabilities of a plasticity-induced crack-closure model to predict fatigue lives of metallic materials using “small-crack theory” for various materials and loading conditions. Crack tip constraint factors, to account for three-dimensional stateof-stress effects, were selected to correlate large-crack growth rate data as a function of the effective-stress-intensity factor...

An understanding of how fatigue cracks grow in bone is of importance as fatigue is thought to be the main cause of clinical stress fractures. This study presents new results on the fatigue-crack growth behavior of small surface cracks (approximately 75-1000 microm in size) in human cortical bone, and compares their growth rates with data from other published studies on the behavior of both surf...

The mean and the life-limiting behavior under fatigue of the nickel-based superalloy, IN100, separated (or converged) as a function of stress level and dwell loading. This behavior was related to the control of the life-limiting behavior by the smallcrack growth regime, producing its much slower response to stress level and dwell-time, relative to the mean-lifetime behavior. The lifetime probab...

Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS) code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b...

Cracks and craze lines are often observed in the enamel of human teeth, but they rarely cause tooth fracture. The present study evaluates fatigue crack growth in human enamel, and compares that to the fatigue response of sintered hydroxyapatite (HAp) with similar crystallinity, chemistry and density. Miniature inset compact tension (CT) specimens were prepared that embodied a small piece of ena...

A nominally straight crack of finite length is subjected to plane-strain loadings. A perturbation method is developed for calculating the stress-intensity factors, based on an asymptotic analysis of the governing hypersingular boundary integral equation for the crack-opening displacement. Known exact results for a shallow circular-arc crack are recovered, correct to second order in the small ge...

Recent finite-element results by S. Cl. Larsson and A. J. Carlsson suggest a limited range of validity to the ‘small scale yielding approximation’, whereby small crack tip plastic zones are correlated in terms of the elastic stress intensity factor, It is shown with the help of a model for plane strain yielding that their results may be explained by considering the non-singular stress, acting p...

A basic assumption often made in risk/reliability based inspection planning is that a Bayesian approach can be used. This implies that probabilities of failure can be updated in a consistent way when new information (from inspections and repairs) becomes available. The Bayesian approach and a no-crack detection assumption implies that the inspection time intervals usually become longer and long...

In this paper, the plates made of functionally graded material (FGM) with and without a crack are numerically simulated, employing the finite element method (FEM). The material property variations are defined to be fully continuous; therefore, the elements can be as small as required. For this purpose, variations of the material properties are applied in both the integration points and in the n...

The difference in the potential energy in an elastic three-dimensional domain with a V-notch with and without a small crack ( δΠ ) under a general mixed mode I+II+III loading is provided as an asymptotic series. It involves the V-notch edge stress intensity functions, the area of the formed crack, and special geometrical functions that can be pre-computed and tabulated. Importantly, the stress ...