A thorough examination of the quasi-static penetration of a floating elastic-brittle plate via a fracture mechanics approach has been presented by Bažant and Kim. Bažant and Kim reach the conclusion that there is a size effect (in terms of the plate thickness, h). A few of the assumptions made by these authors will be examined in this discussion. The formulation presented by Bažant and Kim assu...

Fatigue crack growth can be strongly influenced by crack closure, i. e., the contacting of the opposing faces of a fatigue crack above the minimum load in a loading cycle. This crack closure shields the crack tip from the full stress field, but different views are held regarding the extent of this shielding. The type of closure, whether it be plasticity-induced, or roughness-induced may also pl...

According to the Gri th criterion, a crack propagation occurs provided that the derivative of the energy functional with respect to the crack length reaches some critical value. We consider a generalization of this criterion to the case of nonlinear cracks satisfying a non-penetration condition and investigate the dependence of the shape derivative of the energy functional on the crack shape. I...

Fretting nucleation models and three-dimensional finite element analyses are used to compute the fretting fatigue life for metallic components. The models predict crack nucleation cycles and location(s). Discrete crack growth simulations provide stress intensity factor histories, with multiple, non-planar, three-dimensional cracks possible. The histories are input into crack growth rate model(s...

Preliminary testing of a complete landing gear under fatigue test has demonstrated the applicability of the test using Acoustic Emission (AE) resonant sensors attached to the outer surface of the landing gear assembly. Attenuation trials were conducted which confirmed that attenuation through the main casing is low and provided data for optimisation of sensor positioning. Background noise level...

The crack growth properties of several sealing glasses were measured by using constant stress rate testing in 2% and 95% RH (relative humidity). Crack growth parameters measured in high humidity are systematically smaller (n and B) than those measured in low humidity, and crack velocities for dry environments are 100 lower than for wet environments. The crack velocity is very sensitivity to sma...

This paper presents a new incremental formulation for predicting the curved growth paths of twodimensional fatigue cracks. The displacement and traction boundary integral equations (BIEs) are employed to calculate responses of a linear elastic cracked body. The Paris law and the principle of local symmetry are adopted for defining the growth rate and direction of a fatigue crack, respectively. ...

Subcritical crack growth in fused silica is treated as a stress assisted chemical reaction between water and strained bonds at the crack tip. In this work, the kinetics of the reaction is modeled by assuming the stress reduces the energy barrier of the activated complex by affecting both the activation enthalpy and entropy, where the stress dependence can take different forms. This theory is co...

Cracks can occur in the articular cartilage surface due to the mechanical loading of the synovial joint, trauma or wear and tear. However, the propagation of such cracks under different frequencies of loading is unknown. The objective of this study was to determine the effect of frequency of loading on the growth of a pre-existing crack in cartilage specimens subjected to cyclic tensile strain....

Abstract: To ensure the rail transportations safety, evaluation of fatigue behavior of the rail steel is necessary. High cycle fatigue behaviour of a rail steel was the subject of investigation in this research using fracture mechanics. Finite element method (FEM) was used for analyzing the distribution of the stresses on the rail, exerted by the external load. FEM analysis showed that the ...