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...

An assessment of the plasticity-induced crack-closure concept is made, in light of some of the questions that have been raised on the validity of the concept, and the assumptions that have been made concerning crack-tip damage below the crack-opening stress. The impact of using other crack-tip parameters, such as the cyclic crack-tip displacement, to model crack-growth rate behavior was studied...

Fatigue crack propagation tests under high–low and low–high block loading sequences have been performed in aluminium alloy specimens. The tests were carried out at constant DK conditions. Two stress ratios were analysed: R = 0.05 and R = 0.4. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. The observed transient post load step behaviour is discussed ...

using cold working fastener holes is a simple life enhancement procedure that strengthens metallic components by retarding crack growth around a hole. in the present paper, the residual stress field that is induced by the hole expansion process is obtained based on different material models namely elastic perfect plastic, isotropic hardening and kinematic hardening using three-dimensional finit...

Fatigue-crack-growth (FCG) rate tests were conducted on compact specimens made of an Inconel-718 alloy to study the behavior over a wide range in load ratios (0.1 6 R 6 0.95) and a constant Kmax test condition. Previous research had indicated that high R (>0.7) and constant Kmax test conditions near threshold conditions were suspected to be crack-closure-free and that any differences were attri...

Interest in extending the high cycle fatigue life of structures has increased in the last decade of the 20th century. Since a long fatigue life depends on keeping cyclic loads near or below the fatigue threshold, understanding near-threshold behavior is now all the more important. This paper reviews the status of the ‘threshold of fatigue’ and to a lesser extent its relation to the ‘fatigue lim...

In the present study, plasticity induced crack closure (PICC) concept and three dimensional (3D) finite element methods (FEM) are used to study the effect of compressive residual stress field on the fatigue crack growth from a hole. To investigate the effect of compressive residual stress on crack opening levels and crack shape evolution, Carlson’s experiments were simulated. Crack shape evolut...

The effect of the specimen (or component) thickness has been shown to have a significant effect on closure behaviour and this seems to be related to the relative size of the plastic zone. Real cracks are inherently three-dimensional; plane stress-like behaviour is found close to the region where the crack front intersects the free surface, whereas most of the crack front will experience somethi...

A detailed model of the role of asperities in crack closure has been initiated in Part 1 of this article. Crack opening stress is defined as the far-field stress required to overcome the asperity-induced contact stresses along the crack. In this Part 2, the magnitude of crack opening stress is established as a function of roughness (s0); asperity density (N); maximum stress level (Smax/Sy); sha...

A modified strip-yield model has been developed to simulate the plasticity-induced crack closure under the constant amplitude (CA) and a single overload loading conditions. The paper focuses on the simulation of the near tip crack profiles and stress distributions during the fatigue process. Detailed information on near-tip stress and displacement fields at the maximum load (Pmax), the minimum ...