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...

Multi-site damage (MSD) has been a challenge to aircraft, civil and power plant structures. In real life components are subjected to cracking at many vulnerable locations such as the bolt holes. However, we do not consider for the presence of multiple cracks. Unlike components with a single crack, these components are difficult to predict. When two cracks approach one another, their stress fiel...

Advanced carbon-fibre composite materials are increasingly used as primary structural components in aviation and aerospace industries due to their high stiffness-to-density ratio. The design of composite aerostructures is required to meet a number of safety criteria, in particular, the damage tolerance. Delaminations, which are caused by the impact of foreign objects (tool drops, runway debris,...

A three-dimensional extended finite element method (X-FEM) coupled with a narrow band fast marching method (FMM) is developed and implemented in the Abaqus finite element package for curvilinear fatigue crack growth and life prediction analysis of metallic structures. Given the level set representation of arbitrary crack geometry, the narrow band FMM provides an efficient way to update the leve...

The effect of stitching on mode I and mode II strain energy release rates for debond configurations is studied using an analysis based on plate finite elements and the virtual crack closure technique. The stitches were modeled as discrete nonlinear fastener elements with a compliance determined by experiment. The axial and shear behavior of the stitches was considered with both the compliances ...

BACKGROUND Following Cambodia's implementation of the 100% condom use program with enforcement of condom use and STI treatment services for sex workers in 2001, sexually transmitted infection and HIV declined markedly. In 2008, Cambodia implemented a law to ban brothel-based sex work. We reported trends in unprotected vaginal intercourse with sex workers among heterosexual men buying sex before...

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...