Stress concentration

About: Stress concentration is a research topic. Over the lifetime, 23250 publications have been published within this topic receiving 422911 citations.

Laser shock processing of 2024-T62 aluminum alloy

Abstract: Laser shock processing (LSP) is a relatively new technique for strengthening metals. A method developed for optimizing the LSP parameters is reported in this paper. The effects of LSP on the microstructure, hardness, surface roughness, residual stress, fatigue life, fatigue crack growth (FCG) of 2024-T62 aluminum alloy were investigated. The fatigue life of the laser-shocked specimens was two times greater than that of the unshocked specimens. The fatigue crack growth rates (FCGRs) at a given stress intensity were reduced by over one order of magnitude. The fatigue behavior improvements were attributed to a combination of increased dislocation density, decreased surface roughness and compressive residual stress induced by the laser shock waves.

Driving forces for localized corrosion‐to‐fatigue crack transition in Al–Zn–Mg–Cu

Abstract: Research on fatigue crack formation from a corroded 7075-T651 surface provides insight into the governing mechanical driving forces at microstructure-scale lengths that are intermediate between safe life and damage tolerant feature sizes. Crack surface marker-bands accurately quantify cycles (Ni) to form a 10–20 μm fatigue crack emanating from both an isolated pit perimeter and EXCO corroded surface. The Ni decreases with increasing-applied stress. Fatigue crack formation involves a complex interaction of elastic stress concentration due to three-dimensional pit macro-topography coupled with local micro-topographic plastic strain concentration, further enhanced by microstructure (particularly sub-surface constituents). These driving force interactions lead to high variability in cycles to form a fatigue crack, but from an engineering perspective, a broadly corroded surface should contain an extreme group of features that are likely to drive the portion of life to form a crack to near 0. At low-applied stresses, crack formation can constitute a significant portion of life, which is predicted by coupling macro-pit and micro-feature elastic–plastic stress/strain concentrations from finite element analysis with empirical low-cycle fatigue life models. The presented experimental results provide a foundation to validate next-generation crack formation models and prognosis methods.

Fatigue crack growth and crack closure in an AlMgSi alloy

Abstract: This study reports an experimental investigation of fatigue crack propagation in AlMgSi1-T6 aluminium alloy using both constant and variable load amplitudes. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. For the constant amplitude tests four different stress ratios were analysed. The crack closure parameter U was calculated and related with AK and the stress ratio, R. The threshold of the stress intensity factor range, ΔK th , was also obtained. Fatigue crack propagation tests with single tensile peak overloads have been performed at constant load amplitude conditions. The observed transient post overload behaviour is discussed in terms of the overload ratio, ΔK baseline level and R. The crack closure parameter U trends are compared with the crack growth transients. Experimental support is given for the hypothesis that crack closure is the main factor determining the transient crack growth behaviour following overloads on AlMgSi1-T6 alloy for plane stress conditions.