Paris' law

About: Paris' law is a research topic. Over the lifetime, 13815 publications have been published within this topic receiving 224818 citations. The topic is also known as: Paris-Erdogan law.

Laser shock peening on fatigue crack growth behaviour of aluminium alloy

Abstract: The effect of laser shock peening (LPS) in the fatigue crack growth behaviour of a 2024-T3 aluminium alloy with various notch geometries was investigated. LPS was performed under a 'confined ablation mode' using an Nd: glass laser at a laser power density of 5 GW cm -2 . A black paint coating layer and water layer was used as a sacrificial and plasma confinement layer, respectively. The shock wave propagates into the material, causing the surface layer to deform plastically, and thereby, develop a residual compressive stress at the surface. The residual compressive stress as a function of depth was measured by X-ray diffraction technique. The fatigue crack initiation life and fatigue crack growth rates of an Al alloy with different preexisting notch configurations were characterized and compared with those of the unpeened material. The results clearly show that LSP is an effective surface treatment technique for suppressing the fatigue crack growth of Al alloys with various preexisting notch configurations.

Particle impact on metal substrates with application to foreign object damage to aircraft engines

Abstract: Foreign object damage (FOD) occurs when hard, millimeter-sized objects such as gravel or sand are ingested into aircraft jet engines Particles impacting turbine blades at velocities up to about 300 m=s produce small indentation craters which can become sites for fatigue crack initiation, severely limiting the lifetime of the blade A framework for analyzing FOD and its e5ect on fatigue cracking is established in this paper Finite element analysis is used to determine the residual stresses and geometric stress concentration resulting from FOD The roles of material rate sensitivity and inertia are delineated The most important non-dimensional parameters governing impact indents are identi7ed, signi7cantly reducing the set of independent parameters The second step in the analysis focuses on the potency of cracks emerging from critical locations at the indents The results have been used to address the question: When and to what extent do the residual stresses and stress concentration caused by FOD reduce the critical crack size associated with threshold fatigue crack growth? For deep indents, it is found that elastic stress concentration is the dominant factor in reducing critical crack threshold when the applied cyclic load ratio, R, is large, otherwise the residual stresses are also important Comparisons with a set of experiments conducted in parallel with the theory show that the numerical approach can account for various phenomena observed in practice ? 2002 Elsevier Science Ltd All rights reserved