Laser Shock Peening on a 6056-T4 Aluminium Alloy for Airframe Applications

Abstract

Laser Shock Peening (LSP) is a material enhancement process used to introduce compressive residual stresses in metallic components. This investigation explored the effects of different combinations of LSP parameters, such as irradiance (GW/cm2) and laser pulse density (spots/mm2), on 3.2 mm thick AA6056-T4 samples, for integral airframe applications. The most significant effects that are introduced by LSP without a protective coating include residual stress and surface roughness, since each laser pulse vaporizes the surface layer of the target. Each of these effects was quantified, whereby residual stress analysis was performed using X-ray diffraction with synchrotron radiation. A series of fully reversed bending fatigue tests was conducted, in order to evaluate fatigue performance enhancements with the aim of identifying LSP parameter influence. Improvement in fatigue life was demonstrated, and failure of samples at the boundary of the LSP treatment was attributed to a balancing tensile residual stress.

Killer notches: The effect of as-built surface roughness on fatigue failure in AlSi10Mg produced by laser powder bed fusion

“…The fact that (in general) most crack initiation occurs on surface or near-surface pores highlights the importance of surface quality for improving fatigue properties. Many studies make use of post-process machining or treatment of the surface for improved surface quality, for example by laser shock peening [20,21]. However, the major advantage of additive manufacturing is the complexity of design.…”

A Critical Review of Laser Shock Peening of Aircraft Engine Components

“…In South Africa, research on LSP was initially academically oriented. [105][106][107] The National Aerospace Centre, the University of the Witwatersrand, the Council for Scientific and Industrial Research (CSIR), and AIRBUS Operations GmbH successfully collaborated to create the South African LSP initiative, which had the goal of creating local capability to support the advanced laser-based manufacturing industry. Driven by the needs of local industry, LSP has led to process research related to industrial applications-mainly in the power generation sector, the mining sector, and the aerospace sector.…”

The role of peening processes as a pre‐treatment to anodizing on fatigue behavior of aircraft aluminum alloy

“…Achieving these characteristics typically requires careful design and control of the peening process. [29][30][31][32][33] In addition, a thorough analysis of the surface integrity and morphological and microstructural properties of the component following the peening process is essential to ascertain the absence of factors, such as high surface roughness or the presence of superficial flaws, which may hurt the fatigue properties of the material. [34][35][36][37][38] In this work, the possibility of using laser shock peening (LP) and shot peening (SP) as a pre-treatment to anodizing will be verified to compensate for the decrease in fatigue properties caused by the presence of the anodic layer.…”

“…In order for such processes to provide the required increase in fatigue life, the induced residual stress field must possess certain characteristics, such as an adequate depth of penetration, a predetermined depth and intensity of the residual stress peak, and a well‐defined trend reversal point. Achieving these characteristics typically requires careful design and control of the peening process 29–33 . In addition, a thorough analysis of the surface integrity and morphological and microstructural properties of the component following the peening process is essential to ascertain the absence of factors, such as high surface roughness or the presence of superficial flaws, which may hurt the fatigue properties of the material 34–38 …”