Abstract
Laser shock processing is a recently developed surface treatment designed to improve the mechanical properties and fatigue performance of materials, by inducing a deep compressive residual stress field. The purpose of this work is to investigate the residual stress distribution induced by laser shock processing in a 2050-T8 aeronautical aluminium alloy with both X-ray diffraction measurements and 3D finite element simulation. The method of X-ray diffraction is extensively used to characterize the crystallographic texture and the residual stress crystalline materials at different scales (macroscopic, mesoscopic and microscopic).Shock loading and materials’ dynamic response are experimentally analysed using Doppler velocimetry in order to use adequate data for the simulation. Then systematic experience versus simulation comparisons are addressed, considering first a single impact loading, and in a second step the laser shock processing treatment of an extended area, with a specific focus on impact overlap. Experimental and numerical results indicate a residual stress anisotropy, and a better surface stress homogeneity with an increase of impact overlap.A correct agreement is globally shown between experimental and simulated residual stress values, even if simulations provide us with local stress values whereas X-ray diffraction determinations give averaged residual stresses.
Highlights
During the past 20 years, laser shock processing (LSP) has been proposed as a competitive alternative technology to classical surface treatments for improving fatigue, corrosion and wear resistance of metals
LSP uses high energy laser pulses to impact the surface of a metal coated with a protective film, and covered with a transparent layer
Determination of residual stresses on a single 1.5 mm impact we considered the pressure dependence of residual stresses for a single impact, together with an experimental validation using the micro X-ray diffraction technique [21], and the classical 2h = f(sin2w) method
Summary
During the past 20 years, laser shock processing (LSP) has been proposed as a competitive alternative technology to classical surface treatments for improving fatigue, corrosion and wear resistance of metals. It has recently been developed as a practical process amenable to production engineering. This process (Fig. 1) aims at introducing a deep (mm range) residual compressive stress field on metallic targets. LSP uses high energy laser pulses (in the GW/ cm range) to impact the surface of a metal coated with a protective film (organic paint, tape or thin metallic film), and covered with a transparent layer (usually water).
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