Finite element analysis of laser shock peening of 2050-T8 aluminum alloy

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.International audienceLaser 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

Random-type scanning patterns in laser shock peening without absorbing coating in 2024-T351 Al alloy: A solution to reduce residual stress anisotropy

“…In addition, when simulating a large number of LSPwC pulses applied at different locations and times, a minimum time interval between successive impacts had to be selected to ensure a quasi-residual stress field (shock and relaxation). A time interval of 10 À 5 s between consecutive pulses is a period of time long enough to calculate the residual stresses [12]. These data and the scanning pattern were programmed using VDLOAD Abaqus subroutine.…”

“…As a result, residual stresses are induced on and around the spot. This stress induction mechanism resembles that of shrink fit technique, where a column is fit into a pipe [12] and [30]. On condition that the outer radius of pipe is infinite, residual stress field generated by shrink fit can be expressed as: s r ¼ Àk and s ϑ ¼ Àk for r rR; s r ¼ Àk(r/R) À j and s ϑ ¼(j À 1)k(r/R) À j for r 4R, where s r is the radial residual stress, s ϑ is the angular residual stress, k is the residual stress in the spot zone and j is the decay exponent (typically between 1.5 and 2).…”

“…Differences between the magnitude of the residual stress after LSP in the x-direction (s x ) and in the y-direction (s y ) in the surface region are found in multitude of Refs. [12][13][14][15], but until now the explanation for this residual stress anisotropy has been an open question [8]. Trdan et al [16] (in which residual stress evaluation also confirmed beneficial compressive residual stresses after LSPwC, with higher compressive residual stress in the advancing LSPwC) studied the LSPwC effects on the dislocation generation, dislocation transition and grain refinement through-depth distribution, which could be related to the residual stress anisotropy.…”

Dynamic Thermo-Elasto-Plasticity FE Analysis on Nano- and Femto-second Laser Shock Peenings for a Ferrite Material

“…Dynamic FE analyses were carried out by means of the property is assumed to be within an elastio-perfectly-plasticity based on the previous study for Alminium alloy 5,6) and the adopted mechanical properties are summarized in Table 1. Figure 2 shows the comparison between the yield stress and strain rate obtained in …”

“…minimum element size of 6x0.4m). Infinite elements were adopted around the analyzed area as boundary conditions in order to avoid the influence of the reflected wave 5,6) . The modeling of immersed water for confinement of the plasma is neglected as in the previous study 5,6) since the shock load due the the ablation of water is directly applied as the surface pressure in this analysis.The time history for the applied pressure (P0(t)) is shown in the Fig.…”