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Research Papers

Parametric Study on Single Shot and Overlapping Laser Shock Peening on Various Metals via Modeling and Experiments

[+] Author and Article Information
Yunfeng Cao, Yung C. Shin

Center for Laser-Based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

Benxin Wu

Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616

J. Manuf. Sci. Eng 132(6), 061010 (Nov 10, 2010) (10 pages) doi:10.1115/1.4002850 History: Received January 20, 2010; Revised October 12, 2010; Published November 10, 2010; Online November 10, 2010

Laser shock peening (LSP) under water confinement regime involves several complicated physical phenomena. Among these phenomena, the interaction between laser and coating material during LSP is very important to the laser-induced residual stress, which has an important effect on the fatigue and corrosion properties of the substrate material. To gain a better understanding of this interaction, a series of experiments, including single shot, single-track overlapping, and multitrack overlapping LSP, has been carried out on various metals with different coatings. A 3D finite element model has also been developed to simulate the LSP process. Combining this with a previously developed confined plasma model, which has been verified by the experimental data from literature, the 3D finite element model is used to predict the residual stresses induced in the substrate material as well as the indentation profile on the substrate surface. The model prediction of indentation profiles is compared with the experimental data. The residual stresses in the depth direction are also validated against the X-ray diffraction measurement data for 4140 steel and Ti–6Al–4V, and good agreements are obtained for both predictions. The effect of process parameters on the residual stress is also investigated both experimentally and theoretically.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental setup of laser shock peening

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Figure 2

Measured beam profiles: (a) 2D profile and (b) 3D profile

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Figure 3

Schematic of laser traveling scheme for overlapping LSP: (a) single-track and (b) multitrack

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Figure 4

Major energy transport processes related to confined plasma in LSP (2)

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Figure 9

Comparison of indentation depth under different laser power densities (substrate: 4140 steel, coating: black paint, and coating thickness: 50.8 μm)

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Figure 11

In-depth residual stress distribution of benchmark cases: (a) 12 Cr, laser power density: 10 GW/cm2, pulse duration: 3 ns, and Al coating and (b) 316L steel, laser power density: 7 GW/cm2, pulse duration: 10 ns, and Al coating

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Figure 12

Prediction of in-depth residual stress for 4140 steel: (a) in-depth residual stress distribution and (b) comparison of compressive zone depth after LSP (laser pulse duration: 6 ns, beam diameter: 300 μm, and coating thickness: 50 μm)

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Figure 14

Residual stress profile after single-track overlapping LSP on 4140 steel with different laser power densities and overlapping ratios: (a) residual stress on substrate surface and (b) in-depth residual stress (black paint coating: 65 μm, beam diameter: 300 μm, pulse duration: 6 ns, and wavelength: 532 nm)

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Figure 15

In-depth residual stress after single-track overlapping LSP on 4140 steel (black paint coating: 65 μm, beam diameter: 300 μm, pulse duration: 6 ns, wavelength: 532 nm, overlapping ratio: 58%, and laser power density: 5 GW/cm2)

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Figure 16

Indentation depth of different samples under the same LSP conditions (all indentation depths are measured at the left edge of shock peened area, black paint coating thickness: 100 μm, overlapping ratio: 39%, power density: 5.8 GW/cm2, beam diameter: 300 μm, pulse duration: 6 ns, and wavelength: 532 nm)

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Figure 17

Indentation profile on 4140 steel surface (black paint coating thickness: 100 μm, overlapping ratio: 39%, power density: 5.8 GW/cm2, beam diameter: 300 μm, pulse duration: 6 ns, and wavelength: 532 nm)

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Figure 18

Beam profile of LSPT laser

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Figure 19

Comparison of measured XRD results and simulation results for multitrack LSPT 4140 steel samples with different overlapping ratios: (a) overlapping ratio: 40% and (b) overlapping ratio: 50% (laser power density: 7 GW/cm2, beam diameter: 5 mm, pulse duration: 20 ns, wavelength: 1064 nm, and vinyl tape coating)

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Figure 5

Plasma pressure history for laser shock peening of 4140 steel (laser wavelength 532 nm, FWHM 6 ns, and 50 μm black paint)

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Figure 6

Scheme of 3D FEM model

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Figure 7

Path definition in 3D FEM model

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Figure 8

FEM calculation procedure (23)

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Figure 10

Indentation depth under different LSP conditions

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Figure 13

Indentation profile of single-track overlapping LSP on 4140 steel: (a) overlapping ratio: 38%, 6 GW/cm2, (b) overlapping ratio: 58%, 6 GW/cm2, (c) overlapping ratio: 58%, 5 GW/cm2, and (d) overlapping ratio: 68%, 5 GW/cm2 (black paint coating: 65 μm, beam diameter: 300 μm, pulse duration: 6 ns, and wavelength: 532 nm)

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Figure 20

Residual stress distribution for laser shock peening on Ti64 under different laser power densities (beam diameter: 1.2 mm, pulse duration: 6 ns, wavelength: 1064 nm, coating: 100 μm black paint, and overlapping ratio: 50%)

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