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TECHNICAL PAPERS

From Incident Laser Pulse to Residual Stress: A Complete and Self-Closed Model for Laser Shock Peening

[+] Author and Article Information
Benxin Wu, Yung C. Shin

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

J. Manuf. Sci. Eng 129(1), 117-125 (Jun 29, 2006) (9 pages) doi:10.1115/1.2386180 History: Received November 30, 2005; Revised June 29, 2006

Laser shock peening (LSP) is emerging as a competitive alternative technology to classical treatments to improve fatigue and corrosion properties of metals for a variety of important applications. LSP is often performed under a water confinement regime, which involves several complicated physical processes. A complete and self-closed LSP model is presented in this paper, which requires a sequential application of three submodels: a breakdown-plasma model, a confined-plasma model, and a finite element mechanics model. Simulation results are compared with experimental data in many aspects under a variety of typical LSP conditions, and good agreements are obtained.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagrams for (a) laser shock peening under the water confinement regime configuration and (b) the structure of a complete model for LSP

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Figure 2

The major (a) energy and (b) mass transport processes related to confined plasma in laser shock peening

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Figure 3

Schematic diagram of the confined plasma model

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Figure 4

Schematic diagram of the geometry for the finite element mechanics model (due to axisymmetry, only half of the cylinder is shown)

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Figure 5

The calculation procedure of the finite element mechanics model

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Figure 6

A typical history of plastically dissipated energy of the target workpiece in LSP

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Figure 7

The profile as a function of time for a laser pulse with a FWHM (full-width-at-half-maximum) duration of 25ns

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Figure 8

Transmitted versus incident peak laser power densities, laser duration: 25ns, 1064nm (measurements from (2))

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Figure 9

Comparison of experimental (4,27) and simulation results for peak pressures of the confined plasma (laser pulse duration 25ns, wavelength 1064nm)

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Figure 10

A typical SRT laser pulse profile (28) (power density: 1.0GW∕cm2)

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Figure 11

Comparison of experimental (28) and simulation results for peak pressures with SRT laser pulses

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Figure 12

The transient number densities of carbon atoms and electrons in the “confined plasma” predicted by the “confined plasma” model (coating material: graphite, laser pulse duration: 20ns, wavelength: 1064nm, power density: 0.52GW∕cm2)

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Figure 18

Residual stress variation with depth for the 12Cr steel workpiece after three LSP impacts, laser pulse duration: 25ns, peak power density: 8GW∕cm2 (the continuous line represents modeling result, and the small rectangles represent experimental result (9))

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Figure 17

Residual stress variation with depth for the 316L steel workpiece after one LSP impact, laser pulse duration: 8.5ns, peak power density: 8GW∕cm2 (the continuous line represents modeling result, and the small rectangles represent experimental result (32))

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Figure 16

Residual stress variation with depth for the A356-T6 alloy workpiece after one LSP impact, laser pulse duration: 25ns, peak power density: 0.9GW∕cm2 (the continuous line represents modeling result, and the small rectangles represent experimental result (31))

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Figure 15

The model predicted shock wave propagation in the A356-T6 alloy workpiece (laser pulse duration: 25ns, peak power density: 1.5GW∕cm2)

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Figure 14

The finite element mechanics model predicted Von Mises residual stress field of the 35CD4 steel workpeice after one LSP impact (laser beam radius: 4mm, stress unit in Pa)

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Figure 13

Residual stress distribution along the 35CD4 steel workpiece surface after one LSP impact (laser beam radius: 4mm, the continuous line represents model predictions, and the small rectangles represent experimental result (11))

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