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TECHNICAL PAPERS

Numerical Investigation of Opposing Dual Sided Microscale Laser Shock Peening

[+] Author and Article Information
Yajun Fan, Youneng Wang, Sinisa Vukelic, Y. Lawrence Yao

Department of Mechanical Engineering, Columbia University, New York, NY 10027

J. Manuf. Sci. Eng 129(2), 256-264 (Aug 30, 2006) (9 pages) doi:10.1115/1.2540771 History: Received February 06, 2006; Revised August 30, 2006

Laser shock peening (LSP) is an innovative process which imparts compressive residual stresses in the processed surface of metallic parts to significantly improve fatigue life and fatigue strength of this part. In opposing dual sided LSP, the workpiece can be simultaneously irradiated or irradiated with different time lags to create different surface residual stress patterns by virtue of the interaction between the opposing shock waves. In this work, a finite element model, in which the hydrodynamic behavior of the material and the deviatoric behavior including work hardening and strain rate effects were considered, was applied to predict residual stress distributions in the processed surface induced under various conditions of the opposing dual sided microscale laser shock peening. Thus the shock waves from each surface will interact in different ways through the thickness resulting in more complex residual stress profiles. Additionally, when treating a thin section, opposing dual sided peening is expected to avoid harmful effects such as spalling and fracture because the pressures on the opposite surfaces of the target balance one another and prohibit excessive deformation of the target. In order to better understand the wave–wave interactions under different conditions, the residual stress profiles corresponding to various workpiece thicknesses and various irradiation times were evaluated.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of opposing dual sided laser shock peening

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Figure 2

The FEM simulation chart for microscale LSP

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Figure 3

Mesh of finite element model for dual sided laser shock peening with axis-symmetric condition

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Figure 4

Schematic of various irradiation methods in LSP. H is the thickness of the processed thin section.

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Figure 5

Comparison of the calculated top surface residual stresses between one sided irradiation and zero phase dual sided irradiation in the samples with different thickness: (a) 100 and (b) 200μm thick. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 6

Comparison of the time history of pressure at the central point in the midplane between one sided irradiation and the zero phase dual sided irradiation on the 100μm thick plate. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 7

The computed residual stress distributions within the 100μm thick plate by various irradiation methods. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 8

The calculated top surface residual stress distributions by various phases in dual sided irradiation. Similar residual stress distributions are also found at the bottoms. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 9

Comparison of the time history of pressure at the central point in the midplane by various irradiation methods on the 200μm thick plate. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 10

The calculated residual stress distributions through the thickness at the central line of the 100 and 200μm thick plates by various irradiation methods. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 11

Wave–wave interactions within the copper plate of 100μm thickness by full phase irradiation. Laser intensity is 4.95GW∕cm2, beam spot size is 12μm, and pulse duration is 50ns.

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Figure 12

The computed residual stress distributions within the 100μm thick plate by various irradiation methods. Beam spot size is 12μm, pulse duration is 10ns, and the same peak pressure (3GPa) of loading is maintained.

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Figure 13

Calculated pressure distributions through the thickness at the central line of the 100μm thick plate in full phase irradiation of micro scale LSP with durations of 10 and 50ns

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