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Research Papers

Three-Dimensional Numerical Simulation and Experimental Study of Sheet Metal Bending by Laser Peen Forming

[+] Author and Article Information
Yongxiang Hu1

School of Mechanical Engineering, State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, Chinahuyx@sjtu.edu.cn

Yefei Han, Zhenqiang Yao, Jun Hu

School of Mechanical Engineering, State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China

1

Corresponding author.

J. Manuf. Sci. Eng 132(6), 061001 (Oct 15, 2010) (10 pages) doi:10.1115/1.4002585 History: Received December 27, 2009; Revised September 10, 2010; Published October 15, 2010; Online October 15, 2010

Laser peen forming (LPF) is a purely mechanical forming method achieved through the use of laser energy to form complex shapes or to modify curvatures. It is flexible and independent of tool inaccuracies that result from wear and deflection. Its nonthermal process makes it possible to form without material degradation or even improve them by inducing compressive stress over the target surface. In the present study, a fully three-dimensional numerical model is developed to simulate the forming process of laser peen forming. The simulation procedure is composed of several steps mainly including the shock pressure prediction, the modal analysis, and the forming process calculation. System critical damping is introduced to prevent unnecessary long post-shock residual oscillations and to greatly decrease the solution time for simulation. The bending profiles and angles with different thicknesses are experimentally measured at different scanning lines and scanning velocities to understand the process and validate the numerical model. The calculated bending profiles and angles agree well with the trend of the measured results. But it is found that simulations with the Johnson–Cook model are more consistent, matching the experimental results for the thick sheet metal with a convex bending, while the elastic-perfectly-plastic model produces a better agreement even though with underestimated values for the thinner sheet metal with a concave bending. The reason for this phenomenon is discussed, combining the effects of strain rate and feature size. Both the simulation and the experiments show that a continuous decrease in bending angle from concave to convex is observed with increasing specimen thickness in general. Large bending distortion is easier to induce by generating a concave curvature with LPF, and the angle of bending distortion depends on the number of laser shocks.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 2

Possibilities of curvature generation by laser peen forming

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Figure 3

Schematic of experimental setup for laser peen forming

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Figure 4

Irradiation of laser pulses on the target surface

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Figure 5

Time history of the shock pressure profile, α=0.20

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Figure 6

The flow chart of the numerical simulation of laser peen forming

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Figure 7

Mesh for the three-dimensional simulation of laser peen forming process, 2 mm thick target

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Figure 8

Calculated vertical displacement with different added damping ratios, 2 mm thick target, JC model: (a) the effect on the initial response at the shocked center on the top surface and (b )the effect on the stabilization of bending at the free end

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Figure 1

Schematic of the laser peen forming process: (a) laser shock peening and (b) laser peen forming

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Figure 9

Simulated transient vertical displacement development at the free end after four successive laser shocks in the first scanning line, JC model: (a) 0.5 mm thick target and (b) 2.0 mm thick target

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Figure 10

The simulated contours of deformation, Ip=3.85 GW/cm2, R=0.6 mm, Nx=7, and Vy=720 mm/min: (a) 0.5 mm thick target, EPP model and (b) 2 mm thick target, JC model

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Figure 11

Bending profiles of numerical and experimental results for different thicknesses, Ip=3.85 GW/cm2, R=0.6 mm, Nx=7, and Vy=720 mm/min: (a) 0.5 mm thick target and (b) 2 mm thick target

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Figure 12

Relationship between scanning-line number and bending angle of numerical and experimental results, Ip=3.85 GW/cm2, R=0.6 mm, and Vy=720 mm/min: (a) 0.5 mm thick target and (b) 2 mm thick target

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Figure 13

Relationship between scanning velocity and bending angle of numerical and experimental results with different thickness, Ip=3.85 GW/cm2, R=0.6 mm, and Nx=3: (a) 0.5 mm thick target and (b) 2 mm thick target

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Figure 14

Bending angles of numerical and experimental results for different thicknesses, R=0.6 mm and Nx=7: (a) Ip=3.85 GW/cm2 and (b) Ip=7.70 GW/cm2

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Figure 15

The surface layer model to explain the size effect in LPF

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