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TECHNICAL PAPERS

The Effect of Nonconventional Laser Beam Geometries on Stress Distribution and Distortions in Laser Bending of Tubes

[+] Author and Article Information
Shakeel Safdar1

LPRC, School of Mechanical, Aerospace and Civil Engineering,  University of Manchester, United Kingdom, M60 1QDs.safdar@postgrad.manchester.ac.uk

Lin Li, M. A. Sheikh

LPRC, School of Mechanical, Aerospace and Civil Engineering,  University of Manchester, United Kingdom, M60 1QD

Zhu Liu

Corrosion and Protection Centre, School of Material,  University of Manchester, United Kingdom, M60 1QD

1

Corresponding author.

J. Manuf. Sci. Eng 129(3), 592-600 (Nov 30, 2006) (9 pages) doi:10.1115/1.2716715 History: Received June 06, 2006; Revised November 30, 2006

Laser forming is a spring-back-free noncontact forming method that has received considerable attention in recent years. Compared to mechanical bending, no hard tooling, dies, or external force is used. Within laser forming, tube bending is an important industrial activity with applications in critical engineering systems such as heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters varied to control the process are usually laser power, beam diameter, scanning velocity, and the number of scans. The thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. The existing laser bending methods use either circular or rectangular beams. These beam geometries sometimes lead to undesirable effects such as buckling and distortion in tube bending. This paper investigates the effects for various laser beam geometries on laser tube bending. Finite element modeling has been used for the study of the process with some results also validated by experiments.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic representation of the experimental setup

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Figure 2

Temp versus time (model and experiments)

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Figure 3

Temp versus time (first scan-model)

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Figure 4

Thermal grad in x-direction versus time (model)

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Figure 5

Thermal grad in y-direction versus time (model)

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Figure 6

Thermal grad in z-direction (scanning direction) versus time (model)

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Figure 7

Conceptual representation of the stress development

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Figure 8

Transient bi-axial stress state for a donut beam

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Figure 9

Stress distribution in z-direction (first scan-model)

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Figure 10

Displacement in y-direction (model and experiment)

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Figure 11

Displacement in y-direction on top path

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Figure 12

Displacement in x-direction on top path

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Figure 13

Displacement in z-direction on top path

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Figure 14

Displacement in x-direction on side path

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Figure 15

Experimental validation of cross-sectional profile for circular beam

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Figure 16

Cross-sectional profile of outer and inner walls for different beam shapes (at z=50)

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