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Dynamic
distortion measurements during laser forming of Ti-6Al-4V
and their comparison with a finnite element model
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Proceedings
of the Institution of Mechanical Engineers, Part B:
Journal of Engineering Manufacture, 1st December, v
217, n 12, 2003, p 1685-1696
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M
Reeves (1), A J Moore (1) , D P Hand (1) , J D C Jones
(1) , J R Cho (2) , R C Reed (3) , S P Edwardson (4)
, G Dearden (4) , P French (4) and K G Watkins (4)
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(1)
- School of Engineering and Physical Sciences, Department
of Mechanical Engineering, Heriot-Watt University, Edinburgh,
Scotland, UK
(2) - Rolls-Royce Ni-base UTC, Department of Materials
Science and Metallurgy, University of Cambridge, UK
(3) - Department of Metals and Materials Engineering,
University of British Columbia, Vancouver, British Columbia,
Canada
(4) - Laser Group, Department of Engineering, University
of Liverpool, UK
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Abstract:
Laser
forming is, potentially, an attractive flexible manufacturing
technique for the controlled forming of aerospace alloys.
Laser forming experiments using a continuous-wave CO 2
laser were performed on coupons of material 80 mm £ 80
mm in area and 2 mm thick, with sequential passes of the
laser beam, at a surface scanning rate of 20 mm/s with
90 s of convective cooling between passes. A novel surface
profilometer that was specifically developed to operate
under the conditions of high vibration and stray light
typically found in laser machining applications recorded
transient surface shape changes during individual laser
passes at frame rates of 4 and 0.2 Hz. A finite element
model was developed using ABAQUS for the laser forming
of linear bends in free Ti-6Al-4V sheets, with sequentially
coupled thermal and elastic-plastic analysis incorporating
temperature-dependent material properties. Transient heat
source scanning was implemented to simulate the experiment.
Good agreement was found between the experimental three-dimensional
shape data and those predicted by the transient model.
In particular, the formation of an unwanted `camber’ distortion
perpendicular to the desired main bend was correctly predicted;
its magnitude and temporal evolution throughout the three
laser passes, and during the periods of convective cooling,
agreed well with the experimental data. The model and
the shape measurement technique will enable the future
predictive controlled laser forming of more complex three-dimensional
shapes.
Keywords: laser material processing, laser forming, shape
measurement, profilometry, finite element modelling
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