COL 9(5), 051402(2011) CHINESE OPTICS LETTERS May 10, 2011
Deformation behavior of laser bending of
circular sheet metal
Q. Nadeem
∗
and S. J. Na
Department of Mechanical Engineering, KAIST, Yuseong-Gu, Daejeon, South Korea
∗
Corresponding author: engr.nadeemqaiser@gmail.com
Received October 26, 2010; accepted January 3, 2011; posted online April 18, 2011
The application of a thermal source in non-contact forming of sheet metal has long been used. However, the
replacement of this thermal source with a laser beam promises much greater controllability of the process.
This yields a process with strong potential for application in aerospace, shipbuilding, automobile, and
manufacturing industries, as well as the rapid manufacturing of prototypes and adjustment of misaligned
components. Forming is made possible through laser-induced non-uniform thermal stresses. In this letter,
we use the geometrical transition from rectangular to circle-shaped specimen and ring-shaped specimen to
observe the effect of geometry on deformation in laser forming. We cond uct a series of exp eriments on a
wide range of specimen geometries. The reasons for this behavior are also analyzed. Experimental results
are compared with simulated values using the software ABAQUS. The utilization of line energy is found to
be higher in the case of laser forming along linear irradiation than along curved ones. We also analyze the
effect of strain hindrance. The findings of the study may be useful for the inverse problem, which involves
acquiring the process parameters for a known target shape of a wide range of complex shape geometries.
OCIS codes: 140.0140, 160.0160.
doi: 10.3788/COL201109.051402.
Forming techniques consist of metal working proc esses in
which the material is shape d in solid state by plastic de-
formation. There are two classifications of forming tech-
niques: bulk forming a nd sheet forming. Bulk forming
comprises rolling, extrusion, and forging. On the other
hand, bending and contouring are common processes of
sheet forming. Conventionally, shee t metal bending us-
ing punch and die requires hard tooling, external forces,
and spring back action. The idea of using lasers for
forming sheet metal was first conceived by Kitamura in
Japan
[1]
. The laser forming process is concerned with
the b e nding a nd correction of sheet metals/tubes using
a laser beam. Laser forming of sheet metal components
and tubes requires no hard tooling and external forces,
and is therefore suited for die-less rapid pr ototyping and
low-volume, high-variety production of sheet metal and
tube components. Moshaiov et al.
[2]
showed that the
process was similar to the well established torch flame
bending used on large sheet material in the ship-building
industry, but it offered much more control over the final
product.
In recent years, laser forming techniques have been
investigated extensively. Empirical, analytical, and fi-
nite element method (FEM) tools
[3,4]
have been used
to predict the distortions and relation between bend-
ing angle and process parameters, such as power of the
laser beam, speed at which the laser beam scans the
sheet metal, and the laser beam spot diameter, among
others. Most researches have focused on the laser form-
ing along linear irradiation paths and over rectangular
plates. Different irradiation strategies have to be devel-
oped for the production of complex shaped parts (e.g., a
spherical dome). A certain deformation can be obtained
if the laser beam scans the sheet several times along the
same path. Edwardson et al.
[5]
studied the forming pro-
cess of saddle-shaped parts using five different scanning
strategies. Their results showed that the warped de-
formation occurred because o f the diss ymmetry of laser
irradiations.
The effect of processing parameters o n the deformation
is not simple because we change linear sc anning paths
to curved paths. Similarly, laser forming of the circular
shape specimens have deformation behaviors different
from rectangular shapes. Hennige proposed a path strat-
egy for ring and circle segments, but the range of segment
angle was limited and the work did not explain the rea-
sons for using arbitrary paths to obtain dome shape
[6]
.
Paths used do not provide information re garding the
offset between successive laser scanning passes, which
initiates the need for further understanding of the pro-
cess of laser forming along curved irradiatio ns and cur ved
geometry as well.
In this letter, we present the change in deformation
behavior during transition from linear to cur ved geome-
tries and irradiations. A significa nt change of the pr ocess
mechanisms and its dependencies on the part geome-
try can be ascertained. The forming of axis-s ymmetric
shapes that include ring-shaped geometry and c ircle-
shaped geometry is investigated and compared with
rectangular-shaped geometry. Moreover, the effects of
strain hindrance on the deformation are investigated.
All the experimental results are compa red with simu-
lated values using the software ABAQUS.
Deformation behavior in the lase r forming process is
entirely dependent on heating and cooling cycles called
thermal cycles. There are three well-known mechanisms
discussed in deformation behaviors: temperature g radi-
ent mechanism (TGM), buckling mechanism (BM), and
up-setting mechanism (UM). TGM is the most widely
reported mechanism and can be used to bend sheet metal
out of plane toward the laser. Figure 1 shows the ex-
perimental set up c omprising a fiber laser, a three-axis
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c
2011 Chinese Optics Letters