most notably the aircraft industry, must precisely shape large
metal parts while maintaining the material’s structural properties.
Shaped parts must also resist cracks from corrosion and fatigue.
The traditional techniques manufacturers use to shape metal, such
as shot peening, have significant limitations, especially regarding
the thickness of pieces that can be formed.
A team of Livermore researchers has developed a new approach that
overcomes these problems by using a laser to form parts. Called
LasershotSM Precision Metal Forming, the technique is especially
effective for forming pieces greater than 2 centimeters thick—pieces
so thick they are difficult to shape without weakening the material
structure. The Livermore team, led by physicist Lloyd Hackel, won
an R&D 100 Award for this innovative technology.
Precision Metal Forming shapes parts to exact curvature and contour
specifications, preserves a smooth surface finish, and leaves the parts resistant
to stress corrosion cracking and failure from fatigue. The process can be applied
to any metal or alloy and is particularly effective with the aluminum alloys
used for structural aircraft components. As the process is introduced commercially,
manufacturers can significantly reduce aircraft design weight, thereby increasing
payloads and fuel efficiency and making new designs possible. The process can
also be used to precisely form the final shape of nuclear waste
canisters. Because it offers higher precision than current methods and the ability
to exactly shape local areas, manufacturers can reduce the number of processing
steps and the amount of material needed for machining components.
Metal Forming was developed jointly with New Jersey–based
Metal Improvement Company, Inc. The technique uses a solid-state laser system
that induces a compressive stress to a depth of 1 millimeter or more on the desired
surface of a section of metal. The strain from the deep level of compressive
stress elongates the treated surface, effectively bending the metal within the
processed area. The straining process also confers a beneficial compressive stress
on both the treated and untreated surfaces.
By applying a much deeper stress, LasershotSM Precision Metal Forming can produce
curvatures three to eight times greater and a surface six times smoother than
the shot-peening process can produce. Manufactured sections also can be larger,
which will reduce the number of welds or joints and, thus, strengthen the structure
while reducing its overall weight. In addition, the precision of the process
results in fewer manufacturing steps required to form large panels and assemble
Comparison of (a) a conventional
metal-forming process and (b) the LasershotSM Precision
Metal Forming process.
Third R&D 100 Award
for LasershotSM Technology
metal-forming technology builds on LasershotSM Peening, a technique
that uses lasers to strengthen metal components, which received
an R&D 100 Award in 1998 (see S&TR, October 1998, Blasts
of Light to Strengthen Metals). It is also related to LasershotSM
Peenmarking, an R&D
100 Award winner in 2001 (see S&TR, September
Makes Its Mark).
Peening has since been deployed commercially to arrest cracking
problems in critical components of jet engines. In its
first 14 months of commercial production, many aircraft engines
have been treated—from large jumbo jets to fast, long-range
corporate jets. As a result of these improvements, the jets are
now allowed to remain in operation as much as 12 times longer between
engine teardown and maintenance. The technique is also being applied
to engine components in other commercial aircraft and is slated
for use in manufacturing military aircraft. Hackel says, “Those
of us on the team expect LasershotSM Precision Metal Forming to
have an effect on the aviation manufacturing industry equal in
significance to LasershotSM Peening.”
heart of the metal-forming process is a neodymium-doped glass laser,
a type of solid-state laser that Livermore scientists have
been using for more than two decades. The laser emits up to 6 pulses
per second of 1-micrometer wavelength light with
25 joules of energy. The pulses, each lasting only 20 billionths
of a second, pass through a 1-millimeter-thick layer of water that
flows over the area to be shaped. This material absorbs the laser
light, creating a high-pressure plasma. The water protects the
metal from scarring or melting, thereby maintaining a high-quality
laser beam’s high irradiance (5 to 10 gigawatts per square
centimeter) and short pulse duration cause a rapid ablation of
the absorption material and form a high-pressure plasma. The plasma
is trapped by the thin film of water and creates an intense pressure
wave (nearly 7 gigapascals). The pressure wave travels into
the metal, plastically straining it and thereby inducing a residual
stress that is 5 to 10 times deeper than the stress achieved by
traditional shot peening. The metal responds to this residual stress
by elongating at the peened surface and effectively bending the
overall shape. In production, the laser beam is scanned across
the metal surface with such accuracy that shaping can be precisely
controlled. The intensity and depth of compressive stress to be
applied to each area is determined by finite-element analysis.
The exact desired stress is then created by controlling the laser
energy, the pulse duration, and the number of pulses.
explains that many structural aircraft components, such as wing
skins, elevator and rudder panels, and winglets, must be
formed to precise complex curvatures so they can carry structural
loads, meet aerodynamic requirements, and fit precisely on the
airframe. It is undesirable to bend these components using hydraulic
or other force-forming techniques because mechanical bending reduces
the component’s structural strength and lowers its fatigue
and corrosion resistance.
Precision Metal Forming also performs better than shot peening
in its ability to shape tight curves—curves with
a small radius—in metal whose cross section is less than
2 centimeters thick. Of greater importance, similar curves can
be formed in metal plates more than 2 centimeters thick—plates
that would be too thick for shot peening to effectively curve.
Members of the LasershotSM Precision
Metal Forming team (left to right): Hao-Lin Chen, Andre
Claudet, Tania Zaleski, C. Brent Dane, Laurie Lane, and
Lloyd Hackel. Not pictured: Fritz Harris and John Halpin.
Process Ideal for Aerospace-Grade Aluminum
Hackel foresees two immediate uses for LasershotSM Precision Metal
Forming. One is shaping structural components for new designs of
very large jet aircraft, which will require bending thick material
without reducing its mechanical strength. The second is precision
final-forming of nuclear waste canisters. The technology can also
be applied to the automotive and nuclear industries to make complex
parts with fewer or no joints without suffering losses from cracks
caused by corrosion or fatigue. Another potential application is
to use it to precisely straighten components such as automotive
and aerospace drive shafts, struts, and spars.
Precision Metal Forming offers many desirable characteristics in
shaped metals: high surface finish quality, tight curvature
on thick material, excellent control and repeatability, and high
resistance to fatigue and corrosion cracking—all of which
should make it a valuable technique for producing components for
a range of industries.
Key Words: aircraft industry, LasershotSM Precision Metal Forming,
nuclear waste canisters, R&D 100 Award, shot peening.
For further information contact Lloyd Hackel (925) 422-9009
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