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12 Industrial Laser Solutions MAY/JUNE 2017
Laser peening enhances
NEW DIODE-PUMPED SYSTEM BRINGS
LASER PEENING TO THE FACTORY FLOOR
Material enhancement has long been at the lead- ing edge of technologi- cal innovation. Powerful machines require robust components, but material imitations present a critical
obstacle to performance optimization. Laser shock peening
(LSP) resides at the forefront of material enhancement, employ-ing high-energy lasers to generate deep compressive residual
surface stresses for proven metal fatigue resistance.
Laser peening has been implemented by original equip-
ment manufacturers (OEMs) in the aviation and power gen-
eration industries to enhance their products’ resistance to
cracking caused by fretting, corrosion, foreign object damage, and fatigue. Now, after nearly 50 years of technological
advancement, the first line of turnkey industrial laser peening
systems is integrating the technology into manufacturing facilities around the world.
Laser peening as a metal improvement process was born in
the 1970s out of research at the Battelle Memorial Institute
(Battelle; Columbus, OH). Researchers at Battelle, led by Dr.
Jeff Dulaney, were exploring whether high-energy, short-pulse
lasers could be used to improve material properties. They initially demonstrated significant tensile strength improvements
in 7075 aluminum alloy specimens after processing them with a
1. 2–2.2GW/cm2, 32ns Gaussian pulse. The Battelle laser delivered energy outputs up to 500J, but the system’s size (over 15m
long) and slow pulse rate (one pulse every 6–8 min.) made it
impractical for industrial material processing.
In the 1980s, Battelle engineers and scientists designed
and built an advanced prototype system for laser peening.
The high-powered system incorporated long-pulse flashlamps
with a high-repetition-rate oscillator, transforming the previ-
ously hulking, single-pulse laser into a 200k W burst laser operating at 1Hz.
In the early 1990s, the US Air Force encountered foreign
object damage (FOD) issues with General Electric (GE) F101
engines in the B- 1 Lancer. GE needed an innovative mate-
rial enhancement solution to mitigate FOD, and they part-
nered with Battelle to explore the benefits of laser peening
F101 fan blades.
After processing samples and subjecting them to fatigue
testing, Battelle scientists demonstrated that laser-peened
blades with simulated FOD damage retained fatigue lifetimes
superior to those of new, undamaged blades. This was a landmark result, as the Air Force had previously dedicated extensive resources to laborious manual inspections of all F101 first
stage fan blades before each flight.
With potential cost savings in the tens of millions over the
life of the B- 1, the Air Force authorized the production development of laser peening for fatigue enhancement, and GE Aircraft
Engines began laser peening all F101 first-stage fan blades
using a newer-generation, two-beam, 50J laser system modeled after the single-beam, 1Hz Battelle design.
Inspired by the results of the F101 study and subsequent Air
Force demand, Dr. Dulaney left Battelle and founded LSP
Technologies (LSPT; Dublin, OH), with the sole purpose of
commercializing laser shock peening. The company acquired
an exclusive worldwide license to Battelle’s laser peening patents, and began marketing laser peening equipment and ser-
vices as a fatigue enhancement solution. LSPT constructed
GE Aviation’s initial laser peening systems, as well as their
own in-house production system for commercial laser peening: a 20W, neodymium (Nd) glass, flashlamp-pumped sys-
tem paired with a production work cell and 400-lb.-capable
FIGURE 1. A schematic that shows the laser peening process.