Lawrence Livermore National Lab (LLNL) and Metal Improvement Company (MIC) developed a version (brand) of laser peening that they call LasershotSM Peening.  In 1999 a web page appeared on the LLNL website tauting the new technology. 

Here is a brief excerpt from the LLNL website:
“The new technology, called the LasershotSM Peening System, is designed to extend the service lifetime of critical metal parts, from aircraft engine fan blades Figure 1 to hip joints, by a factor of three to five times over conventional peening treatments. The process also holds the promise of lighter, stronger products of entirely new designs.
In traditional shot-peening procedures, each metal or ceramic ball acts as a minuscule ball-peen hammer, imparting on a metal surface a small indentation or dimple. This process produces, below the dimple, a hemisphere of highly shocked and compressed material. In time, overlapping dimples provide a very thin about 0.25 millimeter, uniform layer that is extremely resistant to cracks, corrosion, and fatigue. Because of these benefits, the springs and transmission components of almost every automobile are shot peened for longer life, as are aircraft structural components.
With the invention of the laser, researchers quickly recognized that peening could be achieved using high-energy lasers with pulse lengths in the tens of nanoseconds billionths of a second, short enough to generate a rapid yet energetic shock. Prototype laser peening machines were developed in the 1970s, but they and subsequent versions over the past two decades were not cost effective because the lasers lacked the high repetition rate required for treating parts rapidly.”

For the entire article click on this link: Blasts of Light to Strengthen Metals

Exciting new applications continue to be found for LSP Technologies’ LaserPeen^® process! Pilger dies are used in the manufacture of high quality tubing for aerospace and nuclear applications. Pilgering is a cold forming process in which tubes are reduced in cross section by a combination of wall thinning and diameter reduction. Pilger die life is a major factor in the economics of the pilgering process.

Laser peening has been used to increase the life of pilger dies made of A2 tool steel by imparting compressive residual stresses to failure-prone areas of the dies.  Deep, high-magnitude compressive residual stresses were generated by LSP Technologies’ LaserPeen^® process, and the treated dies showed a significant increase in service life.

Click on the link below to download an article on laser peening of pilger dies.

Laser Peening of Pilger Dies

Originally presented at the ASME/JSME 2004 Pressure Vessels and Piping Division Conference, July 25-29, 2004.

Authored by David W. Sokol, Allan H. Clauer, Ravi Ravindranath.

ABSTRACT
Laser peening has been a commercial surface enhancement process for over six years, and has been gradually expanding the number of applications being laser peened in production ever since. LSP Technologies has been a major developer of the process and new applications for laser peening. It has developed production laser peening systems and innovative laser peening technology to increase throughput and reduce cost. Some of these production and technology developments will be discussed in this paper. Also, an evaluation of applying laser peening to increase the fretting fatigue resistance of titanium alloys, based on Ti-6Al-4V has been made. Included in this evaluation is the use of small spot laser peening to enable the processing of the inside of small, generally inaccessible areas such as the insides of holes and slots. Laser peening with either large or small spots dramatically increased the fretting fatigue life under both R=0.5 and R=0 fatigue conditions with three different contact pad pressures. Fretting fatigue life was increased by at least 25 times. Actual increases in fatigue life and fatigue strength could not be determined because most specimens ran to the runout life of 106 cycles without failure. The laser peening does not appear to affect the fretting behavior, but instead inhibits the initiation of fatigue cracks at the fretting cracks developed from the fretting process. The compressive residual stress from laser peening also would slow the growth rate of any fatigue crack that does eventually initiate at a fretting crack.

INTRODUCTION
LSP Technologies has designed and built two production laser peening systems with the support of the Air Force Materials and Manufacturing Directorate. In 2003 it began production laser peening of an integrally bladed rotor for the F119 engine being built by Pratt & Whitney. To increase throughput and reduce the cost of the process, several technology improvements have also been developed and are being implemented into production. Among these is the RapidCoater™ system, which allows continuous processing of a part. Under a NAVAIR Phase II SBIR, LSP Technologies has investigated the effect of laser peening on fretting and fretting fatigue in dovetail slots. An outcome of this program is a laser peening system that enables the interior of dovetail slots to be accessed by laser peening. Because of the dovetail geometry, small spots (<1 mm in diameter) and underwater laser peening were used to treat the interior of the slots.

To download the entire article as a pdf: Applications of Laser Peening to Titanium Alloys

Originally published in Amptiac Quarterly, Volume 7 Number 2, 2003

Authored by Richard D. Tenaglia David F. Lahrman LSP Technologies, Inc. & David W. See AFRL/MLMP?

INTRODUCTION
Laser peening is an innovative surface enhancement processsed to increase the resistance of aircraft gas turbine engine compressor and fan blades to foreign object damage (FOD) and improve high cycle fatigue (HCF) life. [1,2,3,4] The process creates residual compressive stresses deep into part surfaces – typically five to ten times deeper than conventional metal shot peening. These compressive surface stresses inhibit the initiation and propagation of fatigue cracks. Laser peening has been particularly effective in aircraft engine titanium alloy fan and compressor blades, however the potential application of this process is much broader, encompassing automotive parts, orthopedic implants, tooling and dies, and more. Significant progress has been made to lower the cost and increase the throughput of the process, making it affordable for numerous applications from gas turbine engines to aircraft structures, land vehicles, weapon systems, as well as general industrial use. Laser peening may also be referred to as laser shock processing (LSP), and various other commercial trade names. This paper reviews the status of laser peening technology, material property enhancements, and potential applications.

To download the entire article- as a pdf: Preventing Fatigue Failures with Laser Peening

Originally published in Technical Bulletin No. 1, 2002

Authored by Dr. Allan H. Clauer

INTRODUCTION
What Does It Do?
Laser Shock Processing (LSP) produces a number of beneficial effects in metals and alloys. Foremost among these is increasing the resistance of materials to surface-related failures, such as fatigue, fretting fatigue and stress corrosion cracking. It does this by driving compressive residual stresses deep into metals and alloys. Much deeper than shot peening. For these applications the process is referred to as laser shock peening.
There are a number of other reasons to use LSP besides increasing fatigue strength and fatigue life; it can be used to strengthen thin sections, work-harden surfaces, shape or straighten parts, break up hard materials, possibly to consolidate or compact powdered metals, and still others remaining to be discovered.

Applying LSP
LSP can often be applied to the finished surface of a part, or just prior to the final finishing step. In machine components, tooling and other parts, application to external surfaces and internal surfaces with line-of-sight access is straightforward. Application to internal surfaces without line-of-sight access is quite possible, but the method used is application specific and requires some development for each application.
LSP works by exerting a mechanical force on the part surface; the surface is not affected thermally. However, process options can be selected which have a limited thermal effect and offer potential cost benefits. The effects of the mechanical force on the surface itself are minimal. In softer alloys, a very shallow surface depression occurs, which decreases in depth in harder materials. For example, in aluminum alloys, the depression is about 250
inches (6
m) deep, but on machined surfaces of harder alloys, it is difficult to see where the surface was laser shocked. The depth of the depression does increase with increasing intensity of shock peening.
With LSP, treating just the fatigue critical area(s) on a part without masking the area around it is easily accomplished. This enables localized treatment around holes, and in and along notches, keyways, fillets, splines, welds, and other highly stressed regions.
The intensity of LSP can be easily controlled and monitored, allowing the process to be tailored to the specific service and manufacturing requirements demanded by the part. The flexible nature of the process accommodates a wide range of part geometries and sizes. It can also be used in combination with other treatments, e.g., shot peening or coatings, to achieve the most beneficial property and cost advantages for each part.
LSP can also be used in manufacturing processes requiring a high, controllable, mechanical impact over a defined area, where mechanical punches are limited in how they can be adapted to the task. The impact area could have a variety of shapes.
The first production application of laser shock peening began in 1997 on a military gas turbine engine blade. More production applications will begin in 1998.

Benefits
The use of LSP to obtain increased strength and resistance to failure offers several advantages. After applying LSP to failure-prone areas on troublesome parts, the service life of the parts and the maintenance intervals of machinery can be increased and downtime decreased, without changing the design. Alternatively, a part or machine can be redesigned to make them lighter, easier to manufacture, or less expensive, using LSP to upgrade the properties to meet the original design performance requirements.
It is a new manufacturing tool that could offer more control, flexibility or unique effects for upgrading current products or developing new ones than other methods.

LSP Technologies, Inc.
LSP Technologies, Inc. provides commercial laser shock processing services and equipment. We are the only company providing LaserPeenTM laser peening services to industry, and building LaserPeenTM equipment specifically for laser shock processing applications. In 2000 we will be introducing our new RapidPeenTM process and associated RapidPeenTM equipment for increased throughput and lower cost. In 2001 we will introduce a factory-floor ready laser shock peening system.
LSP Technologies’ key management and staff have many years of experience in the development and use of laser-generated shock waves for a wide variety of applications. Our staff’s experience dates back to the early 1970’s, when we began developing the technology at Battelle Memorial Institute in Columbus, Ohio.
The company is located in Dublin, Ohio, a suburb of Columbus, in new facilities for production processing of parts and development of new applications. The facility has two laser shock peening systems that provide flexibility for processing a wide variety of parts.

To download the entire article- as a pdf: Laser Shock Processing

Originally published in Surface Performance of Titanium, J. K. Gregory, H. J. Rack, and D. Eylon (eds.), (1996), pp. 217-230.

Authored by Allan H. Clauer

ABSTRACT
Laser shock peening produces a compressive residual stress in the surface of metallic materials, which significantly increases fatigue life in applications where failure is caused by surface-initiated cracks. Laser shock peening is applied by using a high energy pulsed laser to create a high amplitude stress wave or shock wave on the surface to be treated. This stress wave propagates into the material, causing the surface layer to yield and plastically deform, and thereby, develop a residual compressive stress. Where comparisons have been made to shot peening, the magnitude of the residual stresses at the surface are similar, but the compressive stresses from laser peening extend much deeper below the surface than those from shot peening. The resulting fatigue life enhancement is often greater for laser peering than it is for shot peening. In addition to fatigue strength improvement, laser peering can also locally strain harden thin sections of parts or strain harden a surface.

INTRODUCTION
Laser shock peening (LSP) or laser peening generally increases the resistance of metals and alloys to fatigue and fretting fatigue. It does this by using a high energy pulsed laser to produce residual compressive stresses and strain hardening into the surface of a laser peened part. The residual compressive stresses from laser shock peening extend deeper below the surface than those from shot peening, usually resulting in a significantly greater benefit in fatigue resistance after laser peening. Laser peening can also be used to locally strain harden thin sections of parts, and, if the part is thin enough, it can be strain hardened through the section thickness.

To download the entire article- as a pdf: Laser Shock Peening for Fatigue Resistance

Originally published in Durability of Metal Aircraft Structures by Atlanta Technology Publications, S. N. Atluri, C. E. Harris, A. Hoggard, N. Miller, and S. G. Sampath (eds.), (1992), pp. 350-361.

Authored by Allan H. Clauer, Jeff L. Dulaney, Richard C. Rice, and John R. Koucky

ABSTRACT
This paper presents an overview of Laser Shock Processing and then discusses how the process can be extended to treat fastener holes on aging aircraft. The process is used to treat localized fatigue-critical areas by developing deep residual compressive stresses to inhibit the initiation and propagation of fatigue cracks. This feature can be applied to fastener holes in aircraft structures to determine whether the fatigue life associated with the failure in these areas can be increased.

INTRODUCTION
Laser Shock Processing (LSP) has become a commercially viable process within the last few years with the design, construction and operation of a prototype laser that is very compatible with a manufacturing environment in size and capability. While still in the development stage, its ability to develop deep, high compressive stresses in the areas treated has been demonstrated on a number of metals and alloys. There have also been demonstrations of large improvements in the fatigue life and fatigue strength in various metals and alloys. In this paper, the laser shocking process and representative examples of property improvements in aluminum and steel will be discussed. In addition, the application of the process to treat fastener holes in aging aircraft will be discussed.

To download the entire article- as a pdf: Laser Shock Processing for Treating Fastener Holes in Aging Aircraft

Originally published in Shock Compression of Condensed Matter 1991, S.C. Schmidt, R.D. Dick, J.W. Forbes, D.G. Tasker (editors) copyright 1992 Elsevier Science Publishers B.V.

Authored by Craig T. Walters

Neodymium-glass laser pulses (1.06-mm wavelength, 25-ns pulse width) have been used to generate shock waves with peak pressures in the 5- to 120-kbar range at the front surface of solids. Relatively uniform irradiance levels were employed with circular beam areas in the 0.4- to 1.5-cm2 range and single pulse energy up to 800 J (fluences ranged from 200-2000 J/cm2). At 1000 J/cm2, the resulting peak shock pressure is about 35 kbar. By confining the plasma with a transparent glass overlay, this peak pressure was raised to 120 kbar. The nature of the plasma initiation process has been revealed through careful simultaneous temporal resolution of the beam-power, temperature, and stress-wave details.

INTRODUCTION
High-power laser pulses have been used to produce stress waves in materials for more than two decades. Most of the measurements of stress wave amplitude have been performed with pulse fluences less than 100 J/cm2. Laser exposures with fluences many orders of magnitude greater than this have been conducted, but pressures have not been directly measured in these cases. We report here measurements of stress-wave amplitudes in laser interactions with fluences in the range 200-2000 J/cm2 with and without plasma confinement (transparent overlays). A map of pressures that may be achieved with single laser pulse interactions is presented in Figure 1 in terms of peak power density. The dashed line at high intensity follows the set of ablation pressures estimated by Cottet et al.1,2 in the correlation of thin aluminum foil spallation data. These estimates follow a 0.7 power dependence on intensity. Similar estimates made by Eliezer et al.3 and Gilath et al.4 are shown in Figure 1 by the dotted line for aluminum and the chain dashed line for carbon/epoxy at lower intensity. The open circles are peak pressures measured recently with 20- to 30-ns pulses at Battelle5,6 at the front surface of stress gage packages coated with either graphite or carbon/polymer (black paint). These data agree with the estimate of Reference 3 at low intensity, but rise nearly linearly up to 5 x 1010 W/cm2 in contrast to the model. The solid circles show the effect of confining the plasma at these intermediate intensities with a transparent overlay. These pressures were in the 90 to 120 kbar range and are believed to be the highest directly recorded pressures generated in laser interactions with solids. The solid squares and triangles present the measurements of confined interactions by Fairand and Clauer7 and by Ballard et al 8 for 30-ns pulses. These data are highly consistent up to about 3 x l09 W/cm2 (90 J/cm2). For fluences in the 100- to 1000-J/cm2 range, the detailed nature of the transparent overlay probably takes on increased importance as breakdown processes interfere with energy delivery to the absorbing interface. Our data indicate that some benefit in increased pressure from a correctly designed overlay may be possible at even higher fluences than those investigated, contrary to the plateau seen in the Ballard data. Careful examination of the pressure histories with different coatings and with and without overlays has also revealed some detail of the plasma initiation process as discussed below.

To download the entire article as a pdf: Laser Generation of 100-kbar Shock Waves in Solids

Originally published by Materials and Processing, 6 (6) 3-5 (Sept. 1991).

Authored by Allan H. Clauer and John R. Koucky.

Laser shock processing (LSP) produces a surface compressive residual stress in the metal part being treated that can significantly improve those properties which are affected by the initiation and propagation of surface cracks. The properties of greatest interest are fatigue life and fatigue strength. But the process also can reduce fretting fatigue and stress-corrosion cracking as well as strengthen thin sections. The potential advantages of LSP include the possibility of direct integration into manufacturing production lines with a high degree of automation, use on machined surfaces, increased quality assurance, treatment of localized fatigue critical areas without masking, and the ability to make design changes that would not be possible using alternative methods for increasing fatigue resistance. Among the applications that have been identified are the manufacture of blades, disks, and vanes for aircraft gas turbine engines; gears, connecting rods, and crankshafts for automotive engines; and medical implants.

To download the entire article- as a pdf: Laser Shock Processing Increases the Fatigue Life of Metal Parts

Originally from the proceedings of the Sixth DOD Conference on DEW Vulnerability, Survivability and Effects, May 12-15, 1987.

Authored by C. T. Walters, A. H. Clauer, and B. E. Campbell

ABSTRACT
The effects of intense single pulses of 1.06 mm radiation on structural composite materials have been investigated. Fluences in the 1000 – 3000 J/cm2 range were delivered in single pulses with 20 ns pulse widths (FWHM) to thermal coupon and tensile bar type samples in vacuum. Materials studied included Kevlar/epoxy, fiberglass/epoxy, and graphite epoxy uniaxial composites in coated and uncoated conditions. Diagnostics were employed to assess energy partitioning in the interaction and stress wave histories in the material. Post-test sample examination and strength tests were conducted on the tensile bar samples. The diagnostics indicated that most of the beam energy goes into a very hot plasma (300,000 K) which drives a shock wave into the material. The shock wave has a peak amplitude of about 30-40 kbars and attenuates as it propagates through the sample. A synergistic damage effect was discovered wherein the sample fails in tension due to addition of the sample preload stress and the axial component of stress due to the shock wave reflected from the rear surface of the sample. Details of the beam energy partitioning and strength degradation in the samples will be presented.

INTRODUCTION
During the past several years, experimental laser effects research has been in progress to understand the effects of single short-wavelength laser pulses on composite materials in vacuum. In most cases, previous studies have been oriented toward understanding fundamental interactions in unstressed samples at low incident laser fluences (< 200 J/cm2 ) and emphasized measurement of integrated response characteristics such as thermal coupling, impulse coupling, and effective heat of ablation, Q*. Recently, research was undertaken to extend some of these basic results to the more realistic case of laser interaction with stressed samples and, in particular, to look carefully at laser-induced shock enhancement of material damage. This paper summarizes results of an 18-month effort to develop an understanding of the damage and degradation of complex structural materials subjected to intense single laser pulses (20 ns, 1.06 mm) in vacuum while they are under preload stress conditions which might be typical of actual applications. (ref. 1) In the high fluence regime investigated, high plasma pressures generate stress waves which have damaging effects in addition to the simple removal of material by vaporization. Under certain conditions, laser induced stress wave components were found to add to the preload stresses to produce enhanced damage effects.

To download the entire article- as a pdf: Laser Shock Effects on Stressed Structural Materials- Experimental Results