Mr. David Lahrman will present a paper he co-authored entitled, “The LaserPeen™ Process and Emerging Applications”  September 12-15, 2011 at the 11th International Conference on Shot Peening.
ABSTRACT

“Laser peening has been demonstrated as a unique and valuable method 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.  Laser peening is also known as the LaserPeen^™ Process or laser shock processing (LSP).

 Laser peening drives a high amplitude shock wave into a material surface using a high-energy laser pulse.  The plastic deformation caused by the shock wave results in deep compressive residual stresses in the surface of the part.  The depth and magnitude of the residual stresses depend upon the material and the processing parameters.  Compressive residual stresses typically extend as deep as 0.040-0.060 inches (1.0 to 1.5 mm) below the surface and can approach the yield strength of the material.  These compressive residual stresses increase the resistance of materials to surface-related failures such as fatigue, fretting fatigue, and stress corrosion cracking.

 The successful use of laser peening on aircraft turbine engines blades is driving development efforts to expand the use of this technology to airframe structures, automotive gears, medical devices, nuclear systems, and general industrial applications.  The laser peening process is described and factors important for successful applications are discussed.”

Two additional papers are planned to be presented.  One by Yunfeng Cao and Yung C. Shin of the Center for Laser-based Manufacturing at Purdue University entitled, “Predictive self-closed modeling of laser shock peening and parametric study,” another by Anoop Vasu1 and Ramana V. Grandhi2 of the Department of Mechanical and Materials Engineering at Wright State University entitled, “Compressive Residual Stress Optimization in Laser Peening of a Curved Geometry.”  Follow the links below to read the abstracts for these two papers.

Predictive self-closed modeling of laser shock peening

Compressive Residual Stress Optimization in Laser Peening of

LSP Technologies attended the Advanced Laser Applications

Workshop held in Plymouth, Michigan May 3 through 5. 

David Lahrman, Director of Business Development, presented a

paper on “Laser Peening for Fatigue Improvement” on May 4th 

at this year’s meeting.  This year’s theme was to adress the

current economic and manufacturing challenges in the USA,

including a new direction for the workshop, looking into

“What’s Going on Outside of Automotive?”

Dr. Jeff Dulaney and Dr. Allen Clauer of LSP Technologies will attend the 3rd International Conference on Laser Peening & Related Phenomena on October 11-14, 2011 in Grand Cube Osaka, Japan.  Dr. Dulaney has joined the conference committee. 

Dr. Dulaney will present on the topic Future Shock: Accelerating Technology, here is the abstract for his presentation. 

It takes an enormous effort to take technology from a laboratory research environment to commercial use.  Laser Shock Processing (LSP) of the 1970s evolved into the commercial success known today as laser peening.  There are several variants of laser peening in use today, and others yet to be discovered, developed, and integrated into commercial use.  The study of the laser-generated shock waves, so critical to laser peening, will find commercial applicability beyond imparting compressive residual stress in metals.  Computer models, currently being used to support commercial applications development, will continue to improve and lead the way to new applications and uses.  Overlay materials will evolve to enhance the effectiveness of laser peening through the use of special materials and techniques.  In situ process controls and diagnostics will continue to be developed to provide real-time feedback for process control and continuous quality assurance as critical parts are being processed.  Advancement of laser peening systems will enable new and unexpected applications. 

Dr. Clauer will present a paper he co-authored with Peter Gaydos entitled, “The Effect of Surface Treatments on Fatigue of Carburized X2M Steel.”   Here is the abstract for his paper.

“Carburized X2M specimens were tested in 3-point bending fatigue after having their surface treated with four different treatments both individually and in combination. The bend specimens were 102 mm x 34 x 8.5 mm, with the longitudinal edges of the tensile surface tapered. The surface treatments were Isotropic Surface Finishing (ISF), Low Stress Grinding (LSG), Shot Peening (SP) and Laser Shock Peening (LSP). The first three were also applied in combination with a follow-up LSP treatment, and also a combined ISF/SP/LSP treatment.
The results show that the fatigue strength increased with the type of surface treatment in the order of ISF, LSG, SP, LSP. The combination treatments produced fatigue strength equivalent to or slightly better than the LSP treatment alone.

These results will be discussed in the context of residual stress profiles and scanning electron microscopy of the surfaces and fracture surfaces. The observed modifications of the surfaces and compressive residual stresses lead to observable changes in crack initiation behavior.”

Other committee members from Ohio include:

Ramana V. Grandhi: Wright State University, USA

Kristina Langer: Wright-Patterson AFB, USA

S. R. Mannava: University of Cincinnati, USA

Visit the conference website to learn more

http://www.mapse.eng.osaka-u.ac.jp/3rdLP/

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