LSP Conference 2010

LSP Technologies, Inc. will be presenting at the 2nd International Conference on Laser Peening. Three of our executives will be presenting, as listed below.

 

The conference is specifically designed to bring together the most relevant scientists/specialists from all over the world. This conference will enable them to exchange their knowledge and to discuss and cooperate on recent state-of-the-art innovative technologies related to Laser Peening/Laser Shock Processing, along with the latest developments and implementations in the industrial applications of laser peening. The scope of the conference will be dedicated not only to the academic or industrial community working on laser-peening systems or applications, but also to all those working on surface modification technologies or structural integrity interested by the emergence of this process.

Monday, April 19, 9:40 AM
“Advances in Modeling of Laser Peening for Carburized Steels”
Mr. Richard D. Tenaglia

Laser peening is being evaluated by the U.S. Army to toughen helicopter gears, transmission components, and other rotorcraft structural parts.  A critical need exists to boost engine power, particularly when operating in high altitude environments.  Laser peening offers the potential to increase the fatigue performance or damage tolerance of these components without increasing the size or the weight of the propulsion system.

Computer simulation is essential for reducing the development time and costs for optimizing the use of laser peening of actual components.  Modeling of advanced carburized gear steels presents unique challenges.  The composition and hardness gradients in the surface of the carburized steel parts cause gradients of mechanical and physical properties, which affect the laser peen processing response.  To simulate the response properly, it is important to carry the residual stress state from heat treatment forward into the laser shock peening models to predict the resulting compressive residual surface stress profiles, and then transition these profiles to the final part loading models for performance prediction.

This paper presents the recent results of modeling and experimental validation efforts to simulate laser peening of carburized steels, with a correlation of residual stress profiles to fatigue performance.

Monday, April 19, 2:10 PM
“Production Laser Peening Using Automated Overlay Applicators”
Dr. Jeff L. Dulaney

Over the past three years, LSP Technologies has developed an automated overlay applicator system suitable for production laser peening.  This automated system increases throughput and decreases production cost by eliminating manual operations typically associated with tape overlays.  The automated overlay applicators are interfaced with the laser and parts positioning equipment to create a smooth production operation.  The part moves into position, the liquid opaque overlay is applied, the transparent water overlay is applied, the laser fires, and a blast of air preps the surface for the next automated sequence.  The sequence is repeated at the repetition rate of the laser system until processing is completed.

This technology represents an important breakthrough in how laser peening will be implemented in the future: no more expensive, labor-intensive manual applications of tape or similar opaque overlays.  We have successfully introduced automated overlay applicator technology into our production operations, using it to process thousands of parts across two different market sectors: gas turbine engines and tooling dies.

In this presentation, the author will discuss the operation of the automated overlay applicator system, critical elements of its operation, and how it transitioned from development to production.  The presentation will include photographs of hardware and an operational video showing the system in action. 

Tuesday, April 20, 8:00 AM
“Fretting Fatigue of Laser Peened Ti-6A1-4V”
Dr. Allan H. Clauer

Fretting fatigue tests of laser peened Ti-6Al-4V were performed. The laser peening conditions included use of large, 5.6 mm diameter, and small, 1 mm diameter spots. Both produced significant increases in fatigue life. Depending on the fatigue loading conditions, fatigue life was increased from 10 to greater than 25 times, with most of the laser peened specimens running out at 106 cycles. Increasing the bulk fatigue loads to produce failures was limited by the capacity of the fatigue testing machinery.  The fretting fatigue cracks observed in the laser peened material, appear to be similar to those formed in non-laser peened Ti-6Al-4V, presumably because the contact stresses dominate the laser peening induced compressive residual stresses at the fretting surface. However, the laser peening compressive residual stress inhibited their evolution into propagating fatigue cracks. The small laser spot patterns produced a rough surface compared to the large spots, and showed a much different fretting behavior. However both spot sizes produced comparable fatigue life increases.  Metallographic examinations of the fretting surfaces and fretting cracks produced within the fatigue bars and the fretting pads by different fretting and laser peening conditions will be presented and discussed.

This investigation demonstrates that laser peening produces a significant life increase in Ti-6Al-4V under fretting fatigue conditions. It also shows that small spots can produce comparable life increases to large spots even though the fretting situation differs due to the rougher surface produced by the small spots.
 


First International Conference on Laser Peening

The first international conference on laser peening will be held in Houston-Texas, USA 15-17 December 2008.  It is an honor to have Dr. Allan Clauer of LSP Technologies, Inc. kicking off the conference with the first of two keynote presentations at 9:15 am on 15 December.  Dr. Clauer has been involved with laser peening from its inception in the early 1970s, back when it was called laser shock processing.

The conference was established by Dr. Omar Hatamleh of NASA-Johnson Space Center.  Dr. Hatamleh is the Conference Chairman.

Topics will include:

  • Laser peening effects on residual stress distribution
  • Modeling of residual stresses from laser peening
  • Laser peening effects on fatigue life, and crack growth rates in base and welded components
  • Laser peening effects on microstructure, mechanical properties, and surface roughness
  • General aspects of laser peening – process parameters, potential applications, commercialization
  • Additional topics within the field of laser peening are welcome

Contributions will be made by attendees from around the world, including presentations by Dr. Todd Rockstroh (General Electric Aviation – USA) on “Laser Shock Processing of Aircraft Engine Components”, Dr. Brent Dane (Metal Improvement Company) on “Recent Developments in Large Scale Industrial Laser Peening”, Dr. Yuji Sano (Toshiba-Japan) on Development and Applications of Laser Peening Systems for Field Operations”, Mr. Brad Cowles (Pratt & Whitney-USA) on “Applications, Benefits, and Challenges of Advanced Surface Treatments”, and Dr. Takafumi Adachi (Fuji Heavy Industry-Japan) on “Effects of Laser Peening on Fatigue Properties for Aerospace Aluminum Alloys”.


Applications of Laser Peening to Titanium Alloys

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


LSPT Wins Two Awards at the Defense Manucaturing Conference

LSP Technologies, Inc won an unprecedented double award at the 2003 Defense Manufacturing Conference.  LSPT received both the Defense Manufacturing Technology Achievement Award and the Excellence Award for its work on ManTech’s Laser Shock Peening Initiative.  Pictured from left to right are: David F Lahrman (LSPT), David W See (USAF), Walter Roy (US Army), Allan H Clauer (LSPT), Jeff L Dulaney (LSPT), Paul Sampson (Consultant), Richard D Tenaglia (LSPT), and Tim Swigart (USAF).  Critical team members that are not pictured: Otha B Davenport (USAF), Steven E Dykes (LSPT), Mark E O’Loughlin (LSPT), Rob Faber (Pratt & Whitney), Todd Rochstroh (GE Aviation), David W Sokol (LSPT), and Steven M Toller (LSPT).

 

 

 



Technical Bulletin on 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. 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.

Learn More: Laser Shock Processing


Laser Shock Peening for Fatigue Resistance

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 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


Durability of Metal Aircraft Structures

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 peening 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