Laser Peening of Raptor Engine Components

Aerospace applications of laser peening include many gas turbine engine components, such as airfoils and integrally bladed rotors (IBRs) because of the enormous benefits of preventing fatigue failures and improving damage tolerance for these critical parts.

 

LaserPeen® Processing of Raptor IBRs Production at LSP Technologies, Inc.

Laser peening is a Production Process for the fan blades of GE Aviation’s F110 engine that powers the Falcon and Lancer.

– F110-GE-129 Engine (F-16 C/D Falcon)
– F110-GE-100 Engine (F-16 A/B Falcon)

– F101-GE-102 Engine (B-1B Lancer)

– Joint Strike Fighter

Production use of the laser peening on the fourth stage Integrally Bladed Rotor (IBR) for Pratt & Whitney’s F119-PW-100 engine, which powers the US Air Force’s F/A-22 Raptor, started at LSP Technologies in March 2003.  LaserPeen® processing increases the damage tolerance and enhances the fatigue performance of this IBR.

 


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


Preventing Fatigue Failures with Laser Peening

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 processed 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 comprehensive 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


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