P. S. Prevey, N. Jayaraman, Lambda Technologies, Cincinnati, OH; M. Shepard, Wright Patterson AFB, WPAFB, OH; R. Ravindranath, NAVAIR, Patuxent River, MD; T. Gabb, NASA, Cleveland, OH
Summary: Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low
plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the
compressive residual stresses that increase fatigue strength must be retained in service. For successful
integration into turbine design, the process must be affordable and compatible with the manufacturing
environment. LPB provides high magnitude deep thermally stable compression, and is performed on CNC
machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engine
and airframe components. Improving fatigue performance by introducing deep stable layers of
compressive residual stress avoids the generally prohibitive cost of modifying either material or design.
The LPB process, tooling, and control systems are described, including recent developments in
process monitoring for quality control. An overview of current research programs conducted to apply LPB
to a variety of engine and aircraft components are presented. Fatigue performance and residual stress
data developed to date for several case studies are presented including:
- Improved fatigue performance of IN718, showing the fatigue benefit of thermal stability.
- Improved damage tolerance of LPB processed Ti-6-4 fan blade leading edges.
- Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB.
- Corrosion pitting and corrosion fatigue mitigation with LPB in AA7075-T6.
- Damage tolerance improvement in 17-4PH steel.
Where appropriate, the performance of LPB is compared to conventional shot peening after exposure
to engine operating temperatures.
