Laser Shot Peening of Landing Gear Components

NCMS Project #: 140158

Problem:

  • Safety of flight issues due to stressed landing gear.
  • A variety of landing gear components are failing without having reached their desired service lives.
  • The failures are due primarily to stress corrosion cracking (SCC) and fatigue.

Benefit:

  • Availability:
    • Increased availability of the T-38 trainer as a result of few failures of landing gear trunnions.
    • Business development on other platforms will greatly increase weapon system availability.
  • Cost:
    • $3.1M avoidance for the T-38 main landing gear trunnions.
  • Reliability:
    • Trunnions previous life span – 6 years; extended to 9-12 years.
  • Cycle Time:
    • No significant effect on cycle time.
  • Safety:
    • Increased safety of flight due to less fatigue fractures.

Solution/Approach:

  • Peening is used to improve material resistance to stress-induced damage such as fatigue and SCC.
  • The peening process compresses the material just below the surface, resulting in a residual compressed load.
  • A laser pulse creates a shock wave that drives a residual stress up to 2-mm deep into the metal part. (8x conventional peening).
  • The increased depth of peening helps prevent crack propagation, and imparts superior performance.
  • Project developed a more economically favorable system, which pulses at a rate 20x faster than other available systems and can peen about one square meter of metal per hour.

DOD Participation:

  • U.S. Air Force (Ogden Air Logistics Center)
  • U.S. Army (Corpus Christi Army Depot)

Industry Participation:

  • Metal Improvement Company
  • Lawrence Livermore National Laboratory
  • University of California-Davis
  • NCMS