Mitigation of SCC and Corrosion Fatigue Failures in 300M Landing Gear Steel Using Mechanical Suppression

Abstract

300M steel is widely used in landing gear because of its unique combination of ultrahigh strength with high fracture toughness. However, 300M is vulnerable to both corrosion fatigue and stress corrosion cracking (SCC) failures with catastrophic consequences for aircraft landing gear. Plating and shot peening surface treatments currently used to extend life are only partly effective. A surface treatment is needed that will mitigate foreign object damage (FOD), corrosion fatigue and stress corrosion cracking. This paper describes the use of low plasticity burnishing (LPB) to mechanically suppress stress sensitive corrosion failure mechanisms in 3.5% salt solution. The fatigue and corrosion fatigue performance of LPB processed 300M steel was compared with shot peened (SP) and low stress ground (LSG) conditions. LPB produced residual compression to a depth of 1.27 mm (0.050 in.), and shot peening only 0.127 mm (0.005 in.), an order of magnitude less. LPB treatment dramatically improved both the HCF performance and corrosion fatigue strength, with and without simulated FOD. The corrosion fatigue strengths of LSG and SP surfaces decreased dramatically, to only 20% and 50%, respectively, of the baseline strength, with no discernible endurance limit behavior under corrosion fatigue conditions. The fatigue behavior was even worse with FOD, simulated with a 0.5 mm (0.020 in.) deep EDM notch, both in air and exposed to salt. In contrast, LPB treated specimens with FOD exhibited a definite endurance limit of 1035 MPa (150 ksi) even under corrosion fatigue conditions. SCC testing of LPB treated landing gear sections at 1030 to 2270 MPa (150 to 180 ksi) static loads was terminated after 1500 hrs without failure, compared to failure in as little as 13 hours without treatment.

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Document Details

Document Type
Technical Report
Publication Date
Aug 01, 2004
Accession Number
ADA444124

Entities

People

  • Jack Coate
  • Michael Shepard
  • N. Jayaraman
  • Neal Ontko
  • Paul S. Prevey
  • Robert Ware

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Aircrafts
  • Cold Working
  • Compression
  • Cracks
  • Engineering
  • Failure Mode And Effect Analysis
  • Fatigue Tests (Mechanics)
  • Foreign Object Damage
  • Heat Treatment
  • Landing Gear
  • Materials
  • Residual Stress
  • Shot Peening
  • Stress Corrosion Cracking
  • Stresses
  • Surface Finishing
  • Tensile Stress

Fields of Study

  • Materials science

Readers

  • Materials Science and Engineering.
  • Structural Health Monitoring of Composite Structures.