Study of the Influence of Metallurgical Factors on Fatigue and Fracture of Aerospace Structural Materials.

Abstract

This report summarizes the results of a two-phase study involving (1) experimental characterization and analytical modeling of fatigue crack tip micromechanics in aerospace structural aluminum alloys, and (2) identification and modeling of key microstructural factors controlling fracture in aluminum-iron-x alloys. Dynamic load cycling within the SEM and stereoimaging strain analysis have been used to characterize crack opening loads, strains, and effective stress intensity (delta/Keff) values for large and small cracks in a variety of alloys; both constant amplitude and overload/underload situations were studied. It was found that delta/Keff based on local crack tip opening load was not an adequate crack growth rate correlating factor. Instead, it was necessary to use a new driving force term which includes both closure and local crack tip plasticity. The latter was computed by calculating delta/J integrals within the crack tip plastic zone using local crack tip strain data obtained via high resolution SEM of loaded and unloaded cracks.

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Document Details

Document Type
Technical Report
Publication Date
Jan 31, 1988
Accession Number
ADA192909

Entities

People

  • David L. Davidson
  • Gerald R. Leverant
  • James Lankford
  • Kwai S. Chan

Organizations

  • Southwest Research Institute

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Aluminum Alloys
  • Amplitude
  • Electron Microscopy
  • High Resolution
  • Materials
  • Materials Science
  • Mechanical Working
  • Mechanics
  • Microstructure
  • Modulus Of Elasticity
  • Plastic Properties
  • Powder Metallurgy
  • Resistance
  • Strain Hardening
  • Tensile Properties
  • Tensile Strength
  • Transitions

Readers

  • Materials Science (Mechanical Engineering).

Technology Areas

  • Space