Accession Number : ADA192909

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

Descriptive Note : Annual rept. 1 Jan 87-31 Dec 87,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TX

Personal Author(s) : Lankford, James ; Davidson, David L ; Chan, Kwai S ; Leverant, Gerald R

PDF Url : ADA192909

Report Date : 31 Jan 1988

Pagination or Media Count : 34

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.

Descriptors :   *AEROSPACE CRAFT, *ALUMINUM ALLOYS, *FATIGUE(MECHANICS), *CRACK PROPAGATION, CONSTRUCTION MATERIALS, CRACKS, DYNAMIC LOADS, J INTEGRALS, MATHEMATICAL MODELS, METALLURGY, MICROSTRUCTURE, PLASTIC PROPERTIES, STRESSES, TWO PHASE FLOW

Subject Categories : Properties of Metals and Alloys
      Research and Experimental Aircraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE