Accession Number : ADA140659

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

Descriptive Note : Annual scientific rept. 1 Jan-31 Dec 83,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TX

Personal Author(s) : Lankford,J ; Davidson,D L ; Leverant,G R ; Hack,J E

PDF Url : ADA140659

Report Date : Feb 1984

Pagination or Media Count : 47

Abstract : This report summarizes the results of a two-phase study involving experimental characterization and analytical modeling of fatigue crack tip micromechanics in aerospace structural (Al and Ti) alloys, and identification and modeling of key factors controlling subcritical crack growth and unstable fracture in single crystal nickel-base superalloys. Crack tip opening displacement, the increment of crack advance, and crack tip strain are assumed to be dependent on the formation of slip lines at the crack tip. Slip line length and dislocation density are parameters in the model which are controlled by the microstructure. The model may be used in two ways: to predict the increment of crack growth, if the slip line length is known, or the length of the slip line may be determined if the crack growth increment is measured. Crack tip plasticity data for 7075-T651 is used to evaluate the model, and the results obtained are compatible with the assumptions, and give a value of slip line length which is compatible with the mean free slip length in the material. In the single crystal nickel-base superalloy task, the details of anisotropic fracture mechanics and crack tip stress field solutions have been reviewed.

Descriptors :   *Metallurgy, *Superalloys, *Fatigue(Mechanics), *Fracture(Mechanics), *Crack propagation, *Structural analysis, Aerospace systems, Nickel alloys, Single crystals, Aluminum alloys, Titanium alloys, Plastic properties, Front ends and surfaces, Factor analysis, Mathematical models, Stress strain relations, Anisotropy, Displacement, Crystallography, Orientation(Direction), Microstructure, Equations, Poisson ratio, Modulus of elasticity, Shear stresses

Subject Categories : Aircraft
      Properties of Metals and Alloys
      Statistics and Probability
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE