Accession Number : AD0635968

Title :   DETERMINATION OF TOLERABLE IMPERFECTIONS IN LIGHT METAL SHEET ALLOYS FOR AEROSPACE APPLICATIONS.

Corporate Author : LOCKHEED MISSILES AND SPACE CO PALO ALTO CALIF RESEARCH LABS

Personal Author(s) : Lewis, Richard E. ; Willner,Elliott

Report Date : JUN 1966

Pagination or Media Count : 35

Abstract : Scratches, gouges, pits, and cracks found in high-strength aluminum and magnesium sheet alloy structural components used in highly stressed, light-weight aerospace structures often cause long and expensive delays in making an acceptance or rejection decision. This study was initiated to establish a useful basis for determining the effect of imperfections on gross fracture strength, thus minimizing time delays. The specimens used are 2 in. wide, 8 in. long, and of sheet thickness. A semi-elliptical groove with controlled depth and length is produced in the surface of each specimen at midlength, forming a plane perpendicular to the long dimension. A fatigue crack is generated at the base of the machined groove in each specimen. This fatigue precracked specimen is then tested to failure by uniaxial static tension or tensile fatigue. After failure, the original crack depth and length arxe measured. Gross and net section stresses and strain energy release rates are then calculated. These results provide quantitative bases for 'tolerable' imperfections. This information can be applied to inspection of as-received sheet material and structural components of aerospace structures. (Author)

Descriptors :   (*ALUMINUM ALLOYS, DEFECTS(MATERIALS)), (*MAGNESIUM ALLOYS, DEFECTS(MATERIALS)), (*SHEETS, TOLERANCES(MECHANICS), FRACTURE(MECHANICS), SURFACE PROPERTIES

Subject Categories : Metallurgy and Metallography
      Mfg & Industrial Eng & Control of Product Sys

Distribution Statement : APPROVED FOR PUBLIC RELEASE