Accession Number : AD0720392

Title :   Fracture Behavior of 1/4-in-Thick 7075-T651 A1 Containing Semielliptical Surface Flaws,

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

Personal Author(s) : Bonesteel,R. M.

Report Date : 26 JAN 1971

Pagination or Media Count : 37

Abstract : The static fracture behavior of surface-flawed and of center-through-crack specimens of 1/4-in.-thick 7075-T651 aluminum plate was investigated. The response of surface-flawed speciments to sustained tensile loading while exposed to aqueous 3-1/2% NaC1 solution was also studied. An equation was developed that yielded a constant value of fracture toughness for the surface-flawed specimens over a wide range of a/t and a/c ratios. Grain boundary delaminations ahead of the periphery were observed following exposure of specimens to the stress-salt water environment. The size of the delamination zone was found to increase with increasing applied stress intensity; the time of exposure was found to be of secondary importance in establishing the size of the delamination zone. Fracturing the specimens in air following exposure to the stress-salt water environment indicated that the delamination process sufficiently 'blunted' the flaws that in all cases except one the calculated fracture toughness increased as a result of the environmental exposure. (Author)

Descriptors :   (*ALUMINUM ALLOYS, FRACTURE(MECHANICS)), LOADS(FORCES), DEFECTS(MATERIALS), ENVIRONMENTAL TESTS

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE