Accession Number : ADP001612

Title :   A Study of Small Crack Growth under Transport Spectrum Loading,

Corporate Author : MCDONNELL DOUGLAS CORP LONG BEACH CA

Personal Author(s) : Wang,D. Y.

Report Date : APR 1983

Pagination or Media Count : 15

Abstract : This paper describes a study of microcrack growth and statistical fatigue in terms of the initial quality of fastener holes in aluminum alloy. A special test procedure was used to obtain a statistically large sample of data under spectrum loading by testing a specimen containing 24 holes with maximum of 48 fatigue data sets. A total of seven specimens was tested. Small crack measurements were taken by fractography and surface observation. Marker cycles, which were designed to be part of the spectrum, served the intended purpose of identifying crack origin and microcrack growth rates using a scanning electron microscope. The phenomena of small crack growth have been analyzed from the extensive data. The essential physical defects in 2024-T3 and 7075-T6 aluminum alloys as origins of micro-fatigue cracking are the inclusions and tool marks.

Descriptors :   *Airframes, *Cracking(Fracturing), *Structural mechanics, Aluminum alloys, Microstructure, Loads(Forces), Crack propagation, Statistical mechanics, Sizes(Dimensions), Growth(General), Fatigue(Mechanics)

Distribution Statement : APPROVED FOR PUBLIC RELEASE