Accession Number : AD0728659

Title :   Mechanisms of Fatigue Crack Propagation in Aluminum Alloys.

Descriptive Note : Final rept. Jan 69-Mar 71,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF METALLURGY AND MATERIALS SCIENCE

Personal Author(s) : Erhardt,K. ; Wilson,A. ; Pelloux,R. ; Grant,N. J.

Report Date : MAY 1971

Pagination or Media Count : 70

Abstract : The mechanisms of crack initiation and propagation in fatigue and of crack propagation under a monotonic load were studied in high strength aluminum alloys. Part I is a detailed report on the use of scanning electron microscopy in fatigue crack propagation research. The results are discussed with reference to the theories of fatigue crack propagation. Part II is a documentation of crack initiation and stage I fatigue fracture in aluminum alloys. The existence of non-propagating cracks in aluminum alloys is discussed by comparing the endurance limit and the stress intensity threshold for non-propagating fatigue cracks. Part III REPORTS THE INFLUENCE OF TEMPERATURE AND CYCLIC RATE ON CRACK GROWTH IN 2024 T3 aluminum alloy. Part IV deals with the role of the cold work of the plastic zone at the tip of a crack on the mechanisms of fatigue crack growth rate. Part V is a study of the correlation between the fracture toughnews index K and the tensile properties. This work was undertaken to understand the dependance of the critical stress intensity factor on aging, the workhardening exponent, and plane strain ductility. (Author)

Descriptors :   (*ALUMINUM ALLOYS, CRACK PROPAGATION), (*FATIGUE(MECHANICS), ALUMINUM ALLOYS), FRACTURE(MECHANICS)

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE