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Accession Number:
AD0670598
Title:
THE EFFECT OF SURFACE ON FATIGUE RESISTANCE AND BRITTLE FRACTURE.
Corporate Author:
MARTIN MARIETTA CORP DENVER COLO DENVER DIV
Report Date:
1968-03-01
Abstract:
The role of the surface layer stress on polycrystalline aluminum specimens subjected to four types of cyclic loading was investigated. The data show that when a specimen is subjected to cyclic tension-tension forces the cyclic creep can be accounted for by a relaxation of the surface layer stress. The relaxation of the surface layer stress causes the specimen to flow plastically at a stress less than the applied maximum stress. Thus, plastic flow occurs at each stress cycle until the specimen fractures. In a similar manner the decrease in the surface layer stress can account for the work softening when prestrained specimens are cycled in tension-compression, and when specimens are cycled in tension-tension to a fixed strain limit. For annealed specimens cycled between fixed strain limits in tension-compression, the increase in the applied stress was found to be equal to the increase in the surface layer stress. The surface layer was found to be important in brittle fracture. A decrease in the surface layer stress by electrochemical removal of metal decreased the ductile-brittle transition temperature by 15 degrees C. Author
Descriptive Note:
Final rept. Jan-Dec 67,
Pages:
0052
Contract Number:
F33615-67-C-1297
File Size:
0.00MB
