THE EFFECT OF SURFACE ON FATIGUE RESISTANCE AND BRITTLE FRACTURE.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1968
- Accession Number
- AD0670598
Entities
People
- I. R. Kramer
Organizations
- Martin Marietta