Accession Number:

AD0684580

Title:

THE EFFECT OF ENVIRONMENT ON THE MECHANICAL BEHAVIOR OF MATERIALS.

Descriptive Note:

Annual summary rept. Dec 67-Dec 68,

Corporate Author:

MARTIN MARIETTA CORP DENVER COLO DENVER DIV

Personal Author(s):

Report Date:

1968-12-01

Pagination or Media Count:

28.0

Abstract:

The surface layer stress of high purity aluminum is lower in vacuum than in air. The relaxation rate, however, is faster in vacuum. The cyclic creep and work hardening rates of high purity and 1100 aluminum are lower in vacuum than in air. These observations are in accord with the concept that cyclic creep and cyclic hardening are controlled by the surface layer and not by the bulk of the material. Data on copper show that decreasing the surface layer stress increases the fatigue life. The difference in fatigue behavior in vacuum and air is caused by the difference in the surface layer stress. It is expected that the fatigue cracks will be initiated when the surface layer stress in a local region reaches a critical value equal to the fracture strength. Author

Subject Categories:

  • Metallurgy and Metallography
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE