Accession Number : AD0265419

Title :   HIGH-TEMPERATURE FATIGUE IN CONTROLLED ENVIRONMENTS

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Danek,G. J. , Jr. ; Smith ,H. H. ; Achter,M. R.

Report Date : 08 SEP 1961

Pagination or Media Count : 14

Abstract : The effect of environment on the high-temperature fatigue properties of nickel, Type 316 stainless steel, and Inconel X was investigated by comparing the fatigue life in air to that in vacuum at 1500 F. Sheet-metal specimens of these materials were cycled in reverse bending at their resonant frequency by means of equipment developed to perform high-temperature fatigue tests in controlled environments. The effect of environment on fatigue properties is similar for all three materials. At high strains fatigue lives are superior in vacuum; with decreasing strain the vacuum and air curves converge. These results can be explained by a mechanism previously proposed to interpret similar findings in creep. This mechanism involves the simultaneous operation of two competing processes: the surface adsorption of gaseous impurities lowers the surface energy and facilitates crack propagation, while oxidation provides a strengthening tendency. (Author)

Descriptors :   *FATIGUE (MECHANICS), AIR, CHROMIUM ALLOYS, CONTROLLED ATMOSPHERES, HIGH TEMPERATURE, NICKEL, NICKEL ALLOYS, STAINLESS STEEL, TEST EQUIPMENT, VACUUM APPARATUS

Distribution Statement : APPROVED FOR PUBLIC RELEASE