Accession Number:

AD0872139

Title:

The Early Detection of Fatigue Damage

Descriptive Note:

Final technical rept. 1 Jul 1968-28 Feb 1970

Corporate Author:

NORTH AMERICAN ROCKWELL CORP LOS ANGELES CA LOS ANGELES DIV

Personal Author(s):

• Martin, George
• Tsang, Schillings

Report Date:

1970-05-31

Pagination or Media Count:

133.0

Abstract:

The fatigue process of 1100-0 aluminum was studied by means of exoelectron emission and ultrasonic surface wave measurements, and correlated with metallographic examination. Measurement of exoelectrons was accomplished by emission counts, amplified by a Channeltron electron multiplier and integrated over short time intervals. It appears that very early in the fatigue process there is an exoelectron emission peak, whose intensity is related to the intensity of the applied stress, coinciding with initial surface layer slip. The emission event lasts not more than a few percent of the fatigue life. No emission occurs thenceforth until in the final stages of fatigue, just prior to failure, when another emission period is observed. It was further noted that, at least at room temperature, light stimulation is necessary for exoelectron emission from 1100-0 aluminum. Preliminary ultrasonic surface wave measurements disclose a change in material response at about 50 percent of the fatigue life, which so far could not be correlated with metallographic observations.

Descriptors:

• *ALUMINUM ALLOYS
• *NONDESTRUCTIVE TESTING
• BIBLIOGRAPHIES
• CRACKS
• ELECTRICAL IMPEDANCE
• ELECTRON DENSITY
• ELECTRONS
• EMISSIVITY
• FATIGUE(MECHANICS)
• MICROSTRUCTURE
• ULTRASONIC RADIATION

Subject Categories:

• Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE