The Early Detection of Fatigue Damage
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 1970
- Accession Number
- AD0872139
Entities
People
- George Martin
- Schillings Tsang