Accession Number : ADD000380

Title :   Method and Means for Determining Fatigue Damage and Surface Stress.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON D C

Personal Author(s) : Coate,Forrest M

Report Date : 17 Dec 1974

Pagination or Media Count : 5

Abstract : In the patent the test specimen is mounted on a movable table, and ultrasonic surface waves are caused to travel across the specimen by a transducer fed from a CW signal source. A laser beam is passed through a beam splitter, one portion being reflected onto a photo-detector measuring signal amplitude. An output signal is compared with the output of the CW signal and the CW signal shifted in phase by 90 degrees. These outputs measure ultrasonic phase difference, at points along the specimen. The second portion of laser beam is reflected from a mirror attached to the specimen table and back to a screen where an interference pattern is formed as the table is moved. Photo detectors sense the changes in the interference pattern and determine the specimen displacement.

Descriptors :   *Fatigue(Mechanics), *Surface properties, *Ultrasonic tests, *Patents, Optical instruments, Metals, Photodetectors, Instrumentation

Subject Categories : Metallurgy and Metallography
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE