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An optical motion measuring system for laterally oscillated fatigue testsThis paper describes an optical system developed for materials testing laboratories at NASA Langley Research Center (LaRC) for high resolution monitoring of the transverse displacement and angular rotation of a test specimen installed in an axial-tension bending machine (ATB) during fatigue tests. It consists of a small laser, optics, a motorized mirror, three photodiodes, electronic detection and counting circuits, a data acquisition system, and a personal computer. A 3-inch by 5-inch rectangular plate attached to the upper grip of the test machine serves as a target base for the optical system. The personal computer automates the fatigue test procedure, controls data acquisition, performs data reduction, and provides user displays. The data acquisition system also monitors signals from up to 16 strain gages mounted on the test specimen. The motion measuring system is designed to continuously monitor and correlate the amplitude of the oscillatory motion with the strain gage signals in order to detect the onset of failure of the composite test specimen. A prototype system has been developed and tested which exceeds the design specifications of +/- 0.01 inch displacement accuracy, and +/- 0.25 deg angular accuracy at a sampling rate of 100 samples per second.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Tripp, John S.
(NASA Langley Research Center Hampton, VA, United States)
Tcheng, Ping
(NASA Langley Research Center Hampton, VA, United States)
Murri, Gretchen B.
(NASA Langley Research Center Hampton, VA, United States)
Sharpe, Scott
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1993
Publication Information
Publication: In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 4 (A93-33876 1
Publisher: American Institute of Aeronautics and Astronautics
Subject Category
Instrumentation And Photography
Report/Patent Number
AIAA PAPER 93-1560
Accession Number
Distribution Limits

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