Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Sources of Strain-Measurement Error in Flag-Based Extensometry



William E. Luecke, J French


This paper examines the sources of error in strain measurement using flag-based extensometry that uses either scanning laser or electrooptical extensometers, These errors fall into two groups: errors in measuring the true gauge length of the specimen, which arise from the method of attachment of the flags, and errors arising from unanticipated distortions of the specimen during testing. The sources of errors of the first type include gauge-length errors from nonparallel flags and uncertainties in the true attachment point of the flag, During the test, strain-measurement errors of the second type can arise from horizontal translation of nonparallel flags, flag rotation that is induced by slippage, and flag motion from bending of the gauge length, Proper care can minimize the effect of these potential errors, so that flag-based extensometry can give accurate strain measurement, if appropriate precautions are taken, Measurements on silicon nitride indicate that the strain measurements are accurate to better than 10%
Journal of the American Ceramic Society


extensometry, creep, strain measurement


Luecke, W. and French, J. (1996), Sources of Strain-Measurement Error in Flag-Based Extensometry, Journal of the American Ceramic Society, [online], (Accessed July 13, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 1, 1996, Updated February 19, 2017