The Effects of Experimental Configuration on the Efficacy of Coda Wave Interferometry
for the Measurement of Thermally Induced Ultrasonic Velocity Variations in CFRP
Laminates
Richard Livings1,2, Viany Dayal1,2, and Dan Barnard2, 1Department of Aerospace Engineering
and 2Center for NDE, Iowa State University, Ames IA 50011
Ultrasonic velocity measurement is a well-established method to measure properties and
estimate strength as well as detect and locate damage. Determination of accurate and repeatable
ultrasonic wave velocities can be difficult due to the influence of environmental and
experimental factors. Diffuse fields created by a multiple scattering environment have been
shown to be sensitive to homogeneous stresses such temperature variations, and Coda Wave
Interferometry has been used to measure the thermally induced ultrasonic velocity variation in
concrete, aluminum, and the Earth’s crust [1, 2, & 3]. In this work, we analyzed the influence of
several parameters of the experimental configuration on the sensitivity and resolution of the
measurement of thermally induced ultrasonic velocity variations in a carbon-fiber reinforced
polymer plate. Coda Wave Interferometry was used to determine the relative velocity change
between a baseline signal taken at room temperature and the signal taken at various
temperatures. Three common interferometric algorithms (Cross-Spectral Moving-Window,
Windowed Cross-correlation, and Stretching) were used and compared. The influence of several
parameters of the experimental configuration, such as the transducer type and aperture size on
the results of the processing algorithms was evaluated in order to determine the optimal
experimental configuration.
This work is supported by the NSF Industry/University Cooperative Research Program of
the Center for Nondestructive Evaluation at Iowa State University.
References:
1. E. Niederleithinger and C. Wunderlich, “Influence of small temperature variations on the
ultrasonic velocity in concrete,” in Review of Progress in Quantitative Nondestructive
Evaluation, eds. D. E. Chimenti, L. J. Bond, and D. O. Thompson, (American Institute of
Physics 1511, Melville, NY) 32, 390-397 (2013).
2. Y. Lu and J. E. Michaels, “A methodology for structural health monitoring with diffuse
ultrasonic waves in the presence of temperature variations,” in Ultrasonics, 43 (9), 707-731
(2005).
3. G. Poupinet, W. Ellsworth, and J. Frechet, “Monitoring Velocity Variations in the Crust Using
earthquake Doublets: An Application to the Calaveras Fault, California,” in Journal of
Geophysical Research, 89 (B7), 5719-5731 (1984).