Impact-Echo Method: An Overview.
Impact-Echo Method: An Overview.
(720 K)
Carino, N. J.
Structures Congress and Exposition 2001. Proceedings.
American Society of Civil Engineers. May 21-23, 2001,
Washington, DC, Chang, P. C., Editor(s), 1-18 pp, 2001.
Keywords:
concretes; flaws; frequency analysis; thickness; stress;
test methods
Abstract:
The impact-echo method is a technique for flaw detection
in concrete. It is based on monitoring the surface
motion resulting from a short-duration mechanical
impact. The method overcomes many of the barriers
associated with flaw detection in concrete based on
ultrasonic methods. The purpose of this paper is to
provide an overview of the technique and to discuss the
important parameters involved in this type of testing.
One of the key features of the method is the
transformation of the recorded time domain waveform of
the surface motion into the frequency domain. The impact
gives rise to modes of vibration and the frequency of
these modes is related to the geometry of the test
object and the presence of flaws. The principles
involved in frequency analysis are discussed. The
importance of the impact duration in relation to flaw
detection and other factors affecting the smallest flaw
that can be detected are also reviewed. The paper
concludes with a summary of the ASTM standard governing
the use of the impact-echo method for measuring the
thickness of plate-like structures.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899