Postprint version. Published in Nondestructive Testing and Evaluation, Volume 22, Issue 2-3, June 1, 2007, pages 83-92.
Copyright © 2007 Taylor & Francis. This is an electronic version of an article published in Nondestructive Testing and Evaluation. The definitive version is available at http://dx.doi.org/10.1080/10589750701447672.
NOTE: At the time of publication, the author John Chen was not yet affiliated with Cal Poly.
We have developed an experiment to study the propagation of laboratory-synthesized fatigue cracks under various controlled conditions during Sonic IR inspection. The experiment provides for good repeatability in testing. The parameters of interest include the initial crack length, load history (stress intensity and load ratio) during crack generation, geometry of the crack, material and also the various conditions involving the ultrasonic excitation source. In general, we find that under typical sonic IR inspection conditions, the initial crack will propagate under sonic IR testing. The crack growth after each inspection event varies and exhibits a distribution in length of propagation. The results show that the average crack propagation decreases with increasing stress intensity factor, and we test two hypotheses about the cause of this. Furthermore, we find that crack propagation is affected by the initial crack length.