A study on crack detection using eigenfrequency test data

In this paper, a simple and easy nondestructive evaluation procedure is pre sented for identifying a crack, the location and size of the crack, in a on e-dimensional beam-type structure using the natural frequency data. The fir st procedure is to find the lowest four natural frequencies of the cracked structure by F.E.M. Then, the approximate crack location is obtained by Arm on's Rank-ordering method that uses the above four natural frequencies. Sec ond, by applying the result of the crack position range, an appropriate F.E .M. model is adopted and the crack size is determined by F.E.M. Finally, th e actual crack location can be identified by Gudmundson's equation using th e determined crack size and the aforementioned natural frequencies. The app lication and accuracy of the proposed procedure can be demonstrated by mean s of an example of the detection of a crack on the cantilever beam which wa s tested and studied by Rites PF, Aspragathos N, Dimarogonas AD. Journal of sound and vibration 1990; 138 (3): 381-388. (C) 2000 Elsevier Science Ltd. All rights reserved.