In this paper the dynamic behavior of a fatigue cracked beam is investigated. The
purpose is to reveal the nonlinear behavior of the structure with fatigue damage by
using wavelet transform. A cracked cantilever beam is modeled by the finite element
(FE) method using ALGORTM software. A breathing crack is described
in the FE method as a surface to surface contact of the two edges of the
crack during vibration. Strain time history in the area adjacent to the crack
has been analyzed using data processing techniques. Nonlinear effects in
signals are usually difficult to detect by conventional data processing methods
such as fast Fourier transform. However wavelet transform has recently been
shown to be an effective method of detecting such nonlinear effects in signals.
Modulus maxima, an important property of wavelet transform, have been used
as an indicator of the crack size. Numerical results obtained from the FE
analysis are presented in this paper, as well as some experimental results.
It is shown that detection of fatigue cracks using breathing behavior and
wavelet transform can be used to develop a vibration-based crack detection
technique.
