title: Ultrasonic surface crack characterization on complex geometries using surface waves.
abstract: The characterization of surface cracks on complex geometries using surface waves is investigated numerically and experimentally. The specimen geometry is implemented in a finite difference code by approximation of the contour using a Cartesian grid. In the experiments the out-of-plane surface displacement is measured by means of a heterodyne laser interferometer. Good agreement is shown by comparison of the calculated out-of-plane displacement with experimental results for both cracked and non-cracked specimens. The crack depth is measured down to a size of 0.7 times the surface wavelength using a time delay approach. The many Rayleigh pulses propagating after the crack can be separated from the other modes by a filtering procedure based on the surface wave propagation velocity. Only a detailed analysis of the scattering phenomenon using the simulation allows an identification of the transmitted pulse required for crack depth measurement. Application of the method to a specimen with a real fatigue crack shows a systematical error possibly due to the inclined crack profile.
authors.affiliation: Institute of Mechanical Systems, ETH Zurich, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland. masserey@imes.mavt.ethz.ch <masserey@imes.mavt.ethz.ch>
authors.forename: B
authors.initials: B
authors.lastname: Masserey
authors.forename: L
authors.initials: L
authors.lastname: Aebi
authors.forename: E
authors.initials: E
authors.lastname: Mazza