ULTRASONIC SIMULATION AND MEASUREMENTS WITH CUT-OFF FREQUENCY EXTRACTIONS
The removal of the effect of imperfect dynamic properties of ultrasonic transducers and associated electronics, as well as the couplant to a structure, from experimental data is presented. The investigation reveals that it is unnecessary for the instrumentation to have an ideal frequency response function for a transducer because imperfect measurement behaviour can be removed with post processing. A computer simulation of a homogeneous, isotropic pipe’s radial displacement is shown to agree closely with a corresponding measurement if a reasonably accurate frequency response function of the measurement chain is incorporated. A procedure to extract the cut-off frequencies of an unblemished pipe and the singularity frequencies of a notched pipe is developed. Frequency differences between the cut-off frequencies and the nearest frequencies of singularities introduced by a circumferential notch are investigated. It is confirmed experimentally that singularities are introduced by a notch and differences are measurable at a 95% confidence level.