A Theoretical Model of Ultrasonic Examination of Smooth Flat Cracks

Ultrasonic modeling for complex geometries and materials

“…It was also found that at oblique incidence bandwidth effects also play a crucial role. While previous studies of Chapman [70] concluded that the Kirchhoff approximation can only predict the pulse-echo response of a circular crack at angles up to 20-30 degrees from the crack normal, we have shown that this conclusion came from the simulation of narrow band system responses and that for wide bandwidths the Kirchhoff approximation can in fact remain accurate for angles up to approximately 55…”

“…Earlier studies have already shown that the Kirchhoff approximation works well for volumetric flaws when the size of the flaw is large compared with the wavelength (i.e. kb»l where k is the wave number and b is a characteristic dimension of the flaw) and that it works well also for flat cracks when both kb»l and the waves are scattered in a direction close to normal incidence on the crack where specular signals dominate the results [70,71].…”

“…The computational inefficiency of numerical methods has led many authors to consider approximate wave scattering models such as elastodynamic ray theory [66,67], low frequency expansions [68,69], and the Kirchhoff and Born approximations [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85]. The Kirchhoff approximation in particular has been found to be very useful and widely studied in the literature [70][71][72][73][74]. In the Kirchhoff approximation, each point on the directly insonified surface of the scatterer is assumed to reflect like an infinite plane with its normal locally coincident with the normal to the flaw surface at that point while on the remaining surface of the scatterer the total field is assumed to be zero.…”

UK Developments in Theoretical Modeling for NDT

“…I concentrate on those areas which are most recent. The consolidat ing work done on modeling of pulse-echo and Tandem inspections is not included since this is reviewed elsewhere [1]. Similarly, work done on Time-of-Flight Diffraction [2] is not included.…”

Finite Element Study of Elastic Wave Interaction with Cracks

“…Analytical work has been carried out for studying particular scattering situations [2][3][4]. Mode conversions are emphasized by many authors and Bond [5] defines a "total-wave technique" which is intended to extract more of the information available in ultrasonic wave fields.…”