Improvements in Ultrasonic Measurement Modeling with Applications to Ultrasonic Reliability
Thompson, R. Bruce
Over the past several years, work has been reported on the development and implementation of a measurement model relating measured ultrasonic signals obtained through planar or cylindrically curved interfaces to far field scattering amplitudes (1). A number of applications have also been described, including obtaining scattering amplitudes (2) to improve sizing capability via the inverse Born approximation (3), predicting detected signals from cracks in planar (4) and cylindrical (5) geometries, and establishing detection filters (6) for improved inspectability. These applications have used models of diffraction effects for the case of piston source radiation (7) which were developed to account only for the axial pressure fields. A number of desired applications such as treating large flaws and scanning modes will require the ability to model the full radiation field of a probe. As a first step, a model of the radiation of Gaussian profile probes through planar or curved surfaces has been developed (8). With suitable normalization, this model can be used to predict the far-field behavior of piston probes. This allows modeling of full field behavior near the focal region of either focussed probes or focussing part surfaces. This paper will discuss the incorporation of the Gaussian beam theory into the measurement model. Also reported will be several new applications of the measurement model to problems associated with ultrasonic reliability.