On the modelling of ultrasonic testing using boundary integral equation methods

Ultrasonic nondestructive testing has important applications in, for example, the nuclearpower and aerospace industries, where it is used to inspect safety-critical parts for flaws.For safe and reliable testing, mathematical models of the ultrasonic measurement systemsare invaluable tools. In this thesis such measurement models are developed for the ultrasonictesting for defects located near non-planar surfaces. The applications in mind arethe testing of nuclear power plant components such as thick-walled pipes with diametertransitions, pipe connections, etc. The models use solution methods based on frequencydomain boundary integral equation methods, with a focus on analytical approaches for thedefects and regularized boundary element methods for the non-planar surfaces. A majorbenefit of the solution methods is the ability to provide accurate results both for low, intermediateand high frequencies. The solution methods are incorporated into a frameworkof transmitting probe models based on prescribing the traction underneath the probe andreceiving probe models based on electromechanical reciprocity. Time traces are obtainedby applying inverse temporal Fourier transforms, and it is also shown how calibration andeffects of material damping can be included in the models