Simulating the ultrasonic scattering from complex surface-breaking defects with a three-dimensional hybrid model

Modelling is increasingly relied on for the design and qualification of ultrasonic inspections applied to safety-critical components. Numerical methods enable the simulation of the ultrasonic interaction with realistic defect morphologies; however, the computational requirements often limit their deployment. The hybrid simulation technique, which combines semi-analytical and numerical methods, realises the potential of high fidelity numerical modelling without the limiting computational factors. The inspection of thick section components for near-backwall surface-breaking defects results in large propagation distances, making them a key application of hybrid modelling. This work presents a methodology for efficiently simulating the ultrasonic inspection of complex surface-breaking defects using a hybrid model. The model is initially verified against full numerical simulation; further validation is presented by comparison to an experimental scan over an artificially machined surface-breaking notch. The potential of the new hybrid method is then demonstrated by carrying out a Monte Carlo analysis on the scattered field from surface-breaking defects with randomly rough surfaces and the results are compared to the Kirchhoff approximation.