Ultrasonic array imaging through an anisotropic austenitic steel weld using an efficient ray-tracing algorithm

• Semi-analytical model for anisotropy effects in austenitic steel welds.
• Calculation of ultrasonic image degradation due to beam-steering effects.
• Ultrasonic beam perturbation modelled by efficient ray-tracing algorithm.
• Defect response modelled by local Finite Element Method (FEM) solution.
• 300-fold computation time decrease as compared to equivalent full FEM approach.

Ultrasonic inspection of austenitic welds is challenging due to their highly anisotropic and heterogeneous microstructure. The weld anisotropy causes a steering of the ultrasonic beam leading to a number of adverse effects upon ultrasonic array imagery, including defect mislocation and aberration of the defect response. A semi-analytical model to simulate degraded ultrasonic images due to propagation through an anisotropic austenitic weld is developed. Ray-tracing is performed using the A⁎ path-finding algorithm and integrated into a semi-analytical beam-simulation and imaging routine to observe the impact of weld anisotropy on ultrasonic imaging. Representative anisotropy weld-maps are supplied by the MINA model of the welding process. A number of parametric studies are considered, including the magnitude and behaviour of defect mislocation and amplitude as the position of a fusion-face defect and the anisotropy distribution of a weld is varied, respectively. Furthermore, the use of the model to efficiently simulate and evaluate ultrasonic image degradation due to anisotropic austenitic welds during an inspection development process is discussed.