Combining simulated and experimental data to simulate ultrasonic array data from defects in materials with high structural noise

Ultrasonic non-destructive testing inspections using phased arrays are performed on a wide range of components and materials. All real inspections suffer, to varying extents, from coherent noise including image artefacts and speckle caused by complex geometries and grain scatter respectively. By its nature, this noise is not reduced by averaging; however, it degrades the signal to noise ratio of defects and ultimately limits their detectability. When evaluating the effectiveness of an inspection, a large pool of data from samples containing a range of different defects is important to estimate the probability of detection of defects and to help characterise them. For a given inspection, coherent noise is easy to measure experimentally but hard to model realistically. Conversely, the ultrasonic response of defects can be simulated relatively easily. This paper proposes a novel method of simulating realistic array data by combining noise-free simulations of defect responses with coherent noise taken from experimental data. This removes the need for costly physical samples with known defects to be made and allows for large data sets to be created easily.