NDT of a Composite Domain Using Ultrasonic Tomography

Non-destructive testing (NDT) of engineering materials, components and structures has steadily increased in recent years at an unprecedented rate because of all-round thrust for improving material quality, component integrity and performance reliability. Ultrasonic testing is a versatile NDT method, which is applicable to most materials, metallic or non-metallic. The relevance of computed tomography (CT) in state-of-the-art non-destructive evaluation (NDE) is enormous. CT uses computer reconstruction to combine the information obtained from multiple projections. For quicker and reliable results there is a need to have clear ideas regarding performances of reconstruction algorithms. In the present investigation, the NDT of a composite domain using ultrasonic CT is presented. The sample is of rectangular shape and consists of a continuous phase made of steel and a square shaped insert made of resin. Reconstruction is done by ART like algorithms on a set of time-of-flight (TOF) data collected between transducers for multiple ray paths in each of the different views. For each reconstruction, the reconstructed image is compared with the actual one and a corresponding L1 error is calculated. Performance of each algorithm, with different relaxation parameters is studied and compared in terms of accuracy and iteration numbers.