Huygen‐fresnel diffraction model (h‐fdm) for the simulation of ultrasonic time‐of‐flight diffraction technique in 2d geometries

TLDR: In this article, the effect of beam refraction from a wedge-based finite transducer has been modeled by treating the finite transducers as an array of line sources, and the model has been used for predicting diffracted signals in time-of-flight from the crack like defect.

Abstract: This paper discusses the evaluation of diffracted signals from cracks in 2D based on a new Huygen‐Fresnel Diffraction Model (H‐FDM). The model employs the frequency‐domain far‐field displacement expressions derived by Miller & Pursey [1] in 2D for a line source located on the free surface of a semi‐infinite elastic medium. At each frequency in the bandwidth of a pulsed excitation, the complex diffracted field is obtained by summing over the unblocked virtual sources located in the section containing a vertical crack. The time‐domain diffracted signal is obtained using standard FFT procedures. The effect of beam refraction from a wedge‐based finite transducer has been modeled by treating the finite transducer as an array of line sources. The model has been used for predicting diffracted signals in time‐of‐flight from the crack like defect. The model allows the evaluation of back wall signal amplitude and lateral wave amplitude as well. Experiments have been carried out on 10 mm thick aluminum sample with s...