Quantitative simulation of ultrasonic time of flight diffraction technique in 2D geometries using Huygens–Fresnel diffraction model: Theory and experimental comparison

A system model for ultrasonic NDT based on the Physical Theory of Diffraction (PTD)

“…This method [11] also seems to be able to deal with the incident shadow boundary, as illustrated by simulation results presented in Fig. 6 in [11]. This figure cannot correspond to the TOFD configuration for a planar component described in Fig.…”

“…This figure cannot correspond to the TOFD configuration for a planar component described in Fig. 5 of [11], since in this configuration the incident wave cannot reach the receiver and the incident shadow boundary cannot be located at the observation angle of 45°as Fig. 6 suggests.…”

“…Therefore, development of a generic model that can account for both reflection and edge diffraction is of great interest in NDT applications. Recently an original 2D approach based on the Huygens-Fresnel diffraction theory has been proposed [11] for evaluating the edge diffracted signal in TOFD configuration. The model uses both the monochromatic far field expressions derived by Miller and Pursey [12] and reciprocity principle.…”

“…Due to this equivalence, the Huygens-Fresnel model is likely to lead to significant prediction errors in diffracted shear waves (see Section 3.2). To account for reflection, the Huygens-Fresnel model [11] has to be modified to sum up virtual sources on the real scatterer as done in [11] for computing the component backwall echo. This method [11] also seems to be able to deal with the incident shadow boundary, as illustrated by simulation results presented in Fig.…”

“…6 suggests. The method [11] is also restricted by being applicable only in TOFD and 2D configurations and since it relies on the Miller and Pursey's solution, it cannot describe scattered head waves or regions surrounding critical rays [14,15].…”