Analytical modeling, finite-difference simulation and experimental validation of air-coupled ultrasound beam refraction and damping through timber laminates, with application to non-destructive testing

Economical Sponge Phantom for Teaching, Understanding, and Researching A‐ and B‐Line Reverberation Artifacts in Lung Ultrasound

“…Smooth regions of the interface led to a coherent reflection parallel to the incident wave front (Figure b, 3), whereas irregular profiles, such as cavities (Figure b, 4), led to multiple reflections in multiple angular directions and diffraction of the incident ultrasound field. The latter can be visualized with the Huygens principle, for which every point of the interface becomes a point source of ultrasound waves . Multiple secondary wave fronts were therefore generated simultaneously and added up, creating a complex interference pattern.…”

“…The ultrasound simulation was conducted with a recently described finite‐difference time‐domain (FDTD) model, which discretizes the elastic wave propagation equations ∂ t u p = ρ –1 ∂ q σ pq and ∂ t σ pq = C pqrs ∂ s u r on a square pixel grid, so that arbitrary values of the density ρ and stiffness C pqrs can be defined at each pixel ( x, y ). The FDTD model is well suited for the simulation of discontinuous material distributions and has been applied to simulate air‐coupled ultrasound propagation in heterogeneous composites .…”

Nondestructive Testing of Polymers and Polymer–Matrix Composites

“…The coupling may be with contact (dry or liquid), immersion, squirter (251), or even in air. The latter, however, is still under development (282,283). A theoretical overview is given in Ref.…”

“…Generally, cylindrical objects are studied to minimize refraction effects, or, Lamb waves are used in case of plates. More complex structures may be studied by time reversal and numerical backpropagation of ultrasound waveforms (283,289).…”

“…A-, B-, and C-scans can be simulated and also the temporal propagation of the wave can be visualized. FE, that is, finite elements (290,291) and FDTD (finite difference time domain) simulations (283) in two dimensions are relatively fast. However, for three dimensions, it is still very time consuming.…”