Effect and identification of parametric distributed uncertainties in longitudinal wave propagation

Surface roughness measurement based on singular value decomposition of objective speckle pattern

This work introduces and investigates a flat acoustic mirror capable of efficiently manipulating a wavefront and creating an arbitrary pressure pattern in a target plane using the sound reflection phenomenon. The mirror is a metallic holographic lens that performs as a spatial ultrasound modulator by introducing a relative phase shift to the reflected wavefront. The phase-shifting lens is designed using an iterative angular spectrum algorithm and 3D-printed from powdered aluminum through direct metal laser melting. The lens's capabilities to construct diffraction-limited complex pressure patterns under water are tested numerically and experimentally. The proposed holographic mirror design can drive immense improvements in applications involving contactless acoustic energy transfer, which is investigated in this Letter.

Holographic mirrors for spatial ultrasound modulation in contactless acoustic energy transfer systems

Crack characterization is one of the central tasks of NDTE an image-processing module, which filters and enhances these images; and an explainable AI module—a decision tree, which selects images of possible cracks, groups those of them that appear to represent the same crack and produces for each group a possible inspection report for perusal by a human inspector. AutoNDE has been trained on 16 datasets collected in a laboratory by imaging steel specimens with large smooth planar notches, both embedded and surface-breaking. It has been tested on two other similar datasets. The paper presents results of this training and testing and describes in detail an approach to dealing with the main source of error in ultrasonic data—undulations in the specimens’ surfaces.

Towards Explainable Augmented Intelligence (AI) for Crack Characterization

This paper proposes a brief review of acoustic wave scattering models from rough surfaces. This review is intended to provide an up-to-date survey of the analytical approximate or semi-analytical methods that are encountered in acoustic scattering from random rough surfaces. Thus, this review focuses only on the scattering of acoustic waves and does not deal with the transmission through a rough interface of waves within a solid material. The main used approximations are classified here into two types: the two historical approximations (Kirchhoff approximation and the perturbation theory) and some sound propagation models more suitable for grazing observation angles on rough surfaces, such as the small slope approximation, the integral equation method and the parabolic equation. The use of the existing approximations in the scientific literature and their validity are highlighted. Rough surfaces with Gaussian height distribution are usually considered in the models hypotheses. Rather few comparisons between models and measurements have been found in the literature. Some new criteria have been recently determined for the validity of the Kirchhoff approximation, which is one of the most used models, owing to its implementation simplicity.

https://www.mdpi.com/2076-3417/10/22/8305/pdf

Michel Darmon

Papers

Acoustic Scattering Models from Rough Surfaces: A Brief Review and Recent Advances