Visualization of Stress Wave Propagation via Air-Coupled Acoustic Emission Sensors

TL;DR

This paper demonstrates a novel air-coupled acoustic emission technique for visualizing stress wave propagation in metallic plates, enabling full-field, remote sensing of wave events with potential applications in structural health monitoring.

Contribution

The study introduces a beamforming-based air-coupled acoustic sensor array for in situ visualization of stress waves, surpassing traditional contact-based methods in efficiency and scope.

Findings

Successful visualization of stress waves in metallic plates under impact

Effective detection of wave attenuation, reflection, and scattering at damage sites

Potential for non-contact damage localization in structural health monitoring

Abstract

We experimentally demonstrate the feasibility of visualizing stress waves propagating in plates using air-coupled acoustic emission sensors. Specifically, we employ a device that embeds arrays of microphones around an optical lens in a helical pattern. By implementing a beamforming technique, this remote sensing system allows us to record wave propagation events in situ via a single-shot and full-field measurement. This is a significant improvement over the conventional wave propagation tracking approaches based on laser doppler vibrometry or digital image correlation techniques. In this paper, we focus on demonstrating the feasibility and efficacy of this air-coupled acoustic emission technique using large metallic plates exposed to external impacts. The visualization results of stress wave propagation will be shown under various impact scenarios. Such wave visualization capability is of tremendous importance from a structural health monitoring and nondestructive evaluation (SHM/NDE) standpoint. The proposed technique can be used to characterize and localize damage by detecting the attenuation, reflection, and scattering of stress waves that occurs at damage locations. This can ultimately lead to the development of new SHM/NDE methods for identifying hidden cracks or delaminations in metallic or composite plate structures simultaneously negating the need for mounted contact sensors.