Contactless Ultrasonic Wavefield Imaging to Visualize Near-Surface Damage in Concrete Elements

Homin Song,John S. Popovics

doi:10.3390/app9153005

Abstract

We present work to detect and visualize near-surface damage in concrete using contactless ultrasonic wavefield imaging technology. A fully contactless ultrasonic scanning system that utilizes a micro-electro-mechanical systems (MEMS) ultrasonic microphone array is used to collect ultrasonic surface wave data from a concrete sample. The obtained wavefield data sets are processed with a frequency-wavenumber (f-k) domain wavefield filtering approach to extract non-propagating oscillatory fields set up by near-surface concrete cracking damage. The experimental results demonstrate that near-surface concrete damage can be detected and visualized using the proposed ultrasonic wavefield imaging approach.

Highlights

The term ultrasonic wavefield imaging implies visualizing ultrasonic wave motion over a region of interest in a test medium
To visually understand the interaction between incident surface waves and surface damage of concrete, impact damage points were introduced on the top surface of the concrete sample using a low-power nail gun
An example time domain ultrasonic surface wave signal collected from the pristine concrete sample case is shown in Figure 3, which reveals suitably high signal-to-noise level

Summary

Introduction

The term ultrasonic wavefield imaging implies visualizing ultrasonic wave motion over a region of interest in a test medium. A source at a fixed position generates ultrasonic waves in a test medium, and a contactless scanning receiver, typically a laser Doppler vibrometer (LDV), collects the corresponding ultrasonic wave responses across a predefined spatial sampling grid on the surface [2,5,6]. Using the scanning measurement data sets, video-like ultrasonic wavefield images are generated, where the interaction between propagating ultrasonic waves and inhomogeneities within a test medium can be observed and intuitively understood. Ultrasonic wavefield imaging technology usually incorporates an additional data processing method to extract damage-induced scattered ultrasonic wavefields, thereby visualizing possible damage in a test medium [5,9,10,11]

Methods

Results

Discussion

Conclusion