A contactless ultrasonic surface wave approach to characterize distributed cracking damage in concrete

Abstract

We describe an approach that utilizes ultrasonic surface wave backscatter measurements to characterize the volume content of relatively small distributed defects (microcrack networks) in concrete. A simplified weak scattering model is used to demonstrate that the scattered wave field projected in the direction of the surface wave propagation is relatively insensitive to scatterers that are smaller than the propagating wavelength, while the scattered field projected in the opposite direction is more sensitive to sub-wavelength scatterers. Distributed microcracks in the concrete serve as the small scatterers that interact with a propagating surface wave. Data from a finite element simulation were used to demonstrate the viability of the proposed approach, and also to optimize a testing configuration to collect data. Simulations were validated through experimental measurements of ultrasonic backscattered surface waves from test samples of concrete constructed with different concentrations of fiber filler (0.0, 0.3 and 0.6%) to mimic increasing microcrack volume density and then samples with actual cracking induced by controlled thermal cycles. A surface wave was induced in the concrete samples by a 50kHz ultrasonic source operating 10mm above the surface at an angle of incidence of 9°. Silicon-based miniature MEMS acoustic sensors located a few millimeters above the concrete surface both behind and in front of the sender were used to detect leaky ultrasonic surface waves emanating from concrete. A normalized backscattered energy parameter was calculated from the signals. Statistically significant differences in the normalized backscattered energy were observed between concrete samples with varying levels of simulated and actual cracking damage volume.

Air-coupled impact-echo damage detection in reinforced concrete using wavelet transforms

“…where N is the number of hidden layer neurons and i is the particular output layer neuron. The summation of the output neurons was found with an updated (2) and (2) for each subsequent (2) . In other words, the (2) value of j = 1 was calculated with the initial weights and bias value, the weights and bias were updated using back propagation and the updated values were used for the j = 2 output neuron.…”

“…Recent research has therefore been focused on identifying several types of internal damage in RC structures. Among these damages are breathing cracks [1,2], micro cracking [3], delamination [4], and voids and inclusions [13]. Voids may be present from conception of new structures if the workability of the concrete is poor or the concrete is not vibrated properly, leading to air pockets in the structure.…”

Image Analysis and Functional Data Clustering for Random Shape Aggregate Models

“…Non-destructive testing (NDT) using a wave propagation is one of the most applicable methods for the concrete material. Various research of wave-propagation-based NDT has been conducted, including advanced approaches: diffuse wave [1], non-linear wave [2], incoherent wave [3], and Coda wave [4]. As with the NDT study, a numerical simulation method has also been improved to understand the non-linear wave propagation behavior in the homogeneous medium.…”

Ultrasonic signal modality: A novel approach for concrete damage evaluation

“…Concrete is the most widely used synthetic material all over the world in civil and building engineering and architecture. It is composed of water, cement, gravel and sand mixed in different proportions depending on 25 the kind of mechanical and physico-chemical properties required by the project. This material has an excellent mechanical and structural performance.…”

“…Nonlinear ultrasonics are also being studied by the Scaling Substraction Method, a novel technique that allows to correlate damage with the loss of linearity based on amplitude scaling in a through-transmission layout [21,22]. Also, ultrasonic surface wave has been used to detect global micro-cracking processes in concrete 75 elements [23,24], even with air-coupling layout [25]. In the present paper, a new signal modality approach for material characterization is presented.…”