Abstract
Cracks in concrete or cement based materials present a great threat to any civil structures; they are very dangerous and have caused a lot of destruction and damage. Even small cracks that look insignificant can grow and may eventually lead to severe structural failure. Besides manual inspection that is ineffective and time-consuming, several nondestructive evaluation techniques have been used for crack detection such as ultrasonic technique, vibration technique, and strain-based technique; however, some of the sensors used are either too large in size or limited in resolution. A high resolution microwave imaging technique with ultrawideband signal for crack detection in concrete structures is proposed. A combination of the delay-and-sum beamformer with full-view mounted antennas constitutes the image reconstruction algorithm. Various anomaly scenarios in cement bricks were simulated using FDTD, constructed, and measured in the lab. The reconstructed images showed a high similarity between the simulation and the experiment with a resolution of λ/14 which enables a detection of cracks as small as 5 mm in size.
Highlights
Cracks in concrete or cement based materials present a great threat to any civil structures; they are very dangerous and have caused a lot of destruction and damage
Besides manual inspection that is ineffective and time-consuming, several nondestructive evaluation techniques have been used for crack detection such as ultrasonic technique, vibration technique, and strain-based technique; some of the sensors used are either too large in size or limited in resolution
The anomaly presents a great threat to any civil structures; it is very dangerous and has caused a lot of destruction and damage
Summary
The 2D domain is considered in this work for the imaging of cracks on the bricks cross section. The 2D domain is considered in this work for the imaging of cracks on the bricks’ cross section because it saves memory space optimally and demands less tasking compared to 3D domain that is computationally time demanding. The main aim of using FDTD model is to be able to test and to verify the capability of the imaging modality in detecting and differentiating cracks of different orientation and sizes from a brick and the constructed structure. Holes of different diameters and lengths were used to characterise different crack sizes. These holes were positioned in the brick model at (x, y) positions measured in millimeter. The perfect match layer (PML) is composed of square of 260 mm by 260 mm to contain the size of the brick and the structure
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