Non-destructive crack detection technique by means of microwave imaging

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Date
2015-01-01
Authors
iya Adama Enoch
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Building and civil structures are often overburdened with load above their threshold value that led to deterioration and weakening of the supporting members, and resulted in cracks. Cracks in concrete or cement based materials present a significant threat to any civil structures; they are very dangerous and have caused much destruction and damages. Even small cracks, which look insignificant grow and eventually lead to severe structural failure. Besides manual inspection that is ineffective and time-consuming, several non-destructive evaluation techniques have been used for crack detection. For instance, ultrasonic, vibration and strain-based techniques, however some of the sensors used are either too big or limited in resolution. The main objective is to study the possibility of crack detection in concrete or cement based materials using microwave imaging with Delay-and-Sum, (DAS) algorithm. First, models of various crack types in bricks were simulated using finite difference time domain method (FDTD) method. The simulation results were used to determine the design parameters for the experimental setup. Single brick and a constructed concrete structure with cracks were used as phantoms. From the experimental results, signal with frequency of 1 to 7 GHz gave an optimum resolution and signal penetration. Cracks of at least 5 mm in size were detected with a resolution of λ/4 that enabled crack detection at the early stage of development. In conclusion, microwave imaging technique showed the potential to detect cracks in concrete or cement-based materials with high-resolution image.
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