Non-Destructive Inspection of Multiple Concrete Cracks Using Ultrasonic Sensor

Non-destructive testing (NDT) of concrete cracks are very important for the maintenance and safeguard of concrete structures. Numerous methods with varying detecting devices have already been developed for this purpose. Although detection of a single crack within the concrete is somewhat easy, simultaneous detection of multiple numbers of cracks in the direction of depth is extremely difficult due to the fact that many reflected waves are often overlapped and that the reflected waves are spindle oscillatory types. The present paper proposes a method to identify multiple numbers of cracks inside the concrete using a multi-reflected wave model and a pattern matching technique. The method uses the pattern matching technique to detect the optimum times of flights (TOEs) of the reflected waves from multiple cracks and thus determines the crack depths. Using this method, not only the depths of the multiple cracks but the attenuation of the reflected waves relative to each other can also be determined. Experiments will show that the method is effective