Non-destructive inspection of concrete structures by ultrasonic sensor taking account of sensor characteristics

For a non-destructive inspection of concrete structures with ultrasonic sensor, a pulse echo method is well known. In the application of the method, however, an accurate detection and measurement are difficult due to various disturbances affecting the sensor output. This paper proposes first to filter the sensor output with a band pass filter to remove a time variant bias and next to apply a maximum likelihood method to the filtered output to realize a reliable and accurate defect detection. Moreover, another detection method of pattern matching is proposed to raise the detection reliability and measurement accuracy in parallel use with the maximum likelihood method.