| 摘要 |
PURPOSE:To measure a decrease in wall thickness on the basis of an ultrasonic porpagation speed inside a pipe material by a method wherein ultrasonic pulses are made to impinge and a vibration cycle which appears in a self-correlation function is found on the basis of its reflected-pulse envelope signal. CONSTITUTION:A pulse signal, from a transmission part 2, which is output by the measurement execution instruction of a control part 1 is changed into ultrasonic pulses by an ultrasonic probe 3, and the pulses are made to impinge vertically to the outer wall surface 4a of a pipe 4. After the pulses have been made to impinge, they are reflected partly by its inside wall rear 4d, and they are transmitted partly through its outer wall rear 4c and its surface 4a. The transmitted and reflected ultrasonic pulses are detected 3, and they are output as received waves by a reception part 5. From the envelope signal, of the received waves, which has been generated by a detection circuit 6, a signal processing part 7 extracts waveform data after the elapse of a definite time td after transmission waves have been transmitted, and its self-correlation function phi (tau) is computed. Then, a vibration cycle which appears in the function phi (tau) is found, it is regarded as the time required when ultrasonic waves go back and forth inside the pipe between an inner wall and an outer wall, a pipe wall thickness d=vT/2 is obtained on the basis of an ultrasonic propagation speed inside a pipe material, and the thickness is displayed 8 as a decrease in wall thickness. |
