Abstract
A non-destructive method is described which tests steel pipes on the basis of the waveform of vibration induced by an impact. An elastic wave generated within a pipe wall by an impact propagates along the pipe, and is reflected at a point where the acoustic impedance of the pipe wall changes. The waveform of particle velocity of the pipe wall thus gives information about the acoustic impedance distribution along the pipe. Since the acoustic impedance changes at a flaw, we can test a pipe from the waveform of elastic wave which is generated by an impact and propagates through the pipe. A simulation test was performed; the aim was to study the classification ability of multi-variable analysis based on the waveform. An impactor employing a piezoelectric actuator was put on one end of a pipe to generate elastic waves. At the other end, the radial component of particle velocity of the pipe wall was picked up by a LASER velocimeter. The output signal was analyzed by a successive feature extraction technique and was given a flaw class membership. The results of the simulation test show that the method described may be a useful complement in the field of non-destructive testing and evaluation.
