| 摘要 |
PURPOSE:To realize a title method which enables echoes from inner flaws of a steel pipe with coarse crystal grains to be inspected with high sensitivity and high S/N ratio by increasing the sensitivity of a probe to low frequencies with regard to this method of inspecting inner flaws of a specimen such as a steel pipe of high attenuation material from outside by using ultrasonic waves. CONSTITUTION:A transmission oscillator 12 is set at low frequencies according to flaw detection positions of a steel pipe 4 and oscillates to output a rectangular or triangular wave of any of first to fourth waves. A transmitter 13 amplifies this rectangular or triangular wave and supplies it to a wide-range probe 3, thereby exciting it to generate ultrasonic waves. Thereby, a low frequency receiving signal of echoes, less than third waves in the number of crystal grain size, reflected by a flaw in the steel pipe 4 is obtained with an amplitude larger than by the prior art, detected by a detector 15 through a receiver 14, amplified by an amplifier 16, and then displayed on a CRT display unit 18. |
