| 摘要 |
PROBLEM TO BE SOLVED: To discriminate, with a body on which ultrasonic wave is reflected, whether it is a defect such as crack or non-defect such as rust, when a reflected wave is obtained in the ultrasonic wave inspection of a low-pressure steam turbine wheel. SOLUTION: With a turbine wheel 1 pressed against a prove 9, the entire prove holder is rotated around a turbine shaft 2 to keep a distance and a swing angle from a center axis of the turbine wheel 1 constant, and the prove 9 is scanned under this condition, so that a ultrasonic wave form and prove position are automatically stored in a storage part 1 based on pulse signal 6 emitted from an encoder 5. With a reflected wave obtained, the correlation coefficient 23 of two wave forms recorded at different prove positions is calculated with a mutual correlation processing part 22 and displayed on a display part 24. When the correlation coefficient is larger than a pre-set threshold value, it is discriminated as a defect while when it is smaller discriminated as other than defect. |
