Mitsuru Odakura

EVALUATION FOR DEFECT DETECTION OVER BENDING ZONE IN PIPING BY GUIDED WAVE

Guided wave inspection technique is effective as detecting defects like corrosion in piping. Effectiveness to the straight parts in piping by the guided wave inspection has been clarified by many researches. The inspection performance using guided wave decreases due to the unwanted wave when there is a bend part in the inspection area. On above motivation, the inspection performance could be improved if the guided wave was transmitted from many circumferentially‐set sensors based on the same principle as for phased‐array methods. Then, the validity of phased array methods using the guided wave technique was confirmed by the following experiments using a piping with bend. The delayed pulse by phased‐array methods was set from the reflected wave which was transmitted from a local defect, and it was calculated based on time reversal theory. This transmission wave was confirmed by one experiment using the guided wave focused over the bend zone. Thus, the unwanted wave caused in the bend zone could be suppress...

DEVELOPMENT OF 3D PHASED ARRAY SYSTEM “3D FOCUS‐UT”

Ultrasonic phased array inspection systems have been used the in various industrial fields recently. For instance, power plants have used these systems to maintain their reliability. The phased array is advantageous because it improves efficiency by imaging the inside of the test subject. This inspection image is obtained by electronic scanning of a focused ultrasonic beam using a phased array sensor. We have developed a 3‐dimensional volume inspection technology to make further efficiency and accuracy improvements in ultrasonic inspections. This study presents the innovative 3D phased array inspection system “3D Focus‐UT” for 3D volume inspection. This system employs (1) a 3D ray‐trace simulator to set up the delay time for the elements in the array sensor and the delay pattern for 3D volume scanning; (2) high sensitivity phased array equipment that has a 256 ch pulsar/receiver to drive/receive a 2D matrix array transducer simultaneously; and (3) high‐speed 3D data processing software. The software conve...

DEFECT SIZING METHOD USING ULTRASONIC GUIDED WAVES IN PIPES

This paper presents a defect‐sizing method using swept‐frequency guided waves. In this technique, reflection coefficients of multiple frequencies were measured, and the coefficients were compared with the 3‐D analysis result that was calculated by integration of reflection waves from divided calculation‐regions that had different characteristic acoustical impedances. The effectiveness of the method was evaluated experimentally using torsional mode guided waves that propagated in pipe specimens. The experimental results were in good agreement with analysis results.