A novel technique for improving of ultrasonic TOFD data

Traditional ultrasonic TOFD (time of flight diffraction) has the major shortcoming of low amplitude of diffractive wave which brings about lack of sensitivity for weld defect detection. Aimed at the technological limitation, a novel TOFD method is proposed by developing a focusing probe. Through the analyses and calculation of sound field distribution based on geometric acoustics, a cylindrical surface wedge is designed and produced. Artificial defect containing testing piece is made and tested using both traditional and focusing TOFD, and the received signal and image are compared. The result shows that the proposed focusing method can converge the emitted sound energy effectively and improve testing sensitivity greatly. Compared with traditional TOFD tested data, focusing TOFD tested defect wave in A-scan line and defect diffractive stripe in D-scan image can be identified easily.