Time-of-flight diffraction ultrasonics

About: Time-of-flight diffraction ultrasonics is a research topic. Over the lifetime, 544 publications have been published within this topic receiving 3189 citations.

Crack Location and Height Measurementby 4 Sensor TOFD Method with Pulse Compression

Abstract: Ultrasonic flaw sizing is important issue for remaining life prediction of industrial plants. Time-of-Flight Diffraction (TOFD) method is recognized as one of the most accurate flaw sizing method. However, to measure the crack height accurately, the crack must be symmetrically placed between transmitter and receiver. When the crack do not exist such position, the B-scan is required for accurate crack sizing. By the way, if additional transmitter or reciever is added to the system, the crack location and height can be estimated without B-scan. In this study, we examined the 4 sensor TOFD method which utilizes two transmitters and two receivers. In the result, the crack location and height can be estimated by 4 sensor TOFD method. However, the estimation errors were large due to the low SN ratio of received signal. Then we applied the pulse compression technique to the 4 sensor TOFD method for improving SN ratio of received signal. In the result, the SN ratio was enhanced about 11 dB by the pulse compression. The average location on error is reduced from 2.49 mm to 1.13 mm, and the average depth estimation error is reduced from 0.28 mm to 0.21 mm.

Advanced Image Processing Techniques For Automatic Interpretation of Time-of-Flight Diffraction Images

Abstract: Time-of-flight diffraction techniques are widely used in NDT and commercial equipment which can produce good quality B-scan images is widely available. Their present application is concentrated on the inspection of metals using frequencies from 1 to 5 MHz and a pulse length of a few cycles. In this range the ultrasonic wavelengths are comparable to the characteristic size of the defects and the geometrical theory of diffraction accurately describes the propagation phenomena involved. In many instances a defect can be considered as a point-like reflector.

Combined detection method of ultrasonic longitudinal wave reflection method and diffraction time difference method, and TOFD probe applied therein

Abstract: The invention discloses a combined detection method of an ultrasonic longitudinal wave reflection method and a diffraction time difference method. The combined detection method comprises the followingsteps that 1, a TOFD probe and a creeping wave probe are installed on a scanning frame; 2, TOFD probe parameters and creeping wave probe parameters are set; 3, a workpiece is scanned; and 4, an imageis analyzed after the scanning is finished. According to the method, the defects that defects near a near surface and a bottom surface are missed and a plurality of pairs of probes need to be adoptedfor thick welding seams in an existing TOFD detection method are overcome, and ultrasonic automatic and semi-automatic detection is more perfect.

Ultrasonic detection and locating method and device based on tofd and phased array

Abstract: An ultrasonic detection and locating method and device based on TOFD and a phased array. The device comprises a TOFD detection unit (10) and a phased array detection unit (20). The TOFD detection unit (10) is used for scanning welded seams by using a TOFD ultrasonic detection method, so as to determine the position of a defect. The phased array detection unit (20) is used for scanning welded seams near the determined defect position by using a phased array ultrasonic detection method, identifying a defect of a size exceeding a preset size threshold, and locating the identified defect. Position information of a defect in a horizontal direction and a depth direction can be accurately determined by means of phased array ultrasonic detection; during location in cooperation with TOFD detection, a defect of a welded seam is accurately located by using TOFD scanning serving as a main method and phased array scanning serving as an auxiliary method, thereby overcoming the problems of poor locating precision of TOFD scanning and failure to detect a transverse defect during non-parallel scanning.