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.

Finite difference time domain simulation of the time-of-flight diffraction technique for imaging and sizing cracks

Abstract: This paper reports on the numerical simulations of the Time-of-Flight Diffraction (TOFD) technique to image and size cracks in plate specimens, using the Finite Difference Time Domain (FDTD) method for modelling the ultrasonic wave propagation. Experiments were conducted to validate modelling results for pitch-catch simulations of transducers on samples with calibrated defects of different configurations and sizes in aluminium plate sections. Defects were imaged and sized taking into consideration the velocity of the wave and the times of arrival of the diffracted echoes. Experiments were carried out using a 5 MHz transmitter-receiver transducer pair mounted on suitable wedges to generate a beam of 50° refracted angle within the specimen to image and size cracks and hence validate the simulations. A front/back-wall correction algorithm coupled with a synthetic aperture focusing of the TOFD signals was also demonstrated for improved sizing of defects.

Inclined crack TOFD quantitative detection method based on geometric relationship

Abstract: For reducing the difficulty of implementation and expanding the scope of application, the invention provides an inclined crack TOFD quantitative detection method based on geometric relationship, and belongs to the field of ultrasonic nondestructive detection. The method adopts an ultrasonic testing system for TOFD scanning of an inclined crack forming a certain angle with a welding seam vertical section in a welding seam structure, and the position of the inclined crack and the projected length of the inclined crack along the welding seam length direction are determined according to a D scanning image, wherein the ultrasonic testing system comprises a TOFD ultrasonic detector, detection probes, a calibration test block and a scanning device; the inclined crack is subjected to B scanning for two times starting from two positions having the same distances departing to the central line of the welding seam, the interval of the two times of B scanning along the welding seam length direction is d, and the moving distances L1 and L2 of the probes when the sonic path distance is shortest can be respectively obtained from the B scanning images. According to a formula tan[theta]=[the absolute value of (L2-L1)]/d, the value of an inclined angle theta of the inclined crack relative to the welding seam vertical section is calculated, and according to a formula L=L(projected length)/cos[theta], the length L of the inclined crack is calculated. The method has the advantages of high operability, wide application range, and relatively good engineering application value.

Time-of-flight diffraction technology for ultrasonic inspection of piping and pressure-retaining components

Abstract: Controle non destructif par ultrasons des tuyauteries et des composants d'enceintes sous pression (diffraction et methode du temps de vol)

Reference wavelets used for deconvolution of ultrasonic time-of-flight diffraction (ToFD) signals

Abstract: One major disadvantage of ultrasonic time-of-flight diffraction (ToFD) technique is the weakness of echoes which are diffracted from crack tips. This shortcoming, to some extent, can be overcome by application of proper signal processing techniques. Deconvolution techniques have shown to be quite effective for this purpose. A deconvolution process needs to use a reference wavelet in order to extract the required information from the signal. Accordingly, one of the major challenges in using deconvolution techniques is the choice of the reference wavelet. This paper discusses some of the problems encountered in the selection of the reference wavelet and proposes methods to overcome these problems. The angle-dependent deconvolution technique is one of these methods in which the reference wavelet used for processing each part of the signal is different from wavelets used for other parts. The principles of this method are described and its effectiveness is demonstrated by both simulation and experiment.

TOFD (time of fight diffraction) detection method and TOFD detection system for docking ring welding seams of cylinder

Abstract: The invention discloses a TOFD (time of fight diffraction) detection method and a TOFD detection system for docking ring welding seams of a cylinder. The detection method comprises the following steps: dividing the cylinder into a first to-be-detected area, a second to-be-detected area and a third to-be-detected area in the thickness direction of each welding seam according to the characteristics of the welding seams; arranging a first probe pair to detect the first to-be-detected area, arranging a second probe pair to detect the second to-be-detected area, and arranging a third probe pair to detect the third to-be-detected area; performing D scanning on each to-be-detected area in a circle of the circumferential direction of each welding seam by using the first probe pair, the second probe pair and the third probe pair, and recording the movement distance and D scanning flaw distribution of each probe; continuously and stably moving each probe pair along the axis of each welding seam, repeatedly executing the previous step, performing D scanning on each to-be-detected area in the circle of the circumferential direction of each welding seam on the cylinder step by step, and recording the movement distance and D scanning flaw distribution of each probe. In the way, the flaws of the docking ring welding seams of the cylinder can be accurately detected.