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.

Development of a 3D Ultrasonic Inspection Device for Pipeline Girth Welds

Abstract: Quality requirements for girth welded joints in gas pipelines necessitate adequate penetration to the inner surface and no harmful defects. Toho Gas has completed development of the world’s first inspection system applying the ultrasonic synthetic aperture method for welds in steel pipes used to carry gas (external diameter 200mm, pipe wall thickness 5.8mm). In recent years, ultrasonic phased-array technology and ultrasonic TOFD methods etc. have attracted attention. However, the ultrasonic synthetic aperture method is an imaging technology that is superior to these, as it can synthesize several thousands of wave form data at high speed, its image clarity is the best in the world. The four features of the system are (1) the ability to provide an image of the interior of a weld, (2) the ability to quantity incomplete root bead penetration, (3) automatic high speed collection of data, and (4) data base management capability. The ultrasonic synthetic aperture method simplifies defect judgments because it does not require that operators possess special qualifications and training. It can produce three-dimensional high picture quality data. It can be handled easily at work sites because it is portable. This report describes the ultrasonic inspection system development process and the results of trial inspections.© 2006 ASME

Manual multichannel TOFD (time of flight diffraction) scanning frame

Abstract: The invention provides a manual multichannel TOFD (time of flight diffraction) scanning frame and belongs to the technical field of machines. The manual multichannel TOFD scanning frame can be used for solving the problems that the existing TOFD scanning frame is inconvenient in operation and scanned data is not accurate enough. The multichannel TOFD scanning frame comprises a total coder, a roller, a pushing handle and a plurality of pairs of probe assemblies as well as a vertical beam and a plurality of cross beams, wherein the probe assemblies are electrically connected with the total coder, the roller and the probe assemblies are arranged on the cross beam, the pushing handle and the total coder are connected above the vertical beam, an alarm and a steering angle instrument are also arranged on the scanning frame, the steering angle instrument is arranged on the vertical beam and is electrically connected with the total coder, and the alarm is electrically connected with the total coder. The multichannel TOFD scanning frame has the advantages that whether the direction of travel of the scanning frame shifts from a desired track or not is detected by virtue of the steering angle instrument, and an alarm is given to inform a scanning worker of adjusting a scanning direction, so that accuracy of defect data obtained by scanning is guaranteed.

Interpretation of Indications Generated by Small Welding Discontinuities in Ultrasonic Time of Flight Diffraction Technique

Abstract: The article presents results of research on non-destructive ultrasonic time of flight diffraction technique TOFD and metallographic examinations of selected cross-sections of a MAG welded joint. The main objective was to compare the results of TOFD and metallographic examination at the locations where a large number of point-like indications, located on specific depths, have been detected on TOFD images and analyse the impact of this type of indication on results of a welded joint evaluation. Considered, that the indications have not exhibited separations between upper and lower diffraction signals, because of their small heights, measuring of height of indications in those cases was impossible. In all cases, the occurrence of discontinuities of 0.16–0.78 mm in height, in locations indicated by TOFD has been confirmed.

TOFD automatic scanning device

Abstract: The invention discloses a TOFD (time of flight diffraction) automatic scanning device. The TOFD automatic scanning device comprises a TOFD automatic scanning frame, one side of the TOFD automatic scanning frame is equipped with a guide rail and magnetic wheels, the guide rail is equipped with a first probe bracket, a second probe bracket and a third probe bracket, and the first probe bracket, thesecond probe bracket and the third probe bracket can slide to the left and right in the guide rail. The bottom of the first probe bracket is equipped with a TOFD emission probe, the bottom of the second probe bracket is equipped with a TOFD receiving probe, and the bottom of the third probe bracket is equipped with a phase control probe. The TOFD automatic scanning device employs the TOFD emissionprobe, the TOFD receiving probe and the phase control probe for combined action, a required detection space is reduced from 110mm in the prior art to only 12mm, thus greatly reducing the non-detection zone in equipment defect detection. The device provided by the invention is particularly suitable for defect detection of weld seams nearby the joints of straight pipelines and assembly parts.

Fourier Analysis of Ultrasonic TOFD Signals for Defect Detection in Austenitic Stainless Steel Welds

Abstract: Non Destructive testing of structural materials is an important activity in many industries. Ultrasonic NDT is one such method widely used in this field. Pulse Echo and Through Transmission are conventional testing techniques which use reflected and transmitted sound energy respectively. But these techniques are highly dependent on defect orientation. Time of Flight Diffraction (TOFD) is a recent method which uses diffracted sound energy to detect the defects and is independent of orientation of the defects in the material. TOFD signals are dominated by noise arriving from various sources namely instrumental noise, material (structural) noise, thermal noise etc. Signal processing is an important step in the evaluation of the signals for detecting, positioning and characterizing the defects. Fourier Transform is widely used in the analysis and de-noising of signals of different kind. In this paper Ultrasonic TOFD signals obtained from Austenitic Stainless Steel weldments are analyzed using Fourier Transforms.