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.

A point source correlation technique for automatic discontinuity identification and sizing using time of flight diffraction

Abstract: This paper proposes a technique for automatic discontinuity location and sizing using the ultrasonic time of flight diffraction technique. Here, the crack tips are modeled as point sources of diffracted waves in a homogenous, isotropic medium. The diffraction arcs are modeled using a ray based approach and the modeled arcs are correlated with the experimental B-scan data. The points of high correlation provide information about the location of the crack tips. A statistical echo separation procedure to isolate the diffraction arcs in the B-scan image is discussed. This paper also addresses the issue of application of this time of flight diffraction technique to a thin section (less than 12 mm [0.47 in.]), wherein the echoes from the various sources (lateral wave, back surface reflection, diffraction from crack tips and so on) interfere with each other, making it difficult to identify diffracted signals from the discontinuity tips.

Method for detecting ultrasonic TOFD (time of flight diffraction) imaging of shaft pressing position

Abstract: A method for detecting ultrasonic TOFD (time of flight diffraction) imaging of a shaft pressing position includes the following steps of firstly, mounting two probes and an encoder, disposing the two probes on two sides of the shaft pressing position respectively, utilizing one of the probes as a transmitting probe and the other as a receiving probe, attaching the transmitting probe and the receiving probe on the shaft surface and connecting the transmitting probe, the receiving probe and the encoder with corresponding ports of an ultrasonic TOFD imaging detector; and then starting the ultrasonic TOFD imaging detector to detect the shaft pressing position. During detecting, positions of the transmitting probe and the receiving probe are kept constant, a shaft rotates freely, the ultrasonic TOFD imaging detector records echo signals and position information thereof, and the echo signals are displayed in an image manner. The method for detecting ultrasonic TOFD imaging of the shaft pressing position can quickly, effectively and completely detect the shaft pressing position and is simple and easy to operate and applicable to detection of solid shaft workpieces, labor intensity is reduced and detecting efficiency is improved.

'Time-Frequency Techniques applied To TOFD for the automation of Rail-track Inspection'

Abstract: Time-Of-Flight Diffraction (TOFD) is a recent innovation in the non-destructive testing field and has proved a highly versatile and valuable technique for the automatic inspection of welds. TOFD can be used for automatic inspection of rail-track particularly the fishplate and welds areas of the track, which are considered high failure-rate places. Novel Time-Frequency analysis is applied to characterise the TOFD signals and classify defect type. Combining these features with an artificial neural network classifier can provide full automation of the defect detection process. The results of a preliminary study are presented and discussed. For the covering abstract see ITRD E123761.

Method and device for measuring flaw height in ultrasonic testing

Abstract: The measurement of a flaw height in a thick welded portion of a stainless steel specimen, which is difficult to perform by the TOFD method, can be conducted with more ease, with higher accuracy and in a shorter time than in the case of using tip echo techniques. In addition, it is possible to reduce variations in measurement results among individual inspectors. An ultrasonic wave 21 is launched by a transmitting probe 1 into a specimen 20 in a direction oblique to a flaw 24 to generate diffracted waves at the tip 25 of the flaw 24, then a diffracted wave 22 propagating upward directly from the flaw 24 and a diffracted wave 23 propagating upwardly of the flaw 24 after once reflected off the back 27 are received by a receiving probe 2 disposed above the flaw 24, and the height of the tip ofthe flaw 24 from the back 27 is measured from the propagation time difference between the received diffracted waves.

Studying Applicability of TOFD Technique to Inspection of Welded Joints in Polyethylene Pipes

Abstract: Issues of quality control of welded joints in hot-tool butt-welded polyethylene pipelines are considered. It is indicated that the main scope of control currently falls on inspections based on the parameters of welding and on selective mechanical testing of welded joints. Physical nondestructive post-welding testing methods are used little, which is generally not typical for the practice of testing welded joints. The reason for this is the general problem of ultrasonic methods, viz., the low detectability of contracted defects, partially transmitting ultrasound. To ensure the detectability of such defects, we evaluate the possibility of increasing the sensitivity of ultrasonic testing by using the ultrasonic time-of-flight-diffraction (TOFD) technique. It is proposed to use the tip of vertical drillings to simulate defects weakly scattering ultrasound. It is shown that when tuning is performed based on such targets, the inspection sensitivity can be increased by at least 6 dB, i.e., two times or more. In this case, the drilling tip can simulate the upper and lower edges of a planar defect vertically oriented in the section of the weld. The results of experimental studies aimed at revealing multidirectional drills with a diameter of 1 mm in welded seams of polyethylene pipes, including pipes with an additional removable outer layer, are presented. The expediency of gathering statistical data on the identification of real defects in welded butt joints of polyethylene pipes using the considered testing method is shown.