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.

Towards automatic analysis of ultrasonic time-of-flight diffraction data using genetic-based Inverse Hough Transform

Abstract: Ultrasonic Time-of-Flight Diffraction (TOFD) is a non-destructive inspection technique that has proved to be very effective for the detection, localisation and sizing of buried crack defects in steel structures. However, it produces a huge amount of data that are manually processed and interpreted. This process is time consuming and painstaking. Moreover, it requires the skill, alertness and experience of the operator. Consequently, it is subject to human errors. In order to save time, effort and inspection cost while at the same time increasing the detection rate, automatic analysis tools need to be developed. This paper presents thus an application of image processing techniques to the B-scan image representation of ultrasonic TOFD data so as to take advantage of the power of image representation of information. In a B-scan image, crack defects are characterised by multiple arcs of diffraction. In order to detect these multiple arcs of diffraction and thus reveal the presence of a crack in the structure under inspection, some methods based on conventional Hough Transform (HT) were proposed in the literature. The main problems related to conventional HT are its large data storage requirements and expensive computation times. To cope with these problems, we propose the use of the Inverse Hough Transform (IHT) where the voting process is performed in the image space rather than the parameter space. With the IHT, the local peak detection problem in the parameter space is converted to a parameter optimisation problem that is solved using Genetic Algorithms. The proposed Genetic-Based Inverse Voting Hough Transform 'GBIVHT' algorithm allows thus the automatic detection of the arcs of diffraction, and therefore the crack defects, while avoiding the computational complexity as well as the huge storage requirement of conventional HT.

IWEX: A New Ultrasonic Array Technology for Direct Imaging of Subsurface Defects

Abstract: Both in new construction and in service, detection, sizing and characterization of defects are essential for integrity assessment of metal components and welds. Ultrasonic Non Destructive Inspection (NDI) using Pulse Echo (PE) technique or Time of Flight Diffraction (ToFD) have been proven to be reliable approaches to assess weld integrity. However, quantitative defect characterization with PE remains challenging because the signal caused by the reflection at the defect is very dependent on defect orientation. ToFD has sizing capabilities, but only limited capabilities in flaw characterization. In phased arrays inspection, the image obtained from sectorial scans can not be directly related to defect size and orientation. Data display and interpretation are not straightforward and require operator skills and experience. A better and more reliable ultrasonic inspection would be achieved if a methodology would be used that allows direct imaging of defects. In this paper, we present the principles of imaging with 2D Inverse Wave Field Extrapolation (IWEX) as used in seismic exploration. The physical basis of this new imaging process is the Rayleigh II integral for back propagation which gives the possibility to extrapolate a wave field from known values at a certain surface to any location in space. The paper discusses this in detail. The potential of IWEX for ultrasonic testing of steel components is demonstrated by several examples by which 2D and 3D images of embedded and surface defects were made. We demonstrate that location, shape, orientation and height of the defect are imaged. The interpretation of the results is straightforward, making the use of reference blocks superfluous.

Ultrasonic flaw detection method and apparatus

Abstract: PROBLEM TO BE SOLVED: To enable not only detection of flaw of the whole of a target region to be inspected but also measurement of the dimension of the whole of the target region to be inspected at a high speed with high accuracy, by electronic scanning different from flaw detection using a conventional TOFD method, an once-reflection method or an array type ultrasonic probe of pair constitution and requiring no mechanical scanning. SOLUTION: One or more of the vibrators of the array type ultrasonic probe 2, which has an integrated structure where a plurality of vibrators are continuously arranged, is selected as an ultrasonic transmitting vibrator. The other one or more of them is selected as an ultrasonic receiving vibrator for receiving the diffracted or reflected waves of the ultrasonic waves transmitted from the ultrasonic transmitting vibrator. The ultrasonic transmitting vibrator and the ultrasonic receiving vibrator are arranged at the positions on both sides of the surface of the array type ultrasonic probe, and in such a state, that the array-type ultrasonic probe is fixed, flaw detection is performed by the electronic scanning of the ultrasonic transmitting vibrator and the ultrasonic receiving vibrator corresponding thereto.

Method and device for TOFD (Time of Flight Diffraction) detection of pressure pipeline on basis of ultrasonic phased array

Abstract: The invention relates to a method and a device for TOFD (Time of Flight Diffraction) detection of a pressure pipeline on the basis of an ultrasonic phased array, and aims to ensure that the provided detection method and a system can be used for performing defect detection on the interior of the pressure pipeline and have the technical characteristics of strong interference resistance, high detection speed, accurate result and convenience in use The technical scheme is as follows: the device for the TOFD detection of the pressure pipeline on the basis of the ultrasonic phased array comprises an ultrasonic detector host, a robot control module, two conic phased array probe devices, an instrument device, a probe clamping device, a pipeline climbing robot, a coaxial cable, a coder, a centering device, a large-angle center fixing device and a metal flexible tube The method using the device for the TOFD detection of the pressure pipeline on the basis of the ultrasonic phased array comprises the following steps: (1) adjusting detection positions; (2) emitting ultrasonic waves; and (3) receiving reflected waves

Ultrasonic Time-of-Flight Diffraction Testing with Linear Frequency Modulated Excitation for Austenitic Stainless Steel Welds

Abstract: The main problems for ultrasonic inspection of austenitic stainless steel welds are low signal to noise ratio (SNR) and detection accuracy, caused by anisotropic and heterogeneous material structure with bulky columnar crystal. In order to overcome the problems mentioned above, a linear frequency modulated (LFM) pulse with a large time-bandwidth product can be used as the exciting signal in the ultrasonic inspection of the austenitic stainless steel welds, which can both enhance the average transmitted power and increase the SNR and time resolution by pulse compression process. Therefore, the ultrasonic time-of-flight diffraction (TOFD) technique with the LFM excitation was carried out to realize an accurate sizing and locating detection in austenitic stainless steel welds. Compared with the conventional TOFD testing, the SNR can be increased 12–15 dB, and the measured accuracy is also enhanced obviously. Accordingly the measured depth error is less than 0.81 % and the length error is less than 2.5 %. The proposed method can both enhance the capabilities of the ultrasonic inspection of austenitic welds and the measurement accuracy of ultrasonic TOFD testing.