15 February 2012
Measurement of the radiation pattern of piezoelectric transducers on a standard sample of CO-3

The possibility of determining the directional pattern of contact piezoelectric transducers on a standard CO-3 sample when registering the field reflected from the concave cylindrical surface of the sample is substantiated. The advantages in comparison with the use of a standard sample of CO-2 are shown. Numerical and model results of the calculation of directional diagrams are presented. With the transition to spherical symmetry, it becomes possible to determine any section of a three-dimensional directional pattern.

15 November 2011
Obtaining an image of defects using the SAFT method, taking into account the variable speed of sound in the control object

A modification of the SAFT method is proposed to obtain an image of defects in control objects with three regions with different sound velocities. Such objects include complex composite welded joints, repair welding. In them, the speed of sound in the welded joint may differ by more than 5% from the speed in the base metal. Therefore, to obtain a high-quality image of defects, it is necessary to take into account different sound speeds. To solve the problem, a method for describing a control object with three regions with different sound speeds is proposed. The calculation of the propagation delays of the ultrasonic pulse is carried out using the Fermat principle. The results of reconstruction of the image of defects in the welded joint Du300 by echo signals obtained as a result of numerical simulation by the finite element method are presented. Images obtained by the SAFT method without taking into account different sound velocities are shifted from their true position, which makes it impossible to determine their coordinates and location. Taking into account different sound speeds makes it possible to obtain unbiased glare images of defects and, therefore, more accurately assess the type and size of defects.

15 January 2011
Determination of the defect type from the images obtained by the C-SAFT method, taking into account the transformation of wave types when ultrasonic pulses are reflected from the uneven boundaries of the control object

The use of antenna arrays (AR) for obtaining images of defects in automated non-destructive ultrasonic testing (NCD) is considered. The traditional mode of using the AP as a phased array antenna (HEADLIGHT) has a number of disadvantages. For example, glare offset and resolution degradation when moving away from the focus line. An alternative approach is proposed, when the registration of echo signals is carried out using an AR operating in double scanning mode, and a modified algorithm of combined SAFT is used to obtain an image of defects, taking into account multipath propagation of ultrasound, taking into account the transformation of the wave type when reflected from the uneven boundaries of the object of control. This approach allows one set of echo signals to receive a set of partial images, the combination of which allows you to determine the type of defect. This is very important for creating a system of ultrasonic testing with reliable automatic recognition of the type of defect. Scanning with an antenna array operating in double scanning mode, the so-called triple scanning mode, allows you to coherently add images for each position of the antenna array, which further improves the quality of the final image.

15 January 2010
Automation of estimation of defect parameters in AUZK systems with coherent data processing

The technology of automating the estimation of the parameters of the discontinuity identified using the AUZK system with coherent processing is described. To determine the parameters of the identified discontinuities, the main, stable signs characterizing the discontinuity are used; fuzzy logic is used to determine the type of discontinuity. The results of testing of this technology on the data of AUZK obtained by the Augur system during the control of austenitic welds are presented. It is shown that it is possible to determine the type of discontinuity (extended, non-stretched, volumetric, planar), its coordinates, real length and height. The results of automated determination of the discontinuity profile and destructive control were compared. The use of the considered technology allows to reduce the influence of the subjective factor on the control results and significantly reduce the time of data analysis.

15 December 2009
The use of linear interpolation to improve the quality of defect images obtained by projection in spectral space during ultrasonic non-destructive testing

The possibility of using linear interpolation of a two-dimensional spatial spectrum in the reconstruction of defect images by projection in spectral space (PSP) according to ultrasonic non-destructive testing is considered. Various interpolation algorithms are analyzed. The results of numerical and model experiments in which images were obtained using interpolation and in the absence of interpolation are presented. The effectiveness of the proposed algorithm for improving the quality of images obtained by the PSP method is shown.

15 July 2007
Obtaining images of defects by coherent methods taking into account multiple reflections from plane-parallel boundaries of control objects during ultrasound control

The problem of obtaining an image of defects from echo signals repeatedly reflected from the boundaries of the object of control is considered. A modification of the PSP and SAFT algorithm for obtaining an image of defects in a control object with plane-parallel boundaries is considered. The reason why it is impossible to obtain information about the depth of the defect by a converter operating on transverse waves in a combined mode is indicated. It is shown that recording signals in the double scanning mode, obtaining a set of partial images by the SAFT method and combining them into a final image allows us to solve this problem. To obtain a combined image, the addition of partial image modules and the calculation of their median were used. Due to problems with the accuracy of determining the speed of sound and the thickness of a particular object of control, coherent addition is potentially the most effective of the above methods of combining, did not allow to obtain a high-quality image. The results of numerical simulation of obtaining an image of point defects are presented. The results of model experiments on obtaining an image of a groove with a height of 1 mm in a metal plate with a thickness of 20 mm are presented. It is shown that the measurement of echo signals in the double scanning mode and the acquisition of an image by the DS-M-SAFT method makes it possible to determine the depth of the defect.

15 April 2007
Evaluation of control results based on acoustic images

The general principles of the formation of tomographic images, which are formed by systems with coherent data processing, are considered; their characteristic features are analyzed. It is shown that the evaluation of the real parameters of defects based on their acoustic images consists of several stages: the selection of image elements belonging to the discontinuity in the three-dimensional image of the internal volume of the controlled object, determining the type of the identified discontinuity, measuring the parameters of the discontinuity: its length, profile (height in various sections along the length), localization. The individual stages of evaluating the parameters of defects are analyzed in detail and a number of common features that are used when performing these stages are formulated. Tables describing the features of acoustic images for various types of defects are given. The tables are illustrated with typical images of various types of defects in the welds of pipelines of various diameters. The reasons for the weak influence of the amplitude of defect images are analyzed to determine their type and real parameters.

15 April 2004
The use of the double scanning method in ultrasonic non-destructive testing to improve the image quality of defects

An algorithm for obtaining an image of defects by double scanning for use in ultrasonic non-destructive testing, when the emitter and receiver move independently of each other along straight parallel lines, is considered. A formula for restoring the image of defects is presented. The advantages of the double scanning method and its disadvantages in comparison with the spectral space projection method (PSP), which is also used for coherent image reconstruction of defects, are discussed. Numerical and model experiments have shown the effectiveness of using the double scanning method to suppress parasitic images formed by transformed and over-scattered pulses. The stability of the method to distortions introduced by an uneven recording surface and higher noise immunity in comparison with the PSP method are also demonstrated.

15 April 2003
Application of homomorphic filtration to improve the image quality of defects during expert inspection of welded seams of NPP pipelines

The possibility of using homomorphic filtering of ultrasonic echoes as a method of data preprocessing to improve the quality of defect images obtained during coherent processing of echoes is considered. Homomorphic filtering makes it possible to reduce the influence of multiplicative interference, such as changes in acoustic contact or uneven surface of the object of control occurring during data recording. Image acquisition consists of the following stages: calculation of holograms from measured echo signals, logarithm of calculated holograms, finding the spectrum of holograms, projection operations in spectral space and Fourier transform. The results of the practical application of homomorphic filtration in the expert assessment of the size of defects in austenitic welds of stainless steel pipelines with a diameter of 325x15 mm2 are presented.

15 March 2003
Error in measuring defects using systems with coherent data processing

The results of the analysis of the influence of practical control parameters (acoustic contact instability, PEP parameters, etc.) on the image quality of defects, the error and accuracy of determining their parameters: coordinates of occurrence, height and length of defects are presented. The error in determining the parameters of defects during primary and repeated control differs. It is shown that with repeated control, the error decreases. The results of comparing the data obtained during destructive testing and non-destructive testing of austenitic welded seams of stainless steel pipelines with a diameter of 325x15 mm2 are presented.

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