Ultrasonic control of welded joints in a Du800-type pipeline. Part II: Improving image quality and comparison with X-ray testing results

It has been shown in the first part of the article that the DFA method in its version intended for ultrasound propagating in a homogeneous isotropic medium does not suffice for reconstructing high-quality images of reflectors in the welded joint of a Du800-type pipeline. To improve the image quality further while using the DFA method, it is necessary to determine the elastic properties of a Du800 pipeline buildup and allow for its anisotropy with respect to the propagation of ultrasound as well as the surface profile. The DFA-Y and maximum-entropy (ME) methods have been applied to increase the resolving ability and reduce the noise level. Comparing the results of ultrasonic and X-ray testing has made it possible to draw a conclusion that the former is more informative for revealing crack-like reflectors.     

Determining Geometric-Acoustic Properties of a Weld as a Solution to the Inverse Coefficient Problem for a Scalar Wave Equation

Russian Journal of Nondestructive Testing - Ultrasonic tomographic methods of nondestructive testing of objects have been developed in order to determine the geometry of a weld and to estimate the...     

The use of an ultrasonic flaw detector with a phased antenna array for the recording of echo signals to reconstruct the images of reflectors by the method of projection in the spectral space

A method of automated ultrasonic testing based on the use of a PAA flaw detector for the recording of echo signals followed by the reconstruction of the image of reflectors by applying the 3D variant of the method of projection in the spectral space (3D-PSS) is considered. Customized setting of the PAA flaw detector makes it possible to simulate the operation of many single-element transducers with different angles of incidence. This approach allows one to obtain the images of reflectors with a high resolution and a high signal-to-noise ratio at a depth of more than 100 mm. A procedure for the calibration of an antenna array on a prism operating in the mode of emulation of several piezoelectric transducers with different angles of incidence is discussed. The results of a testing a fragment of the support billet for the ITER diverter when obtaining the images by the classical PAA method and with the use of 3D processing, which demonstrate the efficiency of the developed testing technology, are presented.     

Increasing Rate of Recording of Echo Signals with Ultrasonic Antenna Array using Optimum Sparsing of Switching Matrix with a Genetic Algorithm

Russian Journal of Nondestructive Testing - To increase the speed of recording of echo signals and increase the speed of reconstruction of the image of reflectors, it is proposed to use a sparse...     

Applying Plane Wave Imaging Technology in Ultrasonic Nondestructive Testing

Russian Journal of Nondestructive Testing - Along with such advantages as high resolution over the entire area of reflector image reconstruction and the ability to produce images taking into...     

Application of super-resolution techniques to expert testing of welded joints in pipelines of nuclear power plants

Utilization of super-resolution techniques in processing reflected signals in ultrasonic testing has proved to be useful with a view to improve expert estimates of defect dimensions and shapes with the help of theAvgur holographic facility. In particular, the improvements in the image quality mostly due to athree-fold increase in the beam coordinate resolution has allowed more accurate determination of defect dimensions and more reliable classification of defects.A lower intensity of the speckle noise due to the broader frequency band can also be considered as a favorable feature of the extrapolation techniques. The signal-to-noise ratio in the images of flaws in materials with an intense structural noise isa factor of about 1.7 higher when super-resolution techniques are used. The paper describes some results of practical utilization of super-resolution techniques in estimating dimensions of flaws detected in welded joints of DU-300 pipelines (an effective diameter of 300 mm) of nuclear power plants.     

Testing Samples Made of Polymer Composite Materials Using Ultrasonic Antenna Arrays

Russian Journal of Nondestructive Testing - The possibility of detecting subsurface stratifications in polymer composite materials (PCMs), local zones with an increased content of pores and...     

Simultaneous measurement of the velocity of an ultrasonic shear wave and the thickness of a test object with plane-parallel boundaries using two antenna arrays

Methods for the determination of the unknown velocity of the propagation of shear US waves and the unknown thickness of a test object were considered. Two antenna arrays working in the double-scanning mode, where echo signals are recorded, which were emitted and received by all pairs of antenna-array elements, were suggested. Antenna arrays on prisms were mounted on the test-object surface towards each other. An algorithm for the treatment of measured echo signals was designed using a method that is similar to the least-squares method. The use of the algorithm enables one to simultaneously determine the sound velocity and thickness of a test object with plane-parallel boundaries with an exactness greater than 0.5%. In this article, the factors were studied that affect the exactness of measurements and methods of their elimination or minimization. The results of numerical experiments and the use of the method on three samples relative to measurements using an IN-5101A instrument are given.     

Application of Superresolution Methods for Expert Control of Cylindrical Objects

The possibility of the combined application of the extrapolation procedure to the spectrum of echo signals during construction of its AR model and of the algorithm for the production of flaw images using a multibeam method of projection in the spectral space (PSS) for testing cylindrical objects is shown. Improvement of the quality of flaw images due to a significant decrease in the “side lobe” levels in the point-spread function is demonstrated in a model experiment. These methods may prove to be especially efficient for testing metallurgical flaws in wheel pairs of rolling stock, workpieces for turbine rotors, and similar items.