Problems and features of spatiotemporal signal processing in ultrasonic testing of products manufactured from complexly structured materials

The main principles of spatiotemporal processing of signals during ultrasonic testing of articles manufactured from complexly structured materials with high signal attenuation are considered. Features of ultrasonic low-frequency testing limiting the application of the simplest algorithms for spatiotemporal signal processing in both ultrasonic flaw detection and ultrasonic tomography of articles manufactured from complexly structured materials are analyzed.     

Frequency separation of signals and interferences in noise-immune ultrasonic testing of articles manufactured from complexly structured materials

Methods for extracting ultrasonic echo signals from interferences (electroacoustic interference and structural noise) correlated with a probing signal are studied in detail. These methods are based on the frequency separation of the spectra of the informative signal and noise. Frequency-separation methods involving lock-in signal detection are considered. Various aspects of using a lock-in detector in flaw detection and tomography of complexly structured articles are analyzed. Examples of applying the frequency decorrelation of signals in ultrasonic testing of large old cast bronze bells of the Ivan the Great Bell Tower in the Moscow Kremlin and large bells of the Cathedral of Christ the Savior in Moscow are considered.     

Features of applying the method of focusing to a point in ultrasonic testing of products manufactured from complexly structured materials

The well-known method of focusing ultrasonic signals to a point implemented using phased antenna arrays is considered as applied to problems of tomography of products manufactured from complexly structured materials. The features of applying broadband ultrasonic complexly modulated signals in phased antenna arrays and the limits of applicability of this method in constructing an image of a reflecting surface are discussed.     

Progress in the theory of ultrasonic flaw detection. Problems and prospects

This paper was prepared upon request from the organizers of the XVIII St. Petersburg conference Ultra-sonic Flaw Detection in Metal Structures. UZDM 2004. The progress made in the theoretical issues of ultrasonic flaw detection over the past 20 years is briefly considered, and some practical issues are discussed. Specific problems that are waiting to be solved are formulated, and the authors opinions about the prospects of developments in ultrasonic flaw detection are presented. The preparation of the paper was much facilitated by book [1], which was published recently.Translated from Defektoskopiya, Vol. 40, No. 10, 2004, pp. 13–48.Original Russian Text Copyright © 2004 by Ermolov.     

A new signal processing technique for detecting flaw echoes close to the material surface in ultrasonic NDT

A new signal processing technique for separating the reflection of a flaw near a surface from the surface reflection itself is proposed. The method is based on ultrasonic scattering energy function model of flaw close to the material surface. Flaw sensitive component in the model, which corresponding to the low frequency signal, is remained by using a low pass digital filter. In order to make the recognition procedure easier and enhance the recognition effect, a reference signal is introduced to avoid the influence of the surface echo. Thus, the surface flaw is easily and clearly recognized. The good performance of the approach is experimentally verified in laboratory on a steel sample with different man-made surface flaws.     

Maximum kurtosis principle for the parameter selection of Gabor wavelet and its application to ultrasonic signal processing

The noise suppression techniques with wavelet transform (WT) are widely used in nondestructive testing and evaluation (NDT&E), especially in ultrasonics. But the wavelet based filter has the property of equal Q-factor, so, it is impossible to choose the central frequency and the bandwidth arbitrarily at the same time. This paper develops a new technique using WT to eliminate this drawback. In this paper, a weak ultrasonic signals identification method by using the optimal parameter Gabor wavelet transform is proposed. We address the choice of the optimal central frequency and bandwidth of the Gabor wavelet using the kurtosis maximization algorithm. The central frequency and bandwidth of the optimal parameter Gabor wavelet matched that of the ultrasonic signal very well. Numerical and experimental results have been presented to evaluate the effectiveness of the optimal parameter Gabor wavelet transform on ultrasonic flaw detection. This technique is a simpler and effective technique for processing heavy noised ultrasonic signals.     

Experimental research on the MRR of ultrasonic vibration aided electric discharge milling of ceramic materials using deionized water as processing medium

Abstract

Electric Discharge Milling Machining (EDMM) simplifies the electrode manufacturing process and reduces the cost. However, the introducing of new parameters, such as the three-dimensional motion and the electrode rotation speed, results in a periodic change of control state that can reduce the control performance and processing efficiency. In this work, ultrasonic vibration of tool electrode was used to improve the processing efficiency of ceramic materials. The effect of ultrasonic vibration on the EDMM process was analyzed by comparing the experimental findings. The results have shown that the ultrasonic vibration can improve the material removal rate, and a treble processing efficiency was achieved. The effect of processing parameters on the material removal rate, such as the open voltage, the peak current, the pulse during time and the pulse off time, was analyzed. When aided with the ultrasonic vibration, the best processing efficiency was achieved at 220?V for the open voltage, 10?A for the peak current and 15?μs for both the pulse during time and pulse off time.     

Two approaches to the solution of problems of ultrasonic flaw metering: Analysis of a high-quality image of reflectors and correlation analysis of measured echo signals

The problem of ultrasonic flaw metering consists in the obtainment of information on the reflector type, its dimensions, and the coordinates of its location. As the accuracy of determining the parameters of a discontinuity increases, the results of ultrasonic testing become more reliable. A highquality image of reflectors, which is reconstructed using the C-SAFT method with consideration for multiple reflections of pulses from the boundaries of a test object that makes it possible to determine the types and dimensions of reflectors, can be considered as one of the tools of flaw metering. However, the C-SAFT method disregards the features of reflections from discontinuities with nonuniform scattering indicatrices. As a development of flaw-metering methods, it is proposed to determine the parameters of a discontinuity from the results of comparison of the measured echo signals and estimated echo signals, which are calculated as functions of the discontinuity parameters. The results of using the proposed methods of ultrasonic flaw metering in numerical and model experiments, which demonstrate the working capacity of the proposed approach, are presented.     

Self-consisted calculation of the magnetic field for problems of magnetic flaw detection. I. Initial model for calculating the field of a magnetic tape magnetized from a wire with a current

The ability to calculate the field of a set of arbitrarily charged and arbitrarily arranged rectangular areas was considered. The result was verified by calculating the recorded field on a magnetic tape.     

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.     

The use of scanning electron microscopy to quantify the burden of particles released from clean-room wiping materials

A procedure is described for the detection and direct enumeration of the number of particles that can potentially be released from wiping materials. The technique involves the use of a scanning electron microscope (SEM) to count the particles from a wiper, first by releasing them in deionized water and then filtering the entirety of the liquid through a submicron membrane filter. To obtain an accurate count, the filtration must produce a normal distribution of particles on the filter, and hence the details of the filtering technique must be performed in a very precise manner. The counting of the particles on the filter is accomplished by scanning a statistically representative number of fields and averaging the number of particles per field. The results can then be checked for statistical precision and accuracy. Our criterion for successful measurement was ± 10% accuracy at a 95% confidence level. We believe that the SEM method described in this article is sensitive enough to quantify very low levels of total particle burden without succumbing to the variability and limitations encountered with other enumeration techniques. Typically, this technique enables the accurate counting of particles of all shapes from below 0.1 μm to hundreds of micrometers. In addition, the SEM technique allows for morphologic identification of particles as well as chemical identification if an energy-dispersive x-ray system (EDS) is employed.     

The development of the tongue of the domestic goose from 9th to 25th day of incubation as seen by scanning electron microscopy

The general development of the tongue in birds was described by Lillie ( 1908 ) in chicken. Bryk et al. ( 1992 ) also studied the tongue development in chicken and they observed development of the conical papillae of the body. Our study aims to describe the timing of the development of the tongue morphological features in the domestic goose by using SEM methods. The tongue of the domestic goose is characterized by the widest variety of shape of the particular part of the tongue and mechanical papillae. Results indicated that the formation of the apex, body, lingual prominence, and the root of the tongue take place between the 10th and 19th day of incubation. The tongue elongates rapidly between the 16th and 18th day of incubation. Simultaneously, the median groove appears on the body and the lingual prominence and elongates towards the rostral part of the tongue. The conical papillae of the tongue develop gradually. On the body, the conical papillae develop from the caudal part of the body to the rostral part and on the lingual prominence from the median part of the prominence to the lateral part. Hair‐like papillae at the caudal surface of the body of the tongue remain primordial to the end of the incubation. Our studies on the morphogenesis of the tongue in the domestic goose revealed changes in shape of the particular part of the tongue and rapid pace of the formation of mechanical papillae. The tongue is completely develop before hatching and ready to collect food. © Microsc. Res. Tech., 2012. © 2012 Wiley Periodicals, Inc.