Comparison of systems for ultrasonic nondestructive testing using antenna arrays or phased antenna arrays

This paper considers the features of forming the images of reflectors using phased antenna array technology and the images obtained by the C-SAFT method by echo signals measured in by double-scanning mode. It is shown that in some cases the images obtained by the phased antenna array technology are less informative, while the images obtained by the C-SAFT method have a higher frontal resolution over the entire area of image restoration; the partial images restored at different positions of the antenna array can be coherently combined to obtain a high and homogeneous resolution throughout the entire volume of thickwalled articles and increasing the signal/noise ratio. For the sake of brevity, the registration of echo signals in the double-scanning mode and restoration of the images of reflectors by the C-SAFT method will be called digital focusing by an antenna array (DFA). The ability to restore the partial images of reflectors by once measured echo signals according to many acoustic schemes with their consequent combination into one high-quality image should provide reliable automation of the process of recognition and dimensioning of scatterers. Another advantage of the images obtained by the C-SAFT method with three-dimensional focusing is the possibility of restoring images in the same coordinate system when using antenna arrays on prisms of different configurations. This facilitates the joint analysis of the images. Speeds of forming the images by the technology of phased-antenna arrays and the images obtained by the C-SAFT method are comparable. If the testing technique is based on the use of nonlinear effects, then in this case PA flaw detectors have a distinct advantage over DFA flaw detectors. However, within the framework of linear acoustics, PA flaw detectors have no fundamental advantages over DFA flaw detectors. It is fairer to say that PA flaw detectors have drawbacks. This article shows images that illustrate the features of the images that were obtained by PA and DFA flaw detectors.     

On calculation of the DGS diagrams of an angle transducer

The acoustic path of an angle transducer is calculated in the Kirchhoff approximation for a reflector of the flat-bottom-hole type. The formula obtained can be used for constructing DGS diagrams. In the limiting case of the far-field zone, an asymptotic formula is obtained for the acoustic path confirming the validity of using analogous relationships, which were heuristically obtained earlier. Numerical calculations of the DGS diagram of an angle transducer are performed, the results of which are compared to those obtained via the recalculation of the diagram for a normal transducer.     

On calculation of DGS diagrams of normal transducers for spherical and cylindrical reflectors

Formulas for the acoustic path were obtained and DGS diagrams were calculated in a general case and in a scalar approximation for a hollow spherical reflector positioned axially symmetrically relative to a normal transducer. The convergence of DGS diagrams to the asymptotic value determined by the formula for the far-field zone, the difference between them obtained using the reflection coefficients with exact and approximate accounting of the boundary conditions at the reflector, and the effect of a pulsed transmission-reception mode were studied. The DGS diagrams for a hollow circular cylindrical reflector (side drilled hole) were calculated using I.N. Ermolov’s method.     

Calculation of DGS diagrams for elliptic flat-bottom holes

The DGS diagrams for a normal transducer and a model of a reflector—an elliptic flat-bottom hole—have been calculated via numerical calculation of the integral representation of the normalized amplitude of a detected signal. The boundary of the reflecting surface is specified by the angular-coordinate-dependent distance from the center to the current point on the contour. Examples of calculations are presented. An effect of the shape of the hole on the change in the DGS curves, which is especially pronounced in the near-field zone, has been established.     

On calculation of DGS diagrams for a normal transducer with a rectangular piezoelectric plate and reflectors in the form of circular flat-bottom holes

Additional results in numerical calculations of DGS diagrams for a transducer with a rectangular piezoelectric plate and a reflector in the form of a circular flat-bottom hole obtained using the formula for an acoustic path, which was obtained earlier, are presented.     

Some special features of using DGS (AVG) diagrams during ultrasonic testing of welded joints

The results of development of a method and piezoelectric probes with DGS (AVG) diagrams for ultrasonic testing devices are considered. The technique is compatible with European standards for ultrasonic testing of welded joints as regards the parameters of piezoelectric probes and sensitivity tuning taking into account damping of elastic waves. The succession of operations in tuning of devices, ultrasonic testing, and evaluation of the results with DGS (AVG) diagrams is considered.     

DGS diagrams used for tuning the sensitivity of the echo-pulse method of ultrasonic testing of railway rolling stock’s wheel-pair axles

Special features of DGS-diagram-based sensitivity tuning of the ultrasonic testing of railway rolling stock’s wheel-pair axles through the use of normal and angle probes from the end and lateral surfaces are considered. The possibility of collecting the reference signals by tuning with reference samples (without artificial reflectors of the “flat-bottom” type) was established. Examples of flaw detection using tuning of the acceptance level as per DGS diagrams based on the practice of acceptance inspection at OAO DMZ are given.     

Calculation of DGS diagrams of a normal transducer with a rectangular piezoelectric plate

In the Kirchhoff approximation, the acoustic path of a normal transducer with a rectangular piezoelectric plate is calculated for reflectors of the type of rectangular and circular flat-bottom holes. The formula for the acoustic path can be used for constructing DGS diagrams. In limiting cases, relationships coinciding with familiar ones follow from this formula for the acoustic path. Numerical calculations of DGS diagrams of a transducer with a rectangular piezoelectric plate with different ratios of sides are performed and certain features are pointed out. Additional results of numerical calculations of a bottom signal of such a transducer performed with the relation obtained above are presented.     

Basic regularities of the behavior of DGS diagrams in the near-field and transition zones of a transceiver

Studies are considered in which calculations of DGS diagrams of an ultrasonic transceiver are proposed. It is shown that the assumptions adopted in these calculations may lead to an unpredictably large error in the near-field and transition zones of the transceiver. New parameters that characterize the behavior of DGS diagrams in the near-field and transition zones (r < 4r _b) are proposed. The dependences of these parameters on the size of a flat-bottom reflector and on the distance between it and the transceiver’s piezoelectric plate are constructed.     

An ultrasound wideband converter with the phased excitation of its two forming piezoplates

Russian Journal of Nondestructive Testing - Calculation results of frequency characteristics, which were obtained by solving the synthesis problem for ultrasound converters that contain two...     

一类时滞系统的PID稳定控制器设计

针对工业控制过程中常见的时滞系统,给出了快速计算PI和PID控制器所有稳定参数集的方法。推导了系统开环不稳定情形下稳定控制器存在的必要性条件．通过在该稳定参数区域上进行性能指标寻优,可以得到满足控制器设计性能指标要求的PID控制器参数区域。仿真实例表明了该方法的优越性。     

Modified method for quasioptimal control of antenna arrays of information systems

A modified quasioptimal method is proposed to control multielement antenna arrays by optimizing its integral parameters in controlling the complex current amplitudes in some of the array elements. Analytical estimates showing a significant reduction in computational effort were supported by calculations.     

The use of expert systems in the design of multi-echelon production distribution systems

Strategic decision making within multi-echelon production distribution systems is a difficult task due to the complex chain structures and inherent operating uncertainties of such systems. Hence there is a need for the application of expert systems methodology in this field. This paper reviews an approach in which industrial dynamics modelling techniques are used to simulate the dynamic behaviour of target systems over specified time horizons. Subsequently, control design techniques are utilised for performance sub-optimisation in order to generate a scenario-oriented knowledge base. A method is also presented for optimised design selection, based on interactive management performance objectives. Mutually conflicting objectives both within and between sub-systems in a multi-echelon production distribution system are also resolved as part of the optimised design. It is felt that such techniques are key components in an expert system for improving the design of high volume process production and distribution chains.     

The use of generalized magnetic parameters for magnetic structural analysis and nondestructive testing

The results of studies regarding the dependence of the product of the coercive force and the initial magnetic susceptibility of a nickel single crystal with an intermediate orientation on the shear stress are analyzed. It is concluded that an increase in the aforementioned product for a nickel single crystal upon cold plastic deformation is due to refining of magnetic domains that is caused by formation of cells and subgrains within the single crystal. The tentative size of magnetic domains was determined based on the value of generalized magnetic parameter . The variations in the product and in the calculated dimensions of magnetic domains in polycrystalline nickel are analyzed using data reported by Kersten-Gottschalt. It was also shown that, the density of dislocations being constant, the generalized magnetic parameter is sensitive to changes in the sizes of nonferromagnetic inclusions, whereas in the case of small nonferromagnetic inclusions, an increase in the generalized parameter is due to an increase in the density of dislocations.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 62–76.Original Russian Text Copyright © 2004 by Bida.     

Using antenna arrays for reference-free measurement of speed of ultrasound and thickness of concrete articles

A reference-free method is considered for concurrent measurement of the speed of ultrasonic vibrations and the thickness of concrete constructional products with ultrasonic antenna arrays that use the “focusing to a plane” algorithm.     

A methodology for testing immunity of field programmable analog arrays to radiated electromagnetic field

Tests of field programmable analog arrays (FPAA) are required to assess tolerance to variations of components, due to aging, uncertainty, or external disturbances. The paper focuses on radiated electromagnetic energy as a cause for a possible faulty behavior: results show that input and output channels of the FPAA are affected by the presence of noise due to the coupling of the incident field with the board, and that the susceptibility profile depends on the configuration of the FPAA and the field’s polarization. Therefore, topology and electromagnetic characteristics of the board must be carefully designed. Moreover, the transfer function is susceptible to the incident field to a degree that depends on the configuration of the FPAA and the field’s amplitude and frequency. This limits application of FPAAs in critical applications like in the automotive and aerospace industry, where fields with large amplitudes are likely to be encountered during normal operation.     

Application of finite-element methods for calculation of reception systems for acoustic-emission inspection

Software as applied to problems of acoustic-emission diagnostics has been developed on the basis of the ANSYS package. Finite-element models of the processes of reception and acoustoelectric transformation of acoustic signals, their interaction with receiving devices, and simulation of contact layers have been developed. The results obtained allow the calculation of propagation of wave signals in elements of articles and receiving devices with allowance for their interaction with tested objects, the presence of connecting cables, and the conditions in the contact area. The experimental study performed has confirmed the efficiency of the numerical approaches proposed.     

High throughput optical readout of dense arrays of nanomechanical systems for sensing applications

We present an instrument based on the scanning of a laser beam and the measurement of the reflected beam deflection that enables the readout of arrays of nanomechanical systems without limitation in the geometry of the sample, with high sensitivity and a spatial resolution of few micrometers. The measurement of nanoscale deformations on surfaces of cm(2) is performed automatically, with minimal need of user intervention for optical alignment. To exploit the capability of the instrument for high throughput biological and chemical sensing, we have designed and fabricated a two-dimensional array of 128 cantilevers. As a proof of concept, we measure the nanometer-scale bending of the 128 cantilevers, previously coated with a thin gold layer, induced by the adsorption and self-assembly on the gold surface of several self-assembled monolayers. The instrument is able to provide the static and dynamic responses of cantilevers with subnanometer resolution and at a rate of up to ten cantilevers per second. The instrumentation and the fabricated chip enable applications for the analysis of complex biological systems and for artificial olfaction.     

准双曲面齿轮刮削的计算

分析由于采用硬质合金刮削刀具 ,使准双曲面齿轮切齿原理产生的变化 ,讨论准双曲面齿轮刮削加工计算中 ,刮削刀具参数的计算。所得结果可用于准双曲面齿轮刮削切齿的精确计算     

An improved evaluation of ladder logic diagrams and Petri nets for the sequence controller design in manufacturing systems

Substrate design is one of the major tasks involved in packaging design. In current business practice, the circuits of a substrate design are mostly designed by professional designers and produced by suppliers. Due to manufacturing limitations, some features of the circuit need to be modified before manufacturing. The original design and the modified design must be compared in order to ensure the desired functions. However, the circuits of a substrate design are highly complex and embedded in several physical layers. This makes the comparison task difficult, even for experienced individuals.The aim of this research is to develop an effective computer-aided inspection approach to decrease the design cost and lead time for substrate design. Three procedures and a knowledge base are developed to identify, categorise, and compare the information extracted from a substrate design drawing. First a feature extraction procedure was developed to search the related information in the data exchange format (DXF) file. Important features such as width and position of traces and vias are extracted from the original and modified designs of a substrate and are classified into three categories. The proposed feature comparison procedure is then used to compare the classified features with the assistance of a pre-defined knowledge base. Finally, the difference between the original and modified designs is marked with diverse colours and restored in a new DXF file.