Investigation of Discontinuities in Rolled Sheets

Ultrasonic tests, metallographic studies, and mechanic tests of sheet samples resulted in the conclusion that shear acoustic waves generated by the electromagnetic-acoustic method are preferable to longitudinal waves in detection of discontinuities. From the viewpoint of a consumer, most discontinuities in rolled sheets of metal should be classified as delaminations.     

Ultrasonic nondestructive testing by head waves: Physical prerequisites and practical use

In 1972, studies on ultrasonic testing of metals from equipment at nuclear power stations performed at TsNIITMASh revealed a phenomenon of excitation of longitudinal waves with angle probes and their further propagation along the contact surface. This phenomenon was further comprehensively studied and called head waves in ultrasonic nondestructive testing of metals. Head waves have found use in practical ultrasonic testing both in Russia and abroad. This paper presents some principal points of the development of the theory and practice of ultrasonic testing by head waves.Translated from Defektoskopiya, Vol. 40, No. 9, 2004, pp. 27–37.Original Russian Text Copyright © 2004 by Razygraev.This paper is based on the materials reported by the author at the International Forum of Specialists of Universities, Research Institutes, and Companies from Different Countries of the World Ultrasonic Nondestructive Testing-75, St. Petersburg, Russia, February 4–5, 2003.     

An IGES pre-processor to integrate CAD and CAPP for turned components

EXCAP, is a knowledge-based process-planning system for rotational components. CADEXCAP is software which has been developed to integrate EXCAP with CAD systems via IGES (Initial Graphics Exchange Specification). CADEXCAP deciphers a full 2D model of a turned component developed on a CAD system and then via IGES it fully automatically generates a product model in a format suitable for EXCAP. CADEXCAP has a modular structure of three modules: readiges, preprocess and postprocess. The preprocess module, which is the concern of this paper, was written in FORTRAN77 to pre-process the IGES entities. The pre-processing process includes two main tasks. The first task is to extract only the necessary information from the IGES entities. The second task is to locate the entities in one coherent coordinate system, which is the model space coordinate system, using transformation matrices.     

Automated Devices for the Testing of Mill Rolls

Multichannel -type devices developed at TsNIITMASh for the automated ultrasonic inspection of cylindrical objects, such as mill rolls, shafts of turbines and compressor units, circular welded joints of thick-walled shell rings, etc., are described. These devices feature from two to eight acoustoelectronic channels. Acoustic contact occurs through industrial water. The testing is performed under workshop conditions; the object being inspected is rotated by a turning lathe or any other handling mechanism. Sonication is simultaneously performed by piezoelectric transducers (PETs) with input angles of 0, 40, 50, 60, and 70° and also by surface and head waves in order to reveal surface and subsurface flaws. A wide-span eddy-current transducer of special design is also used for this purpose. All data are stored in flash memory and retrieved on a PC located in an office. The inspection results are displayed as C- and B-type scanning defectograms. Moreover, it is possible to obtain an isometric image of flaw zones. -type devices have been used for over one and a half years in two workshops at OAO Severstal'.     

Development of a knowledge-based manufacturing modelling system based on IDEF0 for the metal-cutting industry

This paper looks into a new area for knowledge-based system application, that of manufacturing modelling. The objective is to develop a knowledge-based manufacturing modelling system that can be used to build company-specific as-is and to-be IDEF0 models, and can therefore greatly reduce the turnaround time and effort involved in IDEF0 modelling of manufacturing systems, which can be time-consuming if done manually or even with the aid of a commercially available software package like DESIGN/IDEF. This is especially so when the systems being modelled are large and complex. Besides, there is also the inconsistency problem associated with conventional IDEF0 modelling systems owing to the terms and terminologies in IDEF0 not being precisely defined, and hence being subject to individual interpretations. In this paper, a knowledge-based IDEF0 modelling system that can not only automate the tiresome and time-consuming process of manufacturing modelling but can also eliminate the inconsistency problem is proposed. The paper explains the knowledge-based approach to automated generation of IDEF0 models, and also identifies the kinds of domain knowledge that are required for the construction of the knowledge-based manufacturing modelling system.     

The capacities of modern EMA thickness gages

The literature concerned with the problem of studies and development of thickness gages based on the EMA method of exciting and detecting ultrasound pulses is analyzed. A new approach to the design of EMA thickness gages is developed. A prototype of the manual EMA thickness gage is designed and tested. It is shown that the EMA device offers considerable benefits when using the correlational data processing.Translated from Defektoskopiya, Vol. 40, No. 12, 2004, pp. 16–25.Original Russian Text Copyright © 2004 by Suchkov.This revised version was published online in April 2005 with a corrected cover date.     

A novel representation of tandem systems with inter-stage storage applied to on-line system monitoring

One of the goals of operating a tandem manufacturing system with finite inter-stage storage and asynchronous operations is to meet the demand without over-producing, under-producing or carrying large quantities of material in storage. We believe that analysing the operation of such a system on a real-time basis helps achieve this goal. The first step in this real-time analysis would be to quantitatively associate the causes and effects of over-production or under-production as they occur. This requires determining the cumulative effect that the performance that any stage has on the system, based on its history, the current system state and the interrelationships between the stages. This paper proposes a method which first represents uniquely and completely each stage and surrounding storage as an element. While this system, which consists only of this simple type of element functions in exactly the same way as the original one, each element is put into an ideal world for decoupled measurement. Though an element behaves in exactly the same way whether it is in the ideal world or in the real world, the elapsed times in the two worlds since the beginning of production can be different, since the responses (occurrences and durations of the blockings and starvations) of the two worlds can be different. A phase parameter is introduced for each element to represent this difference. Once the formation of the phase parameter of the output element is formulated, quantitative relationships between causes and effects of over-producing or under-producing can be explained as they occur.     

Single-Electron Characteristics of a ФЭУ-184U Photomultiplier Tube

Single-electron and time characteristics of a -184U photomultiplier tube with a uviol window are presented. The -184U single-electron resolution can reach a value of 63–64%, and, in case of single-electron light-striking of the photocathode, the photoelectron transit time distribution (full width at half maximum) is 6 ns.     

Improving the Accuracy in Determining the Insulator Capacitance in Metal–Insulator–Semiconductor Structures

The results of the voltage–capacitance spectroscopy of interface states in metal–insulator–semiconductor (MIS) structures are critical functions of the accuracy in determining the insulator capacitance C _i, which is typically no higher than a few fractions of a percent. This substantially limits the energy range of the observed spectrum of the interface states (E 0.5 eV for Si-based MIS structures) and the sensitivity to the density of the interface states at the spectrum edges (N _ss 1 × 10¹⁰ cm^–2 eV^–1). We propose a method for minimizing these errors that is based on a sequential variation of the initial estimate C _i C _{i 0} C _ij, j = 0, 1, 2, ... and the identification of singular points in the dependences and on C _ij, where are the mean arithmetic values of the voltage difference between the experimental and ideal voltage–capacitance characteristic and are the rms deviations of the voltage values taken in the high-accumulation (ac) and inversion (in) regions from values. The highest (10^–4%) accuracy in determining C _i is achieved in the regions of the equidistant experimental and ideal voltage–capacitance characteristic. This method, combined with the technique of _s / _s diagrams, ensures an extension of E to 0.9 eV at N _ss 1 × 10¹⁰ cm^–2 eV^–1 and the possibility of determining the sign and density of the fixed charge in the gate insulator.     

A Coordinate Detector for Studying Horizontal Fluxes of Cosmic Rays

A DECOR coordinate detector is a multilayer system of plastic streamer tube chambers located around a NEVOD Cerenkov water calorimeter. The basic characteristics of the detector are as follows: the area is 100 m², the angular resolution is 1°, and the space resolution is 1 cm. The structure of the detector, data acquisition and trigger systems, and results obtained during the operation of a pilot assembly (8 chamber layers and a working area of 8.4 m²) are given.     

A 14-Bit Code-to-Current Converter

A high-precision code-to-current converter ensuring a conversion error corresponding to 14 bits is described. The output current of the converter is ±250 mA, and the conversion nonlinearity is 0.015%. The converter circuit has insignificant time (0.001%/h) and temperature (0.001%/10°) drifts. The suppression of supply voltage variations is 70 dB.     

General Shear-Thinning Dynamics of Confined Fluids

The shear properties for a number of thin fluid films under high pressure were investigated as a function of sliding velocity (shear rate) using the surface forces apparatus. It was found that the relationship between the effective viscosity _eff and shear rate in the shear-thinning regime could be expressed by a simple equation, log_10eff=C-nlog₁₀, where C4.7±0.2 and n0.9±0.1. This equation can be applied to a variety of fluid systems from simple liquids to polymer melts, which transition to glasslike phases in confined geometries. Since the effect of confinement on the slowing down of molecular motions is equivalent to that of decreasing temperature, this universally can be explained using conventional glass-transition theories for bulk fluids. Assuming the confined fluid to be in a state where dynamics are dominated by excluded volume effects, its _eff should correspond to that of the bulk at or near the glass-transition temperature. Thus, characteristic relaxation times in the system should correlate with the time scales of the primary relaxation processes associated with submolecular rearrangements, which are an essential feature of the glass transition and not very different for various fluid materials.     

Adapting IDEF0 modelling to perform manufacturing diagnosis

This paper presents the work done to adapt a system modelling methodology, ICAM DEFinition Zero (IDEF0), to perform manufacturing diagnosis. It describes the basic notions of IDEF0 modelling and the underlying principle of a novel reasoning technique, the worst-first search, developed for manufacturing diagnosis. The reasoning technique which was originally based on graph theory and possibility theory, has been adapted to access the information stored in an IDEF0 model. Details of a prototype IDEF0-based system for manufacturing diagnosis are presented. The results of system validation based on a manufacturing system for the production of mechanical components are reported.     

Efficient Generation of Microwave Oscillations at Harmonics of the Conductance of a Gunn Diode

Basic characteristics of prototype oscillators operating at the second (19 GHz) and third (36 GHz) harmonics of the negative conductance of a 3715 Gunn diode are presented. The output power of these oscillators is 1.5–8.0 mW and the range of electronic frequency tuning is up to 390 MHz.     

Temperature Correction of the Spectral Response of a Photodiode

A method for compensating the temperature instability of the photodiode response is tested. The method is based on the simultaneous measurement of the photocurrent and temperature of the photodiode. A subsequent digital correction reduces the temperature fluctuations of the photocurrent down to the intrinsic noise level. This method, in contrast to the traditional active thermostabilization method, excludes heating of the photodiode and provides an order of magnitude smaller threshold of detectability. Experimental results for a -10 photodiode are presented; the temperature coefficients of the photodiode's spectral response are determined for several wavelengths.     

Interferometric Methods for Surface Testing. High-Order White-Light Interferometer

A high-order white-light interferometer for three-dimensional fast noncontact testing of optical surface profiles is described. The device ensures measurements of absolute flatness deviations to an accuracy of /1000 within a wide technological field of 80 mm (the resolution in the plane is 0.1 mm).     

Modelling and forecasting industrial innovations via the transfer function S-shaped learning curve

Algorithms are derived for the four-parameter transfer function S-shaped curve, using a least-squared-error (LSE) method for an exponential function. The S-shaped curve is just one in a family of industrial dynamics learning-curve models of increasing complexity which may be used to replicate and forecast the start-up of industrial innovations.Controlled experiments are undertaken, via simulation of message and noise, to test the modelling and forecasting capabilities of the algorithms. A number of strategies are introduced to improve forecasting performance, such as boots-trapping, sequential and parallel adaptation, and alternatively adopting the simplified three-parameter S-curve model.Four examples of modelling industrial innovations via the transfer function learning curve models are presented. The paper concludes that although there is now the capability to model the general four-parameter S-curve, its applications are limited. This is because simpler (and hence less accurate) transfer function models tend to be more robust.     

Monitoring of the electrical discharge machining process by abductive networks

The paper describes the use of abductive networks to monitor the electrical discharge machining (EDM) process. The voltage and current across the gap between the tool and workpiece are fed into the developed networks for the recognition of various pulse types in EDM in a winner-take-all fashion. Experimental results have shown that EDM pulses can be clearly classified even with different machining conditions. Hence, a reliable technique has been developed to monitor the EDM process.     

An Energy Source Based on Helical Explosion–Magnetic Generators for High-Impedance Loads

A transportable standard module developed at the Institute of Experimental Physics as a component of an energy source for modeling current pulses of positive lightning is described. The source is designed as a combination of several unified helical explosion–magnetic generators with output transformers and an inner diameter of the stator of 200 mm. According to our calculations, the source generates current pulses with an amplitude of up to 100 kA in loads with an inductance of 100 H and a resistance of several tens of ohms. The results from testing a typical module operating with a circuit having an inductance of 100 H and a resistance of 4 are presented. The experimental data coincide well with the results of a mathematical simulation of the module's operation.     

A System for Stabilizing the Temperature of the Shells of High-Power Electronic Devices

A method for thermostatting high-power gas lasers is described. This method is based on the secondary utilization of the thermal energy stored in the waste heat-transfer medium. The design of the system and the analytical relations for calculating its basic elements are presented. Test results have shown the rather high efficiency and profitability of this thermostatting technique.