Laboratory power supply

Розглянуто практичні підходи до реалізації лабораторного блоку живлення на основі спеціалізованої мікросхеми LM317/337. Наводиться структурно-функціональна та практична схема.Practical approaches to implementation of a laboratory power supply based on specialized LM317/337 chip. Provides functional and schematic diagram

Assessment of in-service degradation of gas pipeline steel taking into account susceptibility to stress corrosion cracking

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Laboratory model «pulse power unit»

Розглянуто практичні підходи до реалізації лабораторного макету імпульсного блоку живлення на основі спеціалізованої мікросхеми UC3843. Наводиться практична схема лабораторного макету та особливості функціонування його складових частин.The practical approaches to the implementation of the laboratory model of the pulse power unit on the basis of the specialized chip UC3843 are considered. The practical layout of the laboratory model and features of the functioning of its component parts are presented

Methodology of hydrogen embrittlement study of long-term operated natural gas distribution pipeline steels caused by hydrogen transport

A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the transportation of hydrogen or its mixture with natural gas by a long-term operated gas distribution network is presented. The importance of comparative assessments of the steel in the as-received and operated states basing on the properties that characterize plasticity, resistance to brittle fracture and hydrogen assisted cracking is accentuated. Two main methodological peculiarities are pointed out, (i) testing specimens should be cut out in the transverse direction relative to the pipe axis; (ii) strength and plasticity characteristics should be determined using flat tensile specimens with the smallest possible thickness of the working part. The determination of hydrogen concentration in metal, metallographic and fractographic analyses have been supplemented the study. The effectiveness of the proposed methodology has been illustrated by the example of the steel research after its 52-year operation

On the relationship between microstructure, mechanical properties and hydrogen embrittlement of pipe steels

The medium carbon casing pipe steels for oil and gas wells with fine grain bainitic microstructure and with coarse microstructure of ferrite-pearlite were tested. The steel with higher strength and with more dispersed microstructure was less susceptible to hydrogen embrittlement than the another one. The finite element method of load simulation of the specimens with crack was used for assessment of the embrittlement of the studied steel

Construction and research of reverse frequency dividers

In the work, the reversible schemes of frequency dividers are constructed based on JK triggers are offered. It is proved that reversible frequency dividers work with insignificant differences in forward and reverse inclusions. When studying the frequency divider with direct inclusion, it was found that its real frequency differs from the calculated by 1.87%. And at return inclusion frequency dividers from are calculated on 2,17%. In general, such a relative error cannot be caused by the inaccuracy of the marker placement in the Multisim virtual oscilloscope. Such reversible frequency dividers can be used in unidirectional automated systems to build neural networks

Peculiarities of the hydrogen effect on the mechanical properties of the clad metals “low-alloyed steel – anticorrosive clad layer”

Досліджено вплив попереднього термоциклування зразків у газоподібному водні як експрес-методу високотемпературної деградації матеріалів, з наступним електролітичним наводнюванням під час оцінювання міцності біметалевих зразків низьколегованих сталей з антикорозійними наплавленими шарами. Показано, що за випроб зрізом попереднє електролітичне наводнювання зразків знижує їх міцність сильніше, ніж термоциклування у газоподібному водні, що зумовлено жорсткішими умовами наводнювання. Виявлено, що зі збільшенням кількості термоциклів у водні механічні властивості за розтягу зразків з біметалевими з’єднаннями знижуються. Деградація двошарових зразків під час термоциклування у водні проявляється зниженням границі міцності за одночасного підвищення межі текучості під впливом електролітичного наводнювання зразків під час випроб розтягом порівняно з випробами на повітрі. Крім того, попереднє термоциклування біметалевих зразків у водні неоднозначно впливає на їх границю текучості, визначену за електролітичного наводнювання під час розтягування. Зафіксовано позитивний вплив наводнювання на границю текучості біметалевих зразків після 30 термоциклів у водні і негативний – після 100. Описано фрактографічні особливості руйнування біметалевих зразків.The effect preliminary thermal cycling in gaseous hydrogen as express-method of high temperature materials degradation, with the next electrolyte hydrogenation during strength tests, on the strength of the clad specimens of low-alloyed steels with anticorrosive clad layer has been investigated. It was shown that preliminary electrolyte hydrogenation of the specimens decreases its strength faster at shear tests than after thermal cycling in gaseous hydrogen what is caused more strong conditions of hydrogenation in the first case. It was revealed that the tension mechanical properties of the clad specimens become more worsen with an increase of number of thermal cycling. Degradation of the two layers specimens during thermal cycling in hydrogen becomes apparent by a decrease of ultimate strength at a rise of yield strength under effect of electrolyte hydrogenation comparatively with the tension tests in air. Besides, preliminary thermal cycling in hydrogen of the clad specimens effects ambiguously on its yield strength determined at tension tests with electrolyte hydrogenation: the positive influence of hydrogen on yield strength of clad specimens was registered after 30 thermal cycles and the negative one – after 100 thermal cycles. The fractography peculiarities of the clad specimens are described

Peculiarities of assessing the degradation of structural steels under the action of cyclic loading and environments

Long-term operation of structural steels often intensifies their degradation, which manifests itself in a decrease in initial physical and mechanical properties. The work highlights the peculiarities of the steel degradation process and its assessment under conditions of cyclic loading, as well as under the action of corrosive hydrogenating environments. Special attention is paid to the role of in-bulk dissipated damage in the metal degradatio

Technique for Measuring Spatial Distribution of the Surface Acoustic Wave Velocity in Metals

In this paper a possibility of determining a local velocity of the surface acoustic Rayleigh waves using a transducer, with the rigidly connected emitting and receiving parts, is considered. A problem on spatial resolution of such a transducer for investigation of inhomogeneous specimens is also examined. A high spatial resolution can be obtained due to the transducer displacement by a value less than the distance between the emitting and receiving parts. It is shown that in this case it is not necessary to measure the transducer displacement with a high accuracy for precise determination of the velocity. Such an effect is obtained through measuring the velocity of surface waves in one local region of the specimen with respect to the other. The criterion for optimal spatial resolution selection during spatially inhomogeneous specimens study is also proposed. The proposed criterion use is illustrated on the example of the determination of spatial distribution of the surface acoustic velocity in a steel specimen subjected to inhomogeneous plastic deformation