NASU Karpenko Physico Mechanical Institute

L'viv, Ukraine

NASU Karpenko Physico Mechanical Institute

L'viv, Ukraine
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Stashchuk M.,NASU Karpenko Physico Mechanical Institute | Dorosh M.,NASU Karpenko Physico Mechanical Institute
International Journal of Hydrogen Energy | Year: 2017

A detailed study of hydrogen behaviour in the metal needs full analysis of the components of the stress–strain tensor field, induced by hydrogen atoms. Modelling of the stress–strain state of the “metal-hydrogen” system was carried out. From the standpoint of the theory of elasticity the appropriate system of basic key equations of the problem for determining stress components caused by hydrogen in metal, were formulated. Such equations were written for a cylindrical body. The plane deformation of a long cylindrical sample with the evident hydrogen concentration was investigated. Appropriate analytical ratios were established and theoretical analysis for the assessment of strain and stress tensor components caused by the concentration of hydrogen were also carried out. Calculation relations for a solid cylindrical sample were received. Computations of the stress tensor components induced by hydrogen in a solid cylinder during hydrogenation or dehydrogenation were done. Evidence of the uniform tensile zone within the cylindrical sample was stated during the sample hydrogenation, and near its surface – intensive compressive stresses. In contrast: during dehydrogenation an appropriate compression zone was evident in the sample while near the cylinder surface the tensile stresses were present. © 2017 Hydrogen Energy Publications LLC

Montresor S.,CNRS Acoustic Lab of Du Maine University | Picart P.,CNRS Acoustic Lab of Du Maine University | Picart P.,University of Limoges | Sakharuk O.,NASU Karpenko Physico Mechanical Institute | Muravsky L.,NASU Karpenko Physico Mechanical Institute
Journal of the Optical Society of America B: Optical Physics | Year: 2017

This paper presents an analysis of phase errors generated by advanced noise removal algorithms applied to phase measurements obtained from digital holographic interferometry. The output phase error is analyzed considering two contributions: the error generated by the denoising method and the error due to phase noise. In addition, a third type of error allows quantifying the ability of any algorithm to estimate the initial noise level. A comparison of several denoising algorithms is presented to independently assess the three types of errors from a data set of simulated fringe patterns with controlled realistic noise. The results exhibit the best method for which the output error, together with the method error, is the smallest one. Knowing the error method is advantageously applied to digital color holography experiments in which deformation measurements of an object submitted to mechanical strength are given with a percentage of error due to the denoising algorithm. © 2017 Optical Society of America.

Trush V.,NASU Karpenko Physico Mechanical Institute
EasternEuropean Journal of Enterprise Technologies | Year: 2017

In contrast to a large number of publications about the influence of interstitial elements (O, N) on the physical-mechanical properties of zirconium alloys, insufficient attention at present is paid to examining their influence on the characteristics of nearsurface layers of the shells of heat generating element (HGE). Therefore, it is expedient to widen the knowledge about the influence of interstitial elements on the properties of zirconium HGE tubes. Authors experimentally established the influence of treatment in the controlled oxygen- and nitrogen-containing gas media on the mass increment and properties of the nearsurface layer of samples-rings, cut out of the shells of heat generating elements. Differences in the saturation of internal and external surfaces of zirconium pipes were described. It was shown that roughness of the internal surface is less compared to that of the external surface. Results of examining the hardness of external and internal surfaces of the samples-rings after oxidizing and nitriding are presented here. For example, treatment of the samples-rings in the oxygen-containing medium (T=650 °C, t=20 h) leads to the formation of hardness at the external surface HV0.49=1190±90, and at the internal surface HV0.49=1190±90. However, after treatment in the nitrogencontaining medium (T=650 °C, t=20 h), the hardness on external surface is HV0.49=615±35, while on the internal surface it is HV0.49 =445±35. For example, after treatment in the oxygen-containing medium (T=650 °C, t=20 h), depth of the strengthened layer at the external surface is l=70...75 μm and at the internal surface, it reaches l=60...65 μm. Treatment in the nitrogen-containing medium (T=650 °C, t=20 h) causes the formation of a strengthened layer on the external surface l=60...65 μm and on the internal surface - l=55...65 μm. The duration of isothermal holding in the oxygen mixture, which can lead to the crack initiation at the internal surface of zirconium HGE pipes, was experimentally discovered. Results of present work may be taken into account for the development of modes of treatment of zirconium alloys. © V. Trush, 2017.

Denys R.V.,Institute for Energy Technology of Norway | Denys R.V.,NASU Karpenko Physico Mechanical Institute | Yartys V.A.,Institute for Energy Technology of Norway | Yartys V.A.,Norwegian University of Science and Technology
Journal of Alloys and Compounds | Year: 2011

The present work gives the data of systematic studies of the influence of magnesium on the crystal structure and hydrogenation behaviour of the PuNi 3-type La1-xMgxNi3 (x = 0-0.67) intermetallic alloys. Synchrotron X-ray diffraction studies revealed that substitution of La in LaNi3 by Mg proceeds in an ordered way, only within the Laves type layers of the hybrid crystal structures build from the MgZn2- and CaCu5-type slabs. When completed, it leads to the formation of LaMg2Ni9 (2MgNi2 + LaNi 5). Gradual increase of Mg content is accompanied by a linear decrease of the volumes of the unit cells. Interestingly, a substantial contraction takes place also for the Mg-free CaCu5-type slabs. Hydrogen interaction with the La1-xMgxNi3 alloys was investigated by in situ synchrotron X-ray, neutron powder diffraction and pressure-composition-temperature studies. In the whole substitution range, La1-xMgxNi3 alloys form intermetallic hydrides with H/M ratio ranging from 0.77 to 1.16. Magnesium influences structural features of the hydrogenation process and determines various aspects of the hydrogen interaction with the La1-xMgxNi3 intermetallics causing: (a) more than 1000 times increase in equilibrium pressures of hydrogen absorption and desorption for the Mg-rich LaMg 2Ni9 as compared to the Mg-poor La2.3Mg 0.7Ni9 and a substantial modification of the thermodynamics of the formation-decomposition of the hydrides; (b) an increase of the reversible hydrogen storage capacities following increase of Mg content in the La1-xMgxNi3 to ∼1.5 wt.% H for La2MgNi9; (c) improvement of the resistance against hydrogen-induced amorphisation and disproportionation; (d) change of the mechanism of the hydrogenation from the anisotropic to isotropic one. Thus, optimisation of the magnesium content provides different possibilities in improving properties of the studies alloys as hydrogen storage and battery electrode materials. © 2010 Elsevier B.V. All rights reserved.

Dmytrakh I.M.,NASU Karpenko Physico Mechanical Institute
Strain | Year: 2011

The work is a compressed review based on the summarised results and the original approach for study of corrosion crack growth, taking into account local electrochemical conditions in the crack tip, which was developed at the Karpenko Physico-Mechanical Institute of NASU. The model scheme of the pre-fracture zone in the corrosion crack tip, which can be defined by the local values of pH of solution, electrode potential of metal E and stress intensity factor K I is proposed. For its realisation, the special method and testing equipment for corrosion crack growth study and local electrochemical measurements in the crack were developed. The variation of the electrochemical conditions in corrosion cracks was studied, and it has been found that some stabilised levels of the pH and E values can be achieved in the tip of a non-propagating and a propagating crack under static and cyclic loading during of exposure time. On this ground, the method for forecasting of the threshold stress intensity factor K ISCC under stress corrosion cracking was proposed using these characteristic values of pH and E. This method was also adopted for the determination of the threshold stress intensity factor K th under corrosion fatigue. The special method for determining corrosion fatigue crack growth rate diagrams based on consideration of extreme electrochemical conditions in the crack tip was developed. It has been proven that such diagrams reflect the extreme influence of the environmental factor on corrosion fracture of material, and they may be recommended as the base for the remaining lifetime calculation of the structural elements exploited under environmental conditions. © 2010 Blackwell Publishing Ltd.

Demyanyshyn N.M.,NASU Karpenko Physico Mechanical Institute | Mytsyk B.G.,NASU Karpenko Physico Mechanical Institute | Sakharuk O.M.,NASU Karpenko Physico Mechanical Institute
Applied Optics | Year: 2014

The anisotropy of piezo- and elasto-optic effects in strontium borate crystals was studied by the indicative surfaces method. The geometry of acousto-optic interaction with maximum efficiency was found on the basis of the surface maxima of the elasto-optic effect. © 2014 Optical Society of America.

Kravets I.B.,NASU Karpenko Physico Mechanical Institute
Radioelectronics and Communications Systems | Year: 2012

Paper presents theoretical results of modeling periodically correlated random processes. We compare the known parametric models: periodic autoregression model of moving average, parametric model of coherent representation and parametric model of harmonic representation. Dependences of properties of correlation and spectral functions related to different models of periodically correlated random processes on their parameters are studied. Main differences between approximations of characteristics of the considered models are revealed. © 2012 Allerton Press, Inc.

Vasyliv B.,NASU Karpenko Physico Mechanical Institute
International Conference on Smart Energy Grid Engineering, SEGE 2015 | Year: 2015

Cyclic treatment technique (redox cycling) comprising stages of material exposition in reducing and oxidizing high temperature environments and intermediate degassing between these stages has been developed to improve the structural integrity of YSZ-NiO ceramic anode substrates for solid oxide fuel cells. Series of specimens were singly reduced in hydrogenous environment (the Ar-5 vol.%H2 mixture or hydrogen of 99.99 vol.%H2 purity) under the pressure of 0.15 MPa or subjected to redox cycling at 600 or 800°C. The influence of redox cycling at the treatment temperatures of 600 and 800°C on the structure, strength and electrical conductivity of the material has been analyzed. Using the treatment temperature 600°C the structure providing improved physical and mechanical properties of the material was formed. However, at the treatment temperature 800°C the anode structure with the array of microcracks was formed that reduced significantly the strength and electrical conductivity of the material. © 2015 IEEE.

Capelle J.,Metz National School of Engineering | Dmytrakh I.,NASU Karpenko Physico Mechanical Institute | Pluvinage G.,Metz National School of Engineering
Corrosion Science | Year: 2010

The assessment of ability to absorb hydrogen of three API grade pipeline steels: X52, X70 and X100 have been evaluated. The factors of cathodic hydrogen charging, time of exposure, and applied stress were taken into account. It has been shown that all steels demonstrate the sensitivity to hydrogenating in deoxygenated, near-neutral pH NS4 solution under relatively "soft" cathodic polarisation, although the efficiency of hydrogen permeation in metal is quite low and depends on time of exposure. Applied tensile stress, which equivalent to gross hoop stress in pipe wall under operating conditions, can accelerate the hydrogen absorption in several times. For studied steels the resistance to hydrogen absorption decreases with decreasing of steel strength. © 2010 Elsevier Ltd. All rights reserved.

Khoma M.S.,NASU Karpenko Physico Mechanical Institute
NATO Science for Peace and Security Series C: Environmental Security | Year: 2013

It has been investigated that influence, in terms of loading and composition of hydrogen sulfide environments, are resistant to corrosion-mechanical destruction of typical steels appointed to marine constructions, gas and oil equipment, and pipelines which are exploited on a marine shelf: steel 20, steels 10CrSiNiCu, 28Cr2M{cyrillic}oVNbCu, 30CrM{cyrillic}o, stainless steel 12Cr21Ni5T{cyrillic}i and steel of 17Mn1Si with the welded joint. It is discovered that the high resistance of steels to sulphide stress corrosion cracking (SSCC) does not guarantee it high endurance in solution of NACE (5 % NaCl + 0.5 % CH3COOH + H2S, sat., r{cyrillic}N{cyrillic}3...4, t = 20 ± 3 °S{cyrillic}) at cyclic tensions: at a symmetric cycle endurance the least resistant to SSCC of steel 20 goes down comparatively with air in ~1.4 times, and more resistant steel 30CrM{cyrillic}o and 12Cr21Ni5T{cyrillic}i - in ~2.6 and 1.9 times, accordingly. An analogical tendency is observed at an asymmetric cycle at amplitude σa{cyrillic} = 0.2σ0.2. In presence of the welded joints asymmetric tensions reduce their resistance destruction in a greater measure, than specimen from basic metal. It has also been established that the addition of 3.5 % solution of marine salt 15 mg/l to H2S does not influence the stress intensity factor of high-strength steel 28Cr2M{cyrillic}oVNbCu. At the repeatedly static loading with frequency f = 1.1 · 10-5 Hz depending on the level of this steel strength, the value of conditional critical stress intensity factors Kscc in this solution goes down on 10-15 %. Thus at the selection of materials for work in hydrogen sulfide environments, it is necessary, except for the generally accepted approaches, for an estimation of high ability to work to take the influence of alternating tensions. © Springer Science+Business Media Dordrecht 2013.

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