Вимірювальна техніка та метрологія

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Author: search.filters.author.Yatsyshyn, SvyatoslavSubject: search.filters.subject.Temperature

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    Electrical properties of Ti-Cu-Co-Si high-entropy alloy
    (Видавництво Львівської політехніки, 2022-02-28) Yatsyshyn, Svyatoslav; Skoropad, Pylyp; Karpinski, Mikolaj; Lviv Polytechnic National University
    To study the metrological characteristics, there were studied manufactured based on the Ti-Cu-Co-Si alloy, obtained by quenching from the melt, the sensitive element of the resistance thermotransducer. The instability of its metrological characteristics as a function of temperature up to 350 oC and operation time up to 3000 hours was investigated; it does not exceed 0.025 % under the worst operating conditions. In addition, the methodological error of measurement caused by heating of the sensitive element by the measuring current was examined. It was shown that the recorded changes in electrical resistance were outside the value of the methodological error. They may be due to the presence of nanostructured fields of mechanical stresses and the formation of nanoprecipitates as a consequence of manufacturing.
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    Thermometry: from sensitive material to thermoelectric thermotransducer
    (Видавництво Львівської політехніки, 2005-02-24) Stadnyk, Bohdan; Skoropad, Pylyp; Yatsyshyn, Svyatoslav; Lviv Polytechnic National University
    The hard operation conditions of temperature thermotransducers which involve their thermal cycling require special attention to the study of processes occurring in structural elements, in particular in thermometric materials. Operation impacts cause the drift of thermometric characteristics due to the influence of the few factors main of which seem to be the thermo structural stresses. Therefore, different kinds of sensitive elements were studied. Since traditional polycrystalline thermoelectrodes of thermocouples are inherent in the well-known drawback linked with recrystallization, there were investigated the liquid metals as the thermometric substances, melts, single-crystal materials, and metallic glasses. The need for metal glasses application in thermometry is substantiated, which allows eliminating thermally activated gradients of internal stresses in thermocouples ensuring high reproducibility and low drift of their thermo-EMF comparing to traditional materials. The analysis of sources of the instability of thermocouples’ drift is carried out. It demonstrates the density of heat and electric flows in stressed thermoelectrodes depends not only on temperature and electric potential gradient but also on the stresses’ gradient. This causes the dependence of thermometric parameters of both poly- and single-crystal substance of thermoelectrodes on the value and nature of stresses occurring within the operation cycle.