Марченко Д.Д.

Electrothermal analysis of elements of the educational and research laboratory stand of the electrotechnical laboratory

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UDC 621.3

O. Kyrychenko1, Candidate of Technical Sciences, Associate Professor
I. Sidorika2, Candidate of Technical Sciences, Associate Professor
D. Marchenko1, Candidate of Technical Sciences
1Mykolayiv National Agrarian University
2National Shipbuilding University named after. Admiral Makarov

Introduction. According to the state educational standards of Ukraine, the passage of laboratory practice in the discipline of electrical engineering and electronics basics involves the practical development of students’ experimental methods for studying electric circuits and consolidation of theoretical knowledge and skills, as well as familiarity with electrical measurements.
The error in determining of parameters and electric circuits operating modes by calculation and obtained experimentally differs in magnitude, which in some cases amounts to 10-15%. One of the reasons that affects the error magnitude is the heat emission in the electric circuit’s elements, which leads to an increase in the spread of their parameters, which was not taken into account before.
Research methodology. The methodology for studying the elements of the training and testing stand of the electrotechnical laboratory envisaged the creation of a geometric, finite-elemental and realistic 3D-resistor models.
Electrothermal analysis of the electrical laboratory training bench elements was carried out using numerical simulation.
Research results. The distribution of the main electric and thermal quantities by the volume of the electrical laboratory’seducational-research stand element is established.
As a result of the electrothermal analysis, different values of the resistor heating were obtained at a different magnitude of the current strength flowing through it, on the basis of which the resistor’s electrothermal characteristics were constructed. The resulting thermal model is adiabatic, and therefore the resulting numerical values for temperature should be considered as the upper thermal limit.
Conclusions. Conducting an electrothermal analysis of elements of the UNSS-1 training laboratory unit allowed to establish the distribution of the main electrical and thermal variables by the volume of the training laboratory stand element.
The influence of heat on the accuracy of calculations in determining the parameters and modes of operation of electric circuits by calculation and determined experimentally is determined. Taking into consideration thermal flux has increased the general accuracy of electric parameters calculations, since the error was not more than 5-7%.

Keyword: electrothermal analysis, educational and research stand, electrotechnical laboratory, modeling, temperature fi eld.

Electrothermal analysis of elements of the educational and research laboratory stand of the electrotechnical laboratory.

Issue 4 (96), 2017

Tribological research on the process of wear of a friction pair «cable block – rope» considering rolling slippage

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UDC 621.7; 621.8; 539.4

D. Marchenko

Introduction. Therefore,  elucidating of the wear in the rolling considering slip is an important task for improving the durability of tribotechnical characteristics of contacting surfaces, such as a friction pair «cable block – rope».
Research methodology. Tests are conducted in accordance with DIN 50324, ASTM G99 «Standard Test Method for wear Testing with a Pin-on-Disk Apparatus», as well as standards ASTM G 133, ASTM D 3702, ASTM D 5183, ASTM D 4172 and ASTM D 2266.
The tests of the samples being rolled with the slip were conducted on a wear machine MI the top shaft of which was able to rotate, and was returned about a vertical axis at an angle of 5°, which provided lateral slip about 10% of that observed in the friction pair «cable block – rope». To measure the wear weight loss of samples used VLR – 200.
The results. Found that wear actually depends on the load, but depends only on the slip.
In the case of rolling with longitudinal slip, equal to 10% of the friction surface become brown color, typical of oxidative deterioration. When cross-slip surface layer due to lateral plastic flow continuously updated. In longitudinal slip surface areas and products of wear, moving along the circle skating, interact repeatedly, increasing the role of corrosion during wear. Speed oxidative deterioration was dependent on the hardness of steel, so the impact of hardness on the results of experiments with longitudinal slip offset that should be considered when analyzing the results of a wear machine MI.
Thus, one could argue that the slip to 10% speed deterioration is almost independent of pressure or even decreases with its increase.
When changing operating conditions tribosystem wear rate may change abruptly, thus changing the surface friction type, size, color and chemical composition of the products of friction, that is a result of the transition from one mechanism to the second wear.
Boundary layers of bodies or surface film, with their contact during the rolling of the sliding friction coefficient reduce to 3 – 4 times and thus the speed and intensity of wear. Therefore, by changing the coefficient of friction may establish a process erase surface films.
Conclusions. Surface roughness effect on friction coefficient of friction and wear rate when rolling with slip, i.e. with decreasing surface roughness decreases.
If the slip is up to 2% it is seen as a sharp change in friction can be observed, after which it remains practically unchanged through the distribution of slip on the entire area of contact.

Key words: pair of friction, slipping, rolling motion, crumpling, coefficient of friction, rolling-off by a roller.

Tribological research on the process of wear of a friction pair «cable block – rope» considering rolling slippage.

Issue 3(91), 2016