The study of the internal friction of electrolytic coatings is complicated by the impossibility of obtaining sufficiently massive samples and testing them independently of the substrate, and therefore it is necessary to evaluate the stress state of the sample-coating system. The aim of the work was to find a relationship between the internal stresses arising in the coating deposited on a circular cross-section specimen during internal friction tests using a torsion pendulum. During the analysis of the stress-strain state of the bimallic sample, expressions were found to calculate the maximum and minimum stresses in the electrolytic coating. The mutual influence of the coating material and the substrate was evaluated numerically using the Comsol Multiphysics program.

Keywords: internal friction, internal stresses, torsion pendulum, beam rotation, electrolytic coatings

"Prediction of carbon concentration profiles depending on the cementation parameters is possible using mathematical models, most of which show good results for austenite Fe-C, without affecting the influence of alloying substitution elements. The paper describes modeling using the finite element method of the diffusion saturation of the austenite of the Fe-C-Cr system with carbon during cementation using 15Cr steel as an example, taking into account the influence of temperature, and also provides practical confirmation of the model. For the numerical solution of the problem, the COMSOL Multiphysics program was used. It has been established that for the one-stage cementation mode, the applied model of carbon diffusion in undoped austenite is in good agreement with the experimental data for austenite of the Fe-C-Cr system of steel 15Cr. For a two-stage process, the calculation of carbon concentration in the surface layer has a slightly larger deviation from the experimental data than at a greater depth."

Keywords: carbon diffusion, COMSOL, final method, carburization, cementation, steel, diffusion, mass transfer, alloyed austenite, modeling, elements

Cementation studies focus almost exclusively on the movement of carbon, described through the diffusion equations, often with constant coefficients and without regard to temperature. This approach does not allow, to take into account the further diffusion of carbon into the workpiece in a lower temperature range at the stage preceding quenching. The paper describes the modeling of the diffusion saturation of steel by carbon in the cementation process, taking into account the influence of temperature on the example of a numerical solution of the gear cementation problem using the COMSOL Multiphysics program. It was shown that the finite element mathematical calculation of the process of saturation of austenite with carbon during cementation gives good agreement with experimental data, and finite element analysis methods can be used for multivariate calculation of the carbon content in austenite after diffusion saturation

Keywords: carbon diffusion, carburization, COMSOL Multiphysics, numerical modeling, carbon distribution, carburization, Fick diffusion law, mass transfer, heat transfer, gear, finite element method

An optical sensor for measuring small displacements and rotation angles is described. Based on a non-contact principle of operation, which can be used to control small movements in installations to determine internal friction by the type of torsion pendulum. The main characteristics of the device are shown and the installation and connection diagram is shown by means of the ADC to the computer

Keywords: optical sensor, angle of rotation, displacement, internal friction, microcontroller, torsional pendulum, photoresistor, signal filtering, signal transmission, non-contact, ADC