Improvement of the tribological properties of heavy-loaded friction units “Centre block-footstep bearing” of a freight car

Various problems and different approaches of solution of such a problematic unit as “centre block-footstep bearing” of freight cars are discussed in the paper. The methods of improving the tribological properties of this friction unit by means of material modification of friction surfaces and perfection of physical, chemical and tribological properties of the used lubricants were studied. Grease lubricants common for friction units of railway machinery were used after being modified with inorganic polymers based on double metaphosphates. Bench and operational tests of the developed additive of the polymeric double metaphosphates were carried out. This additive reduces wear and increases the service life of the friction unit, due to the better adhesion properties of this additive. The variants with a change in the geometry of the contact surface of the disk between the bolster and the “centre block-footstep bearing” arrangement of the car are considered. Simulation of the parameters of movement in curved sections is proposed.

Introduction of innovative technologies in friction units of heavy-duty tribosystems and monitoring of their condition

The article describes studies of heavy-duty metal-polymer tribosystems: wheel-brake pad and pyatnik-podpyatnik of rolling stock, as well as spline couplings of the MI-26 helicopter tail rotor transmission. Tests of the wheel - brake pad system were carried out on an inertial stand with two-way braking at loads and speeds close to real operating conditions. Methods for modifying polymers, fillers, and nanoscale additives have been developed for the Pyatnik - podpyatnik tribosystem of rolling stock. To increase the wear resistance of work surfaces two-layer carbon fibers were applied to the spline couplings. DLC- coatings. Bench tests of these coatings showed a 4.5-fold reduction in wear when testing full-scale slots with a load of 30,000 kg. H and the number of completed cycles in 1,000,000. Methods for monitoring spline couplings based on the analysis of the frequency spectrum of the acoustic-emission (AE) vibration signal generated during the operation of the friction unit are considered. The results of studying the working state of spline couplings obtained by vibration diagnostics in the acoustic frequency range are presented. The state estimation is based on both the characteristics of the time signal and the transformation of the signal in the frequency domain using modal decomposition of the signal using Hilbert-Huang transformations. It is shown that for the effective for monitoring heavy-duty tribosystems, it is advisable to use neural networks.

Ion beam technology for the resource enhancement of responsible parts of a high speed friction unit

The needles from carbon steel “U10”, a details of high speed couple of friction “needle-thrust plate” of the gas centrifuge is investigated, in the initial, post-operational state and after irradiation by C+ ions different doses on the pulse-frequency “Raduga” accelerator. The purpose of this study is to increase the operability and service life of the responsible friction unit of the gas centrifuge. This purpose is achieved by mod-ification of the working sliding surface of the needle (which is a responsible part of the high-speed friction pair “needle-thrust plate”) by the pulse-frequency implantation with carbon ions. The dose of implantation (1018 cm−2 of C+ ions), was established, at which an optimal combination of mechanical and tribological properties of the working surface is achieved, which provides wear resistance increase during the operation of the friction pair. This method of surface treatment is recommended to use in case of operation of couple of friction “needle-thrust plate” for the purpose of increase in working capacity and a resource of operation of high speed couple of friction of the gas centrifuge.

The performance evaluation of heavy loaded tribosystems with vacuum ion-plasma PVD and DLC coatings

The results of studies of the physical, mechanical and tribological characteristics of PVD and DLC coatings are presented. The complex of basic mechanical properties (hardness H and elastic modulus E), as well as derivatives of mechanical characteristics H/E and Н3/Е2 , were investigated by the method of continuous indentation at various loads. The friction coefficient, the wear rate of the sample and the counterbody were determined as tribological indicators. The applied purpose of the work was to determine the friction unit for applying the developed coatings, materials and modes of applying PVD and DLC coatings. To solve this problem, a test bench was designed and built that simulates the operation of the selected friction unit. As a result of the research carried out, the results of laboratory and bench tests were compared. The performance of the coatings was determined by the volume of the tooth wear of the sleeve and the tip with the help of the method of micrometric measurements. As a result of the study of the surface morphology, the volumes of wear of rubbing conjugations and the intensity of their wear were determined. It has been established that the results of bench tests confirm laboratory studies and suggest that such an installation can be used for researching other heavily loaded spline conjugations.

Improving the Dynamic Characteristics of Precision Lathes Used in the Repair of Agricultural Machinery

A model of a friction unit of a lathe in the form of a thin layer of material of a honeycomb structure is described to determine the dynamic characteristics of a movable carriage to guide joint. The analysis of the mathematical model of friction for different sliding pairs with varying load and sliding speed is performed. It is shown that the presence of an abrasive impurity in the lubrication of the guide enhances the effect of the low-frequency component of the carriage vibrations on the dynamics of the machine tool and the presence of pockets for retaining the lubricant in the joint of the guide makes it possible to reduce the amplitude of the longitudinal vibrations of the carriage to 30-50 %.

Development of Metal Cladding Additives for Agricultural Machinery Friction Unit Parts

The choice of materials for the formulation of the metal cladding additive has been theoretically substantiated. A process has been developed and a copper-containing lubricant composition has been synthesized. It is shown that the use of a metal cladding additive having antifriction and antiwear properties reduces 2.9 times the part wear rate. The effect of the additive on the anticorrosion properties and thermal-oxidative stability of the base oil has been studied.

Increasing the life of the center plate-center bowl friction unit of a freight car by applying a combined coating formed by electrospark alloying

An increase in the operational reliability of friction units of railway transport by applying antifriction combined coatings formed by electrospark alloying, which ensures their greater strength and adhesion to metal, is considered. Keywords: electrospark alloying combined antifriction coating, strength, adhesion. [email protected]

Algodoo for Interactive Learning: Effects on Students’ Achievement and Motivation Towards Science

This study investigates the effects of the Algodoo interactive learning program on fifth-grade students’ achievement in science and motivation towards science. The research was carried out in the fall semester of the 2020-2021 academic year with the participation of 110 fifth grade students. In the study, a pre-test-post-test control group quasi-experimental design was used. Within the scope of the study, the “Force Measurement and Friction” unit was taught during three weeks through Algodoo in the experimental group and traditional teaching in the control group. In the study, data were collected through an achievement test including multiple-choice questions and Science Motivation Scale. Both instruments were applied to the groups twice as pre and post-test. Independent samples t-test was conducted separately for the quantitative data obtained from each instrument. Moreover, a paired-samples t-test was conducted to compare the pre-and post-test scores of each instrument. According to the findings, Algodoo applications had positive effects on science achievement and motivation towards science.

Rational design for a friction unit of a disc-shoe brake

In this study, we develop a rational design for a friction unit provided that restrictions are imposed on the fly-wheel masses of rotating elements and the onset of a thermal stabilization state. The input calculation data were the braking torque, specific pressure in the friction pair, angular velocity and the diameter of the brake disc hub. The geometric programming method was used at the preliminary stage to calculate the design and operational parameters of a discshoe brake. Further, the parameters were refined based on the conditions of mutually exclusive factors (energy intensity and braking time) and the stress-strain state. On the basis of the proposed rational design for a friction unit, a software application for calculating in the DELPHI programming language was developed. The ranges of design parameters were determined at the preliminary design stage: a brake disc diameter from 0.237 to 0.37 m; the width of working surfaces from 0.0335 to 0.1 m; and the thickness of half-discs from 0.012 to 0.026 m. The final result of the rational design method was the specified ranges of design parameters: diameter from 0.31 to 0.324 m; width from 0.041 to 0.0485 m; and thickness from 0.0148 to 0.0151 m. The developed method of rational design reduces the diameter ranges of the designed brake disc in comparison with the preliminary calculation by 9.5 times, while the ranges of the width of the working surfaces are reduced by 8.9 times, and the thickness range – by 46.6 times. At the final stage, the secondary design and operational parameters of the friction unit were determined: the areas of the working and non-working surfaces of the friction pairs and the coefficient of their mutual overlap. The proposed method of rational design reduces the selected range of design parameters, which will provide a more rational choice of compliance with their specified performance characteristics.