Research of tribological properties of 34CrNiMo6 steel in the production of a newly designed self-equalizing thrust bearing

There are many cases when in large power equipment (such as a turbine or compressor) asymmetrically loading on bearings due to thermal deformations, production inaccuracies, or simple deflection of the shaft occurs. This asymmetrically loading means misalignment of rotor against stator in angle more than several tenths of a degree and it has an influence on a journal and thrust bearings. Over the last few years, thanks to increasingly precise manufacturing, solutions that can eliminate this phenomenon have been revealed. In the case of the thrust bearing, it is a system of very precise manufactured levers, which are in close contact each to other, so they have to be not only properly designed from the geometrical point of view but the important role plays a quality of the functional surfaces of these levers. The article deals with the surface treatment effect on tribological properties of 34CrNiMo6 steel used for the production of bearing levers, which are the critical parts of a newly developing self-equalizing thrust bearing. The samples with cylindrical and plate shapes were produced from 34CrNiMo6 steel as representatives of the most suitable geometries for contact surfaces. All samples were heat-treated. The surfaces of some samples were treated by electroless nickel plating or nitriding, some of the samples were treated by tumbling. Gradually, the surface roughness, microhardness, metallographic analysis and the influence of selected types of surface treatments on the wear for individual samples were evaluated within the research presented in the article. As the testing methods for evaluation of tribological properties were selected Pin-on-disc test and frequency tribological test. The results showed that the best tribological properties achieved samples treated by electroless nickel plating compared with the nitrided or only heat-treated samples. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education of the Slovak Republic [APVV-19-0550, KEGA 007TUKE-4/2018

Kinematic analysis of quick-return mechanism in three various approaches

Članak se bavi kinematičkom analizom Whitwordovog mehanizma koja je izvedena u tri različite metode. Suvremene metode su računalno potpomognute s posebnim softverom za analizu obrade, koji može simulirati ne samo gibanje mehanizma, već može odrediti i položaj, brzinu, ubrzanje, sile, momente te druge parametre u svakom trenutku vremena, ali je potrebna provjera i razumijevanje zakona mehanike. Cilj je kinematičke analize istražiti gibanje pojedinih komponenti mehanizma (ili njegovih važnih točaka) u ovisnosti o gibanju pobuđivača. Ovdje su opisani osnovni principi triju pristupa te prednosti i nedostaci prezentiranih rješenja. Dobiveni se rezultati mogu usporediti, ako su rabljeni isti ulazni parametri.The article deals with kinematic analysis of quick-return mechanism that is executed by three various methods. The modern methods are computer aided with the special software for analysis processing, which can simulate not only the motion of the mechanism, but can define the position, velocity, acceleration, forces, moments and other parameters at every moment of time, but verification and mechanics laws understanding are necessary. The goal of the kinematic analysis is to investigate the motion of individual components of mechanism (or its important points) in dependence on the motion of drivers. The article describes the basic principles of three approaches, as well as the advantages and disadvantages of presented solutions. The obtained results can be compared, if the same input parameters are used

Three views on kinematic analysis of Whitworth mechanism of a shaping machine

Machines play a very important role in today's industry because they are the foundation of automation. An essential integral part of each machine is the mechanism. In many cases, there are several mechanisms working independently inside the machine or the movements of the individual mechanisms are joined. It is necessary to understand a mechanisms motion to be possible to set up its right working conditions and so also to achieve the most appropriate machine efficiency. The article deals with the kinematic analysis of a Whitworth mechanism. This mechanism is a part of a shaping machine that is used in real technical practice. Three approaches (analytical, graphical and solution with computer aid) to the specification of kinematics characteristics of a cutting tool motion are presented in the article. Also, the advantages and disadvantages of the presented approaches are briefly described in the paper. A comparison of results of kinematic analysis has shown that there are no differences in the achieved values; they are only in an accuracy that follows from the essence of individual approaches to the solution. © 2020 Int. J. Mech. Eng. Rob. Res

Investigation of toothed shaft from the view of modal parameters

The paper deals with the investigation of toothed shaft from the view of modal analysis, which is a base of dynamic analysis. The gear mechanism is newly designed based on new principle, at which the motion and power are transferred from one input shaft to two output shafts in one direction. Considering that structures vibrate in special shapes when excited at their resonant frequencies, by understanding the mode shapes, all the possible types of vibration can be predicted. The paper aimed to create experimental and computational model of the shaft with subsequent verification of selected theories, to compare results obtained by numerical and experimental modal analysis and to assess the dynamic characteristics of the component with respect to its operating conditions. There are described conditions of both numerical and experimental modal analysis in the paper. The measurements have shown that the values of natural frequencies along with the natural shapes are adequate and comparable within both of the investigation methods. Moreover, from the results it is clear that output shaft should not be subjected to resonance. On the other hand, by means of modal analysis, the number of teeth was specified, that can be risky at the dynamic load of the gear, if the gear ratio changes. © 2019, Strojarski Facultet. All rights reserved.Ministry of Education, Science, Research and Sport of Slovak Republic [KEGA 007TUKE-4/2018, VEGA 1/0795/19, APVV-17-0380

Effect of the weight reduction of a gear wheel on modal characteristics

The paper deals with the influence of gear weight reduction on its modal properties. The aim of the paper is to use the simulation tools to introduce the dependence of natural frequencies on the change in the shape of the gear, which is reflected in the change in weight. At the beginning of the paper, the theory and experimental bases of vibration testing and analysis are introduced to understand the principles of modal parameter specification. Verification of the boundary conditions used in the simulation was performed using the experimental method and it is described in the next part of the article. Tests confirmed the consistency of the values achieved by both approaches. Thus, the same boundary conditions could be used to specify the dependence of natural frequencies on the change in the geometry of the gear (which is associated with weight reduction). Numerical analysis was performed by FEM analysis using PTC Creo software. Experimental modal analysis was performed using a PULSE measurement system.Ministry of Education, Science, Research and Sport of SR [KEGA 007TUKE-4/2018, VEGA 1/0440/18

Analiza čimbenika bočnog glodanja koji utječu na nepravilnost površine visokokvalitetnog čelika E295

The paper deals with experimental research and evaluation of side milling by evaluation of technology factors, which influence the surface profile parameter peak to valley of high-grade steel E295 by means of design of experiments. Four selected technological factors (diameter of milling cutter, spindle speed, feed per tooth and depth of cut) which enter into technological process of side milling of slots have been evaluated by means of full factories analysis. The surface quality has been evaluated by static quality characteristic the peak to valley Rz parameter. The multiple linear regression equation obtained after analysis of variance gives the level quality Rz as a function of the significant factors. Different factors main effect and their interaction significance have been found, which generated surface profile under defined conditions by side milling.U radu je prikazano eksperimentalno istraživanje i procjena bočnog glodanja pomoću procjene tehnoloških čimbenika koji utječu na parametar profila površine visokokvalitetnog čelika E295 pomoću pokusa. Četiri odabrana tehnološka čimbenika (promjer glodala, brzina osovine, sadržaj po zubu, dubina rezanja) koji spadaju u tehnološki proces bočnog glodanja utora ispitana su pomoću potpune analize čimbenika. Kvaliteta površine je ispitana pomoću Rz parametra. Višestruka jednadžba linearne regresije dobivena nakon analize varijance daje razinu kvalitete Rz kao funkciju važnih čimbenika. Uočen je glavni utjecaj raznih čimbenika i važnost njihova međudjelovanja, koji su dali profil površine u zadanim uvjetima pomoću bočnog glodanja

Innovation of the production process of coin dies to increase their service life

The article deals with the problem related to the service life of the coin dies. The faultless condition of tools during the long-time process of the production of the coins is a basement for their quality. It is influenced by several aspects. The most important factors can be considered the material of the coin die - especially its purity, relief production technology, heat treatment - especially the correct observance to procedures and the choice of equipment, achieved mechanical properties, method of final relief treatment - e.g., coating and the existence of residual stresses in the tool. The aim of the present research was to examine the cause of the failure and damage of the coin dies after production of a small number of coins and, accordingly, to make changes in the production process to prolong their service life. By monitoring the individual steps of the production process, it was possible to identify specific causes of premature decommissioning of coin dies. Innovations have been made at each step of the production process to extend the life of the coin. The paper presents the modifications in the heat treatment of the coin dies as one of the basic improvements in their no-failure long time operation. This, together with other identified shortcomings in the tool manufacturing process, has contributed to an increase in the number of coins minted from around 6,000 to 740,000 coins. © 2023 The Authors. Published by Elsevier B.V.Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky, (APVV-19-0550); Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA, (005TUKE-4/2021

Study of the sound absorption properties of 3D-printed open-porous ABS material structures

Noise pollution is a negative factor that affects our environment. It is, therefore, necessary to take appropriate measures to minimize it. This article deals with the sound absorption properties of open-porous Acrylonitrile Butadiene Styrene (ABS) material structures that were produced using 3D printing technology. The material's ability to damp sound was evaluated based on the normal incidence sound absorption coefficient and the noise reduction coefficient, which were experimentally measured by the transfer function method using an acoustic impedance tube. The different factors that affect the sound absorption behavior of the studied ABS specimens are presented in this work. In this study, it was discovered that the sound absorption properties of the tested ABS samples are significantly influenced by many factors, namely by the type of 3D-printed, open-porous material structure, the excitation frequency, the sample thickness, and the air gap size behind the sound-absorbing materials inside the acoustic impedance tube. © 2020 by the authors.Ministry of Education, Science, Research, and Sport of the Slovak Republic [KEGA 007TUKE-4/2018, APVV-19-0550]; European Regional Development Fund in the Research Centre of Advanced Mechatronic Systems within the Operational Programme Research, Development, and Education [CZ.02.1.01/0.0/0.0/16_019/0000867

Tensile properties of four types of ABS lattice structures—A comparative study

This article aims to compare the behaviour of four types of lattice structures named Cartesian, Rhomboid, Octagonal, and Starlit under tensile stress loading. The structures were made of Acrylonitrile Butadiene Styrene (ABS) material using the Fused Filament Fabrication (FFF) technique with three different specific volumes (24, 42, and 60%). Five samples of each type were produced, and a total of 60 samples were tested. Experimental testing was performed according to EN ISO 527-1:2012 and EN ISO 527-2:2012. The obtained data were statistically processed, while no outliers were identified. The experimental results pointed out that the specimens' topology, together with the specific volume, very significantly affected the resultant ABS properties of the tested samples made of the same material. The comparative study showed that in terms of ultimate strength, yield strength, and Young's modulus, the Cartesian structure appeared to be the most suitable for tensile stress, and the least suitable structure was the Rhomboid structure. On the other hand, the Rhomboid-type of the structure showed not only the highest amount of absorbed energy but also the highest toughness among the investigated lattice structures, so in the near future, its behaviour under an impact test should be studied.Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky, (APVV-19-0550); Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA, (005TUKE-4/2021, 032TUKE-4/2022)The authors would like to thank the Ministry of Education, Science, Research, and Sport of the Slovak Republic for the direct support of this research through the projects APVV-19-0550, KEGA 005TUKE-4/2021 and KEGA 032TUKE-4/2022. [APVV-19-0550, KEGA 005TUKE-4/2021]; Ministry of Education, Science, Research, and Sport of the Slovak Republic [032TUKE-4/2022]; KEG

Effect of the pore shape and size of 3D-printed open-porous ABS materials on sound absorption performance

Noise has a negative impact on our environment and human health. For this reason, it is necessary to eliminate excessive noise levels. This paper is focused on the study of the sound absorption properties of materials with open-porous structures, which were made of acrylonitrile butadiene styrene (ABS) material using additive technology. Four types of structures (Cartesian, Octagonal, Rhomboid, and Starlit) were evaluated in this work, and every structure was prepared in three different volume ratios of the porosity and three different thicknesses. The sound absorption properties of the investigated ABS specimens were examined utilizing the normal incidence sound absorption and noise reduction coefficients, which were experimentally determined by the transfer function method using a two-microphone acoustic impedance tube. This work deals with various factors that influence the sound absorption performance of four different types of investigated ABS material’s structures. It was found, in this study, that the sound absorption performance of the investigated ABS specimens is strongly affected by different factors, specifically by the structure geometry, material volume ratio, excitation frequency of an acoustic wave, material’s thickness, and air space size behind the tested sound-absorbing materials. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Science, Research, and Sport of the Slovak Republic [APVV-19-0550, KEGA 007TUKE-4/2018]; European Regional Development Fund in the Research Centre of Advanced Mechatronic Systems project within the Operational Programme Research, Development and Education [CZ.02.1.01/0.0/0.0/16_019/0000867