Papers by Keyword: Friction

Abstract: With today's proliferation of various polymers, it is necessary to assess the feasibility and feasibility of replacing rubber with more modern materials. The purpose of the tests was to study the effect of abrasive wear, the effect of temperature on material properties, resistance to chipping and other types of wear. This will allow assessing the possibility of application in well conditions, as well as determining the magnitude of the effect of each type of wear on the product. We were faced with the task of testing new protectors in conditions close to full-scale ones. For this, a stand was designed, which allows you to reproduce the lateral load, add abrasive and corrosive agents that affect the wear of the product, ensure circulation of the model fluid, with the characteristics of the drilling fluid, as well as study the effect of elevated temperature on the change in material properties. Due to the fact that in a real well the protector is not under constant load, especially in the vertical sections of the wellbore, but can rotate on the pipe, a day on the test bench can be equivalent to months when the protector is in the well. Therefore, the tests carried out can predict the wear of tread parts, as well as assess the reliability of the use of treads made of polymer materials.

Abstract: The drilling conditions are becoming more severe, which leads to the need to select new polymeric materials that can withstand heavy loads, provide a longer resource and are more resistant to high temperatures. To solve the problem, a set of laboratory tests on standard and specialized tribological equipment is proposed. The friction force, wear resistance under various conditions and according to various criteria, hardness at normal and elevated temperatures, thermal field during tests, change in the roughness of a steel counterbody as a result of tests are evaluated. Wear resistance is determined using a PBD-40 friction machine. Samples are cylindrical bodies with a diameter of (5.0 ± 0.5) mm, a height of 10.0 mm from the materials under study. The samples are fixed in the designed fixture. As a result of the tests, the average values ​​of the parameters for the investigated materials were determined, and the effects arising from friction were noted. The criteria for choosing a material have been formulated and the most suitable material for the tread has been selected.

Abstract: Warp knitting is appointed as a manufacturing method for high-performance and high-quality textiles due to its versatility and production speed. To ensure a continuous and error-free manufacturing process under highly dynamic production conditions, a high level of knowledge of the yarn and machine interaction is required. Mechanical stresses from the machine are transferred to the yarn via friction points, as well as during the stitching process from one yarn to another, where the yarn is subjected to high stresses.Therefore, the focus of this research is the investigation of the friction between the yarn and yarn guiding elements and the friction between the yarns themselves during the stitch formation. For this reason, all contact points between yarn and yarn guiding elements as well as between the yarns themselves are examined and classified. A test rig is set up to determine all occurring frictions as a function of various machine parameters.The knowledge gained and the derived analytical expressions between machine settings and occurring friction can thus become the basis for modeling the friction points of the warp knitting machine, which is also presented. Furthermore, based on the findings a design improvement of the machine can be achieved and the friction model can serve as part of a simulation model of the entire warp knitting machine, which will be the focus of further publications.

Abstract: One of the problems in orthodontic treatment is friction. Some of the factors that support friction are archwire material, archwire dimensions, bracket material, surface roughness, type of ligation, environmental humidity, and bracket position, angulation angle between bracket and wire, changes in the surface of the archwire and bracket. The aim of this study is to analyse the difference in friction between the two branded bracket designs and a new patented bracket (patent no. IDP000069597). The production method for this new bracket is different, however, uses the same material of 17-4 PH stainless steel. There are three groups in this research, one sample of bracket each from two different branded and one sample of a new bracket design. All three groups were tested for microstructure, then tested for measurement of friction between bracket slots and archwire. The microstructure of the two branded brackets has a martensitic phase that is not as dense as the new bracket, which is due to the different manufacturing method processes. The two branded brackets use the metal injection molding method, while the new brackets use the investment casting method. The friction test results show that there are significant differences between the three groups of brackets. One of the branded brackets (A) has the lowest friction, but branded bracket (B) does not have different friction with the new bracket. Differences in design and manufacturing methods of orthodontic bracket affect the friction between orthodontic brackets and archwires even though they use the same material.

Abstract: During the hot piercing phase of seamless tube production, friction and contact conditions between tools and workpiece significantly influence final product quality and energy consumption. The friction effects on the production of high alloyed steels like Super Cr13 steel are critical. This study analyses the effect of different friction conditions at the workpiece-tool interface in the piercing of Super Cr13 steel bars to minimize total energy consumption in such a manufacturing process. For this purpose, a three-dimensional finite element method (FEM) is employed to simulate and analyze the piercing process. The variety of tools (plunge, rollers, and Diescher disks) and contact conditions lead to differences in the applied stress at different workpiece areas. Consequently, various friction models and friction coefficients were selected for different interfaces. The relation between strain rate, temperature, and geometry of pierced tube are discussed, and the selected friction relation with total power and energy consumption is presented. Experimental tests have been used for FEM validation and result analysis, and finally, the most effective conditions with lower total energy consumption are presented.

Abstract: The overwhelming majority of automotive part manufacturing processes successfully process hot dip galvanized sheet metal. However, there were reported situations were abrasive wear (galling), visible as narrow and long scratches, was observed on the surface of the formed parts. Investigations using a Slider On Sheet Tester (SOST) were performed in order to determine the conditions that lead to scratch forming on the galvanized sheet metal surface and to identify parameters that would guarantee a scratch free situation. The tests identified the tool roughness and the contact pressure as important parameters governing the coating wear phenomena. The tests proved that the coating resists relative high contact conditions in case of smooth tool surface, explaining why in the large majority of the industrial applications coated materials can be used without issues.

Abstract: The quality of a part produced using stamping process is dependent on many parameters such as the geometries of the tools and the initial blank, their surface state, the clamping force or contact pressure, the tools velocity and the lubrication. In order to discriminate different lubricants for stamping process in automotive industry under various conditions of clamping force and punch velocity, the Swift cup drawing test is used to evaluate the performance of three lubricants, i.e., two oil-based liquids and one dry film, applied on AA5182-O sheets. Moreover, finite element simulations are used to estimate friction coefficients of these lubricants.

Abstract: The reliability of the pertinent parameters set of Johnson-Cook constitutive model is highly linked with the friction condition at the tool-chip-workpiece interface. In the present work, a study on the influence of Coulomb’s friction coefficient on the observables such as forces, chip thickness and chip curvature by FE simulation of orthogonal cutting of Ti6Al4V alloy has been carried out. A FE model with an Arbitrary Lagrangian-Eulerian (ALE) approach is employed to simulate the cutting process for different cutting conditions. The simulated results, for a wide range of friction conditions, are analyzed and compared with experimental results. The analysis show that the Coulomb’s friction coefficient has a direct link with the observables. The paper reveals that for accurate prediction of observables an optimized value of the coefficient of friction in correlation with the parameters values of the constitutive model is imperative.

Abstract: This study is aimed at strengthening the working surfaces of the jewelry tool - scraper. This tool is used for fine cutting work. The object of research is a method of additional thermofrictional hardening of samples of jewelry tool - scrapers made of carbon steel tool grade U8A. In the course of work the complex of metallographic, mechanical and analytical researches of samples in an initial condition after hardening and low-temperature release which includes is carried out which includes:1) preparation of samples in the form of plates and their preliminary heat treatment;2) surface thermofrictional strengthening (STS);3) conducting metallographic analysis of samples; measuring the microhardness and depth of the layer with a changed cross-sectional structure of the samples after STS;4) analysis of the influence of STS on changes in the structure and properties of steel on the basis of the obtained results, as well as identification of the degree of its strengthening and the role of deformation.The methodology of experimental researches is presented. Photographs of samples and some equipment at different stages of the study are given. Data on the distribution of microhardness, photographs of microstructures in cross section of samples after additional strengthening are presented. The efficiency of strengthening of samples after use of additional processing is shown.

Abstract: Fused Deposition Modeling (FDM) is generally used to fabricate complex geometry structures and it has found applicability in various industries, such as the biomedical, aerospace, automotive, and building industries. As the mechanical properties and tribological behaviour of the 3D printing components are critical during operation, it is necessary to study the influence of process parameters and chemical composition on these specific characteristics. The paper aims to determine the coefficient of friction and wear behaviour of three different 3D-printed polylactic acid (PLA) materials in contact with a metallic counterbody. 3D printing process of the proposed PLA filaments was achieved by applying the FDM technique, using same deposition parameters for all three types of materials. Tribological characteristics of the 3D printed polymers were evaluated using pin-on-disk method and a comparison among the obtained frictional features of the specimens has been analyzed. The printed PLA samples show significant differences in sliding wear behaviour, the material loss of Co-reinforced PLA specimen is much more substantial than that obtained for PLA and tough PLA samples, due to the presence of metallic particles, hence for this specimen, an inferior wear resistance is attributed.