Papers by Keyword: Friction Coefficient

Abstract: The silica element in palm ash has the potential to be an alternative source of silica material to replace mineral silica, making it more environmentally friendly and reducing production costs. This research aims to utilize silica from palm ash waste as an abrasive material in brake friction composites. The silica from palm ash was isolated by a leaching process using 1 M HCl solution at a temperature of 70 °C for 90 minutes. Isolated silica was then characterized by X-ray fluorescence (XRF). The composition of silica was varied by volume fraction (0, 2, 4, and 6%). The mixing process of the powder mixture was conducted using a chopper mixer for 5 minutes, The powder mixture is then hot compressed using uniaxial hot pressing at a pressure of 47 MPa and a temperature of 165 °C for 15 minutes. Post-curing of the samples was carried out at a temperature of 165 °C for 10 hours. The samples were characterized by density, porosity, hardness R-scale, friction coefficient, and specific wear rate. The research results showed that the palm ash was successfully purified with a silica content of 27.3% to 57.2%. Increasing volume fraction of palm ash silica decreases in density and hardness, while porosity increases. The sample with 4% volume of palm ash silica exhibited better friction performance and a lower specific wear rate. Palm ash silica has the potential to replace the silica mineral for brake friction composites.

Abstract: Forging dies serve as essential tools in shaping workpieces during the forging process to achieve the desired shape and geometry. In hot forging processes, wear is a significant concern due to the high temperatures involved. The repeated contact between the die and the hot workpiece can lead to abrasive and adhesive wear, where material is gradually removed from the die surface. This wear directly impacts the overall production cost. It also affects the shape, dimensions, and surface quality of the final product. The present study focuses on a comprehensive wear analysis of a hot forging die. The influence of critical process variables, including billet temperature, die temperature, friction coefficient, and percentage deformation on die wear, was examined. Employing three-dimensional finite element analysis with DEFORM software, the study utilizes the Taguchi experimental method to systematically design parametric combinations. Analysis of Variance (ANOVA) is then applied to determine the parameters significantly influencing die wear. The results highlight that the billet temperature and percentage deformation are critical factors affecting die wear. The optimal process settings, which lead to minimal die wear, were validated through a confirmation experiment. Additionally, empirical models were developed to establish correlations between die wear and various forging parameters.

Abstract: Titanium and its alloys have a wide range of applications in various industries, including medicine. However, the low strength and high friction coefficient hinder their development in contact friction due to fretting fatigue. Among many factors, structure refinement, temperature and amplitude are the most responsible for fretting wear of structural materials. The purpose of the article is to investigate the effect of displacement amplitude, size of grain and test temperature on the fretting wear of the pure titanium in coarse-grained and ultrafine-grained states. It is shown that an increase in the test temperature for both structural states leads to a multiple increase in wear. Structural refinement of titanium to hundreds of nanometers helps to reduce wear at room and elevated temperatures.

Abstract: In the article, the interaction of the coefficient of friction for friction pairs operating under conditions of abrasive wear is considered, depending on a number of factors. Thus, the friction coefficient is one of the main indicators characterizing the performance of friction nodes. Analytical expressions obtained based on the calculation of the results of the conducted tests using mathematical statistical and mathematical methods allow to determine the coefficient of friction and allow the designer to effectively choose the material and oils before designing.

Abstract: The composition, structure, and tribological characteristics at 20 °C and 500 °C of coatings obtained by the vacuum arc deposition method using a MAX phase Ti₂AlC based cathode were investigated. These characteristics were compared to those of titanium nitride coating. It was shown that at a potential of -50 V, a composite coating of TiC and Ti₃AlC phases forms. Meanwhile, at a potential of -100 V, a composite consisting of TiC and α-Ti is formed. At 20 °C, the friction coefficient and specific wear rate of these coatings in contact with a ball made of ShKh15 steel under a load of 2 N are comparable to those of TiN coating. At 500 °C, the wear resistance of the composite (TiC+α-Ti) coating is twice as high as that of TiN coatings. There was no clear correlation between microhardness and the tribological characteristics of the coatings.

Abstract: Start-stop rolling contact fatigue tests of PEEK-PTFE hybrid radial bearings were carried out, to investigate the influence of start-stop heat cycle on the friction coefficient of PEEK-PTFE hybrid radial bearings. It was found in all start-stop tests, the temperature of sample side increased as the friction coefficient increased. RCF cycles to reach 50 °C of the third start-stop phase clearly increased from the second start-stop tests, and then kept constant value.

Abstract: In recent days there are many possibilities in develop solutions for industrial manufacturing process thanks to the emerging technology based in Industry 4.0, where one can measure and manage data from an industrial process in real time been able to know more information than ever before from the process. But still having challenges in complex process where monitoring data and give a solution is less intuitive, mostly due to a complex physical definition of the process and manufacturing car body parts in automotive is a clear example. In deep drawing process is common to have variations in the process parameters and they can carry out bad manufactured parts. The cycle time, the robust process and the complex physics in the process are the main problems to obtain feasible information from the process. In the following it is proposed a new methodology to have full knowledge of the process applying the so-called method Hybrid Twin.

Abstract: Bearing sleeve, as one of important parts of bearing structure, determine the bearing performance directly. In this paper, based on the ball joint structure, the tribological properties between Polyoxymethylene (POM) and 40Cr are studied with Ring-Block method. The effects of friction velocity and applied load on friction coefficient are tested and analysed, the analytical model in friction force, friction velocity and applied load are created, which will provide useful technical data to the application.

Abstract: Improving the tribological properties of Inconel 625 is of great significance for its application in slewing bearing and bearing parts of mechanical transmission system in nuclear power plants. In this study, the tribological properties of textured surface (GTSs) and smooth surface (SS-20) of Inconel 625 under different loads during dry sliding friction were researched. The results show that GTSs improves tribological properties of Inconel 625 obviously. The friction coefficient of GTSs is lower than that of SS-20. The grooves on GTSs play a role in capturing wear debris during the friction process, which improve the contact surface characteristics between counterpart ball and substrate, leading to the reduction in wear loss. When the load is 20 N, the Inconel 625 with textured surface has the best tribological performance. The excessive load will cause the big deformation of material and decrease the capacity of capturing wear debris of grooves, resulting in the accumulation of debris and the severe wear of wear track.

Abstract: In cold forging, the temperature difference between the workpiece and the tool is small and thus deformation analysis is rarely coupled with thermal analysis. However, the friction coefficient of zinc phosphate coating with metal soap has a large temperature dependence. Consideration of the effects of workpiece and tool temperature change on the friction coefficient is thus expected to improve the analytical accuracy of cold forging. Thermally coupled cold forging analysis requires thermal conductivity, specific heat, heat transfer coefficient between the workpiece and the tool, in addition to the temperature dependence of flow stress and friction coefficient. The heat transfer coefficient between workpieces coated with zinc phosphate with metal soap and tools is investigated in this paper. Cold backward extrusion was performed with a 50% reduction of area, and the temperature history in the punch was measured with a thermocouple. The forging speed was 1, 3, and 10 spm. FEM analysis was performed to simulate the experiment by considering the temperature dependence of flow stress and friction coefficient. The heat transfer coefficient was estimated at 20 kW/(m2•°C) by comparing the experimental result and calibration curves.