Papers by Keyword: Coefficient of Friction

Abstract: This material presents the research of AlTiN coating properties, deposited at low temperature by cathodic arc physical vapor deposition technology. As well as evolutionary development of coating when is added Cr element to it, or creating multilayer structure adding a CrN as internal layer on it. Each of these steps results in increasing with almost 80% of coating resistance to plastic deformation and a huge reduction in the wear rate of the resulting coating.

Abstract: The peeling efficiency is approximately 80% when processing buckwheat using a peeling machine that relies on friction and shear forces. In order to improve this efficiency, the design of this type of machine needs to be modified to better suit the unique characteristics of buckwheat grains. Thus, a mathematical model of the buckwheat peeling process has been developed using a peeling device with a new deck design. The model is based on a theoretical understanding of the process and takes into account the effects of friction and elastic deformation. The model accurately predicts the outcomes of the peeling process and the forces acting on the grain. In the deck compression design, forces are generated that act periodically at right angles to the grain direction, within the limits of material flexibility. Frictional forces, directly related to normal forces, are generated by the movement of the rotating roller and are determined by the elastic forces generated by the grain. Under the influence of these alternating forces, the grain is peeled in the gap between the rotating roller and the compressing deck. If the force applied to the grain is not greater than the elastic limit, there is no risk of kernel crushed. Based on these forces, a mathematical model has been developed to describe the process of grain hulling in the device. This model takes into account the physical properties of the grain and the design parameters of the device to predict the optimal conditions for hulling machine.Using the derived equation of motion, we can conclude that the larger the diameter of the rotating roller in the hulling device, the more accurate the simulation will be and the better the conditions will be for capturing grains within the working gap. This equation also allows us to calculate the productivity and power requirements of the hulling machine.

Abstract: Various steels with suitable properties can be used as barrel steel. Most of the steels intended for the production of barrels are low or medium alloy steels. Barrel steels are significantly stressed by high pressures and temperatures during firing. During the shot, various forms of wear occur in the barrels, mostly abrasive, adhesive, and erosive wear. One of the most widely used steels for greater traction, from which barrels are made, is 34CrNiMo6. This steel is normally used for larger calibers, such as artillery, or for more stressed small-caliber weapons. This steel and its derivatives are the most widely used steels for the production of highly stressed barrels. We subjected the 34CrNiMo6 steel to tribological tests. In this article, we evaluated the coefficient of friction between 34CrNiMo6 steel and a G40 bearing ball. All measurements were performed on a UMT TriboLab universal tribo-meter (TA Instruments, New Castle, Delaware, USA) in dry conditions. The main goal of the experiments was to analyze the friction properties and wear of steel for the production of stressed 34CrNiMo6 barrels in contact with a G40 bearing ball with a diameter of 6.35 mm. In this evaluation of measurements, the authors of the article focused mainly on the influence of the peripheral speed on the change in wear and the coefficient of friction for two types of surfaces.

Abstract: The article deals with the creation of a mathematical model that can be applied in the testing of various materials. These are testing cases where the measurement and subsequent evaluation of the value of the coefficient of friction in various tribological measurements is considered. The mathematical model considers the static and dynamic coefficient of friction. It started with the creation of a simpler mathematical model, which was subsequently modified to a more sophisticated one, considering the real situation, which is closer to the real case. With the mathematical model created in this way, various simulations were performed and evaluated for cases of (constant) permanent load, but also repetitive (periodic) load. In another case, an improvement of the mathematical model was carried out, which represented the addition of an option that allows considering the degradation of the investigated material. Degradation of the material represents only part of the surface of the material, which during testing is exposed to contact with another material with a higher hardness than the tested material.

Abstract: Advanced high-strength steels (AHSS) have their current applications directed mainly to the automotive industry, where they use modern metallurgical techniques to develop microstructures with retained austenite, which leads to an improvement in the combination of strength and ductility through transformation-induced-plasticity (TRIP). The main priority of the research work will be a detailed examination and optimization of the heat treatment parameters of medium-manganese steels, specifically by the Quenching and Partitioning (Q&P) method and the expansion of experimental data related to the increase of wear resistance of these materials. The issue of the application of medium-manganese high-strength AHSS steels in the field of tribology is currently very relevant. Mid-manganese AHSS steels, which show significant wear resistance, have the potential to replace traditional Hadfield Mn steels that contain 10-14 wt. % manganese. With the help of specifically designed heating and cooling cycles, it is possible to improve their wear resistance through metastable retained austenite, which has significant potential in demanding industrial environments. This scientific study examines the possibilities of increasing the economic efficiency of the production and use of AHSS steels in various industrial areas and at the same time reducing costs compared to expensive wear-resistant steels. A key aspect of the research is the experimental evaluation of heat treatment optimization to maximize resistance to mechanical damage and extend the life of materials in various applications.

Abstract: In this paper, the steels used in MN knife mills, which are used for plastic recycling, are investigated. 90MnCrV8 steel is commonly used in these mills, which will be replaced by X153CrMoV12 steel. The main goal of the presented contribution is to perform tribological tests and verify the wear rate of both steels experimentally with subsequent practical verification in the knife mill MN. Partial results relate to the analysis of hardness, roughness, and overall wear mechanism. A hardened steel ball of material G40 with a diameter of 4.76 mm was used as the contact material. The steel ball performed reciprocal linear motion on the surface of the experimental materials at room temperature and without the use of lubrication. The measurements were carried out in three-time intervals of 20, 30 and 40 min. The experimental material X153CrMoV12 can fully replace the material 90MnCrV8 in processes where its degradation occurs due to the friction mechanism. The material X153CrMoV12 showed significantly better results in all the values ​​we measured. It can be expected that the knife in the MN knife mill made of X153CrMoV12 steel will last several times longer in the working environment, which was also proven by practical verification in production.

Abstract: Self-lubricating spherical plain bearings are widely used in industry due to their high load capacity, excellent self-lubrication performance and superior impact resistance. The composite made of PTFE/Nomex fabrics and phenolic resin is selected as self-lubricating liners because of the great tribological properties. In this study, the effect of stress during press-fitting process on the tribological behavior of the composite liners in bearings was investigated. Five levels of stresses within a range of 0MPa~680MPa were firstly applied by upsetting process, and then ball-on-disk friction tests were conducted to evaluate the tribological properties. The variation of measured friction coefficient over testing time under different stresses was measured, and the microscopic surface morphology before and after friction tests was observed. Results show that the stress generated during the press-fitting process increases the friction coefficient, while decreases the fluctuation of friction coefficient. In addition, the fluctuation amplitude of the friction coefficients introduced by stress reaches 5.6%.

Abstract: Ti₄₈Al₄₈Cr₂Nb₂ intermetallic alloy was studied for its tribological properties. The as-received TiAl alloy was prepared by spark plasma sintering (SPS) at 1200 °C for 5 and 7 min using 50 and 100 °C/min heating rates. Wear tests were done on the sintered TiAl under 10 N at room temperature in air. Results showed that an increase in relative density and superior microhardness led to a reduced material loss in the sample sintered for 7.5 min using a 100 °C/min heating rate. Scanning electron microscopy (SEM) images of the worn surface showed the wear widths and wear marks on the surface of TiAl alloy. The wear track width indicated the degree of wear, and the samples sintered for 7.5 min using a 100 °C/min heating rate showed improvement in wear resistance.

Abstract: Tribofinishing is a mechanical-chemical process that utilizes low-frequency vibrations in the presence of abrasives and chemical additives. This process is primarily dependent on frequency and amplitude, which generally leads to improvements in characteristics, mechanical properties, physical attributes, and metallography of the treated surfaces. This document examines the influence of abrasives, specifically bakelites used as unguided cutting tools, on the wear resistance of AISI 1010 carbon steel. It takes into account the variation of influential parameters, namely frequency, amplitude, and treatment duration. The use of Minitab version 16 software enabled us to statistically analyze and interpret the obtained results, both numerically and graphically. This analysis also allowed us to determine the order and degree of influence of the factors on the response. The obtained results are highly interesting. The coefficient of friction decreased significantly with an increase in the treatment time, up to 90 minutes, while maintaining a frequency of up to 90 Hz and a maximum amplitude of 5 mm.

Abstract: The Chemical Mechanical Planarization (CMP) process (polishing and substrate cleaning) results in defects that can be classified as mechanical (i.e., scratching), chemical (i.e., corrosion), or physiochemical (i.e., adsorbed contaminants) according to the mechanism of formation. This work will focus on the rationale design of p-CMP cleaning systems for emerging materials (silicon carbide (SiC)) that activate the cleaning chemistry via external stimuli such as megasonic energy. More specifically, using megasonic energy in the presence of supramolecular assemblies such as micelles and vesicles was employed for a “soft” (low shear force) defect removal process. Results indicate a correlation between the structure of the “soft” cleaning additives and induced megasonic energy on overall simulated defect removal. It was determined that effective particle removal was a second-order kinetic process with a concentration dependency (i.e. above and below the critical micelle concentration (CMC)) emerging as a key driver for the defect removal rate. Although, one apparent drawback is the generation of post-cleaning carbon residue due to the adsorption of the supramolecular structures to the SiC substrate.