Papers by Keyword: Tribology

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: This study evaluates the effect of the vibration assisted ball burnishing method on surface integrity of maraging C300 steel surfaces printed by additive manufacturing with Selective Laser Melting (SLM) technology. The analysis contemplates variations in tool preloads and applied force. The analyzed C300 material is based on the as-built (AM), machined (M) and vibration assisted ball burnishing (VABB) states. Surface roughness was evaluated to assess topographical conditions both before and after the burnishing process. Microstructure and mechanical deformation were analyzed by Scanning Electron Microscopy (SEM) technique to examine the stresses generated by compression effect. It was found that forces in the range of 180 to 220 N reduce the roughness Sa value by up to 59% with respect to the M finish and up to 97% with respect to the AM finish. Furthermore, burnishing parameters significantly vary the final quality of the surfaces depending on the initial state of the surface and the conditions of the material.

Abstract: Technological advancements and changing global needs drive deposition techniques, widely used for altering surface properties of components. The crosswinds from global technological advancements in the mobility and power sectors have piqued the interest in sustainable renewable energy tapping devices. Thin aluminium oxide (Al2O3) films are highly valued for various applications in the manufacturing industry, such as cutting tool coatings, optics, energy, and microelectronics. A novel and facile approach has been adopted in the present work to fabricate an oxide-based thin film on a BK7 glass substrate. The aluminium oxide film is deposited by reactive radio frequency (RF) magnetron sputtering by impinging adequate argon to oxygen ratio in a high vacuum environment. Furthermore, Al2O3 is deposited by an alumina target with the same deposition technique, and the results were compared. A digital thickness monitor (DTM) is used to assess the thickness of the deposited film for both processes. The films were first characterized by X-ray diffraction and then analysed by other characterization methods, including Scanning Electron Microscopy, Atomic Force Microscopy, Tribometer and Nanoindentation, and UV-visible spectroscopy. The results indicated that Al2O3 deposited by reactive RF magnetron sputtering performed better in terms of surface morphology, UV-absorbance, nanohardness, and wear resistance and is therefore, more reliable and sustainable when compared with non-reactive RF magnetron sputtering.

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: In industrial settings, the use of frictional noise to improve wear monitoring is highly promising. It enables the identification of changes in friction and wear conditions, the assessment of different phases of wear, and the examination of the impact of wear on machine performance. By analysing acoustic signatures, it is conceivable to continuously monitor the wear characteristics and surface conditions. This helps in predicting wear and detecting aberrant wear regimes in real-time. The data demonstrate that in dry conditions, the aluminum disc has higher coefficients of friction relative to cast iron and mild steel, likely due to the absence of graphite flakes in aluminum. Under lubricated conditions, a layer of lube significantly decreases the coefficient of friction, with no apparent deviations across the materials, demonstrating that complete lubrication avoids direct metal contact. In lubrication-starved applications, oily depictions nevertheless help minimize friction, though less efficiently than complete lubrication. In dry conditions, frictional sound levels for mild steel are higher due to direct surface hits, while lubrication reduces noise by eliminating metal-on-metal contact. As a result, monitoring noise levels is a helpful indicator of lubrication difficulties, aiding in maintenance and repairs.

Abstract: In the present study, the production of aluminum foam was carried out using the powder metallurgy technique, specifically employing the sintering – dissolution process (SDP). The SDP method, which constitutes a sequential series of four well-defined steps, was employed to achieve the desired foam structure and properties. These steps involved carefully controlling the parameters and conditions throughout the process to ensure successful foam formation. Aluminum powder with a particle size of (1.99 μm) as a raw material was mixed with NaCl with a particle size between (150-425μm) used as a space holder at different ratio (25, 35, 45and 55 wt. %.). Obtained Al-foam with 45% NaCl demonstrated the most optimal structure. Some additives (Mg) added to the powder mixture, it was found that the mechanical and the tribological properties of the produced foam were improved. The introduction of metal’s micro-particles led to a notable enhancement in both compressive stress and micro-hardness, the compressive stress increased substantially from 15.2 MPa to 56.5 MPa for the foam containing 45% NaCl and 45% NaCl + Add., respectively. While the micro-hardness exhibited a noteworthy increase from 51.5 HV to 62.1 HV. Results also showed important reduction in the wear rate from (0.00000155 g/cm) to (0.00000079 g/cm) for the Al-samples of (45% NaCl) and (45% NaCl+ Additive) respectively, the lowest value recorded for the coefficient of friction was (0.15) for (Al-Foam with 45% NaCl + Additive) compare to (0.19) and (0.21) for (Al-foam with 45% NaCl) and (pure Al) respectively at 10 N applied load and 800 rpm.

Abstract: Tungsten (W) reinforced diamond-like carbon (DLC) nanocomposite thin films were deposited on silicon substrates by magnetron sputtering in a CH₄/Ar discharge. The W content of the films was varied by varying the W target power (20, 40, 60, 80, and 100 W). The evolution of the W-DLC nanocomposites was studied by high-resolution transmission electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, 3D optical profilometry and Raman spectroscopy. Increasing the W target power resulted in an almost liner increase in the W content, reduced the hardness and the sp³/sp² ratio in the films, while it increased the surface roughness and promoted formation of WC nanoparticles. Tribological properties were studied by conducting sliding reciprocating testing. Wear tracks were analyzed with Raman spectroscopy and 3D optical profilometry. Increasing the W content in the films (increasing target power) resulted in a reduction of both, the friction coefficient and wear rate. The film deposited at 80 W target power (~8 at. % W) exhibited the lowest friction coefficient (0.15) and wear rate (6x10^-7 mm³N^-1m^-1). The observed low friction and wear rate were attributed to the particular nanocomposite structure of the films involving a fine distribution of WC nanoparticles surrounded by a sp² dominant carbon network. The present W-DLC nanocomposite films offer a highly desirable combination of low friction and low wear rate.

Abstract: The aim of this study is predict tool wear in the fine-blanking process using a tribometer tester with ASTM G99-17 standard. Then, the result of wear volume and tool life were confirmed with finite element simulation and experiment. The punch material used in fine blanking process was selected to be hight speed steel JIS.SKH51 with surface coating thickness 4 µm of TiCN, the work piece material was used as hot-rolled steel JIS.SPHD P/O, with a thickness of 8 mm. The experimented and simulated results were found that the pressure, and sliding velocity were increase in term of linear curve with slope K = 2.09x10^-6 and K = 2.07x10^-6 ,respectively, and the hardness of material was increase in term of power at 1.983 and slope of K = 2.14 x10^-6. These three factors were effect to the wear volume and tool life, simultaneously, the summation of three factors will average as K = 2.10 x10^-6. From comparison of the applied wear equation model with tribology tester the simulated and experimented results were similarly equal with 0.05 by significance at 95% reliability confident. The resulted were precisely confirmed according to the previous research.

Abstract: This project aims to investigate and compare the tribological properties of copper-based alloys produced by the die-casting method. Tribological properties, such as wear resistance and frictional behavior, play a crucial role in determining the suitability of materials for various engineering applications. Copper has many useful properties, such as high thermal and electrical conductivity, corrosion resistance, and antibacterial properties. It is used in a variety of industries, including electrical and electronics, construction, transportation, and healthcare. The study involves conducting wear tests on various copper-based alloys using a linear reciprocating tribometer. These tests were performed under different loading conditions (5N, 10N, and 15N), varied time durations (5 min, 15 min, and 30 min), Wear rates and morphologies of the specimens were determined by SEM. The effect of composition, microstructure, and hardness on the wear behavior of copper-based alloys has been carried out. The correlation between hardness and wear resistance was analyzed. The findings of this study could provide valuable information for the selection and optimization of copper-based alloys for trigolocal applications. The copper alloys has been characterized by an optical microscope, scanning electron microscope, and Energy dispersive X-ray analysis was used to analyze the wear surfaces.