Papers by Keyword: Coefficient of Friction

Abstract: In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

Abstract: This work is devoted to studying the impact of carbon fibers with vermiculite and ultrafine polytetrafluoroethylene on the structure and properties of polytetrafluoroethylene. The mechanical and tribological characteristics of composites based on PTFE was compared depending on the content of carbon fibers. The yield strength and compressive strength improvement with increase of contents carbon fibers of the PTFE was showed. The method of X-ray analysis showed that with by introducing of complex fillers in the PTFE leads to the increasing the degree of crystallinity. PTFE-based composites reinforced complex fillers have shown a significant improvement in wear resistance compared to initial polymer. The study of the worn surface using scanning electron microscopy and IR spectroscopy to describe the tribological behavior of PTFE-based composites was carried out. Using IR spectroscopy, it was revealed that in the process of friction on the worn surface of PTFE-based composites products of tribo-oxidation are formed. It has been established that in the friction process of polymer composite materials, secondary structures are formed on the friction surface of the material, which protects the material from abrasion.

Abstract: The present study investigates the influence of carbon fibers of «Belum» brand on the performance properties of polymer composites based on ultrahigh-molecular weight polyethylene. It was established that the composite complex with the content of carbon fibers in the amount of 5 wt.% has the optimum complex of properties. The rate of mass wear is reduced by 3.3 times while maintaining the physical and mechanical characteristics at the level of the original polymer. It was established that the creep of PCM with the composition of UHMWPE + 5 wt.% Belum is 2 times less than the initial polymer. Also, the properties of the developed material based on UHMWPE were compared with unfilled and modified polytetrafluoroethylene (PTFE). It is shown that the creep of UHMWPE is less than the creep of PTFE by 12.5 times. The creep of the composite based on UHMWPE is less than the creep of the composite based on PTFE 13 times.

Abstract: This paper presents the results from the investigation of effect the carbon fibers with tungsten disulfide on the mechanical and tribological properties of PTFE. Is carried out a comparison of mechanical and tribological properties of polymer composites PTFE-based with carbon fibers and PTFE with complex filler (carbon fibers with tungsten disulfide). It is shown that at a content of 8 wt.% CF+1 wt.% WS₂ in PTFE, wear resistance increases significantly while maintaining the tensile strength, relative elongation at break and low coefficient of friction at the level of initial PTFE. The results of X-ray analysis and investigation of SEM supramolecular structure and friction surfaces of PTFE and polymer composites are presented. It is shown that the degree of crystallinity of polymer composites increases in comparison with the initial PTFE. The images of scanning electron microscope reveal that particles of tungsten disulfide concentrating on the friction surface is likely responsible to a reduction in the coefficient of friction and increase the wear resistance of PTFE-based polymer composites with complex fillers.

Abstract: This paper evaluates the tribological behavior of borided AISI 316L steel after being exposed to a secondary process to form a thin film of a solid lubricant. The process known as Short Annealing Process (SAP), allows creating a thin film of boric acid (H₃BO₃) on the surface of metallic materials previously exposed to boriding. The H₃BO₃ film acts like solid lubricant due to its lamellar crystalline structure. First samples of AISI 316L were exposed to boriding to temperatures of 875, 925 and 975 °C during 2, 4 and 6 h each temperature. Then, samples were heated to 750 °C during 5 min and cooled to room temperature at 60 % of Relative Humidity. The tribological behavior of the treated samples was evaluated by pin-on-disk test equipped with friction coefficient measurement system. Samples were characterized by Scanning Electron Microscopy, X-Ray Diffraction and Vickers microhardness test. The results showed an evident influence of the experimental parameters on the thickness of the boride layers and their mechanical properties. The layer ́s thickness was ranged from 10.51±0.71 to 51.57±5.12 μm. The hardness of the coatings was increased from 264 to 1685 HV. Finally, the Coefficient of Friction was diminished from values of 0.7 for the as-received material to 0.29 for the borided samples and to 0.06 for those after SAP, which indicates that the post-treatment SAP enhances the tribological properties of the biomedical steel.

Abstract: Tribotesting is necessary to understand the behaviour of the material under various operating lubrication conditions. This paper deals with the training of an artificial neural network (ANN) model with Bio-lubricant properties and machining conditions for prediction of surface roughness and coefficient of friction in Tribotesting by Tool chip Tribometer. Experimental results obtained from Tool chip tribometer for tested bio-lubricants are compared with those obtained by ANN prediction. A good agreement in results recommends that a well trained neural network is competent enough to predict the parameters in Tribotesting process.

Abstract: In the paper is presented the analysis of tool steel used for making a knife for a mill for grinding plants. The material used for the knife is about 1% carbon and is symbolized by RWL34. To improve the properties of the material, especially the knife cut, a thermal treatment were made and was measured hardness, wear resistance and microscopic analyzes of the metal. The paper presents the values of the mechanical properties on the initial sample, on the hardening sample and on the sample subjected to a hardening and tempering treatment, as well as the graphs related to them. The next step in finalizing the analysis of the grinder mill knife is to study the behavior in operation and the possible corrections that should be made.

Abstract: Copper-Titanium alloy was subjected to multi axial forging (MAF) at cryogenic temperature. Microstructure evolution was observed using optical microscope (OM). After 9 pass of MAF, grain size reduced to 2 µm. As number of MAF pass increases, hardness of the sample increased, due to strain hardening effect. Dry sliding wear test was performed on as-received and MAF processed samples using pin on disc wear machine. Tests were performed at 30 N and 40 N loads at 3 m/s constant speed and at 1000 m and 2000 m, sliding distance. Scanning Electron Microscope (SEM) and EDS was used to analyze the worn-out surface of the specimen. Wear mass loss of MAF processed sample reduced, with increased number of MAF passes. Frictional Coefficient (COF) reduced with increase in MAF passes and improved with increase in load, because of increase in contact area between sample and disc.

Abstract: Bronze, an industrially relevant material, is always at a constant need for improvement in its properties. It should possess superior hardness, wear resistance and high tensile properties. The microstructure of the composite was characterized by using an optical microscope. The mechanical and tribological tests were carried out on the developed composite samples as per ASTM standards. It was observed that the hardness of the developed bronze composite increases with an increase in the reinforcement addition. The tensile properties were found to improve with addition of reinforcement particles into bronze matrix but, there observed a decrease in the ductility of the composite as compared to the regular bronze alloy. The wear rate of the developed composite was found to be low as compared to that of the regular bronze alloy

Abstract: It was shown that under dry contact conditions, under normal load of to 2 MPa, all coatings demonstrated a significant increase in wear resistance compared to that of the substrate. However, among them, the Mo coating showed the highest wear resistance: ~20 times higher than that of the uncoated steel. That was caused not only by the Mo high microhardness and the lowest initial roughness, but also by the structure of this coating. Meanwhile, the Ti + SiC samples displayed the highest microhardness among investigated coatings. A correlation was established between the microhardness of the coating and the friction coefficient: the larger the microhardness of the coating, the higher is the coefficient of friction. An X-ray analysis of the coatings obtained by ESA on steel with compositions (Ti + Al + C), (Ti + AlN) and (Ti + SiC) revealed phases of titanium carbide, titanium nitride, intermetallic compound AlFe₃, and small amounts of aluminum nitride, silicon dioxide and titanium dioxide. This could explain the high microhardness (from 6.8 up to 13.8 GPa) of the obtained coatings.