Papers by Keyword: Coefficient of Friction

Abstract: Aluminium is a popular choice for structural applications because of its low weight, large specific strength, excellent heat transmission capabilities, and mostly due to its strength-to-weight ratio being high. Any desired shape or form of aluminium may be manufactured using permanent mould casting operation. However, porosity arises as a typical defect where pores cause an increase in surface roughness, which in turn increases wear and friction of the surface and reduces material strength. A variety of porous characteristics on the surface are formed in the casting process by regulating casting pouring parameters like the temperature and velocity of pouring. The presented research establishes a better knowledge of the relationship between the wear and frictional behaviour with temperature and velocity of pouring. In this context, the casting process has been done by creating a three-dimensional model by Ansys Fluent. Observations reveal that the frictional and wear behaviour of pure aluminium increases with the temperature of pouring and reduces with the velocity of pouring.

Abstract: Coefficient of friction (cof) is an important variable when dealing with con-tact between mechanical parts. It depends on various tribological variables and the value can be determined only by experiments. Cof correlates with the wear of material and this is a severe problem in biomedical engineering. This research numerically studied the effects of cof between talar and bear-ing in the total ankle replacement (TAR) implants. The aim is to evaluate the contact situations affected by cof. The TAR models consist of cobalt chrome (CoCr) alloy and ultra high molecular weight polyethylene (UHMWPE) bio-materials. Five cof values of the dry, lubricated and frictionless TAR me-chanical contacts under ankle gait load were examined. The models use a fixed 1 mm element size for UHMWPE bearing component and four element sizes for the talar component, range from 1 mm to 0.4 mm. Results show that, 1) higher cof induces higher contact pressure, 2) contact stress is not af-fected by cof, 3) proper talar element size is 0.4 mm and 4) frictionless model can be used for the TAR contact mechanic computation. Frictionless model calculates equal contact stress and lower contact pressures with an error of 2.68 % compared to the smooth model.

Abstract: This paper mainly studied the coefficient of friction (COF), wear performance and frictional vibration performance of polyphenyl ester modified polytetrafluoroethylene under dry friction and water lubrication friction conditions. Polyphenyl ester modified polytetrafluoroethylene composites were prepared by blending 20% polyphenyl ester with polytetrafluoroethylene, and the COF, wear performance and frictional vibration properties of such composites were tested. The results showed that: (1) Under dry friction conditions, as the specific pressure between the friction pairs increased, the volume of wear and the thickness of the wear increased, the COF decreased at first and then increased, the frictional vibration increased and stabilized after the pressure of 0.5 MPa. (2) Under water-lubricated friction conditions, as the specific pressure between the friction pairs increased, the COF increased, and the frictional vibration increased and stabilized after the pressure of 0.5 MPa; (3) The wear resistance of polyphenyl ester modified polytetrafluoroethylene composite under water-lubricated friction was better than that under dry friction, the COF was less than that under dry friction, and the total level of frictional vibration was slightly lower than that under dry friction. Therefore, in order to reduce frictional vibration and improve service life, the working pressure should be reduced, and the lubrication performance between the friction surfaces should be improved. Under water-lubricated friction, the maximum working pressure of the polyphenyl ester modified polytetrafluoroethylene composite system is recommended not to exceed 0.8 MPa.

Abstract: The awareness on sustainability of the environment among the researchers leads to the exploration of natural fiber composite materials. Hybridization of synthetic fiber and natural fiber is one of the potential strategies to enhance the mechanical properties as well as the degradability of such composite materials. However, less information concerning the optimization of tribological properties of this hybrid composite is available in literature. The aim of this study is to propose a statistical model to predict and optimize wear and coefficient of friction of kenaf/carbon reinforced epoxy composite. The value of parameters; load and sliding velocity ranges from 10 to 30 N and 20.9 to 52.3 m/s, respectively, are used to assess wear and coefficient of friction (COF) of different stacking sequences using the Analysis of Variance (ANOVA). The tribological test was conducted using a pin-on-disc tribometer. Multifactorial design analysis was employed to optimize the test control variables. It was found that, the optimized factors that affects the coefficient of friction and wear is at load 30 N and sliding velocity of 52.36 m/s. The proposed statistical models for wear and COF have 99.5% and 97.6% reliability, respectively. The generated equation models are bounded within the wear test control factors and ranges. The outcome from this study will be very useful for main parameter prediction for an optimized wear and COF.

Abstract: The possibility of introduction of antifriction and wear-resistant modifying agents into the matrix of a composite nickel-phosphorus coating to obtain effective composite coatings, is considered. The analysis of the possible influence of modifying additives in the form of ultrafine powders on the tribological properties of the developed coatings, is carried out.

Abstract: The article discusses the effect of epilamated coatings during mandrelling. The picture of the change in contact stresses in the DEFORM-3D system is presented. It was established that a decrease in the coefficient of friction from 0.9 to 0.6 leads to a decrease in the number of foci and areas of contact stresses, as well as temperature analysis showed that a decrease in the friction forces reduces heat transfer in the cutting zone by about 40 ° C.

Abstract: In this paper, the specific wear rate (SWR) and the coefficient of friction (CoF) of steel embedded glass/epoxy hybrid composites were examined and compared. Experiments were carried on the pin-on-disc machine on different types of composite materials like plain composite (steel volume 0%) and hybrid composites (steel volume 5% and 10%) pressed against a rotating steel disc (EN 31). Composites were fabricated using the hand-lay-up method. The volume percentage of steel pin/pipe varied from 0 to 10% and glass fiber from 50 to 60%, while the percentage of epoxy was kept 40% stable. The experiments were carried out on a group of samples for duration 20 minutes for different loads of 70N, 80N, 90N, 100N, and 110N with a varying sliding distance of 1000 m, 1250 m, 1500 m, 1750 m, and 2000 m. The results show that the SWR and CoF vary with different load and sliding distance. In general, CoF rises for some time of rubbing, and then it remains constant for the rest of the testing time. The results obtained show that the SWR and CoF increase with increasing sliding distance and load for all the composites. However, SWR and CoF decrease as an increase in the volume percentage of steel. An SWR of hybrid composite is observed to be reduced by 28.02% and 45.98% with an increasing percentage of steel by 5% and 10% respectively. CoF of hybrid composite is observed to be reduced by 14.11% and 24.02% with an increasing percentage of steel by 5% and 10% respectively. At last, the worn surfaces of the hybrid composites were studied through a Scanning Electron Microscope (SEM). Shallow and fine grooves appeared on the worn surfaces of hybrid composites at low loads and cracks were found in large quantities at high load which increased weight loss.

Abstract: The influence of oxygen flow rate is examined on structural, optical and tribological properties of molybdenum oxide films deposited by reactive magnetron sputtering. The films were characterized by X-ray diffraction, scanning electron microscope (SEM), and contact angle measurement system. The optical properties of the films were measured by UV-Vis-NIR spectrophotometer and transmittance of ∼73% in the visible region of the spectrum was achieved. The band gap increases with increases in oxygen gas flow rate. AFM figure illustrates that the roughness of surface increases as oxygen flow rate increases. As oxygen increases wear rate and COF decreases while at the 18 sccm the lowest wear rate found.

Abstract: We have shown how different micellar (SDBS) vs. polyelectrolytic (PSSA) supramolecular assemblies in post-CMP cleaning solutions differ in their tribological performance when used in a novel PVA scrubber for 300-mm silicon dioxide wafer cleaning. Significant differences in real-time shear force and coefficient of friction data from the wafer-solution-brush interface (both in time domain as well as frequency domain) have been attributed to differences in each supramolecule’s chemical functionality and structure, which in turn, have been correlated to wafer-level defects. The work has underscored the importance of measuring the tribological attributes of post-CMP cleaning processes in an effort to improve cleaning performance.

Abstract: The present work aims at the study of the dry disc pion contact and the complex phenomenon of the wear as well as the sliding friction of our sample elaborated by a hot isotactic compression and the pion. This study consists in determining the coefficient of friction and the influence of the tribological parameters on this phenomenon as well as determining the loss of mass and the wear rate of study sample. In order to enhance the assurance of the validity of the results of tribological study of Ni-Cr-B-Si-C-W alloy in laboratories and compare that to the tribological conditions in reality and industries. This work presents the results of the new approach to compares the wear behavior of the sample between a theoretical study (tribometer)and another in service (a test bench) that reproduces approximately the same conditions as the tribometer (normal load, sliding speed and distance traveled) by measuring the loss of mass and wear rate.