Prediction of Wear Rate Dispersion in Mixed Lubrication

2005 ◽  
Author(s):  
F. Robbe-Valloire ◽  
R. Progri ◽  
B. Paffoni ◽  
R. Gras
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Boundary Lubrication ◽  
Mixed Lubrication ◽  
Tribological Behaviour ◽  
Low Friction ◽  
Local Boundary ◽  
Physico Chemical ◽  
Lubricant Films ◽  
Second Category

Mixed lubrication is usually related to the partition of contacts, and these latter may be divided into two categories. The first includes all asperities working in thin lubricated film (physico-chemical film) conditions. This situation corresponds to local boundary lubrication and is characterised by a local friction coefficient around 0.1. The second category contains all other asperity types. Due to the existence of a thick lubricant films asperities belonging to the second category exhibit a low friction coefficient. The global tribological behaviour for a given contact, however, is function of both categories, since it involves asperities from both categories.

A Mixed-TEHL Analysis of Cam-Roller Contacts Considering Roller Slip: On the Influence of Roller-Pin Contact Friction

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Shivam S. Alakhramsing ◽  
Matthijn B. de Rooij ◽  
Aydar Akchurin ◽  
Dirk J. Schipper ◽  
Mark van Drogen
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Sudden Increase ◽  
Low Friction ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Film Lubrication

In this work, a mixed lubrication model, applicable to cam-roller contacts, is presented. The model takes into account non-Newtonian, thermal effects, and variable roller angular velocity. Mixed lubrication is analyzed using the load sharing concept, using measured surface roughness. Using the model, a quasi-static analysis for a heavily loaded cam-roller follower contact is carried out. The results show that when the lubrication conditions in the roller-pin contact are satisfactory, i.e., low friction levels, then the nearly “pure rolling” condition at the cam-roller contact is maintained and lubrication performance is also satisfactory. Moreover, non-Newtonian and thermal effects are then negligible. Furthermore, the influence of roller-pin friction coefficient on the overall tribological behavior of the cam-roller contact is investigated. In this part, a parametric study is carried out in which the friction coefficient in the roller-pin contact is varied from values corresponding to full film lubrication to values corresponding to boundary lubrication. Main findings are that at increasing friction levels in the roller-pin contact, there is a sudden increase in the slide-to-roll ratio (SRR) in the cam-roller contact. The value of the roller-pin friction coefficient at which this sudden increase in SRR is noticed depends on the contact force, the non-Newtonian characteristics, and viscosity–pressure dependence. For roller-pin friction coefficient values higher than this critical value, inclusion of non-Newtonian and thermal effects becomes highly important. Furthermore, after this critical level of roller-pin friction, the lubrication regime rapidly shifts from full film to mixed lubrication. Based on the findings in this work, the importance of ensuring adequate lubrication in the roller-pin contact is highlighted as this appears to be the critical contact in the cam-follower unit.

Tribological behaviour of graphene oxide sheets as lubricating additives in bio-oil

2018 ◽  
Vol 70 (8) ◽  
pp. 1396-1401 ◽  
Author(s):  
Daoyi Wu ◽  
Yufu Xu ◽  
Lulu Yao ◽  
Tao You ◽  
Xianguo Hu
Keyword(s):  
Graphene Oxide ◽  
Friction Coefficient ◽  
Wear Loss ◽  
Tribological Behaviour ◽  
Low Friction ◽  
Content Type ◽  
Base Oil ◽  
Lubricating Film ◽  
Bio Oil ◽  
Practical Implications

Purpose This paper aims to study the upgradation of the lubricating performance of the renewable base oil , and to study the tribological behavior of graphene oxide (GO) sheets used as lubricating additives in bio-oil for iron/steel contact. Design/methodology/approach A multifunctional end-face tribometer was used to characterize the friction coefficient and wear loss of the tribosystem under different lubricants. Findings The experimental results show that GO sheets with small size benefit lubricating effects and the optimal concentration of GO sheets in bio-oil is 0.4-0.6 per cent, which can form a complete lubricating film on the frictional interfaces and obtain a low friction coefficient and wear loss. Higher concentration of GO sheets can result in a significant aggregation of the sheets, reducing the content of the lubricating components in the bio-oil, which results in the increase in friction and wear; at this stage, the main wear pattern was ascribed to adhesive wear. Practical implications These results show a promising prospect of improving the tribological performance of renewable base oil with the introduction of GO sheets as additives. Originality/value No literature has covered the tribological behaviour of GO sheets in bio-oil. This study contributes to accelerating the application of bio-oil.

scholarly journals Theoretical Analysis of the Influence of Asperity’s Dimensions Affected by a Scale Factor on the Mixed Lubrication between Parallel Surfaces

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
F. Robbe-Valloire ◽  
R. Progri ◽  
T. Da Silva Botelho
Keyword(s):  
Theoretical Analysis ◽  
Boundary Lubrication ◽  
Scaling Factor ◽  
Mixed Lubrication ◽  
Local Boundary ◽  
Mixed Regime ◽  
Parallel Surfaces ◽  
Speed Parameter ◽  
Theoretical Results ◽  
Good Agreement

Mixed lubrication between a given pair of surfaces is directly related to the parameter ηu/p. Any change in microgeometry produces a shift in the transition between the boundary and lubricated regimes. Using an asperity based model including five families of asperities (2 for full fluid lubrication and 3 for local boundary lubrication), we simulate mixed lubricated behavior. Our theoretical results confirm the relation between the mixed regime and the ηu/p parameter. All homothetic changes in microgeometry affecting the vertical and horizontal directions by the same scaling factor Sc induce a shift in the transition. The most interesting result is that this shift is exactly the same if speed u is scaled by 1/Sc with the initial microgeometry. This particular behavior, which is in good agreement with experimental results proposed in the literature, comes from the fact that behavior at each asperity can be written using dimensionless parameters. Most of these parameters are independent to any scaling of the microgeometry and only one, the speed parameter, needs to be artificially scaled in order to remain unchanged by the modification of the microgeometry.

Studies Concerning Variation of the Friction Coefficient in Case of Polymeric Composite Materials Reinforced with Carbon Fibers

2013 ◽  
Vol 371 ◽  
pp. 343-347
Author(s):  
Radu Caliman
Keyword(s):  
Friction Coefficient ◽  
Carbon Fiber ◽  
Wear Rate ◽  
Carbon Fibers ◽  
Polymeric Composite ◽  
Tribological Behaviour ◽  
Fiber Concentration ◽  
Rotating Speed ◽  
Mechanical And Tribological Properties ◽  
Pin On Disc

Thanks to their low density, good thermal, mechanical and tribological properties, composites made of carbon fibres and epoxy are particularly adapted to the manufacturing of aircraft brake discs. Several methods have been developed to improve their performance. The purpose of the present study was to evaluate the influence of different epoxy/carbon fibers ratio enhance modification on the friction behaviour and to identify the related mechanisms. Nine different hybrid matrix composites were elaborated. These samples were submitted to structural and mechanical characterization, then to friction and wear tests using a pin-on-disc tribometer, at ambient temperature and humidity, constant rotating speed, varying the loading pressure. As the content of carbon fiber increased, the wear rate of the composites trended to increase. Under the friction condition of high applied load, the friction coefficient inclined to decrease while wear rate increased. When slided under a relatively high load of 12 daN, the wear resistance behaved was better as the content of carbon fiber increased. The aim of the present study was to understand the friction mechanisms of these composites, dealing with the effects of varying the carbon fiber concentration within the matrix, not only on the tribological behaviour but also on the superficial mechanical properties.

scholarly journals MICROSTRUCTURE AND WEAR RESISTANCE OF A COMPOSITE Gr/Al2O3/Al PRODUCED BY RECIPROCATING EXTRUSION

2012 ◽  
Vol 05 ◽  
pp. 646-653
Author(s):  
Z. M. Zhang ◽  
G. P. Zhu ◽  
C. J. Xu ◽  
B. Hu
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Extrusion Process ◽  
Pure Aluminium ◽  
Low Friction ◽  
Graphite Particles ◽  
Al Composite ◽  
Alumina Particles ◽  
The Matrix ◽  
Reciprocating Extrusion

A reciprocating extrusion process was used to produce graphite and alumina reinforced pure aluminium composite. The graphite particles (0~5vol%), alumina particles (10 vol%) and pure aluminium particles (balanced) were dehydrated separately at 70°C in vacuum for 3 hours, and then mixed together. A round billet with 50 mm in diameter was prepared by hot pressing at 350°C with the mixed particles and then extruded to a fully-consolidated goblet-like sample at 480°C and 430MPa by reciprocating extrusion. The results showed that all reinforced particles were refined and uniformly distributed in the matrix by reciprocation extrusion severe plastic deformation. The presence of graphite particles caused the reduction in the friction coefficient and wear rate of the Gr / Al 2 O 3/ Al composite. Compared with the composite prepared only by alumina particles (10 vol%) and pure aluminium particles, the friction coefficient and wear rate of the Gr / Al 2 O 3/ Al composite, which contains 5vol% graphite and 10vol% alumina particles, decreased 45.3% and 33.5%, respectively, and thereafter it displays an excellent combination of low friction coefficient (0.37) and wear rate (2.2×10-7mm3/(N.m)), and appears to be more promising.

Newly synthesized Ionic Liquids as potent lubricants and additives to existing lubricant oils

2021 ◽  
pp. 135065012110601
Author(s):  
Thomas Myrdek ◽  
Michael Stapels ◽  
Werner Kunz
Keyword(s):  
Ionic Liquids ◽  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Alkyl Ether ◽  
Tribological Behaviour ◽  
Low Friction ◽  
Low Performance ◽  
Long Chain ◽  
Anionic Part

Ionic Liquids are promising candidates for next generation green lubricants. We have synthesized 39 Tetraalkylammonium Alkyl Ether Carboxylate Ionic Liquids and tested them for their lubricant capabilities. We measured friction coefficient to assess the transition from the boundary to the hydrodynamic lubrication, the hydrodynamic area and the minimum friction value. Some Ionic Liquids are capable of forming a hydrodynamic layer fully separating two specimens. Compounds with short C-chain of the cationic part show poor tribological behaviour. Similarly, increasing the PO-degree of the anionic part lowers the lubrication power. An increase of the C-chain length improves the tribological behaviour, i.e. the minimum friction value becomes lower. This is due to the formation of a uniform tribolayer of the long-chain carboxylic acids. Higher viscosity of the Ionic Liquids results in low friction coefficients and the development of a hydrodynamic layer. This is due to a strong hydrodynamic pressure, which is formed by the more viscous compound. Addition of small amounts of Ionic Liquids to low performance oils increases their capability to from tribolayers and thus improves their lubricant capability.

scholarly journals Micro/Nanostructure and Tribological Characteristics of Pressureless Sintered Carbon Nanotubes Reinforced Aluminium Matrix Composites

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
P. Manikandan ◽  
R. Sieh ◽  
A. Elayaperumal ◽  
H. R. Le ◽  
S. Basu
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
High Energy ◽  
Wear Behaviour ◽  
Powder Metallurgy Method ◽  
Pure Aluminium ◽  
Matrix Composites ◽  
Reinforced Composites ◽  
Tribological Behaviour ◽  
Mechanically Alloyed

This study reports the manufacture, microstructure, and tribological behaviour of carbon nanotube reinforced aluminium composites against pure aluminium. The specimens were fabricated using powder metallurgy method. The nanotubes in weight percentages of 0.5, 1.0, 1.5, and 2.0 were homogeneously dispersed and mechanically alloyed using a high energy ball milling. The milled powders were cold compacted and then isothermally sintered in air. The density of all samples was measured using Archimedes method and all had a relative density between 92.22% and 97.74%. Vickers hardness increased with increasing CNT fraction up to 1.5 wt% and then reduced. The microstructures and surfaces were investigated using high resolution scanning electron microscope (SEM). The tribological tests showed that the CNT reinforced composites displayed lower wear rate and friction coefficient compared to the pure aluminium under mild wear conditions. However, for severe wear conditions, the CNT reinforced composites exhibited higher friction coefficient and wear rate compared to the pure aluminium. It was also found that the friction and wear behaviour of CNT reinforced composites is significantly dependent on the applied load and there is a critical load beyond which CNTs could have adverse impact on the wear resistance of aluminium.

Tribological Properties Between a-C:H Coatings and SiO2 at High Temperature

2020 ◽  
Author(s):  
Noritsugu Umehara ◽  
Kota Konishi ◽  
Motoyuki Murashima ◽  
Takayuki Tokoroyama
Keyword(s):  
High Temperature ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Tribological Properties ◽  
Friction And Wear ◽  
Wear Track ◽  
Severe Damage ◽  
Friction Test ◽  
Low Friction ◽  
Disk Friction

Abstract Tribological properties of a-C:H coatings has been investigated in various friction conditions. It is clear that temperature and mating materials give effects on tribological properties. In this study, we especially focus on the effect of mating material on its tribological properties of a-C:H coatings. Ball-on-disk friction test is conducted between a-C:H coating and 5 kinds of mating material, which is SiC, SiC(O)_800 (SiC oxidized at 800°C), SiC(O)_1050°C, SiC(O)_1300°C, and Quartz glass. It is found that a-C:H coatings shows low friction coefficient and low specific wear rate when O/Si ratio of the element content of mating material is 2, in other words, mating material is SiO2. In the wear scar of a-C:H coating after friction test with SiC, severe damage was confirmed. It is considered that a-C:H coating and SiO2 show low adhesion even at high temperature, which leads low friction and wear. Compared SiC(O) with Quartz, the friction coefficients with a-C:H coatings are respectively 0.013 and 0.038. Even though SiC(O) and Quartz are both SiO2, the tribological properties are different. On the wear track of SiC(O), transferred things from a-C:H coating are confirmed.

Micromechanical Behaviour of Amorphous Hydrogenated Silicon Carbide Films

1993 ◽  
Vol 308 ◽  
Author(s):  
J. Meneve ◽  
R. Jacobs ◽  
F. Lostak ◽  
L. Eersels ◽  
E. Dekempeneer ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Chemical Vapour ◽  
Diamond Like Carbon ◽  
Ambient Atmosphere ◽  
Low Friction ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Low Wear

ABSTRACTAmorphous hydrogenated silicon carbide (a-Si1-xCx:H) films (x = 0.65 to 1) were deposited by radio frequency plasma assisted chemical vapour deposition (RF-PACVD). Their friction and wear properties were investigated by means of a conventional ball-on-disk apparatus. The results were correlated with film mechanical properties. It was found that adding silicon to a-C:H (also called diamond-like carbon (DLC)) films reduces the hardness, elastic modulus and internal stress values by 15 to 30 %. Scratch testing induces film spallation from stainless steel substrates at low loads (1 N). In the low normal load (1 N) ball-on-disk tests under humid N2 conditions, a-Si1-xCx:H films (0.7 < x < 0.9) combine a very low wear rate of both the film and the counterbody with a steady state low friction coefficient below 0.1. For higher loads (5 and 10 N), however, this low friction coefficient only lasts for a relatively short time. In this case, the harder diamond-like carbon films perform tribologically better because of their higher wear resistance, low wear rate of the counterbody and generally low friction coefficients between 0.15 and 0.35 in a humid ambient atmosphere. In a dry N2 atmosphere, pure DLC films perform tribologically better than a-S1-xCx:H films in all respects.

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