scholarly journals Boundary Friction of ZDDP Tribofilms

2020 ◽  
Vol 69 (1) ◽  
Author(s):  
Jie Zhang ◽  
Mao Ueda ◽  
Sophie Campen ◽  
Hugh Spikes
Keyword(s):  
Friction Coefficient ◽  
Group Structure ◽  
Boundary Friction ◽  
Considerable Proportion ◽  
Base Oil ◽  
Characteristic Boundary ◽  
Long Duration ◽  
Structure Boundary ◽  
Alkoxy Groups ◽  
20 Nm

AbstractThe frictional properties of ZDDP tribofilms at low entrainment speeds in boundary lubrication conditions have been studied in both rolling/sliding and pure sliding contacts. It has been found that the boundary friction coefficients of these tribofilms depend on the alkyl structure of the ZDDPs. For primary ZDDPs, those with linear alkyl chains give lower friction those with branched alkyl chain ZDDPs, and a cyclohexylmethyl-based ZDDP gives markedly higher friction than non-cyclic ones. Depending on alkyl structure, boundary friction coefficient in rolling-sliding conditions can range from 0.09 to 0.14. These differences persist over long duration tests lasting up to 120 h. For secondary ZDDPs, boundary friction appears to depend less strongly on alkyl structure and in rolling-sliding conditions stabilises at ca 0.115 for the three ZDDPs studied. Experiments in which the ZDDP-containing lubricant is changed after tribofilm formation by a different ZDDP solution or a base oil indicate that the characteristic friction of the initial ZDDP tribofilm is lost almost as soon as rubbing commences in the new lubricant. The boundary friction rapidly stabilises at the characteristic boundary friction of the replacement ZDDP, or in the case of base oil, a value of ca 0.115 which is believed to represent the shear strength of the bare polyphosphate surface. The single exception is when a solution containing a cyclohexylethyl-based ZDDP is replaced by base oil, where the boundary friction coefficient remains at the high value characteristic of this ZDDP despite the fact that rubbing in base oil removes about 20 nm of the tribofilm. XPS analysis of the residual tribofilm reveals that this originates from presence of a considerable proportion of C-O bonds at the exposed tribofilm surface, indicating that not all of the alkoxy groups are lost from the polyphosphate during tribofilm formation. Very slow speed rubbing tests at low temperature show that the ZDDP solutions give boundary friction values that vary with alkyl group structure in a similar fashion to rolling-sliding MTM tests. These variations in friction occur immediately on rubbing, before any measurable tribofilm can develop. This study suggest that ZDDPs control boundary friction by adsorbing on rubbing steel or tribofilm surfaces in a fashion similar to organic friction modifiers. However it is believed that, for primary ZDDPs, residual alkoxy groups still chemically bonded to the phosphorus atoms of newly-formed polyphosphate/phosphate tribofilm may also contribute to boundary friction. This understanding will contribute to the design of low friction, fuel efficient crankcase engine oils. Graphical Abstract

Boundary Friction for a Line Contact Model: An Empirical Approach

2015 ◽  
Vol 642 ◽  
pp. 8-12
Author(s):  
William W.F. Chong ◽  
Miguel de La Cruz
Keyword(s):  
Steel Plate ◽  
Friction Model ◽  
Boundary Friction ◽  
Slider Bearing ◽  
Base Oil ◽  
Atomic Force ◽  
Alternative Approach ◽  
Nanoscale Friction ◽  
Friction Measurements ◽  
Good Agreement

The paper introduces an alternative approach to predict boundary friction for rough surfaces at micros-scale through the empirical integration of asperity-like nanoscale friction measurements. The nanoscale friction is measured using an atomic force microscope (AFM) tip sliding on a steel plate, confining the test lubricant, i.e. base oil for the fully formulated SAE grade 10w40. The approach, based on the Greenwood and Tripp’s friction model, is combined with the modified Elrod’s cavitation algorithm in order to predict the friction generated by a slider-bearing test rig. The numerical simulation results, using an improved boundary friction model, showed good agreement with the measured friction data.

scholarly journals Tribology Properties of Synthesized Multiscale Lamellar WS2 and Their Synergistic Effect with Anti-Wear Agent ZDDP

2019 ◽  
Vol 10 (1) ◽  
pp. 115 ◽  
Author(s):  
Na Wu ◽  
Ningning Hu ◽  
Jinhe Wu ◽  
Gongbo Zhou
Keyword(s):  
Friction Coefficient ◽  
Synergistic Effect ◽  
Solid Phase ◽  
Friction Reduction ◽  
Lubricating Oil ◽  
Solid Phase Reaction ◽  
Phase Reaction ◽  
Wear Properties ◽  
Base Oil ◽  
Electron Probe Micro Analyzer

The microscale/nanoscale lamellar-structure WS2 particles with sizes of 2 µm and 500 nm were synthesized by solid-phase reaction method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The synergies between microscale/nanoscale WS2 particles and ZDDP as lubricating oil additives was evaluated by means of UMT-2 tribometer at room temperature. The wear scars were examined with SEM and electron-probe micro-analyzer (EPMA). The results show that the anti-wear properties were improved and the friction coefficient was greatly decreased with the simultaneous addition of WS2 particles and ZDDP, and the largest reduction of friction coefficient was 47.2% compared with that in base oil. Moreover, the presence of ZDDP additive in the lubricant further enhances the friction-reduction and anti-wear effect of microscale/nanoscale WS2. This confirms that there is a synergistic effect between WS2 particles and ZDDP.

Tribological Investigation of Nanographite Platelets as Additive in Anti-Wear Lubricant: A Top-Down Approach

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Flavio A. C. Vidal ◽  
Antonio F. Ávila
Keyword(s):  
Friction Coefficient ◽  
Friction Reduction ◽  
Wear Properties ◽  
Top Down ◽  
Base Oil ◽  
Graphene Layers ◽  
Sliding Mechanism ◽  
Wear And Friction ◽  
Different Types ◽  
Mineral Base

A top-down approach is employed to investigate the tribological effect of adding nanographite platelets (NGPs) to mineral base oil (MBO). The performance of the NGP-modified MBO was evaluated by examining the friction and anti-wear properties. Four different types of NGPs produced by two different processes were employed. The optimal NGP-modified MBO attained a significant wear and friction reduction when compared with the MBO without NGPs. The process used to exfoliate the graphite nanoplatelet samples provided better wear properties because of the graphene layers' smoother sliding mechanism. Graphene layers seeped inside the groove marks to keep the friction coefficient low.

scholarly journals Ice friction: the effect of thermal conductivity

2010 ◽  
Vol 56 (197) ◽  
pp. 473-479 ◽  
Author(s):  
Anne-Marie Kietzig ◽  
Savvas G. Hatzikiriakos ◽  
Peter Englezos
Keyword(s):  
Thermal Conductivity ◽  
Friction Coefficient ◽  
Boundary Friction ◽  
Sliding Velocity ◽  
Ice Friction ◽  
Mixed Friction ◽  
Friction Regime ◽  
Wide Range

AbstractThe effect of thermal conductivity on ice friction is studied systematically for different metallic slider materials over a wide range of temperatures, and sliding velocities. By thermally insulating the slider with fiberglass, the isolated effect of thermal conductivity on ice friction is investigated. A decrease of the friction coefficient in the boundary friction regime and an earlier onset of the mixed friction regime in terms of sliding velocity are found. Furthermore, the dependence of the ice friction coefficient on sliding velocity is compared for different sliding materials. It is found that the influence and importance of thermal conductivity decreases with increasing sliding velocity.

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.

Frictional Performance of an Ionic Liquid/Graphene Composite Additive in Lubricating Oil

NANO ◽  
2021 ◽  
pp. 2150111
Author(s):  
Shengli You ◽  
Ming Zhou ◽  
Mingyue Wang ◽  
Xin Chen ◽  
Long Jin ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Friction Pair ◽  
Testing Machine ◽  
Steel Ball ◽  
Wear Scar ◽  
Wear Testing ◽  
Lubricating Oil ◽  
Wear Scar Diameter ◽  
Base Oil ◽  
Frictional Performance

In this study, we used a four-ball friction and wear testing machine to test the tribological properties of [HPy]BF4 ionic liquids (ILs), low-layer graphene (G), and IL and G compounds (IL/G) as lubricant additives at variousconcentrations, loads, and speeds. The morphology of the wear scar was characterized by a white-light interferometer and a scanning electron microscope (SEM). The results showed that the optimal concentrations of IL and G were 0.10[Formula: see text]wt.% and 0.05[Formula: see text]wt.%, respectively. When the IL concentration was 0.10[Formula: see text]wt.%, the friction coefficient and the wear scar diameter (WSD) reduced by approximately 18% and 8%, respectively, compared to the base oil. When the concentration of G was 0.05[Formula: see text]wt.%, the friction coefficient and WSD reduced by approximately 23% and 12%, respectively, compared to the base oil. After adding the optimal concentration of the IL/G composite additive under the same test conditions, the average friction coefficient of the steel ball reduced by approximately 30%, and the average WSD reduced by approximately 18%. IL/G nanoadditives could be easily attached to the pit area on the friction surface of the steel ball, which made the contact surface of the friction pair smoother and the area of the oil film bearing the load larger, compared to those using the base oil. These two combined phenomena promoted synergistic antifriction and antiwear effects, which significantly improved the frictional performance of the base oil.

The Statistical Application of a Thermal EHL Theory for Individual Asperity-Asperity Collisions to the Sliding Contact of Rough Surfaces

1975 ◽  
Vol 97 (2) ◽  
pp. 311-318 ◽  
Author(s):  
P. E. Fowles
Keyword(s):  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Sliding Contact ◽  
Unit Load ◽  
Lubrication Regime ◽  
Statistical Application ◽  
Model Surfaces ◽  
Mixed Lubrication Regime ◽  
Thermal Ehl ◽  
20 Nm

The numerical results of a previously developed thermal EHL theory describing the collisions between idealized asperities are analyzed statistically to obtain macroscopic values of unit load, traction, and friction coefficient for two model surfaces in sliding contact under a range of conditions. It is shown that significant unit loads and tractions can be generated as a result of the microsopic EHL contacts alone. The variation of friction coefficient with load and sliding speed corresponds qualitatively with experiment in the mixed lubrication regime between boundary and hydrodynamic lubrication, but quantitatively the friction coefficients are two to three times too high. The results imply that the lubricant becomes non-Newtonian and/or exhibits a limiting shear strength in virtually all asperity interactions, even those in which the thickness of the intervening lubricant film is maintained in the 20-nm range.

Minimizing of the boundary friction coefficient in automotive engines using Al2O3 and TiO2 nanoparticles

2016 ◽  
Vol 18 (12) ◽  
Author(s):  
Mohamed Kamal Ahmed Ali ◽  
Hou Xianjun ◽  
Ahmed Elagouz ◽  
F.A. Essa ◽  
Mohamed A. A. Abdelkareem
Keyword(s):  
Friction Coefficient ◽  
Tio2 Nanoparticles ◽  
Boundary Friction ◽  
Automotive Engines

The effect of particle size on the dispersion and wear protection ability of MoS2 particles in polyalphaolefin and trimethylolpropane ester

2017 ◽  
Vol 232 (8) ◽  
pp. 987-998 ◽  
Author(s):  
M Gulzar ◽  
Khalid Mahmood ◽  
Rehan Zahid ◽  
Abdullah Alabdulkarem ◽  
HH Masjuki ◽  
...  
Keyword(s):  
Particle Size ◽  
Sliding Wear ◽  
Base Oil ◽  
Force Microscopy ◽  
Wear Protection ◽  
Atomic Force ◽  
Nominal Size ◽  
Load Carrying ◽  
Effect Of Particle Size ◽  
20 Nm

The effect of particle size and surfactant on dispersion stability and wear protection ability was experimentally evaluated for polyalphaolefin (PAO 10) and bio-based base oil (palm trimethylolpropane ester) added with molybdenum disulfide (MoS2) particles. Nanolubricants were developed by adding 1 wt% of MoS2 particles that varied in size. In addition to the variation in particle size, an anionic surfactant was also used to analyze its interaction with both types of nanoparticles for stable suspensions and for the related effects on the antiwear characteristics. The wear protection characteristics of the formulations were evaluated by four-ball extreme pressure tests and piston ring on cylinder sliding wear tests. The wear surfaces were analyzed by scanning electron microscopy along with an energy-dispersive X-ray and an atomic force microscopy. The MoS2 nanoparticles with a nominal size of 20 nm exhibited a better load-carrying capacity, while better sliding wear protection was provided by nanoparticles with a nominal size of 50 nm.

Sign in / Sign up

Export Citation Format

Share Document