scholarly journals Superlubricity of molybdenum disulfide subjected to large compressive strains

Friction ◽  
2021 ◽  
Author(s):  
Shengcong Wu ◽  
Zhisen Meng ◽  
Xiaoma Tao ◽  
Zhao Wang
Keyword(s):  
Coefficient Of Friction ◽  
Large Deformations ◽  
High Strain ◽  
Compressive Strain ◽  
Friction Reduction ◽  
Molybdenum Disulphide ◽  
Dramatic Decrease ◽  
Tomlinson Model ◽  
Zigzag Direction ◽  
The Coefficient Of Friction

AbstractThe friction between a molybdenum disulphide (MoS2) nanoflake and a MoS2 substrate was analyzed using a modified Tomlinson model based on atomistic force fields. The calculations performed in the study suggest that large deformations in the substrate can induce a dramatic decrease in the friction between the nanoflake and the substrate to produce the so-called superlubricity. The coefficient of friction decreases by 1–4 orders of magnitude when a high strain exceeding 0.1 is applied. This friction reduction is strongly anisotropic. For example, the reduction is most pronounced in the compressive regime when the nanoflake slides along the zigzag crystalline direction of the substrate. In other sliding directions, the coefficient of friction will reduce to its lowest value either when a high tensile strain is applied along the zigzag direction or when a high compressive strain is applied along the armchair direction. This anisotropy is correlated with the atomic configurations of MoS2.

Friction Reduction in the Sliding of an Elastic Half-Space Against a Rigid Surface Due to Incident Rectangular Dilatational Waves

1999 ◽  
Vol 122 (1) ◽  
pp. 10-15 ◽  
Author(s):  
George G. Adams
Keyword(s):  
Normal Stress ◽  
Half Space ◽  
Coefficient Of Friction ◽  
Tangential Velocity ◽  
Elastic Half Space ◽  
Body Waves ◽  
Friction Reduction ◽  
Rigid Surface ◽  
Rectangular Wave ◽  
The Coefficient Of Friction

The steady sliding of a flat homogeneous and isotropic elastic half-space against a flat rigid surface, under the influence of incident plane dilatational waves, is investigated. The interfacial coefficient of friction is constant with no distinction between static and kinetic friction. It is shown here that the reflection of a harmonic wave under steady sliding consists of a pair of body waves (a plane dilatational wave and a plane shear wave) radiated from the sliding interface. Each wave propagates at a different angle such that the trace velocities along the interface are equal and supersonic. The angles of wave propagation are determined by the angle of the incident wave, by the Poisson’s ratio, and by the coefficient of friction. The amplitude of the incident waves is subject only to the restriction that the perturbations in interface contact pressure and tangential velocity satisfy the inequality constraints for unilateral sliding contact. It is also found that an incident rectangular wave can allow for relative sliding motion of the two bodies with a ratio of remote shear to normal stress which is less than the coefficient of friction. Thus the apparent coefficient of friction is less than the interface coefficient of friction. This reduction in friction is due to periodic stick zones which propagate supersonically along the interface. The influences of the angle, amplitude, and shape of the incident rectangular wave, the interfacial friction coefficient, the sliding speed, and of the remotely applied normal stress, on friction reduction are determined. Under appropriate conditions, the bodies can move tangentially with respect to each other in the absence of an applied shear stress. [S0742-4787(00)00201-0]

The Influence of Temperature in Wear Resistance Characteristic of Palm Fatty Acid Distillate

2013 ◽  
Vol 388 ◽  
pp. 63-67
Author(s):  
Samion Syahrullail ◽  
Muhammad Amirul Abdul Rahman
Keyword(s):  
Fatty Acid ◽  
Coefficient Of Friction ◽  
Normal Load ◽  
Oil Refinery ◽  
Friction Reduction ◽  
Wear Scar Diameter ◽  
Hydraulic Oil ◽  
Palm Fatty Acid Distillate ◽  
The Coefficient Of Friction ◽  
Fatty Acid Distillate

Palm fatty acid distillate (PFAD) has potential to be used as a lubricant. PFAD is a by-product from palm oil refinery, and it is classified as non-edible oil. However, vegetable oil has poor thermal performance and high oxidation rate. In this paper, the tribological performance of PFAD in different working temperature was investigated by using four-ball tribotester. Tests were conducted at temperatures 50oC, 75oC, 100oC and 125oC, under a normal load of 40 kg for one (1) hour. The rotational speed was set at 1200rpm. Similar tests were conducted using industrial hydraulic oil as a comparison lubricant. Analyses were focused on the coefficient of friction (CoF), wear scar diameter (WSD) and worn surface observation. Results show that coefficient of friction and wear were increased with the increment of temperature. However, palm fatty acid distillate show a better performance in term of friction reduction compared to industrial hydraulic oil.

scholarly journals An Experimental Study of the Frictional Properties of Steel Sheets Using the Drawbead Simulator Test

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4037 ◽  
Author(s):  
Trzepiecinski ◽  
Kubit ◽  
Slota ◽  
Fejkiel
Keyword(s):  
Coefficient Of Friction ◽  
Extreme Values ◽  
Rolling Direction ◽  
Frictional Resistance ◽  
Friction Reduction ◽  
Experimental Investigations ◽  
Sheet Rolling ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Lubrication Conditions

This article presents the results of an experimental investigation of the frictional resistance arising in a drawbead during sheet metal forming. The frictional characterization of DC04 deep drawing quality steels commonly used in the automotive industry is carried out using a friction simulator. The effects of some parameters of the friction process on the value of the coefficient of friction have been considered in the experimental investigations. The friction tests have been conducted on different strip specimens, lubrication conditions, heights of drawbead and specimen orientations in relation to the sheet rolling direction. The results of drawbead simulator tests demonstrate the relationship that the value of the coefficient of friction of the test sheets without lubrication is higher than in the case of lubricated sheets. The lubricant reduces the coefficient of friction, but the effectiveness of its reduction depends on the drawbead height and lubrication conditions. Moreover, the effectiveness of the reduction of the coefficient of friction by the lubricant depends on the specimen orientation according to the sheet rolling direction. In the drawbead test, the specimens oriented along the rolling direction demonstrate a higher value of coefficient of friction when compared to the samples cut transverse to the rolling direction. The smaller the width of the specimen, the lower the coefficient of friction observed. The difference in the coefficient of friction for the extreme values of the widths of the specimens was about 0.03–0.05. The use of machine oil reduced the coefficient of friction by 0.02–0.03 over the whole range of drawbead heights. Heavy duty lubricant even reduced the frictional resistances by over 50% compared to dry friction conditions. The effectiveness of friction reduction by machine oil does not exceed 30%.

Study of behaviour of aluminium oxide nanoparticles suspended in SAE20W40 oil under extreme pressure lubrication

2015 ◽  
Vol 67 (4) ◽  
pp. 328-335 ◽  
Author(s):  
Avinash A. Thakre ◽  
Animesh Thakur
Keyword(s):  
Coefficient Of Friction ◽  
Normal Load ◽  
Friction Reduction ◽  
Lubricating Oil ◽  
Extreme Pressure ◽  
Sliding Speed ◽  
Content Type ◽  
Base Oil ◽  
Pin On Disc ◽  
The Coefficient Of Friction

Purpose – The purpose of this paper is to include investigation on extreme pressure lubrication behaviour of Al2O3 nanoparticles suspended in SAE20W40 lubricating oil. Effects of nanoparticles size (40-80 nm) and its concentration (0-1 per cent) on the coefficient of friction is studied using pin-on-disc tribotester. Design/methodology/approach – Taguchi technique is used to optimize the process parameters for lower coefficient of friction. L18 orthogonal array involving six levels for one factor and three levels for remaining three factors is selected for the experimentation. The parameters selected for the study are sliding speed, normal load, nanoparticles size and its concentration in base oil. Findings – It has been found that the presence of nanoparticles in proper concentration shows excellent tribological improvement in frictional characteristics compared to the base oil. The optimal combination of the parameters for minimum coefficient of friction is found to be 0.8 per cent concentration of 60 nm sized Al2O3 nanoparticles, 1,200 rpm sliding speed and 160 N of normal load. The mechanism of friction reduction in presence of nanoparticles is investigated using scanning electron microscopy. Originality/value – This is the original work.

Synthesis of nanostructured flower-like MoS2 and its friction properties as additive in lubricating oils

2016 ◽  
Vol 68 (6) ◽  
pp. 658-664 ◽  
Author(s):  
Gustavo Tontini ◽  
Guilherme Dalla Lana Semione ◽  
Cristian Bernardi ◽  
Roberto Binder ◽  
José Daniel Biasoli de Mello ◽  
...  
Keyword(s):  
Hydrothermal Method ◽  
Coefficient Of Friction ◽  
Absolute Ethanol ◽  
Molybdenum Disulphide ◽  
Content Type ◽  
Lubricating Oils ◽  
The Coefficient Of Friction ◽  
Powder Particles ◽  
The Stability ◽  
Pin On Disk

Purpose This paper aims to synthesize nanostructured flower-like molybdenum disulphide (MoS2) particles and evaluate their suitability to act as additives for lubricants. Design/methodology/approach A hydrothermal method without any surfactant successfully produced 250 nm mean diameter Nanostructured flower-like MoS2 particles. The resulting product was then solvothermally treated with absolute ethanol producing lipophilic powder particles which after being dispersed in two different lubricants were tribologicaly characterized by using a pin-on-disk tribometer geometry with reciprocal movement under immersion. Findings The influence on the stability and the coefficient of friction of the nano-oils is shown to be strongly dependent on their molecular structure. After 1 h of tribological testing, a ramified polyolester oil with 1 Wt.% of MoS2 nanoflowers did not show decrease in its average coefficient of friction, while an additive naphthenic oil with the same concentration of nanoparticles showed a decrease of 86 per cent. Originality/value In this paper, nanostructured flower-like MoS2 synthesized by the hydrothermal method was dispersed in lubricating oils to study its stability and tribological properties. To ensure good stability of the nano-oils, the particles were solvothermally treated with absolute ethanol to dehydrate and lipophilize them. A ramified polyolester-based nano-oil with 1 Wt.% of MoS2 nanoflowers showed no decrease in its steady state coefficient of friction, while a naphthenic-based nano-oil with the same concentration of nanoparticles presented a remarkable 86 per cent reduction.

The Sliding of an Elastic Half-Space Against a Rigid Surface With Friction Reduction due to Incident Dilatational Waves

1999 ◽  
Author(s):  
George G. Adams
Keyword(s):  
Normal Stress ◽  
Half Space ◽  
Coefficient Of Friction ◽  
Tangential Velocity ◽  
Elastic Half Space ◽  
Body Waves ◽  
Friction Reduction ◽  
Rigid Surface ◽  
Rectangular Wave ◽  
The Coefficient Of Friction

Abstract The steady sliding of a flat homogeneous and isotropic elastic half-space against a flat rigid surface, under the influence of incident plane dilatational waves, is investigated. The interfacial coefficient of friction is constant with no distinction between static and kinetic friction. It is shown here that the reflection of a harmonic wave under steady sliding consists of a pair of body waves (a plane dilatational wave and a plane shear wave) radiated from the sliding interface. Each wave propagates at a different angle such that the trace velocities along the interface are equal and supersonic. The angles of wave propagation are determined by the angle of the incident wave, by the Poisson’s ratio, and by the coefficient of friction. The amplitude of the incident waves is subject only to the restriction that the perturbations in interface contact pressure and tangential velocity satisfy the inequality constraints for unilateral sliding contact. It is also found that an incident rectangular wave can allow for relative sliding motion of the two bodies with a ratio of remote shear to normal stress which is less than the coefficient of friction. Thus the apparent coefficient of friction is less than the interface coefficient of friction. This reduction in friction is due to periodic stick zones which propagate supersonically along the interface. Under appropriate conditions, the bodies can move tangentially with respect to each other in the absence of an applied shear stress. The influences of the angle, amplitude, and shape of the incident rectangular wave, the interfacial friction coefficient, the sliding speed, and of the remotely applied normal stress, on friction reduction are determined.

scholarly journals Impact of Tungsten Incorporation on the Tribomechanical Behavior of AlCrWxSiN Films at Room and Elevated Temperature

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1033
Author(s):  
Wolfgang Tillmann ◽  
Alexander Fehr ◽  
Dominic Stangier
Keyword(s):  
Magnetron Sputtering ◽  
Coefficient Of Friction ◽  
Friction And Wear ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Wear Behavior ◽  
Friction Reduction ◽  
Wear Coefficient ◽  
The Coefficient Of Friction

AlCrWxSiN thin films (0 ≤ x ≤ 17.1 at.%) were synthesized by means of a hybrid magnetron sputtering process, merging direct current (DC) as well as tungsten high power impulse magnetron sputtering (HiPIMS) supplies. The influences of increasing the tungsten contents on the structural as well as the friction and wear behavior at room and high temperatures (500 °C) were elaborated. As a reference, a W61.4N38.6 system served to analyze synergetic effects on the oxidation behavior. Increased tungsten contents in AlCrWxSiN resulted in more distinctive (200)-, (202)-, and (311)- crystal orientations. A W/Cr ratio of ~1 could be correlated with a denser film growth, the highest hardness (24.3 ± 0.7 GPa), and a significantly decreased wear coefficient (<0.3 × 10−5 mm3/Nm). Tribological tests performed at room temperature revealed that the coefficient of friction decreased with higher tungsten contents to µ~0.35. In contrast, at elevated temperatures, the coefficient of friction increased with higher W concentrations due to spotty oxidations in the wear track, which resulted in a locally increased surface roughness. Finally, a phase transformation of the WN film to m-WO3 did not contribute to a friction reduction at 500 °C.

scholarly journals Tribological evaluation and lubrication mechanisms of nanoparticles enhanced lubricants in cold rolling

2020 ◽  
Vol 21 (1) ◽  
pp. 108
Author(s):  
Liang Hao ◽  
Zheng Wang ◽  
Guoyuan Zhang ◽  
Yangyang Zhao ◽  
Qingjuan Duan ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Coefficient Of Friction ◽  
Tribological Properties ◽  
Friction Reduction ◽  
Base Oils ◽  
Lubrication Performance ◽  
Protective Films ◽  
The Coefficient Of Friction ◽  
20 Nm ◽  
Lubrication Mechanisms

Base oils containing different nanoparticles with varying concentrations are prepared, in which SiO2, TiO2 and ZnO (20 nm) nanoparticles are employed to improve the lubrication performance. Their tribological properties are evaluated on a ball-on-disk tribometer. The results show that the nano-additive lubricants exhibit a good friction reduction and anti-wear ability at the optimal concentration of 1.0 wt.%, in which SiO2 nanoparticles can reduce the coefficient of friction (COF) and the area of wear scar (AWS) by 45.6% and 35%, respectively. The SiO2 nanoparticles exhibit the best potential additive tested. The lubrication mechanisms of the nanoparticles can be attributed to the rolling, mending and the protective films.

Experimental Investigation of aluminum doping crumb rubber/epoxy composite in reciprocating motion

2015 ◽  
Vol 3 ◽  
pp. 1
Author(s):  
Goutam Chandra Karar ◽  
Nipu Modak
Keyword(s):  
Experimental Investigation ◽  
Coefficient Of Friction ◽  
Epoxy Composite ◽  
Normal Load ◽  
Crumb Rubber ◽  
The Other ◽  
Reciprocating Motion ◽  
Molding Process ◽  
Friction Tester ◽  
The Coefficient Of Friction

The experimental investigation of reciprocating motion between the aluminum doped crumb rubber /epoxy composite and the steel ball has been carried out under Reciprocating Friction Tester, TR-282 to study the wear and coefficient of frictions using different normal loads (0.4Kg, 0.7Kgand1Kg), differentfrequencies (10Hz, 25Hz and 40Hz).The wear is a function of normal load, reciprocating frequency, reciprocating duration and the composition of the material. The percentage of aluminum presents in the composite changesbut the other components remain the same.The four types of composites are fabricated by compression molding process having 0%, 10%, 20% and 30% Al. The effect of different parameters such as normal load, reciprocating frequency and percentage of aluminum has been studied. It is observed that the wear and coefficient of friction is influenced by the parameters. The tendency of wear goes on decreasing with the increase of normal load and it is minimum for a composite having 10%aluminum at a normal load of 0.7Kg and then goes on increasing at higher loads for all types of composite due to the adhesive nature of the composite. The coefficient of friction goes on decreasing with increasing normal loads due to the formation of thin film as an effect of heat generation with normal load.

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