Effect of Surface Microtexturing on Friction at Unidirectional Sliding Depending on Lubricant Viscosity

2012 ◽  
Author(s):  
Karl-Heinz Zum Gahr ◽  
Mario Mann
Keyword(s):  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Sliding Velocity ◽  
Mineral Oils ◽  
Texture Parameters ◽  
Load Carrying ◽  
Glycerine Water ◽  
Lubricant Viscosity ◽  
Increasing Load ◽  
Effect Of Surface

Effect of surface microtexturing with spherical dimples of 60 μm diameter on friction behaviour of steel 100Cr6/sapphire pairs was studied as function of lubricant viscosity. Tests were run at unidirectional sliding up to 0.30 m/s using a pellet-on-disc geometry with flat contact area and drip lubrication with liquids such as glycerine-water solutions, distilled water and different mineral oils without additives. The texture pattern was produced on the polished sapphire discs by laser ablation processes. Friction force and film thickness of the lubricating liquid were continuously measured during the tests at different sliding velocities. Results showed that effectiveness of microtexturing in reducing friction and increasing load-carrying capacity depended on viscosity of the lubricant, operating conditions such as sliding velocity and applied load as well as texture parameters.

Paper 1: The Hydrodynamics of Flat Contacts: Friction Studies in the Pin and Disc Machine

1965 ◽  
Vol 180 (11) ◽  
pp. 49-60
Author(s):  
W. G. Robertson ◽  
D. T. Spillman
Keyword(s):  
Carrying Capacity ◽  
Electrical Contact ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Practical Application ◽  
Test Rig ◽  
Mineral Oils ◽  
Wide Range ◽  
Load Carrying ◽  
Flat Steel

The friction of run-in flat steel specimens lubricated with plain mineral oils has been measured in a pin and disc machine over a wide range of operating conditions. The hydrodynamic region was identified with the aid of electrical contact measurements and the corresponding friction data were considered in terms of the various theories which have been proposed to explain hydrodynamic action in nominally flat sliding contacts. It was concluded that the Lewicki inflow, the surface roughness, and the viscosity-density wedge mechanisms could not explain the observed friction; but that it could be explained if the surfaces formed a wedge whose angle was constant over the whole range of operating conditions. It is suggested that the wedge may be formed during the running-in process by mechanical effects such as flexural distortion. Particularly striking is the strength of the hydrodynamics which can occur in such ‘flat’ contacts: in terms of the wedge analysis the contact was operating close to the maximum theoretical load-carrying capacity. The implications with respect to the use of the pin and disc machine as a test rig are discussed and it is suggested that there might be a practical application in the design of ‘self-adjusting‘ slider bearings.

scholarly journals Manufacturing, Characterisation and Mechanical Analysis of Polyacrylonitrile Membranes

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2378
Author(s):  
Mertol Tüfekci ◽  
Sevgi Güneş Durak ◽  
İnci Pir ◽  
Türkan Ormancı Acar ◽  
Güler Türkoğlu Demirkol ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Main Idea ◽  
Mechanical Analysis ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
The Finite Element Method ◽  
Load Carrying ◽  
The Impact ◽  
Static Behaviour ◽  
Modelling Process

To investigate the effect of polyvinylpyrrolidone (PVP) addition and consequently porosity, two different sets of membranes are manufactured, since PVP is a widely used poring agent which has an impact on the mechanical properties of the membrane material. The first set (PAN 1) includes polyacrylonitrile (PAN) and the necessary solvent while the second set (PAN 2) is made of PAN and PVP. These membranes are put through several characterisation processes including tensile testing. The obtained data are used to model the static behaviour of the membranes with different geometries but similar loading and boundary conditions that represent their operating conditions. This modelling process is undertaken by using the finite element method. The main idea is to investigate how geometry affects the load-carrying capacity of the membranes. Alongside membrane modelling, their materials are modelled with representative elements with hexagonal and rectangular pore arrays (RE) to understand the impact of porosity on the mechanical properties. Exploring the results, the best geometry is found as the elliptic membrane with the aspect ratio 4 and the better RE as the hexagonal array which can predict the elastic properties with an approximate error of 12%.

Computational Fluid Dynamics Thermohydrodynamic Analysis of Three-Dimensional Sector-Pad Thrust Bearings With Rectangular Dimples

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
C. I. Papadopoulos ◽  
L. Kaiktsis ◽  
M. Fillon
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Carrying Capacity ◽  
Thermal Effects ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Performance Indices ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Texture Design

The paper presents a detailed computational study of flow patterns and performance indices in a dimpled parallel thrust bearing. The bearing consists of eight pads; the stator surface of each pad is partially textured with rectangular dimples, aiming at maximizing the load carrying capacity. The bearing tribological performance is characterized by means of computational fluid dynamics (CFD) simulations, based on the numerical solution of the Navier–Stokes and energy equations for incompressible flow. Realistic boundary conditions are implemented. The effects of operating conditions and texture design are studied for the case of isothermal flow. First, for a reference texture pattern, the effects of varying operating conditions, in particular minimum film thickness (thrust load), rotational speed and feeding oil pressure are investigated. Next, the effects of varying texture geometry characteristics, in particular texture zone circumferential/radial extent, dimple depth, and texture density on the bearing performance indices (load carrying capacity, friction torque, and friction coefficient) are studied, for a representative operating point. For the reference texture design, the effects of varying operating conditions are further investigated, by also taking into account thermal effects. In particular, adiabatic conditions and conjugate heat transfer at the bearing pad are considered. The results of the present study indicate that parallel thrust bearings textured by proper rectangular dimples are characterized by substantial load carrying capacity levels. Thermal effects may significantly reduce load capacity, especially in the range of high speeds and high loads. Based on the present results, favorable texture designs can be assessed.

The Wear Characteristics of Graphene as an Atomically-Thin Protective Coating

2012 ◽  
Author(s):  
Emil Sandoz-Rosado ◽  
Elon J. Terrell
Keyword(s):  
Protective Coatings ◽  
Solid Lubricants ◽  
Atomistic Simulations ◽  
Great Promise ◽  
Load Carrying Capacity ◽  
Sliding Velocity ◽  
Substrate Rigidity ◽  
Macro Scale ◽  
Load Carrying ◽  
The Impact

Lamellar atomically-thin sheets such as graphene (and its bulk equivalent graphite) and molybdenum disulfide have emerged as excellent solid lubricants at the macro scale and show great promise as protective coatings for nanoscopic applications. In this study, the failure mechanisms of graphene under sliding are examined using atomistic simulations. An atomic tip is slid over a graphene membrane that is adhered to a semi-infinite substrate. The impact of sliding velocity and substrate rigidity on the wear and frictional behavior of graphene is studied. In addition, the interplay of adhesive and abrasive wear on the graphene coating is also examined. The preliminary results indicate that graphene has excellent potential as a nanoscale due to its atomically-thin configuration and high load carrying capacity.

scholarly journals Effectiveness of Geogrids on Rutting and Bearing Capacity of Sub-base Course

2015 ◽  
Vol 15 (1) ◽  
pp. 77-80
Author(s):  
Ali Reza Mardookhpour
Keyword(s):  
Bearing Capacity ◽  
Soil Mechanics ◽  
Research Work ◽  
Polymer Materials ◽  
Load Carrying Capacity ◽  
Highway Projects ◽  
Load Carrying ◽  
Two Factors ◽  
Base Course ◽  
Increasing Load

Geogrids are being used in transportation application often in embankment construction due to their ease of construction and economy compared to traditional methods. Utilizing polymer materials in order to improve the performance of road structure is based on two factors, decreasing deformation and increasing bearing capacity. In this study geogrids were tested to check the ability of increasing load carrying capacity for highway projects. The purpose of this research work was to find a relation between the loading of the geogrid, the thickness of the aggregate layer and its bearing capacity. This would normally lead to an investigation on the lateral restrain behavior of a geogrid. According to the results obtained from soil mechanics laboratory, it could be demonstrated that by utilizing geogrids , the probability of occurring rutting decreases 30% and the bearing capacity of soil increase 40 % respectively.DOI: http://dx.doi.org/10.3126/njst.v15i1.12020  Nepal Journal of Science and TechnologyVol. 15, No.1 (2014) 77-80

Static and dynamic performance characteristics of powder lubricated symmetrical three-lobed bearing

2020 ◽  
pp. 135065012092632
Author(s):  
Jijo Jose ◽  
Niranjana Behera
Keyword(s):  
Carrying Capacity ◽  
Elevated Temperatures ◽  
Dynamic Performance ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Oil Degradation ◽  
Static And Dynamic Characteristics ◽  
Load Carrying ◽  
The Coefficient Of Friction ◽  
Ellipticity Ratio

Hydrodynamic oil bearings applied at elevated temperatures and extreme operating conditions are subjected to the problem of oil degradation. In order to overcome such conditions, dry powder lubricants are used as lubricants in the hydrodynamic journal bearings. Thus the problem of thermal degradation of oil at high temperatures can be eliminated. In this work, the static and dynamic characteristics of a symmetric three-lobed bearing lubricated with powdered particles have been predicted. Influence of the ellipticity ratio on the performance of the three-lobed bearing has also been investigated. It is observed that an increase in the ellipticity ratio increases the coefficient of friction and stability, but decreases the side leakage and the load carrying capacity of the three-lobed bearing. Also, it was observed that the large-sized powdered particles induce better load carrying capacity and better stability than the small-sized particles.

scholarly journals Combined Effect of Slip Velocity and Surface Roughness on a Magnetic Squeeze Film for a Sphere in a Spherical Seat

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
G. M. Deheri ◽  
Sejal J. Patel
Keyword(s):  
Surface Roughness ◽  
Slip Velocity ◽  
Type Equation ◽  
Velocity Slip ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Slip Model ◽  
Load Carrying ◽  
Effect Of Surface

This investigation analyzes the performance of a magnetic fluid based squeeze film for a sphere in a rough spherical seat with slip velocity. The slip model of Beavers and Joseph has been deployed to study the effect of velocity slip while the stochastic model of Christensen and Tonder has been used to calculate the effect of surface roughness. The concerned statistically averaged Reynolds’ type equation is solved to derive the pressure distribution which results in the calculation of load carrying capacity. The results presented in graphical forms confirm that the adverse effect of slip velocity can be overcome to a large extent at least in the case of negatively skewed roughness. However, lower values of slip may be preferred for enhancing the performance characteristics of the bearing system. Besides, variance (−ve) provides a little support to improve the performance characteristics.

The Role of Oleophilic Surface in Lubrication

1968 ◽  
Vol 183 (16) ◽  
pp. 197-201 ◽  
Author(s):  
A. J. Groszek
Keyword(s):  
Polar Compounds ◽  
Rolling Contact ◽  
Polar Regions ◽  
Load Carrying Capacity ◽  
Mineral Oils ◽  
High Affinity ◽  
Low Surface Energy ◽  
Load Carrying ◽  
Steel Surfaces

Surfaces of MoS2 and graphite are composed of ‘oleophilic’ regions, which have a strong affinity for long-chain normal hydrocarbons, and polar regions. The oleophilic regions adsorb hydrocarbons in preference to polar compounds, such as water and alcohols. Conversely, water and alcohols easily displace hydrocarbons adsorbed in the polar sites. A study of MoS2 and graphite having different proportions of oleophilic and polar sites shows that the lubricating effectiveness of these solids increases with the proportion of oleophilic sites on their surfaces. For MoS2 the sites consist of regularly disposed sulphur atoms in the basal planes of individual crystallites, and it is postulated that they can become chemically bonded to steel surfaces. When one basal plane side of a MoS2 crystallite is bonded to the steel surface, the other side presents an oleophilic surface to the surroundings, which has a low surface energy and high affinity for mineral oils. The oleophilic ‘sites’ produced in this way on the metal surface are believed to be instrumental in increasing the load-carrying capacity of the steel surfaces in sliding and rolling contact, especially in the presence of mineral oils.

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