Paper 8: The Fundamentals of Lubrication Processes

1966 ◽  
Vol 181 (12) ◽  
pp. 32-38
Author(s):  
D. Dowson ◽  
J. A. Robertson
Keyword(s):  
Boundary Lubrication ◽  
Operating Conditions ◽  
Lubrication Conditions

The authors outline the fundamental aspects of lubrication conditions and distinguish between hydrodynamic, elastohydrodynamic, and boundary lubrication. The discussion is concerned with the physics rather than the mathematics. The important lubricant properties and the role of bearing geometry are considered. This discussion of modern views on lubrication is perfectly general but operating conditions encountered in textile machinery are considered so that the various types of lubrication in practice can be identified.

Experimental Investigation of Porous Bronze Bearings

1973 ◽  
Vol 95 (2) ◽  
pp. 173-179 ◽  
Author(s):  
C. Cusano ◽  
R. M. Phelan
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Coefficient Of Friction ◽  
Boundary Lubrication ◽  
Operating Conditions ◽  
The Coefficient Of Friction ◽  
Theoretical Analyses ◽  
Lubrication Conditions

An experimental study was made of the performance of porous bronze bearings under different operating conditions. A PV value of 50,000 psi ft/min was found to be too high for the assembly used when the bearings were lubricated only by the oil initially provided within their structure. Tests at a PV value of 33,000 psi ft/min gave satisfactory results. The coefficient of friction was found to vary with load and to be almost independent of speed for the bearings tested under boundary lubrication conditions. Except for relatively light loads and moderate and higher speeds, the bearings operate under boundary lubrication conditions. When pressurized oil was supplied to the bearings, it was found that, for the same operating conditions, porous bearings run at higher eccentricity ratios than solid bearings, as predicted by theoretical analyses.

Role of Reynolds and Archimedes numbers in particle-fluid flows

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Haim Kalman
Keyword(s):  
Flow Regime ◽  
Power Function ◽  
Fluid Flows ◽  
Limited Range ◽  
Operating Conditions ◽  
Pneumatic Conveying ◽  
Particulate Materials ◽  
Simple Power ◽  
Simple Power Function

AbstractAny scientific behavior is best represented by nondimensional numbers. However, in many cases, for pneumatic conveying systems, dimensional equations are developed and used. In some cases, many of the nondimensional equations include Reynolds (Re) and Froude (Fr) numbers; they are usually defined for a limited range of materials and operating conditions. This study demonstrates that most of the relevant flow types, whether in horizontal or vertical pipes, can be better described by Re and Archimedes (Ar) numbers. Ar can also be used in hydraulic conveying systems. This paper presents many threshold velocities that are accurately defined by Re as a simple power function of Ar. Many particulate materials are considered by Ar, thereby linking them to a common behavior. Using various threshold velocities, a flow regime chart for horizontal conveying is presented in this paper.

scholarly journals Comparison Between the Action of Nano-Oxides and Conventional EP Additives in Boundary Lubrication

Lubricants ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 54
Author(s):  
Valdicleide Silva Mello ◽  
Marinalva Ferreira Trajano ◽  
Ana Emilia Diniz Silva Guedes ◽  
Salete Martins Alves
Keyword(s):  
Friction Coefficient ◽  
Boundary Lubrication ◽  
Friction And Wear ◽  
Film Formation ◽  
Environmental Issues ◽  
Protective Film ◽  
Extreme Pressure ◽  
Extreme Pressure Additives ◽  
Environmental Requirements ◽  
Lubrication Conditions

Additives are essential in lubricant development, improving their performance by the formation of a protective film, thus reducing friction and wear. Some such additives are extreme pressure additives. However, due to environmental issues, their use has been questioned because their composition includes sulfur, chlorine, and phosphorus. Nanoparticles have been demonstrated to be a suitable substitute for those additives. This paper aims to make a comparison of the tribological performance of conventional EP additives and oxides nanoparticles (copper and zinc) under boundary lubrication conditions. The additives (nanoparticles, ZDDP, and sulfur) were added to mineral and synthetic oils. The lubricant tribological properties were analyzed in the tribometer HFRR (high frequency reciprocating rig), and during the test, the friction coefficient and percentual of film formation were measured. The wear was analyzed by scanning electron microscopy. The results showed that the conventional EP additives have a good performance owing to their anti-wear and small friction coefficient in both lubricant bases. The oxides nanoparticles, when used as additives, can reduce the friction more effectively than conventional additives, and displayed similar behavior to the extreme pressure additives. Thus, the oxide nanoparticles are more environmentally suitable, and they can replace EP additives adapting the lubricant to current environmental requirements.

Wear Behavior and Chemical Friction Modification in Binary-Additives System under Boundary-Lubrication Conditions

1981 ◽  
Vol 24 (4) ◽  
pp. 517-525 ◽  
Author(s):  
Masayuki Kagami ◽  
Masataro Yagi ◽  
Seiichiro Hironaka ◽  
Toshio Sakurai
Keyword(s):  
Boundary Lubrication ◽  
Wear Behavior ◽  
Lubrication Conditions

The Role of Offshore Monitoring in an Effective Deepwater Riser Integrity Management Program

2007 ◽  
Author(s):  
Brittany Goldsmith ◽  
Elizabeth Foyt ◽  
Madhu Hariharan
Keyword(s):  
Failure Modes ◽  
Human Life ◽  
Management Program ◽  
Measured Data ◽  
Operating Conditions ◽  
Environmental Damage ◽  
Positioning Systems ◽  
Integrity Management ◽  
Deepwater Riser

As offshore field developments move into deeper water, one of the greatest challenges is in designing riser systems capable of overcoming the added risks of more severe environments, complicated well requirements and uncertainty of operating conditions. The failure of a primary riser component could lead to unacceptable consequences, including environmental damage, lost production and possible injury or loss of human life. Identification of the risks facing riser systems and management of these risks are essential to ensure that riser systems operate without failure. Operators have recognized the importance of installing instrumentation such as global positioning systems (GPS), vessel motion measurement packages, wind and wave sensors and Acoustic Doppler Current Profiler (ADCP) units to monitor vessel motions and environmental conditions. Additionally, high precision monitoring equipment has been developed for capturing riser response. Measured data from these instruments allow an operator to determine when the limits of acceptable response, predicted by analysis or determined by physical limitations of the riser components, have been exceeded. Regular processing of measured data through automated routines ensures that integrity can be quickly assessed. This is particularly important following extreme events, such as a hurricane or loop current. High and medium alert levels are set for each parameter, based on design analysis and operating data. Measured data is compared with these alert levels, and when an alert level is reached, further response evaluation or inspection of the components in question is recommended. This paper will describe the role of offshore monitoring in an integrity management program and discuss the development of alert levels based on potential failure modes of the riser systems. The paper will further demonstrate how this process is key for an effective integrity management program for deepwater riser systems.

Efficient Simulation of Gear Contacts Including Transient Elastohydrodynamic Effects

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Peter Fietkau ◽  
Bernd Bertsche
Keyword(s):  
Three Dimensional ◽  
Direct Determination ◽  
Simulation Method ◽  
Elastic Half Space ◽  
Operating Conditions ◽  
Multibody Simulation ◽  
Multibody Model ◽  
Gear Contact ◽  
Oil Films ◽  
Lubrication Conditions

This paper describes an efficient transient elastohydrodynamic simulation method for gear contacts. The model uses oil films and elastic deformations directly in the multibody simulation, and is based on the Reynolds equation including squeeze and wedge terms as well as an elastic half-space. Two transient solutions to this problem, an analytical and a numerical one, were developed. The analytical solution is accomplished using assumptions for the gap shape and the pressure in the middle of the gap. The numerical problem is solved using multilevel multi-integration algorithms. With this approach, tooth impacts during gear rattling as well as highly loaded power-transmitting gear contacts can be investigated and lubrication conditions like gap heights or type of friction may be determined. The method was implemented in the multibody simulation environment SIMPACK. Therefore it is easy to transfer the developed element to other models and use it for a multitude of different engineering problems. A detailed three-dimensional elastic multibody model of an experimental transmission is used to validate the developed method. Important values of the gear contact like normal and tangential forces, proportion of dry friction, and minimum gap heights are calculated and studied for different conditions. In addition, pressure distributions on tooth flanks as well as gap forms are determined based on the numerical solution method. Finally, the simulation approach is validated with measurements and shows good consistency. The simulation model is therefore capable of predicting transient gear contact under different operating conditions such as load vibrations or gear rattling. Simulations of complete transmissions are possible and therefore a direct determination of transmission vibration behavior and structure-borne noise as well as of forces and lubrication conditions can be done.

The role of surface topography and normal load in the initiation of ratchetting-peak friction, seizure, scuffing, and elastic shakedown

2021 ◽  
pp. 1-12
Author(s):  
Vimal Edachery ◽  
V. Swamybabu ◽  
Gurupatham Anand ◽  
Paramasamy Manikandan ◽  
Satish V. Kailas
Keyword(s):  
Steady State ◽  
Surface Topography ◽  
Sliding Wear ◽  
Friction And Wear ◽  
Critical Parameter ◽  
Normal Load ◽  
Sliding Direction ◽  
Elastic Shakedown ◽  
Lubrication Conditions

Abstract Surface topography is a critical parameter that can influence friction and wear in engineering applications. In this work, the influence of surface topography directionality on seizure and scuffing initiation during tribological interactions is explored. For this, unidirectional sliding wear experiments were carried out in immersed lubrication conditions for various normal loads. The tribological interactions were studied using EN31-60 HRC flats and SAE52100-60HRC pins in a sphere on flat configuration. The results show that, in some cases, the sliding interactions in the initial cycles lead to a high friction coefficient of up to ∼0.68 in lubricated conditions, which was termed as ‘peak friction’, and this was accompanied by scuffing. The existence of peak friction was found to be dependent on surface topography directionality, especially when the directionality in topography was parallel to the sliding direction. Continuous ratchetting was found to be the cause of peak friction which was accompanied by seizure and scuffing. When the topography directionality was perpendicular or independent of sliding direction, elastic shakedown occurred at earlier cycles and prevented peak friction initiation, scuffing and also facilitated for higher steady-state friction values.

Thin coatings with tetrahedral amorphous carbon structure and their behavior in boundary lubrication conditions

2020 ◽  
pp. 506-511
Author(s):  
V.D. Samusenko ◽  
I.A. Zavidovskii ◽  
O.A. Streletskii ◽  
I.A. Buyanovskii ◽  
M.M. Khrushchov ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Boundary Lubrication ◽  
Carbon Structure ◽  
Thin Coatings ◽  
Tribological Tests ◽  
Tetrahedral Amorphous Carbon ◽  
Structural Peculiarities ◽  
Lubrication Conditions

The results of an investigation of the structural peculiarities of the thin ta-C coatings obtained by the method of impulse arc sputtering of graphite and of their tribological tests in boundary lubrication conditions are presented.

scholarly journals Thermal and Chemical Integrity of Ru Electrode in Cu/TaOx/Ru ReRAM Memory Cell

2019 ◽  
Vol 8 (12) ◽  
pp. N220-N233
Author(s):  
Mohammad Al-Mamun ◽  
Sean W. King ◽  
Marius Orlowski
Keyword(s):  
Memory Cell ◽  
Operating Conditions ◽  
Electrical Performance ◽  
Pt Electrode ◽  
Switching Performance ◽  
Inert Electrode ◽  
Work Function Difference ◽  
The Impact ◽  
Si Wafer

A good candidate for replacing the inert platinum (Pt) electrode in the well-behaved Cu/TaOx/Pt resistive RAM memory cell is ruthenium (Ru), already successfully deployed in the CMOS back end of line. We benchmark Cu/TaOx/Ru device against Cu/TaOx/Pt and investigate the impact of embedment of Cu/TaOx/Ru on two different substrates, Ti(20nm)/SiO2(730nm)/Si and Ti(20nm)/TaOx(30nm)/SiO2(730nm)/Si, on the cell's electrical performance. While the devices show similar switching performance at some operating conditions, there are notable differences at other operation regimes shedding light on the basic switching mechanisms and the role of the inert electrode. The critical switching voltages are significantly higher for Ru than for Pt devices and can be partly explained by the work function difference and different surface roughness of the inert electrode. The poorer switching properties of the Ru device are attributed to the degraded inertness properties of the Ru electrode as a stopping barrier for Cu+ ions as compared to the Pt electrode. However, some of the degraded electrical properties of the Ru devices can be mitigated by an improved integration of the device on the Si wafer. This improvement is attributed to the suppression of crystallization of Ru and its silicidation reactions that take place at elevated local temperatures, present mainly during the reset operation. This hypothesis has been corroborated by extensive XRD studies of multiple layer systems annealed at temperatures between 300K and 1173K.

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