Friction Coefficients Measured at Lubricated Planar Contacts During Start-Up

1988 ◽  
Vol 110 (3) ◽  
pp. 533-538 ◽  
Author(s):  
E. H. Gassenfeit ◽  
A. Soom
Keyword(s):  
Static Friction ◽  
Transient Behavior ◽  
Molybdenum Disulphide ◽  
Friction Behavior ◽  
Friction Characteristic ◽  
Friction Coefficients ◽  
Motion Data ◽  
Start Up ◽  
Planar Contact ◽  
Lubrication Conditions

Measurements of instantaneous coefficients of friction and associated motions during start-up at a planar contact are presented for four different lubrication conditions. The various patterns of transient behavior are discussed. Difficulties in interpreting static friction coefficients during rapidly applied tangential loads are described in relation to the motion data. It is shown that a molybdenum disulphide grease yields a friction characteristic that is quite different from either dry or boundary lubricated conditions in the presence of liquid lubricants. Transition distances from a static or maximum initial friction to kinetic conditions are examined and found to be considerably longer than had been previously found for concentrated contacts. Some suggestions regarding future studies of unsteady friction behavior are made.

Experimental Investigation on the Friction Coefficients for Different Materials, Lubrication Conditions and Coatings in Bolted Joints

2021 ◽  
Author(s):  
Stefano Fini ◽  
Massimiliano De Agostinis ◽  
Dario Croccolo ◽  
Giorgio Olmi ◽  
Francesco Robusto ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Bolted Joints ◽  
Friction Coefficients ◽  
Lubrication Conditions

Frictional Vibrations

1955 ◽  
Vol 22 (2) ◽  
pp. 207-214
Author(s):  
David Sinclair
Keyword(s):  
Coefficient Of Friction ◽  
Equations Of Motion ◽  
Static Friction ◽  
Uniform Motion ◽  
Friction Characteristic ◽  
Stick Slip ◽  
The Coefficient Of Friction ◽  
Brake Lining ◽  
Solid Bodies ◽  
Frictional Vibrations

Abstract Frictional vibrations, such as stick-slip motion and automobile-brake squeal, which occur when two solid bodies are rubbed together, are analyzed mathematically and observed experimentally. The conditions studied are slow uniform motion and relatively rapid simple harmonic motion of brake lining over a cast-iron base. The equations of motion show and the observations confirm that frictional vibrations are caused primarily by an inverse variation of coefficient of friction with sliding velocity, but their form and occurrence are greatly dependent upon the dynamical constants of the mechanical system. With a constant coefficient of friction, the vibration initiated whenever sliding begins is rapidly damped out, not by the friction but by the “natural” damping of all mechanical systems. The coefficient of friction of most brake linings and other organic materials was essentially invariant with velocity, except that the static coefficient was usually greater than the sliding coefficient. Most such materials usually showed a small decrease in coefficient with increasing temperature. The persistent vibrations resulting from the excess static friction were reduced or eliminated by treating the rubbing surfaces with polar organic compounds which produced a rising friction characteristic.

Experimental investigation on Stribeck curves of different elastic modulus materials under oil and water lubrication conditions

2020 ◽  
Vol 72 (6) ◽  
pp. 805-810
Author(s):  
Hua Zhang ◽  
Guangwu Zhou ◽  
Ping Zhong ◽  
Kepeng Wu ◽  
Xingwu Ding
Keyword(s):  
Elastic Modulus ◽  
Friction Coefficient ◽  
Friction Pair ◽  
Water Lubrication ◽  
Contact Friction ◽  
Friction Coefficients ◽  
Content Type ◽  
Low Viscosity ◽  
Stribeck Curves ◽  
Lubrication Conditions

Purpose The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions. Design/methodology/approach Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system. Findings In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered. Originality/value The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

scholarly journals Evaluation of Friction Behavior and Surface Interactions of Cyano-Based Ionic Liquids under Different Sliding Contacts and High Vacuum Condition

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 69 ◽  
Author(s):  
Shouhei Kawada ◽  
Seiya Watanabe ◽  
Shinya Sasaki ◽  
Masaaki Miyatake
Keyword(s):  
Mass Spectrometry ◽  
Ionic Liquids ◽  
High Vacuum ◽  
Mass Spectrometry Analysis ◽  
Low Friction ◽  
Friction Behavior ◽  
Friction Coefficients ◽  
Spectrometry Analysis ◽  
Worn Surface ◽  
Nascent Surface

The friction coefficients of ionic liquids were evaluated by many investigations. Most investigations used fluorine-based ionic liquids as lubricants. However, these ionic liquids produce the corrosion wear. This investigation focuses on the use of cyano-based ionic liquids as lubricants. Compared to fluorine-based ionic liquids, cyano-based ionic liquids exhibit high friction coefficients against steel material. This work examines how the friction coefficients of cyano-based ionic liquids are influenced by the type of sliding material used (AISI 52100, TiO2, and tetrahedral amorphous carbon). TiO2 lubricated with 1-ethyl-3-methylimidazolium tricyanomethanide, and ta-C lubricated with 1-butyl-1methylpyrrolidinium tetracyanoborate exhibited very low friction coefficients, smaller than fluorine-based ionic liquids. Time-of-Flight Secondary Ion Mass Spectrometry analysis showed that anions adsorb onto the worn surface, suggesting that anion adsorption is a critical parameter influencing friction coefficients. Quadrupole Mass Spectrometry measurements revealed that cations decompose on the nascent surface, preventing adsorption on the worn surface. These results suggest that low friction coefficients require the decomposition of cations and adsorption of anions. The reactivity of nascent surface changes with the sliding material used due to varying catalytic activity of the nascent surfaces.

Coefficient of Start-Up Friction of Early Stage Osteoarthritic Cartilage Is Not Larger Than Normal Cartilage

2002 ◽  
Author(s):  
Hiromichi Fujie ◽  
Yoji Suzuki ◽  
Michi Ota ◽  
Kiyoshi Mabuchi
Keyword(s):  
Early Stage ◽  
Cruciate Ligament ◽  
Static Friction ◽  
Clinical Situation ◽  
Osteoarthritic Cartilage ◽  
Rabbit Knee ◽  
Start Up ◽  
The Coefficient Of Friction ◽  
Anterior Cruciate ◽  
Acl Transection

It is well known that the disease of osteoarthritis (OA) deteriorates the lubrication properties of articular cartilage. Previous studies [1,2] have demonstrated that the coefficient of friction of rabbit knee cartilage increases significantly in OA models. The coefficient of start-up (static) friction in the normal canine knee joint has also been observed to increase with the duration of static loading [3], and further increases in the start-up friction of osteoarthritic cartilage were induced by surface abrasion and papain injection [4]. However, the change in the start-up friction due to OA disease induced by anterior cruciate ligament (ACL) transection (ACL transection model), has not been fully determined in previous studies, although such a model is considered to display symptoms similar to the clinical situation. Therefore, we investigated the effect of osteoarthritic deterioration on the start-up friction in the ACL transection OA model in the present study.

Characteristics of Magneto-Rheological Elastomer under Stick-Slip Condition

2020 ◽  
Vol 842 ◽  
pp. 193-198
Author(s):  
Kwang Hee Lee ◽  
Chul Hee Lee
Keyword(s):  
Magnetic Field ◽  
Glass Plate ◽  
Static Friction ◽  
Low Noise ◽  
Friction Behavior ◽  
Stick Slip ◽  
The Difference ◽  
Magneto Rheological ◽  
Squeal Noise ◽  
The Magnetic Field

This paper examines the characteristics of stick-slip phenomena between the glass plate and Magneto-Rheological Elastomer (MRE) surface. Stick-slip phenomena are the spontaneous jerking motion that occurs while two objects are sliding over each other, usually accompanied by noise. Stick-slip is generated when it involves discontinuous frictional degradation when moving from static friction to dynamic friction. The phenomena can lead to uneven wear patterns, vibration and squeal noise which cause a shorter lifespan for the corresponding mechanical elements. MREs are kind of function materials to consist of a polymeric matrix with embedded ferromagnetic particles. Mechanical properties of the MREs can be controlled by the application of magnetic fields. The magnetic field-based controllability can be applied to the control of stick-slip phenomena. The friction experiment is conducted with the Reciprocating Friction Tester (RFT). The sliding speed of the RFT should be in low-speed conditions in order to make the stick-slips relatively easy to occur. A uniform magnetic field and a weight load are applied to the MRE sample to observe the effect of various experimental parameters on the movement of the stick-slip. In addition, frictional sounds due to the stick-slip phenomenon under different loads and magnetic field strength are measured and analyzed. The results of this experiment show that as the strength of the magnetic field increases, the difference in stiffness between the wipers-glass decreases, mitigating fricatives. The result is expected to be well applied to low-noise automotive wipers based on the controllability of friction behavior and squeal noise.

Influence of Water Absorption on Static Friction of Pure and Friction-Modified PA6 Polymers

2019 ◽  
Vol 799 ◽  
pp. 59-64
Author(s):  
Igor Velkavrh ◽  
Stefan Klien ◽  
Joel Voyer ◽  
Florian Ausserer ◽  
Alexander Diem
Keyword(s):  
Water Absorption ◽  
Static Friction ◽  
Polyamide 6 ◽  
Coated Steel ◽  
Friction Modifiers ◽  
Test Conditions ◽  
Influence Of Water ◽  
Steel Surfaces ◽  
Contact Pressures ◽  
Lubrication Conditions

In the present study, static coefficients of friction of pure and friction modified (FM) polyamide 6 (PA6) polymers against primer-coated steel surfaces were investigated under a series of nominal contact pressures and by considering the influences of water absorption by the polymer, temperature, counter-body surface roughness and lubrication conditions. Under the majority of the test conditions investigated, FM PA6 exhibited lower static friction than pure PA6. Under unlubricated conditions, this was due to the low adhesion of the FM PA6 provided by its friction modifying inclusions; while under lubricated conditions, a combination of softening due to water absorption and decreased adhesion provided by its friction modifiers enabled lower static friction, especially at medium and high contact pressures.

scholarly journals X-Ray Measurements in a Cavitating Centrifugal Pump During Fast Start-Ups

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
G. Bois
Keyword(s):  
Centrifugal Pump ◽  
Rocket Engine ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
X Ray ◽  
Speed Increase ◽  
Start Up ◽  
Fast Start ◽  
Start Ups

The start-up of rocket engine turbopumps is generally performed in a few seconds or even less. It implies that these pumps reach their nominal operating conditions after a few rotations only. During the start-up, the flow evolution within the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed increase. Significant pressure fluctuations, which may result in the development of cavitation, are observed. A centrifugal impeller whose transient behavior during start-ups has been detailed in a previous publication is considered. Three different cases of fast start-ups have been identified according the final operating point (Duplaa et al., 2010, “Experimental Study of a Cavitating Centrifugal Pump During Fast Start-Ups,” ASME J. Fluids Eng., 132(2), p. 021301). The aim of this paper is to analyze the evolution during the start-ups of the local amount of vapor in the blade to blade channels of the pump by fast X-ray imaging. This technique has enabled to calculate the time-evolution of the fluid density within the pump, which appears to be correlated with pressure time-evolutions. For each investigated start-up, X-ray measurements have been performed at three different sections of the impeller height. For each investigated start-up and section tested, measurements have been performed for several initial positions of the impeller, to estimate the measurement uncertainty, and to obtain records from different beam angles, like in tomography.

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