Friction Coefficients Compendium

8/2/2019 Friction Coefficients Compendium

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Friction Factors

Note: I have tried to include a wide range of relevant information on this topic. It will be noted that friction values in one section do notnecessarily agree with values in another section...Please use the linked references at the bottom of the page for more detailed information.

Factors Affecting friction..... Static Friction.....Sliding/dynamic/kinetic friction.....Coefficients of Friction.....Rolling Friction..... Plain Bearings Friction..... Rolling Bearing Friction.....Clutch Brake Friction.....Bolted Joints..... Power Screws.....Press Fits....Test Methods.... Civils friction values.... Linked Reference Info
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Factors affecting the friction between surfacesDry surfaces

1. For low surface pressures the friction is directly proportional to the pressure between the surfaces. As the pressurerises the friction factor rises slightly. At very high pressure the friction factor then quickly increases to seizing

2. For low surface pressures the coefficient of friction is independent of surface area.3. At low velocities the friction is independent of the relative surface velocity. At higher velocities the coefficent of

friction decreases.

Well lubricated surfaces

1. The friction resistance is almost independent of the specific pressure between the surfaces.2. At low pressures the friction varies directly as the relative surface speed

3. At high pressures the friction is high at low velocities falling as the velocity increases to a minimum at about 0,6m/s.The friction then rises in proportion the velocity 2.

4. The friction is not so dependent of the surface materials

5. The friction is related to the temperature which affects the viscosity of the lubricant

Please refer to...Surface Friction Notes

Static Coefficient of Friction

The static friction coefficient () between two solid surfaces is defined as the ratio of the tangential force (F) required to produce sliding divided by

the normal force between the surfaces (N)

= F /N

For a horizontal surface the horizontal force (F) to move a solid resting on a flat surface

F= x mass of solid x g.

If a body rests on an incline plane the body is prevented from sliding down because of the frictional resistance. If the angle of the plane isincreased there will be an angle at which the body begins to slide down the plane. This is the angle of repose and the tangent of this angle is the
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Links to Friction Information

1. Carbide Depot.. Friction Coefficients

2. Supercivilcd Com.. Coefficient of Sliding Friction for various civil Materials

3. Fastener Design Manual...NASA GRC RP-1228 (9,6 Mbyte pdf file) Includes comprehensive table withfriction values.

4. Physlinks - Coefficient of Friction...A Table of Friction Coefficients

5. Engineers Edge- Coefficient of Friction...A Table of Friction Coefficients

6. School for Champions...Lots of very useful Notes

7. Bolt Council...Guide to Design Criteria for Bolted and Riveted Joints.(6,7 Mbyte pdf ). Info on Slipcoefficients (P.82) etc

8. MD Metric...Datasheet for PTFE

9. Friction coefficients in "Rail- Wheel" contacts .......Downloadable paper providing very theoreticalinformation

10. Hypertextbooks _Physics Factbooks.....Physics Factbook .A page inlcuding a number of very good (school)articles on coe-fficents of friction of different materials

11. Fund'ls ofFriction and Wear of Automobile Brake Materials .....Paper Download ..Very informativedocument

12. Classical Friction...A very simple and clear description of what determines the coefficient of friction.

13. 12 Friction...Brown University-Division of Engineering..Very clear document on friction

14. Rolling Friction...Very useful notes on rolling friction

15. Friction of Rocks...Interesting paper related to earthquakes and the friction forces involved

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Last Updated 28/01/2012
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Friction Coefficients Compendium