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Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy needed for deformation (or movement) of the wheel, roadbed, etc., is recovered when the pressure is removed.
This theory is exact for the situation of an infinite friction coefficient in which case the slip area vanishes, and is approximative for non-vanishing creepages. It does assume Coulomb's friction law, which more or less requires (scrupulously) clean surfaces. This theory is for massive bodies such as the railway wheel-rail contact.
The coefficient of friction depends on the materials used; for example, ice on steel has a low coefficient of friction, while rubber on pavement has a high coefficient of friction. Coefficients of friction range from near zero to greater than one. The coefficient of friction between two surfaces of similar metals is greater than that between ...
Tribology is the science and engineering of understanding friction, lubrication and wear phenomena for interacting surfaces in relative motion.It is highly interdisciplinary, drawing on many academic fields, including physics, chemistry, materials science, mathematics, biology and engineering. [1]
Definition Field of application Coefficient of kinetic friction: mechanics (friction of solid bodies in translational motion) Coefficient of static friction: mechanics (friction of solid bodies at rest) Dieterich-Ruina-Rice number
Thurston did not have the experimental means to record a continuous graph of the coefficient of friction but only measured it at discrete points. This may be the reason why the minimum in the coefficient of friction for a liquid-lubricated journal bearing was not discovered by him, but was demonstrated by the graphs of Martens and Stribeck.
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls.
The coefficient of friction at the interface is usually lower. Example: If a 100 kg object is dragged for 10 m along a surface with the coefficient of friction μ = 0.5, the normal force is 981 N and the work done (required energy) is (work=force x distance) 981 × 0.5 × 10 = 4905 joules. Now give the object 4 wheels.