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Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. [7] [8] Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. [9] [10] [11] Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
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.
Thus, for a given viscosity and load, the Stribeck curve shows how friction changes with increasing velocity. Based on the typical progression of the Stribeck curve (see right), three lubrication regimes can be identified. Boundary lubrication Solid surfaces come into direct contact, load supported mainly by surface asperities, high friction
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]
An animation of a sphere pressing against an elastic material, increasing the contact area. Classical contact mechanics is most notably associated with Heinrich Hertz. [3] [4] In 1882, Hertz solved the contact problem of two elastic bodies with curved surfaces. This still-relevant classical solution provides a foundation for modern problems in ...
Mechanical advantage that is computed using the assumption that no power is lost through deflection, friction and wear of a machine is the maximum performance that can be achieved. For this reason, it is often called the ideal mechanical advantage (IMA). In operation, deflection, friction and wear will reduce the mechanical advantage.
The impulse excitation technique (IET) is a non-destructive material characterization technique to determine the elastic properties and internal friction of a material of interest. [1] It measures the resonant frequencies in order to calculate the Young's modulus , shear modulus , Poisson's ratio and internal friction of predefined shapes like ...
Friction, the force opposing to the relative motion, is usually idealized by means of some empirical laws such as Amonton’s First and Second laws and Coulomb's law. At the nanoscale, however, such laws may lose their validity. For instance, Amonton's second law states that friction coefficient is independent from the area of contact.