Hertz contact theory
Hertz contact theory is a classical theory of contact mechanics and is a very useful tool for engineers and researchers. Even though the derivation of the theory is relatively difficult, the final solution is a […]
Tribology Wiki
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Hertz equations for elliptical, spherical and cylindrical contacts
A theoretical background to the Hertz contact theory can be found here. Line Contact (Cylindrical contact) In case of two cylinders in contact (with radii ), as shown in Fig. 1, the Hertzian radius of […]
What Are Lubricants?
Definition Lubricant is a substance which is used to control (more often to reduce) friction and wear of the surfaces in a contact of the bodies in relative motion. Depending on its nature, lubricants are […]
Coefficients of Kinetic and Static Friction
Friction is a force resisting relative motion and it occurs at the interface between the bodies, but also within the bodies, like in case of fluids. The concept of friction coefficient was first formulated by […]
Archard Wear Equation
The importance of wear losses leads to considerable effort in establishing theories and predictive models of wear. Meng and Ludema [1] have identified 182 equations for different types of wear. Among them were empirical relations, […]
Hydrodynamic Lubrication (HL): Theory and Definition
Definition of Hydrodynamic Lubrication (HL) Hydrodynamic lubrication theory is a theory used to reduce friction and/or wear of rubbing solids with the aid of liquid lubricant. For a vast majority of the surfaces encountered in […]
Elastic Deformation
Definition Elastic deformation is a change of the shape of the body as a reaction to applied stress. This deformation is only temporary and once the stress is released, the undeformed shape of the body […]
Tribometers
Tribometers are the devices used to analyze and characterize tribological systems. The most common direct measurement is the measurement of friction coefficient (and shear strength). During the post processing stage other quantities can be measured, […]
Analytical Solution of Reynolds Equation: Grubin’s Approximation
Derivation of famous analytical solution of EHL equations is presented here. In 1949, Grubin obtained a solution for so called elasto-hydrodynamic lubrication (EHL) line contact problem with simplifications known as Grubin approximation. He was the […]