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Normal contact stiffness is a physical quantity related to the generalized force displacement behavior of rough surfaces in contact with a rigid body or a second similar rough surface. [ 1 ] [ 2 ] Specifically it is the amount of force per unit displacement required to compress an elastic object in the contact region.
Contact mechanics is the study of the deformation of solids that touch each other at one or more points. [ 1 ] [ 2 ] A central distinction in contact mechanics is between stresses acting perpendicular to the contacting bodies' surfaces (known as normal stress ) and frictional stresses acting tangentially between the surfaces ( shear stress ).
Stiffness depends upon material properties and geometry. The stiffness of a structural element of a given material is the product of the material's Young's modulus and the element's second moment of area. Stiffness is measured in force per unit length (newtons per millimetre or N/mm), and is equivalent to the 'force constant' in Hooke's Law.
Values for the flexural strength measured with four-point bending will be significantly lower than with three-point bending., [8] Compared with three-point bending test, this method is more suitable for strength evaluation of butt joint specimens. The advantage of four-point bending test is that a larger portion of the specimen between two ...
Approximate specific stiffness for various materials. No attempt is made to correct for materials whose stiffness varies with their density. Material Young's modulus Density (g/cm 3) Young's modulus per density; specific stiffness (10 6 m 2 s −2) Young's modulus per density squared (10 3 m 5 kg −1 s −2) Young's modulus per density cubed ...
The equation based definition of hardness is the pressure applied over the contact area between the indenter and the material being tested. As a result hardness values are typically reported in units of pressure, although this is only a "true" pressure if the indenter and surface interface is perfectly flat. [citation needed]
where S = dP/dh is the apparent tip-sample contact stiffness at the onset of unload, ˙ is the displacement rate just before the unload, ˙ is the unloading rate, and is the true (i.e. viscosity-corrected) tip-sample contact stiffness which is related to the reduced modulus and the tip-sample contact size by the Sneddon relation.
Structural dynamics is a type of structural analysis which covers the behavior of a structure subjected to dynamic (actions having high acceleration) loading. Dynamic loads include people, wind, waves, traffic, earthquakes, and blasts.