Normal contact stiffness is a physical quantity related to the generalized force displacement behavior of

rough surface Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, ...

s in contact with a

rigid body In physics, a rigid body (also known as a rigid object) is a solid body in which deformation is zero or so small it can be neglected. The distance between any two given points on a rigid body remains constant in time regardless of external force ...

or a second similar rough surface. Rough surfaces can be seen as consisting of large numbers of

asperities In materials science, asperity, defined as "unevenness of surface, roughness, ruggedness" (from the Latin ''asper''—"rough"), has implications (for example) in physics and seismology. Smooth surfaces, even those polished to a mirror finish, a ...

. As two solid bodies of the same material approach one another, the asperities interact, and they transition from conditions of non-contact to homogeneous bulk behaviour. The varying values of stiffness and true contact area that is exhibited at an interface during this transition are dependent on the conditions of applied pressure and are of importance for the study of systems involving the physical interactions of multiple bodies including

granular matter A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when grains collide). The constituents that compose gra ...

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

contacts, and thermal contacts, where the interface-localized structures govern overall system performance.Contact stiffness of multiscale surfaces
International Journal of Mechanical Sciences, 2017

Surface structure

The role of surface structure in normal contact mechanics, in terms of stiffness and true contact area is a frequently studied topic. Parameters of roughness,

fractal dimension In mathematics, more specifically in fractal geometry, a fractal dimension is a ratio providing a statistical index of complexity comparing how detail in a pattern (strictly speaking, a fractal pattern) changes with the scale at which it is meas ...

and asperity geometry are often discussed{{citation needed, date=November 2016 with reference to their significance on contact mechanics of surfaces.

References

Surfaces Tribology Mechanics Friction Classical mechanics Force