The Abbott-Firestone curve or bearing area curve (BAC) describes the
surface texture of an object. The curve can be found from a profile trace by drawing lines parallel to the datum and measuring the fraction of the line which lies within the profile.
Mathematically it is the
cumulative probability density function of the surface profile's height and can be calculated by integrating the profile trace.
The Abbott-Firestone curve was first described by
Ernest James Abbott and
Floyd Firestone in 1933. It is useful for understanding the properties of sealing and bearing surfaces. It is commonly used in the engineering and manufacturing of
piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas- ...
cylinder bores of
internal combustion engines
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...
.
The shape of the curve is distilled into several of the
surface roughness parameters, especially the Rk family of parameters.
References
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Engineering mechanics
Tribology