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.[1]
Mathematically it is the cumulative probability density function of the surface profile's height and can be calculated by integrating the probability density function.[2]
The Abbott-Firestone curve was first described by Ernest James Abbott and Floyd Firestone in 1933.[3] [4] It is useful for understanding the properties of sealing and bearing surfaces. It is commonly used in the engineering and manufacturing of piston cylinder bores of internal combustion engines.[5] The shape of the curve is distilled into several of the surface roughness parameters, especially the Rk family of parameters.