Sheetmetal K-Factor
K-Factor is a ratio that represents the location of the neutral sheet with respect to the thickness of the sheet metal part.
2015 Solidworks Help - K-Factor
Bend allowance with a K-Factor is calculated as follows:
BA=pi(R + KT) A/180
where:
BA = bend allowance
R = inside bend radius
K = K-Factor, which is t/T
T = material thickness
t = distance from inside face to neutral sheet
A = bend angle in degrees (the angle through which the material is bent)