Another way to compute the sheet metal deformation is the neutral fiber
definition (K Factor):
W = a * (R + k * T)
W is the flat bend width
R the inner bend radius
T the sheet metal thickness
a the inner bend angle in radians.
If b is the opening bend angle in degrees:
a = p * (180 - b) / 180
Physically, the neutral fiber represents the limit between the material
compressed area inside the bend and the extended area outside the bend.
Ideally, it is represented by an arc located inside the thickness and centered
on the bend axis. Therefore the K Factor always has a value between 0 and