Ok, try one more time.
Here is an equation for the k-factor given by SolidWorks in the Help file for bend calculation table, with no explanation:
The "lg(r/s)" is the part that gets me. I have no idea what "lg" is. (r/s) is probably the ratio of the bend radius to the thickness. With no "*" between the lg and the (r/s), it means the whole thing is probably one term.
I know what you're thinking. "Why is Lombard wasting his time on something so esoteric?" I'm with you. It's just that I'm kind of obsessed with explaining stuff that SW leaves unexplained. I feel the need to figure this out, even though it does seem like a complete waste of time.