K Factor for Different Metals

[13]

Let us see how many sheet metal gurus are out there...

Is the K-factor purely a geometric coefficient for sheet metal bending, or does it change depending on the material? Take for instance, form-bending with a male and female die..will the K-factor be different for different metals give the same geometry, ie .125 thick metal of different varieties? And, if so please explain why.
I believe that the K-factor is different because the modulus of elasticity and poissons ratio. Different metals will exhibit different values of deformation.
Published values, for ex. in the machinery handbook are different for copper, aluminum, stainless, etc. The bottom line is, is the neutral axis different, and will different "flat" lengths for different metals be required to produce the same formed/finished product. Good luck and please keep posting with all of your comments. Thanks in advance, 13

 

[metman]

You answered part of your question... does it change depending on the material?... I don't think Machinery's Handbook would publish values without empirical results to establish the values.

I could be wrong but I don't see poisson's ratio entering into the equation since by definition a sheet has a large w/t ratio so that it is difficult for me to envision triaxial stresses applying.

 

[PeterCharles]

We used the Bendworks document to "reverse engineer" the K factors for brakepresses we use to fold up steel plate, then use that in Inventor to good effect.