I haven't seen anything in opencascade pertaining to sheet metal. Are you talking doing a FEA forming simulation, or are you talking about simple linear bends(think angle iron)? I haven't been around the forming simulations in a while, but aren't they still using a surface mesh and not a solid? I don't know of any FEA for sheet metal in the open-source world. I had a friend tell me that the first go around of ls-dyna was in the public domain.....and wiki says it's there http://en.wikipedia.org/wiki/LS-DYNA
I looked for it years ago and never found it.
Nobody mentioned romans blog so here. he has a lot of good articles, but I gave you a link to the start of the geometry.
http://opencascade.blogspot.com/2009/02 ... scade.html
Assuming you have the opencascade doc look for tutorial.pdf modata.pdf modalg.pdf.
as a Die Designer, this intersests me, so fire away with questions and I will answer the ones I can. Good luck.