I am attempting to create a simulation study that would match real world results for an aluminum profile that we have designed (96" long, 6063-T5; fixed on both sides and has a 200 lb concentrated load in the middle). We have the real world displacement data for the described loading situation, and I want to get close to it in a reasonable and reproducible manner.

I have attempted modelling the profile as a beam, and running the simulation in the von-Mises plasticity material model, but that fails almost immediately, stating that the iterations are not converging.

I also modelled it as a solid, fixed both end faces and tried both a concentrated force (at a point) and a force at a face made by a split line, and received the same error (albeit with a  longer solve time). 

I've attached screenshots to show how the profile looks, and the loading situation. I can't help feeling that I am missing something fundamental to how I am supposed to set this up. Please help!

PS. The only successful runs I've had were through the solid model, utilizing the "Plasticity - Tresca" material model, though I haven't the slightest idea why and it makes me question the validity of those results (along with the fact that the resultant displacement implies that it is significantly stiffer than it's real world counterpart, which is not expected due to the way the test was conducted).

PPS. I did try to increase the convergence tolerance, from the default 0.0001 all the way up to 10, but it always fails.