Simulation Pressure Disc

I am new to Simulation and want to be sure I am doing this right.

Enclosed are pictures of a viewport in a hyperbaric chamber. Image #1 is the viewport housing. The viewport opening is 8” diameter on the outside and will accept an 11” O.D. viewport disc. Image #2 is the replacement viewport disc with an access tube welded into it & some tapped holes for stuffing tubes. Image #2 is replacing an 11” diameter x 1-1/2” thick acrylic viewport that was used for observation. The new replacement viewport disc & tube are made of 316L Stainless Steel. The backing plate (not shown) will hold the viewport in place.

What I want to do is to apply a pressure of 100 psi to the inside of the disc and see where the stresses build; at the weld around the tube and/or at the 8” outside viewport dia. (Assume the pressure inside the tube is also 100psi.)

I have done a couple of simulations of this but I'm just not sure I got the right result. It should be simple. Apply a 100PSI force to the backside & weld, then fixture it at the 8" dia viewport opening. In actuality, as you apply force to the inside, the disc will balloon and "slide" into the opening. If I fixture it at an 8" diameter circle then those points do not move & give me a result that is not real.

My gut feeling says this will work, no problem, but I have to prove it thru FEA. To make sure I am doing it right can someone give me a step by step guide. Or better yet actually do a study that I could reverse learn it. I can provide SW files in SolidWorks 2011 SP3.0 if I get an email address.

SolidworksSimulation