The above picture is the simulation in question.  I have applied 100Mpa of pressure to the cavity surface. 

My first question is why are the arrows so speratic?  there are no arrows showing pressure in the corrner even though I do have pressure applied there...  Do the arrows really mean anything at all?

The more pressing matter is the stress ammounts.  From what I understand I should be seeing an equarilibrium on the surface where the pressure is being applied.  That means I should see -100Mpa across the whole thing or blue in the picture.  Why do the corners show above -70Mpa?  Is the program for some reason only applying pressure to the flat surfaces that could explain the odd numbers.