I am trying to perform an impact test on a bicycle frame (ISO 4210-6).  I have the following problems:

1. Forcing a load doesn't seem to make sense, since the maximum load might occur before the impact energy is absorbed.  Therefore, I think I need to simulate a displacement.  My end goal is to simulate this in a non-linear study, but to start I just want to set the model up to simulate a fixed displacement well below the yield strength.  The technique that I am using gives two different stresses though even when the load is set up to produce the same displacement:

Using a fixed load:

Using a fixed displacement:

To summarize,

     275N load on left most surface                    2.1mm displacement               3.1E7 N/m^2          0.25J Total strain energy

     2mm displacement, left-most surface          2.1mm displacement               3.2E8 N/m^2          0.29J Total strain Energy

So, not a good match. I have never done a fixed displacement set-up before, so very possible I'm doing something silly.

2. The color gradient does not work on the fixed displacement.

The assembly file (2015) is attached, but I had to strip the results out to be able to post this at a reasonable size.  Please note that the original frame has been replaced by a very, very simplistic entity just for the sake of portability and so that confidentiality is not breached.

Any observations would be appreciated.