Solidworks simulation - Part file Vs assembly file with same part

Hi,

I was trying to run study for some problem and just wanted to run a simple study to compare results between part file simulation and assembly file.

For this -  I created a simple square part 12 in X 12 in X 0.125 in thick.

               Applied Aluminum 6061-T6 from soldiworks library

               created static study with fixed both left & right faces & applied 144 lbf force on top face as shown in attached results file & ran the study.

             - Inserted same file into assembly file and re-created same simulation model and ran the study to compare results.

I found that assembly simulation model seeing more stresses and displacements. Could somebody help me understanding why results were so different?

thanks,

pavv

Solidworks 2012

Windows 7 X 64 bit

SolidworksSimulation