Cyclic Symmetry, Pressure Loads on assembly

Hi,

I am running Creo 3 Simulate, we are trying to determine the stress within the walls of a pressure vessel assembly from external pressure, but using cyclic symmetry to speed up the process.

The model runs ok and the analysis completes, but the result is always far beyond the material yield turning the model red, this happens even if the external pressure load is very low, say around 100psi, the material yield is 130ksi, the walls are more than capable of with standing this pressure, normal operating pressure would be 10kpsi.

Thanks

Geoff.