Unconstrained model?

[HVSmith]

Hi - I am working on a steady state thermal analysis. I have several heat fluxes defined, along with the thermal conductivity of the material. I wish to see the nodal temperature contour plot to show the temperature distribution. But when try to solve the model I always get an error such as:

The value of TEMP at node 529 is 3.114444971E+12. It is greater than
the current limit of 1000000. This generally indicates rigid body
motion as a result of an unconstrained model. Verify that your model
is properly constrained.


I have searched everywhere to try to understand what this means, or what can be done to solve the problem but have come up with nothing so far. Are you able to advise of any possible causes of this error?

There is only conduction in the model at present. The system is under vacuum conditions, so there will be no convection. I will need to add in radiative effects at a later date but just wanted to see the initial temperature distribution for now...

Thank you for any help you can give.

HVSmith

PS, very new to ANSYS, have done many tutorials but they do not seem to help with my actual problems!!

 

[seymours2571]

HVSmith,

I have seen this error before in other FEA software packages and it was related to not having a prescribed temperature or a global initial starting temperature in the model. This might be the case here, but not 100% sure.

Hope this helps,

Steve

Stephen Seymour, PE
Seymour Engineering & Consulting Group

http://www.seymourecg.com

 

[HVSmith]

Hi Steve

Thanks for your message.
When setting up the "solution" phase of the model, I had added an applied thermal load, initial condition, set to 293 (where the thermal system is Kelvin/Rankin). This was applied to all available areas.

Would this have been sufficient for creating the global starting temperature?

Or is there something else I should have been doing?

I tried varying the value of heat flux I enter. If I reduce it to values of the order E-13 then it says a solution is made, however when I look at the nodal temperature plot both the SMN and SMX values read -5188, and I can't understand where it would get this from!

I am obvioulsy doing something blatantly wrong somewhere...

Thanks again for any help/advice!

HVSmith