Thermal stress in piston engine - constrains problem

[Greg84]

Dear All,

I am working with Ansys Classic.
I am trying to calculate thermal stress in aluminium piston engine (it's student's project).
After getting temperature results I want to calculate thermal stress.
I have problem with setting correct boundary conditions (displacements in structural analysis).
When I apply all DOF constrains in pin hole I could find in this area very high stress.
How should I model it?
Should I model pin and apply contact between it and piston?

Best Regards.
Greg

 

[FEAdesserve]

Hi
I saw your problem and my recommendation will be
1. create a negligible mass element at the pin center and attach the mass element with the surface of hole by means of cerig. After that you can fix the mass element points and then run simulation to see thermal stresses.

Regards,
Raj
Desserve Engineering

 

[Greg84]

Dear Raj,

Thank you for hints.
Unfortunately I am not familiar with Rigid Regions (CERIG).
I am trying to find some tutorials but it's difficult.
Do you know why I don't have possibility to choose: Main Menu>Preprocessor>Coupling / Ceqn>Rigid Region?

Best Regards,
Greg

 

[flash3780]

If the interaction between the pin and the piston is important to your solution, you should model the pin and use contact elements to correctly capture the interaction.

If you're not interested in stresses at the pin-joint you could simplify the model by constraining the piston radially at the pin location.

If the pin interaction is required to model the loading on the piston properly, but the local interaction doesn't have to be perfect, you can model a simplified pin (e.g. create a rigid pin or use rigid constraint equations as mentioned above).

Plenty of ways to skin a cat.