Thermal stress question

[Tom690]

Hi everyone, so im analysing brake discs and the heat caused under braking. I have made models where both pad and disc are rigid, and where both are deformable. Now, rhe deformable models take a very long time to run. I’m wondering if thermal stress output for the rigid body models (or maybe only rigid pad?) would be accurate or would the rigidity cause it to be wrong? Also is Von Mises stress the best way to find thermal stress? Thanks!

 

[SWComposites]

Von Mises stress is a yield criteria for materials like metals that have a yield behavior. Might be ok for the discs; probably not the appropriate criteria for the pad material.

 

[Tom690]

Thanks for the reply! Well thats good as im only interested in the disc haha. Would you be able to comment on the validity of rigid bodies in my case?

 

[FEA way]

How do you get stresses in rigid (undeformable) bodies ?

 

[SWComposites]

Sorry, the only thermal models I have done were very very long ago.
Are you running some sort of coupled stress/thermal analysis?
And yeah, a rigid element is not going to output any stresses.

 

[Tom690]

Ah yeah that was dumb of me haha. How about only a rigid pad? Would that cause a large increase in stress? And yes this is a coupled stress temp analysis

 

[SWComposites]

a rigid pad is likely to produce very high peak stresses in the rotor as the edges of the pad.
can you show a stress contour plot of the rotor?

 

[FEA way]

Check the documentation example "Thermal-stress analysis of a disc brake" (Example Problems guide). You can easily modify it by making the pad rigid (just apply a rigid body constraint to it) to see what happens.