Learning Forum

[Anurag4]

I have solid plastic cyclinder enclosed inside a thinner plastic cylinder made out of different material. The inner cylinder is expanding because its getting heated by the outer cylinder. Is there a way to setup this Analysis such that:

1. The heat transfer analysis is done first and obtain the expansion and shrinkage of both polymers.
2. Then use the expanded and shrunk state to determine stresses due to interference.

This is a simplified injection molding problem, the mould expands and the part shrinks and I want to determine the stress developed due to interference.

Thanks

[1shan]

You could check this tutorial- https://www.youtube.com/watch?v=yh346v-tsFo - to understand how to perform a thermo-structural analysis. You will have to perform a steady state thermal analysis with appropriate thermal conditions. Once this is done you can link it to a structural analysis, apply necessary constraints and calculate thermal stresses that are developed. You may also define a temperature dependent thermal expansion coefficient in tabular data, check this Thermal Expansion.
Regards Ishan.

[Anurag4]

Thanks. I will try this and update it.

[Anurag4]

Hello, I tried this. However i am running into a problem. I run the thermal simulations and get the temperature distribution and run the static structural. But here is a tricky situation, one of the my parts is cooling down from a higher temperature to lower and other part is going from a lower temp to higher. So one body should be shrinking and other expanding. But currently all bodies expand in my Ansys simulation. Im guessing this is because it takes the starting temp as ambient and then the temperature from the thermal analysis as the final state.
Is there a way to define different initial temperatures to different parts of the assembly and then give the temperature distribution at the end ? Basically a shrink fitting kind of analysis.

[peteroznewman]

Here is a simple model of a shrink fit. The Polyethylene part has a Reference Temperature of 180 C, while the Tool part has a Reference Temperature of 22 C.
The model has a Thermal Condition of 22 C. That means the plastic part will cool down from 180 C to 22 C in the simulation. There is a frictional contact between the two parts in the 2D axisymmetric model. You can see that the part is shorter when it cools, and is being stretched by the tool, which did not change size as the temperature on it did not change.