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marlon September 27, 2015 12:11

How to disregard thermal stresses?

When I simulate a simple block, 2D, free, and I apply an uniform thermal condition (cooling in my case), It starts to shrink (as we expected) and we can see a displacement in the result. Ok.

However, Ansys also shows a stress happening. One can say there's stress since Sigma = E*Epsilon (Hook's Law), however, since the body is free in all directions, it shouldn't show any stress. It's just a shrinkage. What can we do to disconsider this stress in the result?

For example:
A material has yield strength = X at 295K and yield strength = Y at 80K (Y use to be >X). So, if I aply a load < Y at 80K, this material will be ok.

But, when I simulate the cooling, Ansys shows me there's a stress = Y-10 MPa acting. Therefore, just applying 10MPa would be enought to damage the body, and it's not true.

Now, why is it a big problem (a bug?): imagine we have two bodies, of different materials, conected side by side. Since they have different expansion coefficients, now we really expect a stress caused by this difference of shrinkage. I'm interessed in this values, disregarding that effect Ansys shows about just cool a body.

Pauli October 2, 2015 14:17

If you are using ANSYS Mechanical go under the Geometry section select the part then set Thermal Strain Effects to no.

marlon October 2, 2015 22:23


Actually, check the thermal stress is important, the problem was they should not exist when a body of just one material is cooled without fixed points.

One said to me change from "Plane Strain" to "Plane Stress" at that analysis and it worked.

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