I have the temperature to be 25C
Reference temperature at zero strain = 70C
Material is 304 steel.
I do not understand why the von Mises stress is close to the yield strength 2.068E8
Is your temperature boundary condition applied to the entire body (a volume selection) or just the exterior faces. If it is just the exterior faces then the temperature is only applied on those faces. The interior volume would then be set, by default, to 0 Kelvin (as it cannot be set to a null value). This would cause extreme stress results outside what you would normally expect.
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