Learning Forum

[sk1793]

I'm running a simple steady-state thermal analysis as temperature input for a static structural analysis (elastic) to find thermal stresses in my part. My goal is to review the FOS for this part.

As the material properties are temperature dependent, I've been able to define most of them fine, but am unable to do so for yield strength, as it only lets me enter a constant value. I've seen an older post recommend using Bilinear Isotropic Hardening to define this, but this then doesn't let me output the FOS for the analysis.

Any recommendations on how to get around this please?

[mrife]

first, can you not use acronyms unless you defined them? I'm guessing FOS = factor of safety. And that you are using the Workbench Mechanical Stress Tool -> Safety Factor [SF] result to post process the FOS. Is this correct? If so that stress tool uses the Workbench Engineering Data "Strength" material models that do not have temperature dependency.
The 'Bilinear Isotropic' material model is a [metal] plasticity material model whose Yield can be temperature dependent, but whose properties are not used in that Stress Tool SF calculation.
How complicated is the temperature dependent Yield Stress function? You could perhaps use a user defined result that operates on a temperature result object [see the worksheet but the structural result will be BFE for 'body force element' i.e. the temperature 'load' applied to the structural model] and translates it into a scale factor. This new result can be used in another user defined result to scale the safety factor result; also done as a user defined result.
So, let's start with the expression for the temperature dependent yield.
Mike

[sk1793]

Hi Mike, thanks for your response, I will take care with acronyms going forward, but that was exactly my problem and your solution is very interesting. I never knew ANSYS offered such flexibility.
My data is really just a few yield strength values at various temperatures. If I understood your approach correctly, I calculated scale factors (in reference to yield strength at ambient temperature) and fitted a polynomial to it, which when applied to the BFE, gave me the scale factor (SF) plot based on temperature results:
I'm now trying to apply this SF plot to the Factor of Safety (FOS) results calculated for yield strength at the ambient temperature. Do you know what code I should use for this please? As it might just be my eyes, but couldn't see anything for FOS in the worksheet. Unless I need to define it explicitly from the stress results? Thanks