Learning Forum

[Haiquan]

Hello

I use INISTATE command to import the initial stess for very element as shown below. Now I want to review the element stress in ANSYS and check whether the element stress has been imported correctly. How to plot the element stress after solution? By the way, my element is SOLID187, second oder. Thank you in advance!

[ErKo]

Hello

With: inistate,list
We can list/print all the inistate data in the solve.out file.

All the best

Erik

[Haiquan]

Thank you very much for your feedback! I can see the initial data in solve.out file now.
I checked this with a linear one element model, solid185, 8 nodes , and I applied initial stress 2Mpa in the X direction for the element as shown below. I didn't apply any load or boundary condition, I just inserted a command to list the initial stress. I solved the case and checked the result, the strain was 1e-5, it made sense, as the material was steel with Young's modulus 200000Mpa(2/200000=1e-5). But if I checked the von-Mises stress, it was 5.2e-9Mpa, it was not the initial stress 2Mpa. I feel very confused about this stress.
By the way, it seems the initial stress is applied to the integration points in the element, am I correct?

[ErKo]

Hello
Well if we apply an initial preload and do not have any boundary conditions then it will deform and we will not have any pre stress as you see - if you fix all faces than you should see the normal stress in x be equal to your initial stress preload. So below all faces are fixed and an SX=1000 has been applied and that is what we get out - so to see all the preload we need to prevent movement otherwise we loose it.

Yes it seems so since we do calculate stresses at Gauss points.

All the best

Erik

[Haiquan]

Thank you very much for your comments, it really helps me to understand the initial preload.
So the initial preload will release when structure deforms. This seems like the thermal expansion, when heated, if the structure is free, it will deform and no stress in the structure, is it correct?
Another question, if the initial stress is self balance in the part, it will not cause deformation and stress will not lose, am I correct?
An example of self balance initial stress is the residual stress in a plastics part after injection(this residual stress is usually evaluated using the method of Environmental Stress Cracking)