Initial stress

[Low12]

Hey, i am interested in applying an initial stress on a coating. I already tried using predefined field and the "initial condition, type Stress" options. I feel like these options didn't solve my problem properly, since i dont want the equilibrium to be calculated at the initial step. What i want is the coating with zero strain and displacement but a defined initial stressfield, and then propagate it to the next step. So far, the initial stress would always reach zero since the coating begins to expand within the initial step.

Is there a possibility, to define an initial stress and use this state as the basis for further calculations (without the coating experiencing strains due to that initial stress)?

Thank you very much in advance.

 

[FEA way]

When you define initial stresses, Abaqus will always automatically check for equilibrium and, if necessary, try to achieve it in the first step. You can find more details in the documentation chapter "Initial conditions in Abaqus/Standard and Abaqus/Explicit" (paragraph "Establishing equilibrium in Abaqus/Standard").

 

[Low12]

Thanks for the answer. Does it mean it is not possible, at least not without a workaround, to achieve waht i want to achieve?

 

[Mustaine3]

What is the purpose of an initial stress that is not allowed to behave like a stress?

 

[IceBreakerSours]

I suspect something isn't quite right in the framing of the question so, to me, it sounds like what you want is a geometry/mesh that has some known stress state at a given time point (in your case, t=0). If that is correct, you have to solve an inverse problem with an algorithm. You have to try to load some initial geometry (pretend, t=-10), apply a load, compare the loaded geometry with what you want the geometry to look like at t=0, and iterate until some error is small enough. Check this paper out for details. There are efficient ways of doing it using invariants, principal components, etc. instead of the deformation gradient tensor but I suspect I am getting into the math weeds by now so I will stop.

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[Low12]

Thank you for the answers so far and for the paper @iceBreakerSours

Maybe my question was unclear so i will try to rephrase: In principle i just want an initial stress state without any strains resulting from it. The background is the deposition process of a coating, during which thermal stresses, quenching stresses.. etc. appear and have an influence on the adhesion of the coating. When i implement a predefined field in the initial step with the usual stress values for the residual stresses, i end up with strains after the initial step which is not what i want.


I hope this makes it a bit more clear and im looking forward to any tips.