Hello Everyone,
I am doing one Abaqus simulation in which I have used user subroutine to define initial stress condition in the geometry. However, I see that this stress condition gets modified and is not propagated as it is across subsequent Abaqus steps. Can anyone suggest me any possible solution to ensure that predefined stress-fields remain as it is subsequent Abaqus steps? In each step I am using different loads to see how they interact with initial stress field.
Thank you in advance,
Nik
So basically you want to do different load cases, all applied to the same initial state, instead of doing several steps subsequently?
Easiest way to do this would be to run a separate analysis for each load case.
You can activate/deactivate steps in the step module if you use CAE; or you can simply comment out/remove steps from the inp-file.
Nik - Do you mean that the predefined stress field changes prior to the first step of loading? If so, this is probably because the stress field that you are applying does not satisfy force equilibrium and so isn't physically realistic. For predefined stress fields that don't satisfy equilibrium, Abaqus has a procedure which lets the stress field partially relax to find an equilibrium state (see the Abaqus Analysis User Guide). This can change it completely - depending on the nature of the stress field, boundary conditions and material constitutive model etc... In most cases, you should make sure that the stress field that you're applying using Predefined Field satisfies equilibrium beforehand.
Otherwise, I agree with Martin's answer.
Hello Harry, Thank you for your answer! Yes, I think you are correct. Initial stress field is not in equilibrium hence it is partially relaxed in subsequent steps. Which I don't want it to happen. I am trying to simulate effect of manufacturing induced residual compressive stresses on Axisymmetric ball plate contact problem. (Martin - To get convergent solution for contact, I am using multiple steps with gradually increasing load). The resultant stress field should be combination of contact load and residual stresses. However, I am seeing that effect of residual stresses is reduced on the final output. Ideally, expected output is superposition of stress fields from contact load and residual stresses. Therefore, I thought somehow Abaqus is manipulating initially predefined stress field in subsequent steps. Can you please recommend any ways to ensure Abaqus does not manipulate initial predefined field? Also is there any way to apply initial stresses along specific orientations at each integration point. Meaning, I would prefer to apply residual stresses in principle stress directions at each gaussian point. I am already using SIGINI subroutine but how can apply predefined stresses in particular orientations? Any suggestions/recommendations are appreciated. Thank you in advance, Nik
Hi Nik,
Apologies for the delay in replying:
Best regards,
Harry
Hi Nik,
i have a similar problem, in my case i import the stress field from another analysis (implicit) into my new model to solve it with explicit. The same thing happens and at very moment of explicit solver the whole stress field will change. i really appreciate it if you help me if you have solved the problem.
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