Could someone help me get a general idea of what is happening in this model? [Interaction module] 1

[bojoka4052]

There are two shell models on top of each other in the Assembly which are constrained with a tie. Then an interaction has been defined for several steps, and as I understand it "propogated" means the interaction in the last step will come over to this step aswell, but what does "built into base state" and "N/A" mean?

As I understand it; when activation state of region elements get deactivated it is as if the shell model is removed, and when its reactivated its placed back and the two shell models will interact? But for example if its reactivated in the first "modified" step (yellow) and then we move to the "Built into base state" (green) what happens? I am trying to get an idea of what is happening in the interaction module.

 

[FEA way]

N/A means non-applicable. It depends on the step type, those steps with N/A must be some analysis procedures in which model change interaction is not supported. Built into base state is also related to the step type, it applies to linear perturbation procedures. Those are perturbations about the base state from the previous step of the general type. Check the documentation chapter "General and perturbation procedures" for more details.

 

[bojoka4052]

One thing I dont understand is how can they choose "Region: entire region of one shell model"? I dont see them mention the other shell model at all in the interaction module, because dont we have to say that this shell model needs to interact with this shell model?

 

[FEA way]

Some types of interactions (like contact or tie constraints) require users to pick two surfaces so that an interaction between them can be modeled. But others (like model change used here) are not typical interactions understood as behavior between two regions. In such cases one region is selected. Here it’s all about activation/deactivation of particular elements. Interaction between these and other elements in the model is handled by a different feature - tie constraint in this case.

 

[bojoka4052]

Do the seperate steps in Abaqus act independent of each other if the steps are "Static, General"? So say I apply gravity load in the first step which will cause some deformation, then I apply hydrostatic pressure in the second step which in itself would cause deformation. Will the deformation in the hydrostatic step be deformation from gravity+hydrostatic or just hydrostatic? Does this just depend on whether the loads and BC's have propogated onto the next step?

I also have a "Type: Frequency" step which I think does modal analysis, and also a response spectrum analysis step, do these act independent from the other steps? Might be a loaded question but I would love to hear your best guess.

 

[NRP99]

If you remove the loads of previous steps, yes the effects will be not present in next step which is obvious. Unless this is nonlinear analysis, the previous step effects are not carried forward to next step if loads are removed or not propagated.

Also regarding the model change interaction, see "Defining a model change interaction" in help manual - "You can create a model change interaction in all Abaqus/Standard steps except for static, Riks steps and linear perturbation steps." So whenever these steps are defined with the model change interaction the abaqus shows N/A -not applicable or for linear perturbation "Built into base state". To get the meanings of these terms see "Terms describing object status" in help manual.