Hi all,
I am trying to run a trimming operation after forming a metal sheet, and I'd like to bring in the residual strains from that operation, however, I can't make it work...
I have run the forming operation with the keyword *INTERFACE_SPRINGBACK_LSDYNA so I can use the dynain file as input for subsequent operations.
I have been successful when running a Springback analysis after forming based on this method; I can post-process the springback analysis and observed initial strains, final shape, etc...
However, when I try do run a trimming operation based on the same method and post-process it, there are no pre-strains during the initial step or at all. I am not sure if this is due to the fact that the termination time needs to be set to zero for the trimming operation, but looking for ideas/suggestions?
Does anyone have an idea on why this may be happening or have an idea of a workaround/different method?
Thank you!
Mariana
Hi @marianadu,
So your issue isn't necessarily with the trimming but concern that you no longer see initial stress/strain from the forming simulation? Are your control cards similar to the springback analysis that was showing these still?
Hi NegativeVolume,
That's right, the problem is that I don't see the initial stress/strain. I checked all the control cards are they are all similar to the springback analysis, with the exception of the control cards specific to each of these operations (e.g. Control_Termination set to 0 for trimming and set to 1 for springback).
I thought it could be related to the number of history variables and the *Interface_Springback_Lsdyna control card, but these are exactly the same for both analyses...
I have run out of ideas...
Mariana
Hi again,
Tried editing my previous post, but it seems like it is not possible to so before moderation... so I'll just add below. I have figured out what was wrong, I'll explain here, in case it helps someone else in the future.
The problem is actually quite obvious, although not so obvious when you setup these analyses using LS-PrePost tool EZ Setup, and that's why I missed it earlier.
When setting up the analysis in EZ Setup, you can tick a box "Blank has initial strain/stress" (which is my case). Once all is setup and you save your input file, EZ Setup will generate 4 files (as it does for springback analyses) which include 2 files in a folder called "blank" and 2 files in separate folder which is named after the operation you are running (e.g. springback, trim, etc...).
The first 2 files (in "blank") include material model, mesh, and initial stresses/strains. I assumed that just like for springback analysis the *Initial_Stress_Shell/Strain control cards would have been imported from dynain file. However, this was not the case for the trimming analysis. So, I copied these control cards directly from the dynain file, ran the trim keyword again and it's working perfectly.
Thanks for looking into it NegativeVolume!
Cheers,
Mariana
Hi @marianadu ,
for a simplified additiv manufacturing simulation I am looking for a way to introduce initial strains, but the INITIAL_STRAIN card is only a set up for the postprocessing. How did you define your initial strains or did you use a other way of input, like inital_stress?
Thanks,
Iron
Hi @ironam ,
I used the results output from a forming simulation, within the dynain file, which you can request for using the *INTERFACE_SPRINGBACK_LSDYNA.
These results, within the dynain file, include *ELEMENT_SHELL_THICKNESS, *INITIAL_STRAIN_SHELL and *INITIAL_STRESS_SHELL. So all I had to do to run a simulation with those initial conditions was to use these within my input file.
Note sure if this helps or answers your question.
Cheers,
Mariana