r/fea • u/Doc9960 • 4d ago

HELP on Spring back analysis

after a impact analys on ls dyna for the correct visualization of the stress i will have to do a springback analysis , how i can do ? i ` ve try several time but after the fist step the analys delete the geometry.(p.s. i have in the explicit analysis a pre stress file) thanks for help anyway.

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u/FiniteRafi 4d ago

Your post is too vague for us to help you. We need all the details, all of them. These are complex analysis that you cannot describe in 3 lines. What are you analysing? What type of elements? What material law? Boundary conditions? Loads? Analysis parameters?

It should take you half and our to write that post, and in the process of doing so you might even understand yourself why it isn't working. There should be pictures, drawings etc.

Usually in a non-linear static analysis the springback analysis is done in the same analysis in new steps, where the load is progressively removed and isostatic boudary conditions are applied to the part which allow it to deform back a bit.

For impact, the object impacting should have kinematic energy, the moment this energy becomes zero (if it bounces off afterwards) or the moment it reaches its minimum (if full penetration is achieved) should correspond to the maximum deformation of the impacted part. After that, the impacted part may vibrate and once it reaches equilibrium the the maximum deformation should have changed back to a lower value. Is that what you are looking for?

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u/Doc9960 4d ago

yes, i`m looking for this, but the plastic deformation after impact remain the same after the springback (?) , i `m lookin for the residual stress.(sorry i know the information are low )

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u/FiniteRafi 4d ago

The plastic deformation should remain the same. Springback is elastic deformation.

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u/Doc9960 4d ago

I think also the stress change after the spring back due to the elastic return, but the question is :how i can do the spring back ?I take the last stage of the simulation ,I removed the impactant object and i write the sif file and then I relaunched the simulation. I don't know if it's the correct procedure.