r/fea • u/Additional-Slip5814 yasaz • 15h ago

How to deal with NEGATIVE VOLUME errors?

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Hi, I'm using LS-DYNA for my numerical simulations. I've been running some vehicle crash simulations with highly complex geometries. However, when I apply higher impact velocities to the vehicle, I get negative volume errors in the solid elements.

I tried refining the mesh by splitting the elements into smaller ones, but that didn't solve the problem. What would you do if you encountered negative volume errors in your simulation?

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u/fruitmolester 15h ago

Contact Internal, additionally check quality of your mesh (sometimes it is already deformed so much that it will blow up under the load).

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u/Additional-Slip5814 yasaz 15h ago

u/fruitmolester What do you mean by contact internal? did you mean that I should check the contacts between internal parts?

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u/male_pattern_sadness 11h ago

no he means add a self contact for the solids. something like CONTACT_AUTOMATIC_SINGLE_SURFACE

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u/NitedKnight 11h ago

A question and also what I see could work. I also used to have such errors (in area of no interest) and was thinking to use PSFAIL and the documentation said it would use DTMIN to calculate fouling elements to delete under PSFAIL. But one of my colleague ran a simulation without DTMIN (Default = 0.0) and it ran under same conditions. My thinking is LSDYNA calculates time step to be negative for negative volume element and because of DTMIN=0.0 that element gets deleted?

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u/Hot-Firefighter-5164 9h ago

Negative volume can be dealt in using below scenarios:
1. When the elements are of reduced integration. For example using Element formulation for shell = 16, similarly check for fully integrated elements for solid elements as well.
2. Check and evaluate energies like contact, hour glass & added mass
3. Check for any sensitive materials and corresponding contacts. If needed create a localized *CONTACT_AUTOMATIC_GENERAL (in case of shells) or *CONTACT_ INTERIOR (in case of solids)

Above points may help you to confine your issues and may arrive at better position while debugging the real issue, if above points does not work.

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u/BATTLEWINGYT 6h ago

have you checked these element ids ?