How to fix negative volume error in solid elements

- July 9, 2025 at 5:17 am
  
  jtowns03
  Subscriber
  
  I'm running into a persistent negative volume element error in LS-DYNA. We’re using a modified GHBMC brain model consisting mostly of solid elements with embedded 1D cable elements (*ELEMENT_BEAM) to represent axons. The cables are embedded using *CONSTRAINED_BEAM_IN_SOLID. I’m prescribing translational and rotational kinematics to the skull using *BOUNDARY_PRESCRIBED_MOTION_RIGID.
  When running the simulation, LS-DYNA terminates with multiple ERROR TERMINATION: NEGATIVE VOLUME IN ELEMENT ##### errors, so I tried lowering the TSSFAC in *CONTROL_TIMESTEP from 0.9 to 0.5, which has been suggested in previous forums, however this had no effect. I then isolated the problem solid elements and tried softening their material definitions, which resolved the error for those elements, but then 6 new elements in a different region of the brain failed in the same way.
  Are there additional parameters we can tweak to help prevent this error? And is there a recommended way to systematically debug negative volume issues in solid-brain FE models, especially when embedded elements are involved?
- July 10, 2025 at 5:52 am
  
  igandiko
  Ansys Employee
  
  Please refer to the tips shown in the below links.
  https://ftp.lstc.com/anonymous/outgoing/support/FAQ/negative_volume_in_brick_element.tips
  https://ftp.lstc.com/anonymous/outgoing/support/FAQ/instability.tips