Learning Forum

[mohan.urs]

Hey,

I noticed you have negative volume errors in about 20 elements. These errors in LS-DYNA usually occur when elements become excessively distorted during a simulation, leading to inversion and negative volume calculations. This can cause the solver to terminate if not addressed. Given the high strain rates in your flow forming simulation, I recommend the following adjustments:

1. Mesh Density: Adjust the mesh density.
2. TSSFAC (Time Step Scale Factor): In *CONTROL_TERMINATION, a higher time step means higher loads, leading to higher strain and distortions. Controlling this might help.
3. ELFORM: Avoid fully integrated  brick element formulations; use 1-point Tetra element integrations for large distortions.
4. Material Plasticity: Ensure the material properly captures plasticity and consider using mesh adaptivity.
5. ERODE=1: Set ERODE=1 in *CONTROL_TIMESTEP or PSFAIL in *CONTROL_SOLID to delete highly distorted elements and obtain a solution.
6. Hourglass Controls: Use better hourglass controls to avoid hourglass modes.