I am trying to simulate a FSSW process but the above/below errors keep on emerging. I have applied adaptive ALE to try and eliminate the issues but the errors remained after submitting the job. I would be extremely glad if I could unravel these issues through your valuable comments.
***ERROR: Zero or negative mass in element number TOPPLATE-1.1793
***ERROR: The Abaqus time increment has become negative?? = -60.918
***ERROR: Excessive distortion of element number 964 of instance TOPPLATE-1
***ERROR: There is only one excessively distorted element
Dear Olatunji
The following checklist may be helpful in diagnosing the error:
1. Check for poor initial mesh definition.
2. Check the parameters used for ALE. Reducing the number of
increments between ALE or increasing the number of sweeps in each ALE
increment may yield a better mesh.
3. Check contact definitions for problems such as excessive initial
overclosure or unrealistic tied definition between contact pairs.
A vector plot of velocities or accelerations will usually help to identify contact problems.
4. Check stiffness (elastic modulus) and mass (density) definitions for
consistent units and verify that the combination is reasonable.
5. Check the boundary conditions for an excessive loading rate. The *DIAGNOSTICS, DEFORMATION SPEED=DETAIL option may be used to obtain detailed diagnostics information.
6. Check the current status of the structure to see if it has
totally failed.
7. A dashpot or a very stiff spring may cause the analysis to go unstable.
Best regards
Panji
This can happen, IIRC, when an element gets so distorted that the volume at the integration point becomes negative in an explicit simulation.
Things to try may be
- locally refining or restructuring the mesh
- changing material parameters to see whether the problem is due to material becoming too soft (ideally plastic)
- use element removal to remove all elements with very high strains
As usual, it is difficult to be more specific without seeing the model.
I quote the answer of Martin Baeker and I add that the countermeasure also depend on the type of analysis and the solver.
Dear Olatunji
The following checklist may be helpful in diagnosing the error:
1. Check for poor initial mesh definition.
2. Check the parameters used for ALE. Reducing the number of
increments between ALE or increasing the number of sweeps in each ALE
increment may yield a better mesh.
3. Check contact definitions for problems such as excessive initial
overclosure or unrealistic tied definition between contact pairs.
A vector plot of velocities or accelerations will usually help to identify contact problems.
4. Check stiffness (elastic modulus) and mass (density) definitions for
consistent units and verify that the combination is reasonable.
5. Check the boundary conditions for an excessive loading rate. The *DIAGNOSTICS, DEFORMATION SPEED=DETAIL option may be used to obtain detailed diagnostics information.
6. Check the current status of the structure to see if it has
totally failed.
7. A dashpot or a very stiff spring may cause the analysis to go unstable.
Best regards
Panji
- Badges
- Science topic