Excessive Distortion

[loyal979]

Hi all,

I am performing an impact simulation using hexahedral solid elements. When never I increase the energy level (e.g. striker mass or initial velocity), I get this error Excessive Distortion in # of elements. I have tried using reduced integration along with Enhanced hourglass control + Distortion control but the issue is still there.

Boundary conditions: Plate is simply supported (in z) in all four edges with have a constraint to prevent translation (in x and y) and rotation. The striker is fixed in all direction except the impact direction (z-direction)
what would be causing this issue? Could it be the mesh (element size)? Or Boundary conditions?

Any suggestions ?

Thanks in advanced..
Mat

 

[FEA way]

I assume that you use Abaqus/Explicit, right ? Check the quality of your mesh but I suspect that the error is caused by extremally high load when compared to the strength of target plate. Is the impactor meshed with rigid elements ? First of all check your units, make sure that the velocity is not physically too high and assign mass/inertia to both parts. Also try fixing this plate's edges in all degrees of freedom (encastre BC).

I once had this error when I accidentally assigned projectile velocity as a BC instead of initial condition but this shouldn't be a problem here, from what you say.

 

[loyal979]

Thank you FEA way!!

Yes I am using ABAQUS/Explicit with having the impactor to be a rigid body. All my units are consistent.

I have written a user subroutine for damage evaluation using the Hashin failure criteria and I noticed that the material degradation is causing the Excessive Distortion issue.

not exactly sure on how the material should be degraded in appropriate way. If there is anybody has an idea please share it with me.

Thanks
Matt

 

[Erik Panos Kostson]

I suppose one could use the standard Abaqus damage evolution functionality.

If you want to see how it is done (using different ways ), have a look at the abaqus doc.

Abaqus - how the elasticity matrix is modified due to damage, see in abaqus help: 19.3.1 Damage and failure for fiber-reinforced composites: overview

https://caeai.com/sites/default/files/CAEA_v15_ANSYS_Composite_Damage.pdf

 

[FEA way]

I agree that it’s a good idea to try with built-in damage evolution criterion first. Then you can test your criterion on a simple model before proceeding to more complicated case. There might be an error in your subroutine.

 

[loyal979]

Sorry for the late response but Thank you both for the help!