adaptive meshing errors

[harry123456]

hello,
I am doing a simulation of a hyperelastic material between two plates compressed by a rivet. I am using adaptive meshing for the hyperelastic material. But the solution aborts saying that one or more elements is highly distorted. Isnt adaptive meshing done to take care of high element distortion? then still why does the solution abort?
harry

 

[Drej]

As far as I'm aware, only the /explicit code supports adaptive meshing, hence is it /standard or /explicit? You say you're using adaptive meshing, but how have you specified the parameters for this? Which adaptive mesh parameters have you input? Which elements are you using? Are you using ABAQUS? Which version of ABAQUS are you using? What is the actual abort message? Is it related to the adaptive elements or some other elements in your model?

etc.
etc.

 

[harry123456]

Hello,
Thanks for your reply.I am doing a 2-D axisymmetric analysis with Explicit now (version 6.4). It has a hyperelastic material between two plates compressed by a rivet. CAX4R elements. Initially, I tried the problem with standard but the hyperelastic material was getting deformed a lot and standard always aborted. Then after going through the manual I tried using adaptive meshing to overcome the distortion with 3 sweeps per increment for the hyperelastic material.But that also aborted with excessive distortion. I tried increasing the frequency of sweeps also (no success).
Now I have just been trying in Explicit with CAX4R, distortion control, enhanced hourglass, Kinematic constraint formulation with surface to surface contact. My analysis does not even start. I have gone through the abaqus documentation on the error (listed below) and I understand where the error is coming from but I did not find in the manuals the way I can take care of the error. I checked all my properties and my model to make sure its right but no success.

Error:
***The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element. This usually indicates an error with the model definition. Additional diagnostic information may be found in the message file.

***The maximum ratio of deformation speed to wave speed is Infinity in element 9 of instance SEALANT-1 at increment 2.

Thanks
harry

 

[Drej]

Try to start off by performing a very simple linear static or modal analysis just to make sure everything is behaving in the model as you expect it to. Then you can try to diagnose the current error by adding more exotic loads. The error message gives no real indication as to the specific problem in the model. If you have contact, you may want to apply that in one step, just so the parts are touching. Then apply the full load in subsequent steps. You have in your favour the /explicit contact algorithm, which is much more forgiving - and in general more efficient - relative to its /standard counterpart.

Cheers,

-- drej --