Abaqus Warning

[kotawsu]

Hello Everyone. I am running a contact analysis with the elements beong brick with incompatible modes. I am getting these warnings and the analysis stops. Could anybody tell me what this exactly means. Thanks for your help.

***WARNING: ELEMENT 14232 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14232 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14232 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14231 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14178 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14177 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14177 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14177 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 13600 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 13600 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14187 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14187 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

***WARNING: ELEMENT 14187 INSTANCE COMPOSITE-1 IS DISTORTING SO MUCH THAT IT
TURNS INSIDE OUT

 

[corus]

An element turning inside out means that the gauss point has gone outside the element. Check the element quality

corus

 

[mrgoldthorpe]

I think you are using the 'NLGEOM' option according to that message. That is when the mesh is updated by the displacements at each increment. Is that the case? If so, does the analysis run OK without NLGEOM?
MRG

http://www.analysis.demon.co.uk

 

[kotawsu]

Hello. Thanks for the reply. Corus, i did check the element quality and i get a 0.2% analysis warning on my mesh.
And thrope, it is a non-linear analysis as i have contact involved in it. is there anythin else i need to check.

 

[corus]

A poorly shaped element near the contact region can cause the element to distort so that the element almost flattens and hence the warning. Look at the results as Abaqus will put those elements into a set for you to see in Viewer. Those elements may be of a poor shape or it may be due to a point contact causing a large nodal displacement into the element. If you have any intermediary results then look at them and you might see the local distortion or poor element shape.

corus

 

[kotawsu]

Thanks corus, i am planning to remesh and see how things would work out. I have a question if i get a numerical singularity warning does it got to do somethin with the boundary conditions. i see that i have prevented all the rigid body motions but in the pretension steo i still get this warning. why would it be? Also what exactly does it mean by introducing springs b4 applying any kind of load? what does this concept mean? Thanks once again.

 

[corus]

You are referring to things that nobody else has seen so your questions about the pretension step and 'what does it mean by introducing springs' can't be answered. I have seen cases where a low stiffness spring is introduced in order to apply a soft restraint and prevent singularities so that contact can be established before applying any load.

corus

 

[kotawsu]

corus, sorry for not being clear. i was talking about the soft restraint. since i am gettin the numerical singularity warning even though my boundary conditions seem to be allright, i was a bit worried. do you know how exactly this soft spring work and where do i need to define it? thanks.
Kota

 

[nodepicker]

Kotawsu,
you can just define soft springs in a manner that your model will not be singular, i.e. so that tou will have stiffness in all directions. Where you put your springs does not matter as they are soft in order not to disturb your analysis.

/Nodepicker

 

[kotawsu]

hello goldthorpe. my analysis runs fine when i switch the nlgeom off. But could you tell me how it makes a difference. You said something about the element updating with respect to the displacements.could you help me in understanding better. Thanks for your time.
Kota

 

[PamCrash]

Forget about the soft springs, they can cause a lot of trouble. Try *STATIC,STABILIZE instead, which is made for such problems. *CONTROLS,ANAL=DISC may also help to find a solution

Pam

 

[kotawsu]

Thanks Pam for your suggestions.