Cavities/Holes in Abaqus

[alexzive]

Hello Everyone,

I am pretty new here. I am with Abaqus since three months.
I am experiencing some problems by modelling holes inside parts or assemblies.

What I have tried to date is to generate some structures with holes inside and perform some simple step with simple loads (i.e. concentrated forces).
It does´t work!!!

My general question:
Can A. handle such problems?
How to handle HOLES/Cavities with A.?
In the official documentation there something about cavity radiation but I am interested in holes for solid mechanics calculations.

Thank you very much,
Alex

PS: I will gladly post here the content of the inp file and the error msg, but first I ask whether I can upload the files instead of posting their content (several rows).

 

[alexzive]

to be more clear:

HOLE:= region which is entirely contained in a solid or planar part (and this part has an assigned section with an assigned material).
Such void region should have no elements/nodes in the mesh.

 

[xerf]

Your post is very general. If you refer to geometrically modeled holes, this should be very simple to accomplish in ABAQUS/CAE.

If you get a error message when trying to run the job, then you should post it to improve your chances of getting help.

 

[alexzive]

Ok, this is the input file (I have omitted several nodes and elements lines with "...")

*Heading
** Job name: Job-5 Model name: Model-3
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Part-1
*End Part
**
**
** ASSEMBLY
**
*Assembly, name=Assembly
**
*Instance, name=Part-1-1, part=Part-1
*Node
1, 15., 5.
2, 15., 15.
3, -5., 15.
...
240, 13., -13.
*Element, type=CPS4R
1, 1, 13, 97, 33
2, 13, 14, 98, 97
3, 14, 15, 99, 98
...
200, 240, 88, 12, 89
*Nset, nset=_PickedSet2, internal, generate
1, 240, 1
*Elset, elset=_PickedSet2, internal, generate
1, 200, 1
** Region: (Section-1icked)
*Elset, elset=_PickedSet2, internal, generate
1, 200, 1
** Section: Section-1
*Solid Section, elset=_PickedSet2, material=Material-1, ref node=Part-1-1-RefPt_
1.,
*End Instance
**
*Nset, nset=_PickedSet5, internal, instance=Part-1-1
10,
*End Assembly
**
** MATERIALS
**
*Material, name=Material-1
*Density
10.,
*Elastic
100., 0.3
** ----------------------------------------------------------------
**
** STEP: Step-1
**
*Step, name=Step-1
*Static
1., 1., 1e-05, 1.
**
** LOADS
**
** Name: Load-1 Type: Concentrated force
*Cload
_PickedSet5, 1, -10.
**
** OUTPUT REQUESTS
**
*Restart, write, frequency=0
**
** FIELD OUTPUT: F-Output-1
**
*Output, field, variable=PRESELECT
**
** HISTORY OUTPUT: H-Output-1
**
*Output, history, variable=PRESELECT
*End Step

 

[alexzive]

and this is the error msg from the .ipm file (this msg is repeated several times:

NODE SET ASSEMBLY_PART-1-1_PART-1-1-REFPT_ HAS NOT BEEN DEFINED
BATCHPRE_PHASE: UNABLE TO LOCATE NODE SET ASSEMBLY_PART-1-1_PART-1-1-REFPT_. THE NODE SET MUST HAVE BEEN PREVIOUSLY DEFINED

many thanks for any help!

 

[alexzive]

ok I found an error in the previous inp file and I removed it (in the Section-1 ---> ref node=Part-1-1-RefPt_, I deleted it)

But I still have an error, this time seems to be more serious:

"The system matrix has 2 negative eigenvalues"
"The system matrix has 2 negative eigenvalues"

 

[corus]

You have negative eigenvalues because you've applied no restraints to the body. It flew away basically.

corus

 

[alexzive]

you are right, thank you!