Defining a stop connector to limit motion? 1

[berounba]

Hi,
can anyone please advise me to define a stop connector inside abaqus cae? I believe I have set up everything correctly, but after adding the stop connect there is no displacment in my model anymore .

I try to stretch a one sided closed tube moving a stamp inside it (rigid body), pressing to the tube bottom until the bottom is contacting a mould (rigid body). Contact is defined as surface to surface and hard contact. The motion of the stamp is limited by a fixed value.

I did:
- Interaction-Module => Menue Connector => Geometry => Create Wire
- Interaction-Module => Menue Connector => Section => Create (Category Basic; Trans. Connection Type Slot, Rot. Connection Type None, Behaveaur Options Stop with Component U1, Positions at Stop 50, 50)
- Interaction-Module => Menue Connector => Assignment (mit CSYS +x-Richtung in Bewegungsrichtung)

After adding the stop connector there is no motion. What could be wrong - any ideas? Is there anybody who has a simple model with a stop connetor to have a look at it and learn/compare with my model?

Is there a simplier possibility to stop the motion without a stop connector?

 

[akabarten]

Hi,

It looks like your connector has stop from the beginning of the analysis.
You can check it with stop/lock connector flag which can be save into history output.

For connector stop you define minimal and maximal connector position (it is connector length no connector displacement).
Lets make simple example with keywords. Initial length of your connector is 25.0 [mm] and you want to set stop
when the connector extend by 10.0 [mm] and shrink by 15.0 [mm] you need to define stop as follow:

**
** min stop = 25.0 - 15.0 = 10.0
** max stop = 25.0 + 10.0 = 35.0
*CONNECTOR STOP, COMPONENT=1
10.0, 35.0
**

Regards,
Bartosz

 

[berounba]

Hallo Bartosz,
thanks al lot for the very helpful hint. Indeed, the connector has stopped from the beginning, but for me it is absolutely unclear why. May be there is a dependency from the node order of definining the wire? After redefining the model again, the connector is free from the beginnning, but unfortunately the model behavier on simulation with the connector is totally different from that model without the connector.

Before adding the connector the model was working well until the point of too much compression in the contact area resulting in excessive material non linearity. After adding the connector with stop and lock behavier to limit motion and compression, the simulation terminated at the first increment with "Too many attempts made for this increment" and "Excessive distortion at a total of 470 integration points in solid (continuum) elements" already from the beginning.

SUMMARY OF JOB INFORMATION:
STEP INC ATT SEVERE EQUIL TOTAL TOTAL STEP INC OF DOF IF
DISCON ITERS ITERS TIME/ TIME/LPF TIME/LPF MONITOR RIKS
ITERS FREQ
1 1 1U 1 1 2 0.000 0.000 1.000e-005
1 1 2U 1 1 2 0.000 0.000 2.500e-006
1 1 3U 1 1 2 0.000 0.000 6.250e-007
1 1 4U 1 1 2 0.000 0.000 1.563e-007
1 1 5U 1 1 2 0.000 0.000 3.906e-008

THE ANALYSIS HAS NOT BEEN COMPLETED

In addition I got a "zero pivot when processing DOF 1" at the connector element, which is defined between two rigid bodies Reference points. One of them is fixed in all directions, because the mould is fixed.

Any ideas for troubleshooting?
Regards berounba

 

[akabarten]

Hi,

May be there is a dependency from the node order of definining the wire?

In one case it is true in other not. It depend what type connector you are using.
For instance it's not true for AXIAL since displacement output is always positive.
But for TRANSLATOR where the output is in local coordinate system node ordering make a difference so it has influence also for connector stop/lock.

Do you mind to share the model so I can tak a look for it.

Regards,
Bartosz

 

[berounba]

Hi,

the definition of the stop should be ok now in general, but I have trouble to avoid the "zero Pivot Message".
Sorry for including instaed of attaching the input file, but I have no idea where to upload the file.

*Heading
** Job name: Stretch-Con-Stop-21-Forum Model name: Model-21-Con-Forum
** Generated by: Abaqus/CAE 6.12-2
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**
** PARTS
**
*Part, name=Bl
*End Part
**  
*Part, name=Pr
*Node
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      2,           0.,         -60.
      3,           0.,        -62.5
      4,   1.04999995,        -62.5
      5,   1.49245393,         -58.
      6,           0.,         -58.
      7,          3.5,  -59.9489822
      8,   4.05190897,  -59.9316063
      9,          3.5,         -58.
     10,   4.05190945,         -58.
     11,   7.05145121,  -55.0523949
     12,   10.0010624,  -55.0523949
     13,   7.14896154,  -59.7868996
     14,   5.70948505,  -57.5004883
     15,   6.41781425,  -56.8445854
     16,   9.96977997,  -56.8445854
     17,           0.,  -60.8333321
     18,           0.,  -61.6666679
     19,   1.19748461,  -61.6635857
     20,   1.34496927,  -60.8271713
     21,   1.49245393,  -58.9953766
     22,           0.,         -59.
     23,   2.49631429,  -59.9740677
     24,   4.05190897,  -58.9658051
     25,   2.49622703,         -58.
     26,   8.52625656,  -55.0523949
     27,   5.60090256,  -59.8692551
     28,   6.42922306,   -58.643692
     29,   4.91751146,  -57.8724098
     30,   8.19379711,  -56.8445854
     31,   9.98542118,  -55.9484901
     32,   6.88033485,  -56.0000038
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    118,    7.8401041,  -9.87049961
    119,   10.7700005,  -9.87049961
    120,   10.7700005,         -11.
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    122,   10.0210447,  -53.9076309
    123,   10.0410261,   -52.762867
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    125,   8.56595516,  -52.7780838
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5, 19, 18,  4
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10, 21,  5,  6
11,  5, 21, 36
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21, 37,  7,  8
22,  8, 24, 37
23, 10, 24, 29
24, 24, 38, 29
25, 24,  8, 38
26,  8, 27, 38
27, 29, 38, 14
28, 38, 28, 14
29, 38, 27, 28
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31, 15, 30, 32
32, 30, 39, 32
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41, 40, 35, 30
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*Nset, nset=Axis
  2,  3,  6, 17, 18, 22
*Elset, elset=Axis
 2, 4, 6, 7, 9
*Nset, nset=_PickedSet16, internal, generate
   1,  162,    1
*Elset, elset=_PickedSet16, internal, generate
   1,  211,    1
*Nset, nset=Mndg
  77, 118, 119
*Elset, elset=Mndg
 209, 211
** Section: Section-Pr
*Solid Section, elset=_PickedSet16, material=Plastics
,
*End Part
**  
*Part, name=St
*End Part
**  
**
** ASSEMBLY
**
*Assembly, name=Assembly
**  
*Instance, name=St, part=St
          0., -57.999999999997,           0.
*Node
      1,           0.,           0.,           0.
*Nset, nset=St-RefPt_, internal
1, 
*Surface, type=SEGMENTS, name=Surf-St
START,           0.,          5.5
 LINE,           4.,          5.5
 LINE,           4., 0.500000000000002
 CIRCL,          3.5,           0.,          3.5, 0.500000000000002
 LINE,           0.,           0.
*Rigid Body, ref node=St-RefPt_, analytical surface=Surf-St
*End Instance
**  
*Instance, name=Bl, part=Bl
*Node
      1,           0.,         -90.,           0.
*Nset, nset=Bl-RefPt_, internal
1, 
*Surface, type=SEGMENTS, name=Surf-Bl
START,           0.,         -90.
 LINE,          14.,         -90.
*Rigid Body, ref node=Bl-RefPt_, analytical surface=Surf-Bl
*End Instance
**  
*Instance, name=Pr, part=Pr
*End Instance
**  
*Element, type=CONN2D2
1, St.1, Bl.1
*Connector Section, elset=Wire-1-Connector-Set-1, behavior=ConnSect-1
Slot,
Csys-1-Connector,
*Nset, nset=Ref_St, instance=St
 1,
*Nset, nset=_PickedSet98, internal, instance=St
 1,
*Nset, nset=_PickedSet172, internal, instance=St
 1,
*Nset, nset=Ref_Bl, instance=Bl
 1,
*Nset, nset=Wire-1-Connector-Set-1, instance=Bl
 1,
*Nset, nset=Wire-1-Connector-Set-1, instance=St
 1,
*Elset, elset=Wire-1-Connector-Set-1
 1,
*Nset, nset=_PickedSet189, internal, instance=Bl
 1,
*Elset, elset=_Surf-Pr-outside_S1, internal, instance=Pr
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 103, 107, 111, 115, 119, 123, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163
 167, 171, 175, 179, 183, 187, 191, 195, 199, 203, 207, 211
*Elset, elset=_Surf-Pr-outside_S2, internal, instance=Pr
  6, 13, 17, 21, 45, 46, 47
*Elset, elset=_Surf-Pr-outside_S3, internal, instance=Pr
  1,  3,  5, 39
*Surface, type=ELEMENT, name=Surf-Pr-outside
_Surf-Pr-outside_S1, S1
_Surf-Pr-outside_S2, S2
_Surf-Pr-outside_S3, S3
*Elset, elset=_Surf-Pre_inside_S2, internal, instance=Pr
 10, 12, 16, 20
*Elset, elset=_Surf-Pre_inside_S3, internal, instance=Pr
 31, 35
*Surface, type=ELEMENT, name=Surf-Pre_inside
_Surf-Pre_inside_S2, S2
_Surf-Pre_inside_S3, S3
*Orientation, name=Csys-1-Connector
          0.,          -1.,           0.,           0.,           0.,           1.
1, 0.
*End Assembly
*Connector Behavior, name=ConnSect-1
*Connector Stop, component=1
1.5, 100.
** 
** MATERIALS
** 
*Material, name=Plastics
*Density
 1.4e-09,
*Hyperelastic, yeoh, test data input, poisson=0.4
*Biaxial Test Data, smooth=3
 1.05, 1.25
  1.4,  1.5
 1.45, 1.75
  1.4,   2.
 1.35, 2.25
 1.25,  2.5
  1.2, 2.75
 1.15,   3.
 1.35, 3.25
*Material, name=steel
*Conductivity
 4.9e+11,
*Density
 7.85e-09,
*Elastic
210000., 0.3
** 
** INTERACTION PROPERTIES
** 
*Surface Interaction, name=IntProp-Bl
1.,
*Friction
0.,
*Surface Behavior, pressure-overclosure=HARD
*Surface Interaction, name=IntProp-St
1.,
*Friction
0.,
*Surface Behavior, pressure-overclosure=HARD
** 
** PHYSICAL CONSTANTS
** 
*Physical Constants, absolute zero=273.15
** 
** BOUNDARY CONDITIONS
** 
** Name: BC-Bf-fix Type: Displacement/Rotation
*Boundary
_PickedSet189, 1, 1
_PickedSet189, 2, 2
_PickedSet189, 6, 6
** Name: BC-Pr-Axis-fix-rad Type: Displacement/Rotation
*Boundary
Pr.Axis, 1, 1
** Name: BC-Pr-Mn-fix Type: Displacement/Rotation
*Boundary
Pr.Mndg, 1, 1
Pr.Mndg, 2, 2
** Name: BC-St_fix_rad Type: Displacement/Rotation
*Boundary
_PickedSet98, 1, 1
_PickedSet98, 6, 6
** 
** INTERACTIONS
** 
** Interaction: Int-Bl-Pr
*Contact Pair, interaction=IntProp-Bl, type=SURFACE TO SURFACE, tracking=STATE
Surf-Pr-outside, Bl.Surf-Bl
** Interaction: Int-St-Pr
*Contact Pair, interaction=IntProp-St, type=SURFACE TO SURFACE, tracking=STATE
Surf-Pre_inside, St.Surf-St
** ----------------------------------------------------------------
** 
** STEP: Stretch
** 
*Step, name=Stretch, nlgeom=YES, inc=1000000
*Static
1e-05, 0.2, 6e-30, 1e-05
** 
** LOADS
** 
** Name: Load-St-ax   Type: Concentrated force
*Cload
_PickedSet172, 2, -63120.
** 
** INTERACTIONS
** 
** Contact Controls for Interaction: Int-Bl-Pr
*Contact Controls, master=Bl.Surf-Bl, slave=Surf-Pr-outside, reset
*Contact Controls, master=Bl.Surf-Bl, slave=Surf-Pr-outside, stabilize=2.
** Contact Controls for Interaction: Int-St-Pr
*Contact Controls, master=St.Surf-St, slave=Surf-Pre_inside, reset
*Contact Controls, master=St.Surf-St, slave=Surf-Pre_inside, stabilize=2.
** 
** OUTPUT REQUESTS
** 
*Restart, write, frequency=0
** 
** FIELD OUTPUT: F-Output-2
** 
*Output, field, variable=PRESELECT, frequency=10
** 
** HISTORY OUTPUT: H-Output-Whole-Model
** 
*Output, history, frequency=10
*Energy Output
ALLAE, ALLCD, ALLDMD, ALLEE, ALLFD, ALLIE, ALLJD, ALLKE, ALLKL, ALLPD, ALLQB, ALLSD, ALLSE, ALLVD, ALLWK, ETOTAL
*Contact Output
CFN1, CFN2, CFN3, CFNM
** 
** HISTORY OUTPUT: H-Output-Connector-Set
** 
*Output, history, frequency=10
*Element Output, elset=Wire-1-Connector-Set-1
CFAILST1, CP1, CSLST1, CU1
*End Step

 

[IceBreakerSours]

Some node(s) is/are free to translate/rotate.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[berounba]

Dear IceBreakerSours,
plaese make a answer in more detail. Which nodes are free in which DOF?

 

[IceBreakerSours]

Check the .msg file. Also, open the .odb file and check for these nodes in the Create Display Group and Job Diagnostics menu items. If you are not familiar, check the CAE manual for more.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[akabarten]

Hi,

I took a look for you inputdeck. I changed your model and I can run it with success but not exactly what you have.

My modifications:
- I change connector type from SLOT to AXIAL
Connector lower node is already constrained with BOUNDARY in all
active DOFs (1,2,6) and upper in 1,6. So the only free direction is 2.
Since there is only one DOF free there is no point to use connector which introducing additional kinematics constrains.
AXIAL does not constrain any DOF so it not lead to model over-constrain , I think.
- I using much smaller force to run model.
You have value of 63120, now is question of what?
Base on your definition of steel I guess you are using mm, tonne, sec system of unit. Am I right?
Then force is in N, are you really apply 63 kN of force? It's huge value.
The model is not able to start any calculation with so high force.
I used 63.120 to my test.
- I changed increment settings under *STEP
- The model is stable until we have a punch displacement more than ~7 mm, after that it crash.
I think the problem here could be contact or high element deformation.

I did what I can, I hope I helped you a little bit.
I am attaching my model.

Regards,
Bartosz

 

[IceBreakerSours]

I must take my previous statements back; I had not tried running your INP.

The zero pivot messages are generated due to overconstraints (as explained by Bartosz above). Sometimes ABAQUS pre-processor releases some overconstraints which can result in unconstrained rigid body rotations/translations showing up as zero pivot messages.

By the way, reducing time increments isn't a great strategy when trying to investigate issues in your model. Default time increments, in a majority of cases, tend to be reasonable.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083