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Interaction module experiments in Abaqus Standardby Rakesh Ramakrishnan, Ajayraj, Lokaditya, Ananth Saran
iitmsat-H-CRR,RA, RL, ASY-2-Feb-13 3 Feb 2013
1 Background: Any 3-D model in real life contains various individual surfaces in contact with each other during its assembly. The property displayed by such a model depends on how the various surfaces interact with each other. For example, in a rotating fan: the blades are rigidly fixed (tied) to the main rotating body, The rotor is fixed rigidly to the motor but also has low friction in the tangential direction to avoid high damping. Abaqus/Standard provides us with a plethora of interaction properties which can be used to model various kinds of interactions. In addition to this, different methods of enforcing such interactions are present which yield different results each time. In this we use a dummy model to model and understand the effect of various constraints and hence understand which to use
2 Model used:
These 2 plates are given different interaction properties. The sides are "clenched" so as to form a realistic version which can even be experimented with. Just having two blocks introduces possibility of them flying apart which makes the simulation exit with an error.
The red and blue dots indicate locations of boundary conditions which are the regions which are rigidly fixed throughout the simulation. The square region on top is where the load is applied and the direction of load is shown by the arrows. In the above shown case, the pressure load is downward-into.
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3 Experiments:
Experiment 1:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 10
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
Yes - ticked Top Bottom Slave finer mesh
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - IntoPenetration into Slave,
Umax = 1.123x10-3m
Distinct Penetration observed even with slave having a finer
meshNo
Figure 1
Experiment 2:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 10
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
Yes - ticked Top Bottom Equal meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - IntoPenetration into Slave,
Umax = 1.121x10-3m
Slightly lesser penetration than expt 1 contradicting previous
knowledgeNo
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Figure 2
Experiment 3:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 10
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
Yes - ticked Top BottomMaster finer mesh
- ratio = 20
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - IntoPenetration into Slave,
Umax = 1.805x10-3mMore penetration than expt 1 -
Follows previous knowledgeNo
Figure 3
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Experiment 4:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
No - Unticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardNo Upward displacement
where no load is applied, sides warped; Umax = 1.2x10-6m
Does strict enforcement of no separation mean more stiffness?
Yes
Figure 4
Experiment 5:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 10
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
No - Unticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardUpward displacement like a an
arch, Umax = 1.121x10-3mExtent to which separation allowed dependent on k??
Maybe - dependence on k
unexpected
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Figure 5
Experiment 6:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
Yes - Ticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardUpward displacement like a an
arch, Umax = 1.121x10-3m
When there is separation, there is NO FORCE indicating non-
linearity in systemNo
Figure 6
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Experiment 7:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Default N/A
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
No - Unticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardNo Upward displacement
where no load is applied, sides warped; Umax = 5.2x10-6m
Umax higher than expt 4 expected since linear
enforcement more strict than default enforcement
Yes - 4 is better
Output similar to figure 4
Experiment 8:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Default N/A
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
Yes - Ticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardUpward displacement like a an
arch, Umax = 1.120x10-3mSimilar to expt 6 - expected No
Output similar to figure 6Experiment 9:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Default N/A
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
No - Unticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - IntoVery minimal Penetration.
Extra force transmitted to sides which warped outward
Exact result we were looking for - Confirms that not allowing
separation removes penetration issues
Yes
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Figure 9
Experiment 10:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Linear Default 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
N/A Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Up - OutwardUpward displacement like a an
arch, Umax = 1.121x10-3mSame as expt 6 - Introduces non
linearityNo - Never use
linear
Output same as figure 6
Experiment 11:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Linear Default 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
N/A Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - IntoPenetration observed in the
load bearing regions, Umax = 5.9x10-6. Sideswarped upwards!
Different result! Unexplained behaviour
No - Never use linear
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Figure 11
Experiment 12:
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Axial Connectors, Linear Uncoupled, F1 ticked 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
N/A Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - Into
Penetration present only in circular region bounded by
connectors, Umax = 8.949x10-
4m
Connectors are working - Absence of interaction caused
penetration
Yes, try with interaction
Figure 12
Experiment 13:Interaction Pressure Overclosure Constraint Enforcement Stiffness (if any)
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Method
Axial Connectors, Linear Uncoupled, F1 ticked 10
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
N/A Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - Into
Penetration present only in circular region bounded by
connectors, Umax = 1.149x10-
3m
More penetration than expt 12 - expected
Yes, try with interaction
Figure 13Experiment 14:
Used a non constrained primitive model comprising only of 2 plates
Interaction Pressure OverclosureConstraint Enforcement
MethodStiffness (if any)
Interaction Hard Contact Penalty - Linear 1 x 1010
Allow separation after contact?
Master Surface Slave surfaceRelative meshing
No - Unticked Top Bottom Equal Meshing
Load Pressure Direction
ResultInference / Additional
RemarksShould we use it for our model?
Downward - Into Each plate rotates Unexplainable result No
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Figure 14
4 Conclusions: The linear type of interaction is never to be used. We now use a hard type of pressure overclosure with penalty type of enforcement method and use a stiffness of 1010 N/m2 for simulating hard contacts and a stiffness of 106 N/m2 for simulating rubber like soft normal interactions.
Also, the finer mesh surface is assigned the slave surface to minimise any possible penetration as penetration is not at all avoidable due to the approximate nature of the solutions.
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