ansys v16 update seminar - cae associates · pdf fileansys v16 update seminar ... • -1...

2015 CAE Associates CAE Associates Inc. and ANSYS Inc. Proprietary 2015 CAE Associates Inc. and ANSYS Inc. All rights reserved.
ANSYS V16 Update Seminar
MAPDL Enhancements

2015 CAE Associates CAE Associates Inc. and ANSYS Inc. Proprietary 2015 CAE Associates Inc. and ANSYS Inc. All rights reserved.
Contact Enhancements
V16 Update Seminar

4 www.caeai.com www.caeai.com
V16 Contact Enhancements
Contact Robustness Automated Stiffness Updates Stabilization Damping Improvements Interference Fit Enhancements
Contact Results Tracking Enhancements Changes in Defaults Cohesive Zone Automatic Contact Generation
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Contact Robustness - Stiffness
The adaptive scheme for evaluating normal contact stiffness has been enhanced so that smoother contact stiffness values are used, resulting in better convergence behavior while keeping contact penetration at acceptable levels.
R15.0.7 Convergence
R16.0 Convergence

All things being equal between R15.0.7 and R16.0, the initially calculated contact properties published in the solver output might be the same R15.0.7 contact properties R16.0 contact properties

Results Tracker (NLHIST) shows very different contact stiffness adjustment pattern and corresponding penetrations between R15.0 and R16.0
R15.0.7 Adaptive Contact Stiffness R16.0 Adaptive Contact Stiffness

Contact Displacement Convergence
R16.0 also activates check on displacement convergence criteria as a supplement to force convergence, for improved accuracy.
R15.0.7 Output R16.0 Output

Contact Robustness
Many contact models solve with default settings or in fewer iterations compared to previous releases. Customer Descriptions R15.0.7 R16.0 Reduction in
Iterations
Iterations Iterations
Panasonic Assembly w/frictional sliding (default program controlled)
Not converged 148 ---
Apple Assembly (FKN=0.1) Not converged 221 ---
GM Plate assembly w/ bolt pretension (FKN=0.1) 162 125 23%
Emergent Systems
Frictional sliding (FKN=0.1; NROPT,unsymm) 874 437 50%
Hyperelastic Hose 1252 756 40%
Thin wall offshore structure 952 743
22%
Wire Bending 1002 836 17%
Cable Hose 377 176 53%
Wiper Slipstick 809 165 80%

Demo Model of Bolted Rail Joint
ANSYS 15 ANSYS 16

Contact Robustness
Contact analyses that most benefit from these enhancements include: Nearly or fully incompressible materials Shells, beams, or thinly-layered solid elements with bending-dominated
deformations. "Program Controlled" defaults appear to be superior to R15.0.7 defaults
Challenging models that already converged in R15.0.7 after some user manipulation of contact properties will likely need further adjustment in R16.0 to achieve convergence.
In some models, longer run times might result from the addition of the displacement convergence criteria as a new default at R16.0.
Displacement Check can be deactivated via Analysis Settings=>Nonlinear Controls (CNVTOL)
Can we go back to R15.0? YES! R15.0 Adaptive Scheme can be retrieved via CNTR,revision,150

Contact Stabilization Damping
Enhanced Contact Stabilization Scheme Prior to this release, automatic contact damping was activated based on the
contact status of the entire contact pair in the previous substep.
Now, automatic damping is activated based on the contact status of the current iteration, and damping is deactivated if any contact detection point that has a closed status.
In addition, the default damping coefficient has been reduced, minimizing the risk of degraded accuracy while still providing effective stabilization.

* Based on comparison with theoretical calculation of 5080N
Stabilization damping improvements result in faster convergence and less error.
R15.0.7 model with FDMN=5e-3 19 N-R Iterations 2 bisections %Error in Reaction Force = 0.2%*
R16.0 model with FDMN=0.1 8 N-R Iterations 0 bisections %Error in Reaction Force = 0.004%*

Improved Stabilization for Sliding Contact.
Can be activated (via KEYOPT(15) = 2 or 3) independent of normal damping.
Contact status of the current contact detection point is closed and sliding FDMT is explicitly specified, either as a factor (positive value) or a coefficient
(negative value).
Helpful to prevent rigid body motion due to larger sliding for no-separation contact definitions.

Modeling Interference Fits
By default, the ramping option (KEYOPT(9) = 2 or 4 on contact elements) resolves initial penetrations following the contact surface normal direction.
This methods is suited for most applications. (Parallel surfaces, relatively small interference)
However, when the contact and/or target surfaces are not smooth, the
contact normal direction varies across the interface which may lead to locking of the press fit.

A new method for interference fit modeling enables you to specify a user-defined normal direction via the SECTYPE and SECDATA commands.
SECTYPE,,contact,normal, SECDATA,csys,NX,NY,NZ
The program automatically ramps the initial penetration down to zero over
time along the user-defined normal direction.

CNCHECK,ADJUST
Use CNCHECK,adjust, to physically move Contact Nodes towards the target surface.
Original mesh
KEYO,,4,2 CNCH,adjust

CNCHECK,ADJUST
There are three new parameters for additional adjustment control. CNCHECK, adjust, , , , , , CGAP, CPEN, IOFF
CGAP - An open gap closes if the absolute value of the gap is smaller
than CGAP.
CPEN - An initial penetration closes if the absolute value of the penetration is smaller than CPEN.
IOFF Input a positive value to adjust the contact nodes towards the target surface with a
constant interference distance equal to IOFF.
Input a negative value to adjust the contact node towards the target surface with a uniform gap distance equal to the absolute value of IOFF.

Contact Debonding
Cohesive Zone Material (CZM) models previously available for use only with Interface elements (INTER20x) can now be used with CONTA17x elements
Exponential (EXPO) (TB,CZM,,,,EXPO)
Bilinear (BILI)
(TB,CZM,,,,BILI)
Contact based debonding is easier to use/model and allows dissimilar mesh at the interface

Enhanced Contact Results Tracking
Two new fields can be used to terminate an analysis automatically based on contact variables tracked by NLHIST command.
NLHIST, Key, Name, Item, Comp, NODE, ELEM, SHELL, LAYER, STOP_VALUE, STOP_COND
STOP_VALUE Critical value of the tracked variable. This value is used to determine if the analysis should be terminated. This field is only valid for contact data (Key = PAIR or GCN).
STOP_COND Specifies the conditional relationship between the variable being tracked and the STOP_VALUE upon which the analysis will be terminated:
-1 Terminate the analysis when the tracked variable is less than or equal to STOP_VALUE.
0 Terminate the analysis when the tracked variable equals STOP_VALUE. 1 Terminate the analysis when the tracked variable is greater than or equal
to STOP_VALUE.

Max
. C
onta
ct P
res.
Time
Crit. Stop Value
Analysis Terminates Automatically
Example: Terminate the analysis if and when the Max. contact pressure in Pair 3 Var. < Stop_Value 1 => Var. > Stop_Value 0 => Var. = Stop_Value

Pair based energy terms can be tracked via NLHIS, NLDIA CTEN: Total strain energy due to

ansys v16 update seminar - cae associates · pdf fileansys v16 update seminar ... • -1...

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