1. Workshop 1 Contact Stiffness
Planar Seal
REFERENCE:
Training Manual
Contact Stiffness (3-10)

2. 1. Contact Stiffness Planar Seal
Purpose
Demonstrate the importance of estimating a good starting value for the contact stiffness
Goal
Impose a displacement controlled loading, solve the contact analysis, and postprocess the results
Model Description
2D hyperelastic planer seal
1/2 symmetry
Seal compression simulation
1/2 symmetry
0.85 inches applied displacement
October 15, 2001
Inventory #
W1-2

3. 1. Contact Stiffness …Planar Seal
STEPS TO FOLLOW:
1. Start an ANSYS Interactive session in the working directory specified by the instructor using “seal” as the jobname
2. Resume the SEAL database
Utility Menu > File > Resume from
Select “seal.db1”
[OK]
OR enter the following command:
RESUME, seal, db1
3. Redirect output to a file
Utility Menu > File > Switch output to > File
seal.output
/OUTPUT, seal, output
NOTE: The seal.db1 database contains the completed geometry, material, and boundary condition definitions for this finite element model.
October 15, 2001
Inventory #
W1-3

4. 1. Contact Stiffness …Planar Seal
4. View contact pair #1
Main Menu > Preprocessor > Create > Contact Pair > View and Edit …
Contact pair real set ID = 1
Select: Contact Pair
Options: normals shown
[Display]
October 15, 2001
Inventory #
W1-4

5. 1. Contact Stiffness …Planar Seal
5. View contact pair #2
Main Menu > Preprocessor > Create > Contact Pair > View and Edit …
Contact pair real set ID = 2
Select: Contact Pair
Options: normals shown
[Display]
[Close]
October 15, 2001
Inventory #
W1-5

6. 1. Contact Stiffness …Planar Seal
6. Review the normal contact stiffness factor for contact pair #1 via the Contact Wizard
Main Menu > Preprocessor > Create > Contact Pair >View and Edit…
Select “Set 1”
[Edit Settings]
[Cancel]
[Close]
NOTE: For bending-dominated problems, use FKN = 0.1 (default) as a starting estimate.
October 15, 2001
Inventory #
W1-6

7. 1. Contact Stiffness …Planar Seal
6. Review the normal contact stiffness factor for contact pair #1 via the Real Constants
Main Menu > Preprocessor > Real Constants > Add/Edit/Delete…
Select “Set 1”
[Edit]
Select “Type 3 CONTA171”
[Cancel]
NOTE: For bending-dominated problems, use FKN = 0.1 as a starting estimate.
October 15, 2001
Inventory #
W1-7

8. 1. Contact Stiffness …Planar Seal
7. Review the normal contact stiffness factor for contact pair #2
Main Menu > Preprocessor > Real Constants > Add/Edit/Delete
Select “Set 2”
[Edit]
Select “Type 3 CONTA171”
[Cancel]
[Close]
NOTE: For bending-dominated problems, use FKN = 0.1 as a starting estimate.
October 15, 2001
Inventory #
W1-8

9. 1. Contact Stiffness …Planar Seal
8. Apply 0.85 inches displacement in the -Y direction (vertical)
Utility Menu > Plot > Elements
Main Menu > Solution > Apply > Displacement > On Nodes
Select node number 259
[OK] UY
Displacement value = -0.85
OR enter the following commands:
/SOLUTION
D, 259, UY, -0.85
Pick Pilot node (number 259)
October 15, 2001
Inventory #
W1-9

10. 1. Contact Stiffness …Planar Seal
9. Specify “Basic” solution control options
Main Menu > Solution > Sol’n Control
Select tab: “Basic”
Analysis Options = Large Displacement Static
Time at end of loadstep = 0.85
Number of substeps = 25
Max no. of substeps = 200
Min no. of substeps = 10
All solution items
Write every substep
[OK]
OR enter the following commands:
NLGEOM, ON
TIME, 0.85
NSUBST, 25, 200, 10
OUTRES, ALL, ALL
October 15, 2001
Inventory #
W1-10

11. 1. Contact Stiffness …Planar Seal
10. Monitor the Y direction reaction force
Main Menu > Solution > Unabridged Menu > Nonlinear > Monitor
Select node number 259
[OK]
Variable 3 FY
OR enter the following command:
MONITOR, 3, 259, FY
11. Solve the contact analysis
Main Menu > Solution > Current LS
SOLVE
Pick node number 259
Note: You will see this error message during solution. Hit OK to continue. We will discuss this at the end.
October 15, 2001
Inventory #
W1-11

12. 1. Contact Stiffness …Planar Seal
12. Redirect output to the output window
Utility Menu > File > Switch Output to > Output Window
OR enter the following command:
/OUTPUT, TERM
13. Read the results for the last substep
Main Menu > General Postproc > Last Set
OR enter the following commands:
/POST1
SET, LAST
14. Plot the deformed shape
Utility Menu > Plot > Results > Deformed Shape
Def shape only
[OK]
PLDISP
October 15, 2001
Inventory #
W1-12

13. 1. Contact Stiffness …Planar Seal
15. Animate the deformed shape
Utility Menu > PlotCtrls > Animate > Over Time
Use Last Display
[OK]
OR enter the following command:
ANTIME, 10, 0.5, , 1
16. Plot the contact pressure
Main Menu > General Postproc > Plot Results
> Element Solu
Contact
Pressure PRES
PLESOL, CONT, PRES
You need to STOP the animation or CLOSE the Animation Controller before you can issue the next plot command.
October 15, 2001
Inventory #
W1-13

14. 1. Contact Stiffness …Planar Seal
17. Plot the equivalent total strain
Main Menu > General Postproc > Plot Results > Nodal Solu
Strain-total
von Mises EPTOEQV
[OK]
OR enter the following commands:
/POST1
PLNSOL, EPTO, EQV
October 15, 2001
Inventory #
W1-14

15. 1. Contact Stiffness …Planar Seal
18. Define the reaction force variable
Utility Menu > Plot > Elements
Main Menu > TimeHist Postpro > Define Variables
[Add]
Reaction forces
[OK]
Pick node number 259
User-specified label = FORCE FY
[Close]
OR enter the following commands:
/POST26
RFORCE, 2, 259, F, Y, FORCE
Pick node number 259
October 15, 2001
Inventory #
W1-15

16. 1. Contact Stiffness …Planar Seal
19. Graph the load vs. deflection curve
Main Menu > TimeHist Postpro > Graph Variables
1st variable to graph = 2
[OK]
OR enter the following command:
PLVAR, 2
For EXTRA CREDIT, try modifying the graph settings to improve the quality of the graph.
October 15, 2001
Inventory #
W1-16

17. 1. Contact Stiffness …Planar Seal
20. Review the contents of the monitor file (seal.mntr).
NOTE: Solution control initiated a bisection at inches of deflection (substep 11).
October 15, 2001
Inventory #
W1-17

18. 1. Contact Stiffness …Planar Seal
21. Review the contents of the output file (seal.output). Can you now explain the error message during solution?
The ERROR occurred after substep 10.
Solution control bisected to a smaller load increment at substep 11 in order to prevent the loss of contact for element 303.
The deformed shape for loadstep 1, substep 10 is shown. Contact element 304 is highlighted.
October 15, 2001
Inventory #
W1-18