Workbench-Mechanical Structural...

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© 2009 ANSYS, Inc. All rights reserved.April 30, 2009

Inventory #002660

Workshop 2B

Assembly Contact

Workbench-MechanicalStructural Nonlinearities

Workbench Mechanical – Structural Nonlinearities



Inventory #002660

Workshop SupplementWorkshop 2B – Assembly Contact

• Goal:

– In this workshop our goal is to investigate the behavior of the pipe clamp

assembly (Pipe_clamp.x_t) shown here. Specifically we wish to

determine the crushing stress and deformation in a copper pipe section

when the bolt in the clamp is torqued down.




Inventory #002660

Workshop Supplement

• We will assume the material used for the pipe is a copper alloy while all other

parts are steel.

• It is assumed the clamp is torqued to 1000 N when placed in service.

• We’ll assume the coefficient of friction between the clamp and pipe is 0.4.

The other contact regions will be treated as either bonded or no separation

as shown in the accompanying figures.

… Workshop 2B – Assembly Contact




Inventory #002660

Workshop Supplement

If previous workshop project is still in

session, clear it from the project page

Utility Menu > File >New…

1. From the Toolbox, double click

“Static Structural” to create a new

system.

2. RMB the geometry cell and “Import

Geometry and browse to

“Pipe_Clamp.x_t”

1.

2.





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Workshop Supplement

• From the “Units” drop down menu:

– Set Project units to “Metric (Tonne, mm, s, C, mA, N, mV).

– “Display Values in Project Units” is checked (on).





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Workshop Supplement

3.

3. Double Click the “Model” cell to open

the Mechanical Application

4. Once inside the Mechanical application,

set the working unit systems

“Unit>Metric(mm,kg,N,s,mV,mA)”

4.





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Workshop Supplement

5. Expand the “Connections” branch

and use the shift key to highlight all

contact definitions.

6. In the details window change the

Formulation to “Augmented

Lagrange.

5.

6.





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Workshop Supplement

7. Highlight the first contact branch. This is the

definition for the pipe to clamp contact.

8. In the detail for the definition change the Type

to “Frictional”.

9. Enter a value for “Friction Coefficient” of 0.4.

7.

8.

9.





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Workshop Supplement

10. Highlight the second contact branch. This is

the definition for the bolt shaft to clamp hole

contact.

11. From the details window change the Type to

“No Separation”.

• The remaining 2 contact regions will be

modeled using the default bonded type of

contact.

10.

11.





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Workshop Supplement

• Create a local coordinate system along the pipe’s axis. Note, we

will use the local coordinate system for post processing later.

• With the Coordinate system branch highlighted:

12. Select the inside surface of the cylinder.

13. “RMB > Insert > Coordinate System”.

12.

13.





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Workshop Supplement

14. From the detail for the new coordinate

system change “Type” to “Cylindrical”.

15. Change the Principal Axis to the “Z”

Direction

16. Defined by “Geometry Selection”

17. “Click to Change” on Geometry , then

select the inner surface of the pipe and

“Apply”

14.

15.

16.

17.





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Workshop Supplement

18. In the Details of “Analysis Settings” Window,

define the following:

– Number of Steps = 2

– Large Deflection = On

This analysis is run in two load steps.

In, Load Step 1, apply the bolt pretension

In Load Step 2, lock this pretension and

postprocess the working load.





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Workshop Supplement

19. Select one of the end surfaces of the pipe.

20. Highlight “Static Structural” Branch

RMB > Insert > Fixed Support.

19.

20.





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Workshop Supplement

21. Select the cylindrical face of the bolt part.

“RMB > Insert > Bolt Pretension”

22. In the Detail of “Bolt Pretension” window

enter a “Preload” value of 1000 for “Load”

Step 1. Using the Timeline, Set load step

to “2” and define Pretension as “Lock”

21.

22.





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Workshop Supplement

23. Switch to “Body” select mode.

24. With Solution Branch highlighted, select the pipe part.

25. “RMB > Insert > Deformation > Directional”.

24.

23.

25.





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Workshop Supplement

26. From the detail for the “Directional Deformation” change to “Coordinate System”.

Note we allowed the default name “Coordinate System” to be used when the local system was created. We could easily change the name to a more meaningful one.

26.





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Workshop Supplement

27. Switch to face select mode.

28. Highlight the outer surface of the pipe.

29. “RMB > Insert > Contact Tool

30. RMB Contact Tool in the Contact Tool Branch

Insert > Pressure

• Repeat step 30 inserting contact “Frictional Stress”.

• Solve

27.

28.

30.

29.





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Workshop Supplement

• The solution for this workshop might take several depending

on the available hardware.

• The use of frictional contact triggers a nonlinear solution

requiring equilibrium iterations. The solution progress can

be viewed by opening the “Solution Information” folder.





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Workshop Supplement

• Recall that the solution triggered the use of

“Weak Spring” stabilization.

• To insure that the weak springs are not the result

of rigid body motion,

– Highlight Solution, “RMB > Insert > Probe> Force

Reaction and specify in the details window the

boundary condition as “Weak Springs”

– Verify that the reaction in the weak springs is of the

order e-5, a negligible value.





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Workshop Supplement

• Highlight Solution. RMB > Insert > Probe > Bolt

Pretension to verify that the bolt pretension working

load equals user defined preload

– In Details of Bolt Pretension, define Boundary as Bolt

Pretension (Trivial since there is only one bolt in this

model).

– RMB > Evaulate Results





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Workshop Supplement

• Insert and plotting the “Total Deformation” for the assembly.

– This plot is not particularly useful for our goal (investigation of pipe’s behavior).

• The “scoped” result we placed in the solution branch earlier will be more

instructive.





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Workshop Supplement

• Highlight and plot the result “Directional Deformation”.

• In this case the result is scoped only to the pipe section. Also,

since we employed a local cylindrical system at the pipe axis, the

X direction here is displayed in the radial sense.





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Workshop Supplement

• Similarly, the behavior of the contact region can be viewed by highlighting

the contact result objects. Again the use of scoped results allows a more

intuitive plot of the quantity displayed.


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