Mech-Intro 14.0 WS03.2 Contact

© 2011 ANSYS, Inc. February 13, 20121 Release 14.0

14. 0 Release

Introduction to ANSYSMechanical

Workshop 3.2Contact Control


GoalsWorkshop 3.2 investigates contact behavior on a simple assembly. It is meant to illustrate how rigid body motion can occur as a result of improper contact set up.

Problem statement:• The model consists of a simple assembly file.• Our goal is to set up contact among the parts in the assembly and see how non symmetric loading can effect the results.


AssumptionsWe’ll assume the friction between the arm shaft and the holes in the side plates is negligible. We’ll make the same assumption for the contact between the arm shaft and the stop shaft. Finally we’ll assume the stop shaft is fixed to each of the side plates.

Stop Shaft

Side Plate

Arm Shaft

Side Plate


Project SchematicOpen the Project page.

From the “Units” menu verify:• Project units are set to “US Customary (lbm, in, s, F, A, lbf, V).• “Display Values in Project Units” is checked (on).


. . . Project Schematic1. In the Toolbox, double click “Static

Structural” to create a new analysis system.

2. RMB on the “Geometry” cell and “Import Geometry”. Browse to “Contact_Arm.stp”.

1.

2.


Preprocessing3. Double click the “Model” cell to open the Mechanical

application.

4. Set/check the working Unit System:• Units > U.S Customary (in, lbm, lbf, °F, s, V, A)

3.

4.


5. RMB the “Connections” branch and “Rename Based on Definition”.

The result is contact regions are now defined with respect to the parts associated with each. Notice the type of contact (e.g. bonded, etc.) is also shown.

. . . Preprocessing

5.


. . . Preprocessing6. Based on the assumptions stated earlier change

3 of the contact regions to “No Separation” as shown here:a. Use the CTRL key and select the 3 contact regions

shown here.b. In the details change the contact type to “No

Separation”.– Each contact region could be changed

individually, selecting all 3 merely saves time.

b.

a.


Environment7. Fix the assembly (highlight the “Static

Structural” branch (A5):a. Select the 2 faces on the ends of the Side

Plates.b. RMB > Insert > Fixed Support.

a.

b.


8. Apply a force load to the ArmShaft:a. Select the end line on the top of the ArmShaft.b. RMB > Insert > Force.c. In the force details change to “Component”d. Set:

– Y component = ‐ 10 lbf (minus 10)– Z component = +1

. . . Environment

d.

c.

b.

a.


Initial Solution9. Highlight the Solution branch (A6) and

RMB > Insert > Deformation > Total.

10. Solve (you will see a warning message that the model may be unconstrained).• Highlight the “Total Deformation” to view

the result.

Although slight, we can see the ArmShaft is beginning to move sideways. We have no contact or boundary condition to prevent this motion as it is currently set up. If the magnitude of the load becomes large enough, the solution will fail.

10.

9.


Modified Environment11. Add a frictionless support to the ArmShaft:

a. Select one of the faces on the end of the shaft for the ArmShaft.

b. RMB > Insert >Frictionless Support.– Either end of the shaft can be chosen.

A frictionless support provides a constraint which is normal to the surface. In this case the shaft will be free to rotate but cannot move out of plane (in this case the Z direction is constrained).

b.

a.


Modified ResultOnce again solve the model and inspect the deformations. As can be seen the ArmShaft is now prevented from moving.

• In setting up contact models it is important to assess what motions have and have not, been accounted for.

Mech-Intro 14.0 WS03.2 Contact

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