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-   -   How to simulate a gripper (http://www.cfd-online.com/Forums/ansys/74693-how-simulate-gripper.html)

maxroucool April 6, 2010 17:09

How to simulate a gripper
 
Hi,

I am trying to simulate in ANSYS Workbench 12 a gripper made in only one piece. It is designed to be in plastic.
I succeed to simulate it alone, but I don't when I try to simulate the gripper grasping something (here a cylinder). The gripper pass through the cylinder, whereas it should adapt itself around it.

The gripper is a part imported from Catia, and the cylinder is just an extrusion in ANSYS.
I set a fixed support in both screw holes of the gripper, and on the lower face of the cylinder. I also impose a displacement at the bottom of the gripper.

Here are 2 screenshots:
The first represents the Displacement and fixed supports
The second represents the problem that I have after deformation

I really don't know why it doesn't work. If you could help me I would be grateful!


Thx!
Max

Michiel April 7, 2010 03:53

Well, this is no CFD but structural finite element analyzing.

Looking at the tree outline of your project I see you don't have any contacts defined. And that is your problem. If you want the model the interaction between parts you must define contact pairs.

To ad the contact: right click on the 'connections' object and insert a 'manual contact region'. Define contact and target areas, one should be the cylinderical surface, and the other should be the face on the gripper which will be in contact with the cylinder. You will need two of these contacts, one for each gripper arm.
For contact type select frictionless or frictional. For other settings i recommend you read the help files on this subject.

maxroucool April 7, 2010 11:47

Hi Michiel,


Thanks for helping me.

I tried what you said, but it didn't work. I add 2 Solid to Solid contacts between the cylinder and both arms of the gripper. I tried every type of contact (frictional, frictionless, rough ...), but it didn't change anything

I now have these error messages:

- "Warning: One or more bodies may be underconstrained and experiencing rigid body motion. Weak springs have been added to attain a solution. Refer to Troubleshooting in the Help System for more details. Project>Model>Static Structural>Solution"
- "Warning: Contact status has experienced an abrupt change. Check results carefully for possible contact separation. Project>Model>Static Structural>Solution"
- "Warning: One or more contact regions may not be in initial contact. Check results carefully. Refer to Troubleshooting in the Help System for more details. Project>Model>Static Structural>Solution"

So I tried to add 2 frictionless supports at the bottom of both cylinder and gripper to constrain them more, but it didn't change anything either.


Thx!
Max

maxroucool April 9, 2010 13:37

up plz! :D


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