# Which constraint should I use on my FEA?

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Hello everyone!

I'm performing a finite element analysis with a pair of gears and another component around this pair of gears. This system is named as "planetary gears". My model is simplified, just to see how will be the behavior of the system, I'm using the software Hypermesh with the solver OptiStruct. My question is, which degrees of freedom on "FACE 1" and "FACE 2" should I constraint to rotate "GEAR A" and "GEAR B" around the axis X.

Degres of freedom:
Displacement: x, y and z
Rotation: x, y and z

I have attached the picture.

Henry

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There're several method to do a static analysis for this. One of them is:

• Outer face of external ring => Fixed translations belong X, Y and Z-axis
• Make a Hinge elements for Gears A & B so they can rotate about their axis.
• Contact condition between external ring & Gear B
• Contact condition between gear A & gear B
• Loading (torque) will be applied on Gear A (via RBE2 for example)

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Hello @Q.Nguyen-Dai,

Thank you for your reply. I assigned a three RBE2. One in the middle of "GEAR A" and one in the middle of "GEAR B" and assigned a constraint in x, y and z (displacement) for each one, and I've assigned one RBE2 on face of "GEAR A" for the input torque. Then I've the following error:

There were 2 error messages during input processing.
The first message is repeated below:

*** ERROR # 339 ***
The dependent d.o.f. is constrained by grid or spc data.
RBE3 element id = 178357.
grid id = 33819.
component = 1.

Do you know how can I solve this?

Thanks!

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You speak about RBE2, but in the error message I see RBE3

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@Q.Nguyen-Dai, you are right, I've used RBE3 instead of RBE2. Could be this the problem?

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Thank you guys, it worked.

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