# nonlinear analysis OS-1520 Stresses

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Hi, I am a beginner about non linear simulation, I want simulate a contact about a gear transmission.
In Altair tutorials I found this example:"OS-1520: Finite Sliding of Rack and Pinion Gear Model" that could help me.
In the simulation, the motion is create by "enf_rotation" from a displacement of 5 radians. The load step hasn't Load declared and the rack is free to move on x.

Now I have three questions:

-What differece is between SPC and SPCD? If I used SPCD for "enf_rotation" would I get a different result?

-Why there are contact stress in results? (There aren't forces or torque, the rack is free to slide)

-If I want evalue the contact stress about a gear trasmition with a motion torque on pinion and a resistence torque on gear wheel, is this hypermesh's tutorial a good way?

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17 hours ago, scyrock said:

What differece is between SPC and SPCD

Hi,

- SPC is an abbreviation of Single-Point Constrained. With a SPC you can define a sets or only a Single-Point that will be constrained. For example, in linear or non linear static analysis, you can use it to apply an enforced displacement, for thermal analysis you can use it to define a temperature BC ...

- SPCD is general, in addition to an enforced displacement (valid in static analysis), you can define velocity or acceleration for dynamic analysis. You can also use it to define an amplitude for a dynamic load.

17 hours ago, scyrock said:

-Why there are contact stress in results?

- Solving the contact problem mean find the contact pressure and hence, the stress and strain ....

Cheers,

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1 hour ago, Farouk Maaboudallah said:

- SPCD is general, in addition to an enforced displacement (valid in static analysis), you can define velocity or acceleration for dynamic analysis. You can also use it to define an amplitude for a dynamic load.

Very well, I can apply a torque on the pinion from SPCD

1 hour ago, Farouk Maaboudallah said:

- Solving the contact problem mean find the contact pressure and hence, the stress and strain ....

I know that solving the contact problem is find the stress; but the question is:

Why are there stresses in the system?

There is no friction on the gears, there are no resistance loads. The system is free to move.

Only potential resistences to slide is the inertial forces, but in my view the stresses result are too high.

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3 hours ago, scyrock said:

Why are there stresses in the system?

There is no friction on the gears, there are no resistance loads. The system is free to move.

Only potential resistences to slide is the inertial forces, but in my view the stresses result are too high.

The normal contact stresses are always here when you solve a frictionless contact problem.