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Some questions for Analysis Result of Press in assembly

Hello,

 

I try to simulate a Shaft press into a Shaft Sleeve,

and find some informaion as follows:

1. How much force can Shaft be pull out of Shaft Sleeve ?

2. Contact Result

 

But i am not so clear for the result:

1. Is Reaction force what i want to pull Shaft out of Shaft Sleeve ?

2. Any difference between Contact Force Nodal and Contace Pressure Nodal ?

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5 REPLIES

Betreff: Some questions for Analysis Result of Press in assembly

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WANGHUA198211,

 

I assume you simulate the load or reaction of an interference fit assembly with NX SOL 601 or 701, right?

 

1. If you did define an enforced displacement over time (as a movement) at your center grid point at rbe-element I think there you can get the desired force for pulling the shaft out of the sleeve.

I believe that the summation of the reaction forces at the bottom of the sleeve shall yield the same value but with negative sign. It depends on the solution you selected because effects dealing with mass inertia can occur if you use 701 with accelerations or so.

 

2. Contact pressure decribes the contact effects at the loaded element in normal (contact related) direction as a scalar and as distribution over the face and

contact force describes the integration of contact pressure and traction at single grid points as a vector. That means you can find anwers for questions dealing with the pulling force also by summation of contact forces in vertical direction as an effect of friction and in radial direction as an effect of interference fit (shrink).

 

I hope I could help you a little bit. Also try to read the following passage in online documentation:

 

SIEMENS Documentation : Contact Output Request

 

Best wishes, Michael

 

Re: Some questions for Analysis Result of Press in assembly

Good point for Michael for explanation @ point 2.

 

 Dear, WANGHUA198211
 
honestly I do not get the question... a little.  You simulated the press of shaft INTO the sleeve. 
Assuming that it is a 601/106 analysis, you got the force vs step that will tell you how much force you need to apply into a shaft in order to push the shaft into sleeve at certain depth.
 
In order to get the force telling how much force you need to apply to get the shaft OUT from sleeve I would apply the enforced displacement symmetrically (meaning 0 -> 1 -> 0):
You now simulated state from 0 -> 1(push)
I would extend it and add additional steps from 1 -> 0 so the solution would simulate: push - zero movement - pull.
 
At the end the results mentioned by Michael should be the same (or very simmilar) if the solver 701 was not used.
 
Two additional things need to be mentioned here in order to get reasonable resuts:
- keep in mind that the material temperature in such analysis may have huge infuence on the resutls (in case you woul like to test such phenomena in reality)
- supporting condition of bottom of the sleeve may also have huhge infulece, especially a the last steps when the shaft reaches the sleeve bottom edge. Probably you fixed all the bottom face of the sleeve, thus the internal edge of the sleeve is over-stiffened and this may lead to unrelistic  results.
- try to do symmetric (quarter even) solution in order to shorten solution time.
- roughness of the surface is a next variable that have huge influence on such simulation resutls.
 
regards. Tomek.

Betreff: Some questions for Analysis Result of Press in assembly

Hello, MiDi1791,

 

Firstly, Thank you very much for your feedback !

 

Yes, i simulated with NX SOL601,106,

and i can get same results by ways you mentioned, now.

 

One more question for Contact traction,

 In the link you attached, describes that Contact traction is in-plane,

Does it means that the direction of Contact traction in the plane of contact faces ?

Re: Some questions for Analysis Result of Press in assembly

Hello, TomekZeWschodu,

 

Thank you for your advices,

and that are very helpful for me!

 

Just one question,

How do you assess the influence of material temperature ?

Do you mean simulate in specified temperature in computer firstly,

and then test in reality in same temperature,

finlly compare the two results ?

Betreff: Some questions for Analysis Result of Press in assembly

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WANGHUA198211,
 

yes, I think so. And because the surface has not only one internal degree of freedom but two (u,v) that behavior is not described with a scalar value like contact pressure but with a tensor containing the spatial decomposition of traction.

 

Keep in mind that different contact algorithms exist with different methods for deriving the normal contact direction in deformed state and sometimes contact pressure can also point into original "traction" direction of undeformed surface. (i.g. compression of an undeformed zylinder transformes it into a barrel and the normal directions of different points of surface get vertical components and aren't parallel to each other and perpendicular to rotation axis anymore).

 

Best wishes, Michael