contact pressure - results clarification

Sid_22073

Hello,

Can you please explain contact pressure. 

In the interferece fit analysis the contact pressure is very high (> 1000 Mpa) at the ends of the shaft.  Why the distribution is not uniform ?

Theoritically how to verify. Can someone explain the formula for same.

How to infer the results of contact analysis to failure limits? so we can make some meaningful suggestions

Appriciate your answers.

 

Fig : Geometry

 

 

Fig : Inner shaft Results

Robinson Ferrari_20451

Hi Sid,

Please refer to this article in our Community: Refer to this article https://altair.service-now.com/csm/en/modelling-interference-fits-and-validating-results?id=kb_article&sys_id=352254571b5805d4507ca6442a4bcb80.

Use two symmetric cylinders (or blocks), and solve the interferences. You will see a uniform distribution of contact pressure. This means, that if the geometry or loads are not uniform, the distribution of contact pressure can not be uniform.
Nonetheless, contact with the smooth option can help with contact pressure distribution in the case of coarse mesh. Also, clearance (in contact) can help with this purpose. Please see this session on the documentation for further details: https://2023.help.altair.com/2023/hwsolvers/os/topics/solvers/os/contact_os_c.htm?zoom_highlight=contact

From your picture, far from the corner, the contact pressure looks constant (uniform). Some stress concentration at the corner can be expected.

Thank you very much,

 

Adriano_Koga

Robinson Ferrari_20451 said:

Hi Sid,

Please refer to this article in our Community: Refer to this article https://altair.service-now.com/csm/en/modelling-interference-fits-and-validating-results?id=kb_article&sys_id=352254571b5805d4507ca6442a4bcb80.

Use two symmetric cylinders (or blocks), and solve the interferences. You will see a uniform distribution of contact pressure. This means, that if the geometry or loads are not uniform, the distribution of contact pressure can not be uniform.
Nonetheless, contact with the smooth option can help with contact pressure distribution in the case of coarse mesh. Also, clearance (in contact) can help with this purpose. Please see this session on the documentation for further details: https://2023.help.altair.com/2023/hwsolvers/os/topics/solvers/os/contact_os_c.htm?zoom_highlight=contact

From your picture, far from the corner, the contact pressure looks constant (uniform). Some stress concentration at the corner can be expected.

Thank you very much,

 

agreed. A paper studying the pressure distribution in press fit shows the trend of stress raising at the corners.

https://www.semanticscholar.org/paper/Prediction-of-stress-distribution-in-press-fit-of-a-Wang-Lou/f9661d5d5b4bb6376aec9da31fb519c1f69eab00/figure/14