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friction force

Question asked by Devi Prasad Samal on Nov 27, 2008
Latest reply on Dec 4, 2008 by Ian Hogg

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How to calculate friction force?

i have one part which roll upon a plate?

if i have to calculate the friction force what to select for define the result?

please help...................

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Ian Hogg Nov 29, 2008 1:01 PM
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Hi Devi,

Can you please provide a litte more information on how you are setting up the problem and what you want to measure. For example are you using 3-D contact with friction enabled? Is the part being driven or is it free to rotate and you are interested in if it will slip or rotate?

You can extract forces for friction. I forget if you're using 2008 or 2007.

Thanks,

Ian
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- Devi Prasad Samal @ Ian Hogg on Dec 2, 2008 2:47 AM
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  Check out ,
  
  this is my assembly attached .....
  
  I have given friction coefficient values during contact option....which are default setting.
  
  if i clear them can i found friction force between the roller & the plate...
  
  please clarify my doubt.....
  
  my assembly is in 2009 solidworks...
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  - 02dec.zip161.4 KB
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  - Ian Hogg @ Devi Prasad Samal on Dec 2, 2008 11:34 AM
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    Hi Devi,
    
    For this model, you have to look at the horizontal contact force. The friction result is only for joints with friction.
    
    I tweaked the model a little to give a more neurtral starting condition (in contact & at reast) and then accelerated the cylinder to 50 RPM (5.23 rad/sec). You can see that the friction force is very low and the speed ramps up smoothly.
    
    In the original model you had, the low friction coefficient caused it to only slowly get up to speed since it was already spinning when it hit the ground so it had the dynamic friction coefficient in play instead of the static friction coefficient.
    
    For more accurate forces, precise 3-D contact is strongly recommended (change this under the options settings).
    
    Cheers,
    
    Ian
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    Wheel_friction.zip264.1 KB
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    - Devi Prasad Samal @ Ian Hogg on Dec 4, 2008 8:52 AM
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      Thanks for the information Ian...
      
      it will be really helpfull in my next projects....
      
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      - Devi Prasad Samal @ Devi Prasad Samal on Dec 4, 2008 8:55 AM
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        ok i have one doubt....
        
        when in 2008 i give contact between two parts & click on calculate, i dont know why.... it does not work....
        
        every option is working in 2008 but
        
        if i select contact option, then calculate button not working.....every thing seems to be dead then...
        
        does you face this kind of problem?
        
        or i am using some wrong settings...........
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        Ian Hogg @ Devi Prasad Samal on Dec 4, 2008 9:48 AM
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        Hi Devi,
        When 3-D contact is active it is checking parts for penetration and then determining forces needed to prevent penetration. At the very first frame, it is getting everything into equilibrium, so it can take a bit of time for larger models or models with lots of contacts or complex geometry that is contacting.
        Always check if there are any interferences in the assembly before doing 3-D contact as this may be causing it to get bogged down.
        
        Cheers,
        
        Ian
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        Devi Prasad Samal @ Ian Hogg on Dec 4, 2008 10:45 AM
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        Yes I know about that if there is any wrong setting, then atleast the error msg appear about any iteration fails or anything but here no msg appear......
        
        when i click on it it seems nothing happen....
        
        may be i should have to attach a video of the issue......
        
        by the way thanks...............
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        Ian Hogg @ Devi Prasad Samal on Dec 4, 2008 12:26 PM
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        Hi Devi,
        
        If it is returning from the solve without an error message and it did not do anything, I would submit this to your support contact as a bug.
        
        If it just sits there for a while without the progress changing and you have to abort the simulaiton. Try supressing portions of the model to diagnose the cause for it getting bogged down.
        
        Cheers,
        
        Ian
        
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