Question about friction coefficient in SW/Simulation

[salmon2]

Hi Experts,

Basically I am running a assembly simulation with 4 components
by using SW/Simulation Static. I have several contact sets beside
global contact. I have set the friction coefficient to be 0.35 for all contact sets because it is steel/steel contact with lubrication. System is fully constrainted and simulation is running smooth.

Problem is when I use "list reaction/contact..." in the result
folder to take a closer look at those contact sets. I found for
two contact sets the ratio between friction force and normal force
to be 0.04X and 0.09X, respectively. Why? Shouldn't they to be roughly 0.35? It is a big deal for us, because a part supposed to be self-locking but it is not right now because of lower friction coefficient. Thanks a lot in advance for everyone's comment.

I am using 2011 Solidworks with simulation premium (highest level). Again it is a static study, the most basic one.

 

[corus]

The friction force will equate to the imposed loads in that direction, and nothing to do with the reaction force. F=0.35xR is the point that the joint slips so that condition imposes a limit on the ration of frction to reaction force.

Tara

 

[kellnerp]

I don't understand your problem. What does a transverse reaction being less that what the coefficient of friction times normal force mean? You are running a static analysis when you should be running a non-linear analysis. And, whether you have friction or the part is fixed, if there is nothing pushing transversely you won't see a transverse force.

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CSWP, BSSE

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[salmon2]

Thanks for your input, I got it straightened out. I just got deeper understanding about simulation now

Here is extremely simple example and a brain teaser for everyone:

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Imagine the above diagram is a block sitting on a flat surface, the friction coefficent is 0.35. Also the block is in contact with a vertical surface on left side surface. There is a force acting on the top surface of block at 10lbf and a horizontal force acting on the right side surface of block at 2lbf. What are reaction force and friction force, respectively?

 

[salmon2]

When I said reaction force, I meant between block and left support.
When I said friction force, I meant between block and bottom flat surface.

The 2lbf force is applied on left side surface of block and pushing the block against the left side surface.

 

[salmon2]

Gee, typo - 2lbf force is applied on RIGHT side of block.