How to interpret total contact force of surface

[aleib]

Hello everyone,

I am having trouble to understand the the whole surface history output CFN: Total Force due to contact pressure.

How does Abaqus compute this value? Looking at the nodal values of CNORMF (Magnitude of contact force) along the surface, I cannot derive the same value by summing up the values.


I could not find any details in the documentation about the computation of this quanitity.

Thank you,

Alex

 

[burningDiesel]

It's directional. So you can request CFN1 to CFN3 or CFNM (magnitude).
It is normal that the sum of the directional ones is not the same as CNORMF resultant.
I've checked and for me the sum is the same. Is the difference small in your case? It might just be because of rounding then.
Are you comparing e.g. CFN1 to CNORMF1?

 

[aleib]

Thanks for your reply!
Yes you are right about the directional aspect.

I found now that CFN as history output gives you the resultant contact force, which means in this case that vectors showing in opposite directions cancel each other out.

CFN for a surface can be computed manually by:
sqrt((sum(CFN1))^2+(sum(CFN2))^2+(sum(CFN3))^2)