Discussion Forum

Dear all,
I have a coupled model with Conductive media and structural mechanics and I want to use contact resistance model which is function of contact pressure. Instead of using a contact model in the structural mechanics (because of convergence problem and time dependency of my model), I just use identity pairs for contact resistance. So, I am able to define contact resistance at boundary of two objects but there is a problem.

Since I use a identity pairs, boundary in structural mechanics module has a pairs too, but I didn't define
any boundary condition at the boundary pairs except free condition (this boundary would be continuity
if I wouldn't use identity pairs for the contact resistance).
And electric conductivity(S/m) is a function of contact pressure, so I use traction force (N/m2) from the
structural mechanics to calculate the conductivity.

However, because of the pairs, two traction forces can be defined at the pair boundary and
the data looks very similar each other, but they are not identity.

The questions are

1. if I define the traction force at the pair boundaries in the boundary expression,
which traction force is used in the COMSOL to calculate the electric conductivity for contact resistance?
(If I omit the expression in one of the pair boundary, COMSOL generate error saying that it can not
calculate the conductivity, Conductivity = fn(tranction force) )

2. and what boundary condition for the identity pairs in the structural mechanics module should I use if the free condition is not correct?

3. Is there any way to avoid this conflicts ?

Thank you very much

Yoon