| Matrix or Vector | Geometry | Shape Functions | Integration Points |
|---|---|---|---|
| Stiffness Matrix | Normal Direction | None | None |
| Sliding Direction | None | None |
The CONTA175 description is the same as for CONTA174 - 3D 8-Node Surface-to-Surface Contact except that it is a one node contact element.
The contact model can be either contact force based (KEYOPT(3) = 0, default) or contact traction based (KEYOPT(3) = 1). For a contact traction based model, Mechanical APDL can determine the area associated with the contact node. For the single point contact case, a unit area will be used which is equivalent to the contact force based model.
In order to satisfy contact compatibility, forces are developed in a direction normal (n-direction) to the target that will tend to reduce the penetration to an acceptable numerical level. In addition to normal contact forces, friction forces are developed in directions that are tangent to the target plane.
 | (13–293) |
where:
| Fn = normal contact force |
| Kn = contact normal stiffness (input as FKN on R command) |
| un = contact gap size |
 | (13–294) |
where:
| FT = tangential contact force |
| KT = tangential contact stiffness (input as FKT on R command) |
| uT = contact slip distance |
|
For orthotropic friction, μeq is computed using the expression:
 | (13–295) |
where:
| μeq = equivalent coefficient of friction for orthotropic friction |
μ1, μ2 = coefficients
of friction in first and second principal directions (input as MU1 and MU2
using TB command with Lab =
FRIC) |