FRIC_COEF

Abaqus provides user subroutine FRIC_COEF, in which complex dependencies of a friction coefficient can be defined on slip rate, pressure, temperature, and field variables. This example verifies the capability by considering the contact response for a Coulomb friction law in which the friction coefficient is of the form

where ${\dot{\gamma }}_{eq}$ is the slip rate, $d_c$ is the decay coefficient, and ${\mu }_s$ and ${\mu }_k$ are the static and dynamic coefficients of friction, respectively. Both the static and dynamic coefficients are functions of contact pressure, $p$ and the average temperature between the two contacting surfaces, $\overline{\theta }$

where $C_s$, $D_s$, $C_k$, and $D_k$ are constants.

The verification test consists of a rod perpendicular to a fixed rigid surface forced into contact with the rigid surface by a concentrated load applied in the axial direction at the top of the rod. Subsequently, prescribed temperatures and displacements are applied to the rod, forcing the rod to slide along the surface. The contact between the bottom end of the rod and the rigid surface is modeled by specifying a master-slave contact pair. A node-based slave surface is defined on the bottom end of the rod. This slave surface has a contact area of unity; hence, the normal force applied on the rod is equal to the contact pressure.

A second identical rod, subjected to the same loading sequence, serves as the reference solution. The friction behavior for this reference model is entered as tabulated data.