  We outline a phenomenological model to assess friction at the interface
between two bodies in mutual contact. Although the approach is general, the
application inspiring the approach is the Discrete Element Method. The
kinematics of the friction process is expressed in terms of the relative 3D
motion of the contact point on the two surfaces in mutual contact. The model
produces expressions for three friction loads: slide force, roll torque, and
spin torque. The cornerstone of the methodology is the process of tracking the
evolution/path of the contact point on the surface of the two bodies in mutual
contact. The salient attribute of the model lies with its ability to
simultaneously compute, in a 3D setup, the slide, roll, and spin friction loads
for smooth bodies of arbitrary geometry while accounting for both static and
kinematic friction coefficients.
