Contacts and Contact Models

Particles in the PFC model interact at contacts by means of a generalized internal force [1] . Contact mechanics is embodied in particle-interaction laws that employ a soft-contact approach, for which all deformation occurs at the contacts between the rigid bodies. The particle-interaction laws are referred to as contact models; each contact is assigned a single contact model.

Contacts are created and deleted automatically during cycling, as outlined in the “35.0 - Create/delete Contacts” section. The kinematic variables [2] , used to describe the motion of bodies and contacts, are defined in the “Contact Resolution” section. These kinematic variables are used by contact models to determine the appropriate interaction, and will be referenced throughout the contact model presentations. Contact models may be assigned manually or via the Contact Model Assignment Table (CMAT).

This section outlines the logistics of contact detection, resolution and contact model assignment. These preliminary topics act as prelude to thorough descriptions of the PFC contact models. Finally, the command and FISH sections detail the mechanics of manipulating contacts and contact models.


[1]The generalized internal force consists of a force and moment that act at the contact location in an equal and opposite sense on the two pieces. An additional moment due to the application of the force at the contact location is added to each piece. Contact models that simulate surface-surface interactions update this force and these moment contributions; however, contact models that simulate interaction at a distance update the force and two internal moments that need not be equal and opposite.
[2]Kinematics considers the motion of systems of bodies without regard to the role of the forces causing the motion, while kinetics considers the relationship of the forces to the kinematic variables. The kinetics of the PFC model is embodied in the particle-interaction laws.