40.0 - Force-displacement Law

Each contact contains a contact model. A contact model provides a particle-interaction law to update the internal force and moment. The contact also has an activity distance and an activity state. If the contact is active, then the particle-interaction law is executed during this cycle point; otherwise, the internal force and moment are set to zero and the computations of the particle-interaction law are skipped. These quantities are zero until the contact gap is below or equal to the contact model activity distance, and it is not necessary to enter the particle-interaction law to determine this fact. It is more efficient to first check if the contact gap is greater than the contact model activity distance. If it is, then the activity state is set to false; otherwise, the activity state is set to true. In this way, the particle-interaction law is bypassed until the contacting pieces actually interact. For most contact models that simulate surface-surface interaction the activity distance is zero, meaning that contacts become active when the contacting pieces actually touch. The details of the particle-interaction law computations are contact model dependent and presented in the detailed description of each contact model.

PFC offers a number of built-in contact models. The linear, linear contact bond, and linear parallel bond contact models share many characteristics, and thus, are referred to as linear-based models (see this section). The linear contact bond, linear parallel bond, smooth joint, and flat joint contact models utilize the bonding concept wherein shear and/or tensile forces may develop as a consequence of relative motion. The hertz and hysteretic contact models are included for the simulation of impact. The user may also build their own contact model using the C++ Plugin capability detailed here.

Next Cycle Point: Accumulate Deterministic Quantities