Page 52 - The Combined Finite-Discrete Element Method

2

Processing of Contact

Interaction in the Combined

Finite Discrete Element

Method

2.1 INTRODUCTION

The combined finite-discrete element method is aimed at problems involving transient
dynamics of systems comprising a large number of deformable bodies that interact with
each other, and that may in general fracture and fragment, thus increasing the total number
of discrete elements even further. Each individual discrete element is of a general shape
and size, and is modelled by a single discrete element. Each discrete element is discretised
into finite elements to analyse deformability, fracture and fragmentation. A typical com-
bined finite-discrete element system comprises a few thousand to a few million separate
interacting solids, each associated with separate finite element meshes. In this context,
one of the key issues in the development of the combined finite-discrete element method
is the treatment of contact, i.e. the enforcement of the constraint that no point in space is
occupied by more than one body at the same time.
From an algorithmic point of view, there are two aspects to contact in the combined
finite-discrete element method:
• contact detection,
• contact interaction.

Contact detection is aimed at detecting couples of discrete elements close to each other,
i.e. eliminating couples of discrete elements that are far from each other and cannot
possibly be in contact. In other words, contact detection is aimed at avoiding processing
contact interaction when there is no contact. In that sense, contact detection is aimed at
reducing CPU requirements, i.e. reducing processing (run) times.
Once couples of discrete elements in contact have been detected, a contact interaction
algorithm is employed to evaluate contact forces between discrete elements in contact.

The Combined Finite-Discrete Element Method A. Munjiza
 2004 John Wiley & Sons, Ltd ISBN: 0-470-84199-0