Civil Engineering Reference
In-Depth Information
contact formulation is primarily intended to avoid localized penetration of a
feature's edge of one surface into a relatively smooth portion of another sur-
face when the normal directions of the respective surface facets in the active
contact region form an oblique angle.
When a surface is used in a general contact interaction, all applicable
facets are included in the contact definition; however, modelers can specify
which edges to consider for edge-to-surface contact. The contact area asso-
ciated with a feature edge depends on the mesh size; therefore, contact pres-
sures (in units of force per area) associated with edge-to-surface contact are
mesh-dependent. Both surface-to-surface and edge-to-surface contact con-
straints may be active at the same nodes. To help avoid numerical overcon-
straint issues, edge-to-surface contact constraints are always enforced with a
penalty method. General contact is defined at the beginning of an analysis.
Only one general contact definition can be specified, and this definition is in
effect for every step of the analysis. Modelers can specify the regions of the
model that can potentially come into contact with each other by defining
general contact inclusions and exclusions. Only one contact inclusions def-
inition and one contact exclusions definition are allowed in the model def-
inition. All contact inclusions in an analysis are applied first, and then, all
contact exclusions are applied, regardless of the order in which they are spec-
ified. The contact exclusions take precedence over the contact inclusions.
The general contact algorithmwill consider only those interactions specified
by the contact inclusions definition and not specified by the contact exclu-
sions definition. General contact interactions typically are defined by spec-
ifying self-contact for the default automatically generated surface provided
by ABAQUS [1.29]. All surfaces used in the general contact algorithm
can span multiple unattached bodies, so self-contact in this algorithm is
not limited to contact of a single body with itself. For example, self-contact
of a surface that spans two bodies implies contact between the bodies as well
as contact of each body with itself.
Defining contact inclusions means specifying the regions of the model
that should be considered for contact purposes. Modelers can specify self-
contact for a default unnamed, all-inclusive surface defined automatically
by ABAQUS. This default surface contains, with the exceptions noted later,
all exterior element faces. This is the simplest way to define the contact
domain. On the other hand, modelers can refine the contact domain defi-
nition by specifying the regions of the model to exclude from contact. Pos-
sible motivations for specifying contact exclusions include (1) avoiding
physically unreasonable contact interactions; (2) improving computational
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