The following types of kinematic constraints can be defined:
- Equations
-
Linear multi-point constraints can be given in the form of an equation (see
Linear Constraint Equations).
- Multi-point
constraints
-
Multi-point constraints (MPCs) specify
linear or nonlinear constraints between nodes. These relations between nodes
can be the default types that are provided in
Abaqus
or, in
Abaqus/Standard,
can be coded in the form of a user subroutine.
General Multi-Point Constraints
explains the use of MPCs and lists the
available default constraints.
- Kinematic
coupling
-
In
Abaqus/Standard
a node or group of nodes can be constrained to a reference node. Similar to
multi-point constraints, the kinematic coupling constraint allows general
node-by-node specification of constrained degrees of freedom (see
Kinematic Coupling Constraints).
- Surface-based tie
constraints
-
Two surfaces can be tied together. Each node on the first surface (the secondary surface) will
have the same values for its degrees of freedom as the point on the second surface (the
main surface) to which it is closest (see Mesh Tie Constraints).
In the case of surface elements tied to a beam surface, the offset distances between the
surface elements and the beam are used in the definition of constraints, which include
the rotational degrees of freedom of the beam.
- Surface-based
coupling constraints
-
A group of nodes located on a surface can be constrained to a reference
node. This constraint may be kinematic, in which the group of coupling nodes
can be constrained to the rigid body motion defined by the reference node, or
distributing, in which the group of coupling nodes can be constrained to the
rigid body motion defined by the reference node in an average sense (see
Coupling Constraints).
- Surface-based
shell-to-solid coupling
-
An edge-based surface on a three-dimensional shell element mesh can be
coupled to an element- or node-based surface on a three-dimensional solid mesh.
The coupling is enforced by the creation of an internal set of distributing
coupling constraints (see
Shell-to-Solid Coupling).
- Mesh-independent
spot welds
-
Two or more surfaces can be bonded together using fasteners such as spot
welds (see
Mesh-Independent Fasteners).
Distributed coupling constraints are created on each of the connected surfaces.
The connection is modeled independent of the mesh.
- Embedded
elements
-
An element or a group of elements can be embedded in a group of host
elements (see
Embedded Elements).
Abaqus
will search for the geometric relationships between nodes on the embedded
elements and the host elements. If a node on an embedded element lies within a
host element, the degrees of freedom at the node will be eliminated by
constraining them to the interpolated values of the degrees of freedom of the
host element. Host elements cannot be embedded themselves.
- Release
-
In
Abaqus/Standard
a local rotational degree of freedom or a combination of local rotational
degrees of freedom can be released at one or both ends of a beam element (see
Element End Release).
Boundary conditions are also a type of kinematic constraint in stress
analysis because they define the support of the structure or give fixed
displacements at nodal points. Specification of boundary conditions is
discussed in
Boundary Conditions.
Connector elements can be used to impose element-based kinematic constraints
for mechanism-type analysis. See
About Connectors.
Contact interactions, described in
About Contact Interactions
can be used to enforce constraints between bodies that come into contact.
Contact interactions can be used in mechanical as well as coupled
thermomechanical, coupled thermal-electrical-structural, and coupled pore
fluid-mechanical analysis.