Flexible joint element

JOINTC elements:

are used to model joint interactions; and
are made up of translational and rotational springs and parallel dashpots in a local, corotational coordinate system.

Details of the element formulation can be found in Flexible joint element.

The following topics are discussed:

Typical Applications
Defining the joint behavior
Using JOINTC elements in large-displacement analyses

Typical Applications

The JOINTC element is provided to model the interaction between two nodes that are (almost) coincident geometrically and that represent a joint with internal stiffness and/or damping (such as a rubber bushing in a car suspension system) so that the second node of the joint can displace and rotate slightly with respect to the first node.

Joints that have only one or two axes of rotation and no relative displacement are better modeled by the REVOLUTE- or UNIVERSAL-type MPCs (see General multi-point constraints).

Similar functionality is available using connectors; see About connectors.

Defining the joint behavior

The joint behavior consists of linear or nonlinear springs and dashpots in parallel, coupling the corresponding components of relative displacement and of relative rotation in the joint. You define the spring and dashpot behavior as described in Springs and Dashpots.

Each spring or dashpot definition defines the behavior for one of the six local directions; up to six spring and six dashpot definitions can be included. If no specification is given for a particular local relative motion in the joint, the joint is assumed to have no stiffness with respect to that component.

The joint behavior can be defined in a local coordinate system that rotates with the motion of the first node of the element (Orientations). If a local coordinate system is not defined, the global system is used.

You must associate the joint behavior with a set of JOINTC elements.

The kinematic behavior of JOINTC elements is described in detail in Flexible joint element.

Input File Usage

Use the following options to define the joint behavior:

JOINT, ELSET=name, ORIENTATION=name
DASHPOT
SPRING
Up to six SPRING and DASHPOT options can appear.

Using JOINTC elements in large-displacement analyses

In large-displacement analysis the formulation for the relationship between moments and rotations limits the usefulness of these elements to small relative rotations. The relative rotation across a JOINTC element should be of a magnitude to qualify as a small rotation.