A flexible mechanism usually consists of flexible and/or rigid parts connected together with joint elements. You can model the flexible parts with any of the 3D solid, shell, or beam elements available in the element library. (For more information, see Building the Model in the Basic Analysis Guide, and Modeling in a Multibody Simulation in this document.)

Rigid bodies are modeled using MPC184 Rigid Link or Rigid Beam elements, or by using the extensive contact capabilities available in Mechanical APDL.

The flexible and/or rigid parts are connected using MPC184 joint elements. For example, two parts may be simply connected such that the displacements at the joining position are identical. In other cases, the connection between two parts may involve a more sophisticated joint such as the planar joint or universal joint. In modeling these joints, suitable kinematic constraints are imposed on the relative motion (displacement and rotation) between the two nodes forming the joint.

An overview of the types of joint elements used in a multibody analysis is available in Connecting Multibody Components with Joint Elements.

To properly perform a flexible multibody simulation, which involves flexible and rigid components joined together with some form of kinematic constraints, use appropriate structural, joint, and contact element types. For more information about element selection, see Modeling in a Multibody Simulation.

Defining the material properties for multibody components is no different than defining them in any other analysis. Define linear and nonlinear material properties via the MP or the TB command. For more information, see Defining Material Properties in the Basic Analysis Guide.

The MPC184 joint elements also allow you to define material properties so that you can control their behavior along the "free" or "unconstrained" DOFs. For example, you can issue a TB,JOIN command to introduce a torsional spring behavior for a revolute joint to model the resistance to the rotation along the revolute axis. For more information, see MPC184 Joint in the Material Reference.

Use the meshing commands to mesh multibody components. For more information, see the Modeling and Meshing Guide.

Issue the LMESH command to mesh rigid bodies defined by MPC184 Rigid Beam or Rigid Link elements. Use the Contact Wizard to mesh rigid bodies defined via the contact capabilities in Mechanical APDL. For more information, see Modeling in a Multibody Simulation.

Two nodes define joint elements and no special meshing commands are necessary to define them.

The solution phase of a multibody analysis adheres to standard Mechanical APDL conventions. For multibody-specific solver information, see Solver Options.