Multibody Dynamics Module
New Functionality in Version 6.4
Physics Interface for Joints
A new physics interface named Joints has been added. It is intended for analysis of mechanical assemblies connected by various joints. The parts in the assembly can be rigid or flexible. Different structural elements can be connected through joints by defining Attachment nodes, and flexible parts can be defined using solid, shell, or beam elements.
The joints are the same as those available in the Multibody Dynamics interface. The main purpose of the new Joints interface is to facilitate couplings in other physics interfaces without having to add the full Multibody Dynamics interface.
New Selections in Roller Chain Parts
In addition to the existing selections, the following predefined domain selections are available in roller chain geometry parts:
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 Rollers
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 Pins
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 Link Plates
General Contact
A new feature, General Contact, is available in the Multibody Dynamics interface. This contact formulation is particularly useful when there are many different boundaries that can come into contact with each other. Using this feature, you can avoid setting up many different contact pairs.
Smooth Penalty Function for Contact
A smooth penalty function has been added to the Contact node. It is also available for the new General Contact feature. The new option uses a nonlinear (smooth ramp) penalty function for the contact pressure. This may improve the convergence significantly.
Point Mass
A new Point Mass node is now available in the Multibody Dynamics interface.
Spring–Damper
A Loss factor damping option is now available in the Spring–Damper node.
Reaction Forces
New variables to compute reaction force and moments are available in the Multibody Dynamics interface. It is now possible to directly obtain the reactions for a single boundary condition, both for pointwise and weak constraints. The following nodes have this capability:
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 Fixed
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 Prescribed Displacement
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 Prescribed Velocity
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 Prescribed Acceleration
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 Roller
Continuity
A new checkbox, Correct for mismatching boundaries, has been added to the settings in the Continuity node. The purpose is to create a more accurate connection for cases when there is a gap or an overlap between the joined boundaries.
Traction Variable
The traction variable, phys.Trac, is now always available on external and internal boundaries in the Multibody Dynamics interface.
Quaternions
The variable for the real part of the quaternion for the Rigid Connector, Rigid Material, and Attachment nodes has changed. The internal dependent variable for the quaternion has been modified in order to be initialized with a zero solution.
Adhesion and Decohesion
Resetting of adhesion and decohesion was previously not possible. The adhesion condition and damage states are stored as internal degrees of freedom (DOFs) that keep track of the maximum value over time. These variables can now be reset to their initial values.
Structural Connections
The transformation matrix for the flexible option in the Solid–Thin-Structure Connection multiphysics coupling has been improved for geometric nonlinear analyses.
The implementation of the Solid–Beam Connection multiphysics coupling has been improved for geometric nonlinear analyses.
Average Rotation
The internal dependent variable for the quaternion has been modified in order to be safely initialized with a zero solution.
The expression for the computation of the angular velocity vector has been corrected to account for large rotations.
Orthonormal Coordinate Systems
Only orthonormal coordinate systems defined in the spatial frame are allowed in the Gravity, Base Excitation, and Linearly Accelerated Frame nodes in all structural mechanics interfaces. This implies that such accelerations must always act in a space-fixed direction.