Understanding constraints

A tie constraint allows you to fuse together two regions even though the meshes created on the surfaces of the regions may be dissimilar. For detailed instructions on creating this type of constraint, see Defining tie constraints, and Using contact and constraint detection. For more information, see Mesh Tie Constraints.

A rigid body constraint allows you to constrain the motion of regions of the assembly to the motion of a reference point. The relative positions of the regions that are part of the rigid body remain constant throughout the analysis. For detailed instructions on creating this type of constraint, see Defining rigid body constraints. For more information on reference points, see The Reference Point toolset. For more information, see Rigid Body Definition.

A display body constraint allows you to select a part instance that will be used for display only. You do not have to mesh the part instance, and it is not included in the analysis; however, when you view the results of the analysis, the Visualization module displays the selected part instance. You can constrain the part instance to be fixed in space, or you can constrain it to follow selected nodes. You can apply a display body constraint to an instance of an Abaqus native part or to an instance of an orphan mesh part. For detailed instructions on creating this type of constraint, see Defining display body constraints. You can customize the appearance of display bodies in the Visualization module; for more information, see Customizing the appearance of display bodies.

A display body constraint is especially useful for mechanism or multibody dynamic problems where rigid parts interact with each other via connectors. In such cases you can create a simple rigid part, such as a point part, and a display body that is more representative of the physical part. For an example of a model that includes a display body constraint combined with connectors, see Display bodies. You can also use display bodies to model stationary objects that are not involved in the analysis but that help you to visualize the results.

For more information, see Display Body Definition.

A coupling constraint allows you to constrain the motion of a surface to the motion of a single point. For detailed instructions on creating this type of constraint, see Defining coupling constraints. For more information, see Coupling Constraints.

An adjust points constraint allows you to move a point or points onto a specified surface. For detailed instructions on creating this type of constraint, see Defining adjust points constraints. For more information, see Adjusting Nodal Coordinates. This adjustment may be useful in assembled fasteners and other applications; see About assembled fasteners, and Creating assembled fasteners.

An MPC constraint allows you to constrain the motion of the secondary nodes of a region to the motion of a single point. For detailed instructions on creating this type of constraint, see Defining MPC constraints. A multi-point constraint between two points is defined using connectors. For detailed instructions, see Connectors. For more information, see General Multi-Point Constraints.

A shell-to-solid coupling constraint allows you to couple the motion of a shell edge to the motion of an adjacent solid face. For detailed instructions on creating this type of constraint, see Defining shell-to-solid coupling constraints. For more information, see Shell-to-Solid Coupling.

An embedded region constraint allows you to embed a region of the model within a “host” region of the model or within the whole model. For detailed instructions on creating this type of constraint, see Defining embedded region constraints. For more information, see Embedded Elements.

Equations are linear, multi-point equation constraints that allow you to describe linear constraints between individual degrees of freedom. For detailed instructions on creating this type of constraint, see Defining equation constraints. For more information, see Linear Constraint Equations.