15.5 Understanding constraints

Constraints defined in the Interaction module define constraints on the analysis degrees of freedom, whereas constraints defined in the Assembly module define constraints only on the initial positions of instances. In the Interaction module you can constrain the degrees of freedom between regions of a model, and you can suppress and resume constraints to vary the analysis model. Currently, you can create the following types of constraints:

Tie

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, Section 15.14.1. For more information, see Mesh tie constraints, Section 28.3.1 of the ABAQUS Analysis User's Manual.

Rigid body

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, Section 15.14.2. For more information on reference points, see Chapter 46, The Reference Point toolset.” For more information, see Rigid body definition, Section 2.4.1 of the ABAQUS Analysis User's Manual.

Display body

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, Section 15.14.3. You can customize the appearance of display bodies in the Visualization module; for more information, see Customizing the appearance of display bodies, Section 36.8.

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 Modeling display bodies, Section 21.5. 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, Section 2.8.1 of the ABAQUS Analysis User's Manual.

Coupling

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, Section 15.14.4. For more information, see Coupling constraints, Section 28.3.2 of the ABAQUS Analysis User's Manual.

Shell-to-solid coupling

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, Section 15.14.5. For more information, see Shell-to-solid coupling, Section 28.3.3 of the ABAQUS Analysis User's Manual.

Embedded region

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, Section 15.14.6. For more information, see Embedded elements, Section 28.4.1 of the ABAQUS Analysis User's Manual.

Equation

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, Section 15.14.7. For more information, see Linear constraint equations, Section 28.2.1 of the ABAQUS Analysis User's Manual.