Distant Connection Properties

Distant connection properties are used to specify the boundary interaction between bodies in an assembled product that are connected but are not expected to make contact. The following sections discuss the distant connection properties available in Nonlinear Structural Analysis:

Creating Rigid Connection Properties: Fastens bodies together at their common interface. Rigid connections do not take into account the elastic deformability of the interfaces.

Creating Smooth Connection Properties: Fastens bodies together at their common interface, but the fastening behaves approximately as if their interface were soft.

Creating Spring Connection Properties: Models flexible connections between points.

Creating Virtual Rigid Bolt Tightening Connection Properties: Models pretension in bolt-tightened assemblies in which the bolt is not explicitly modeled, and takes into account the elastic deformability of the assembly.

Creating Virtual Spring Bolt Tightening Connection Properties: Models pretension in bolt-tightened assemblies in which the bolt is not explicitly modeled, and takes into account the elastic deformability of the bolt in addition to that of the assembly.

Creating Rigid Connection Properties

A rigid connection property is the link between two part bodies that are stiffened and fastened together at their common boundary and behave as if their interface were infinitely rigid. Since part bodies can be meshed independently, rigid connection properties are designed to handle incompatible meshes.

Rigid connection properties do not take into account the elastic deformability of the interfaces.

A rigid connection property is defined in terms of the two surfaces that may interact, called a contact pair. These surfaces are indicated through the definition of a general analysis connection. The general analysis connection can connect a point, edge, or face to a point, edge, or face. Table 6–5 summarizes the connections that can be used to define a rigid connection in Nonlinear Structural Analysis.

Table 6–5 Rigid connection properties.

Assembly Design Workbench		Nonlinear Structural Analysis
Coincidence Constraint	Contact Constraint	General Analysis Connection

You can request history output of relative displacements and rotations and of total, elastic, viscous, and reaction forces and moments from a rigid connection property. The support for the history output request is the connection mesh.

This task shows you how to create a rigid connection property between two parts.

Click the Rigid Connection Property icon .

The Rigid Connection Property dialog box appears, and a Rigid Connection Property object appears in the specification tree under the Properties objects set.
You can change the identifier of the rigid connection property by editing the Name field.
In the specification tree, select a general analysis connection created previously in Nonlinear Structural Analysis.

The Supports field is updated to reflect your selection.
By default, rigid connection properties constrain all degrees of freedom and are associated with the global, rectangular Cartesian axis system. To change the default behavior, click Transmitted Degrees of Freedom and do the following:
1. Toggle off the degrees of freedom from which you want to remove the rigid connection property.
2. Specify a local coordinate system for the degrees of freedom. Local coordinate systems are defined in the CATIA Part Design workbench.
Click OK in the Rigid Connection Property dialog box.

A symbol representing the rigid connection property appears on the corresponding faces.

Creating Smooth Connection Properties

A smooth connection property is the link between two part bodies that are stiffened and fastened together at their common boundary and behave as if their interface were smooth. Since part bodies can be meshed independently, smooth connection properties are designed to handle incompatible meshes.

A smooth connection property is defined in terms of the two surfaces that may interact. These surfaces are indicated through the definition of a general analysis connection. The general analysis connection can connect a point, edge, or face to a point, edge, or face. Table 6–6 summarizes the connections that can be used to define a smooth connection in Nonlinear Structural Analysis.

Table 6–6 Smooth connection properties.

Assembly Design Workbench		Nonlinear Structural Analysis
Coincidence Constraint	Contact Constraint	General Analysis Connection

You can request history output of relative displacements and rotations and of total, elastic, viscous, and reaction forces and moments from a smooth connection property. The support for the history output request is the connection mesh.

This task shows you how to create a smooth connection property between two parts.

Click the Smooth Connection Property icon .

The Smooth Connection Property dialog box appears, and a Smooth Connection Property object appears in the specification tree under the Properties objects set.
You can change the identifier of the smooth connection property by editing the Name field.
In the specification tree, select a general analysis connection created previously in Nonlinear Structural Analysis.

The Supports field is updated to reflect your selection.
By default, smooth connection properties constrain all degrees of freedom and are associated with the global, rectangular Cartesian axis system. To change the default behavior, click Transmitted Degrees of Freedom and do the following:
1. Toggle off the degrees of freedom from which you want to remove the smooth connection property.
2. Specify a local coordinate system for the degrees of freedom. Local coordinate systems are defined in the CATIA Part Design workbench.
Click OK in the Smooth Connection Property dialog box.

A symbol representing the smooth connection property appears on the corresponding faces.

Creating Spring Connection Properties

A spring connection property is a flexible link that fastens two part bodies together. Since part bodies can be meshed independently, spring connection properties are designed to handle incompatible meshes. Spring connection properties also take into account the elastic deformability of the interfaces.

The support for a spring connection property is a general analysis connection defined in Nonlinear Structural Analysis. When creating a spring connection property, you can use only general analysis connections that join one point to another point—connections that include a face or an edge are not allowed. If the general analysis connection uses the same vertex for both points, Nonlinear Structural Analysis assumes that the spring connects the vertex to ground. Table 6–7 summarizes the connections that can be used to define a spring connection in Nonlinear Structural Analysis.

Table 6–7 Spring connection properties.

Assembly Design Workbench		Nonlinear Structural Analysis
Coincidence Constraint	Contact Constraint	General Analysis Connection

You can use spring connection properties to model actual physical springs and idealizations of axial or torsional components. You can model axial springs whose force acts only along the length of the spring or general springs where you define the spring stiffness associated with each linear and rotational degree of freedom. For each spring type you can choose a linear, constant stiffness definition or enter tabular stiffness data corresponding to the relative displacement of the spring.

You can request history output of relative displacements and rotations and of total, elastic, viscous, and reaction forces and moments from a spring connection property. The support for the history output request is the connection mesh.

This task shows you how to create a spring connection property between two parts.

Click the Spring Connection Property icon .

The Spring Connection Property dialog box appears, and a Spring object appears in the specification tree under the Nonlinear and Thermal Properties objects set.
You can change the identifier of the spring connection property by editing the Name field.
In the specification tree, select a general analysis connection created previously in Nonlinear Structural Analysis. The connection must join one point to another point. The connection can use the same vertex for both points, in which case Nonlinear Structural Analysis assumes that the spring connects the vertex to ground.

The Supports field is updated to reflect your selection.
Select an axial or general spring type.
Select a linear or nonlinear spring definition.
If you are creating a general spring, select the desired axis system.
If you specified a local axis system, select a Cartesian, a Cylindrical, or a Spherical local orientation. See Using Local Coordinate Systems for more information.
Enter the spring force data for the selected spring type and definition as follows:

Axial linear springs

Enter the axial stiffness.

General linear springs

Enter the directional stiffness components.

Nonlinear springs

Complete the table for an axial nonlinear spring—or the component tables for a general nonlinear spring—by entering the spring force and relative displacement values in ascending order of relative displacement.
Click OK in the Spring Connection Property dialog box.

A symbol representing the spring connection property appears on the corresponding faces.

Creating Virtual Rigid Bolt Tightening Connection Properties

A virtual rigid bolt tightening connection property takes into account pretension in a bolt-tightened assembly in which the bolt is not modeled explicitly with a part. The computation is carried out according to a two-step approach. In the first General Static Step of the analysis the model is submitted to tension forces due to bolt tightening by applying opposite forces on the two surfaces representing the assembly constraint. In general, the first step in your simulation history will not contain other loads, so the bolt tightening connection property can be evaluated and used as a precondition for the rest of the analysis. Then in the second General Static Step of the computation the relative displacement of the two bolt surfaces (obtained in the first step) is fixed while further loading is applied to the model. During these two steps the relative motions of both surfaces and the translations perpendicular to the coincidence constraint axis are linked. Since bodies can be meshed independently, virtual rigid bolt tightening connection properties are designed to handle incompatible meshes.

Virtual rigid bolt tightening connection properties do account for the elastic deformability of the interfaces but do not account for elasticity in the virtual bolt.

A virtual rigid bolt tightening connection property is defined in terms of the two surfaces that may interact. These surfaces are indicated through the definition of an assembly constraint or an analysis connection. You can use an assembly constraint defined in the Assembly Design workbench to define the contact surface pairing between the bolt thread and the bolt support tapping. Alternatively, you can use a general analysis connection defined in Nonlinear Structural Analysis to define the contact surface pairing. Table 6–8 summarizes the constraints that can be used to define a virtual rigid bolt tightening connection property in Nonlinear Structural Analysis.

Table 6–8 Virtual rigid bolt tightening connection properties.

Assembly Design Workbench		Nonlinear Structural Analysis
Coincidence Constraint	Contact Constraint	General Analysis Connection

This task shows you how to create a virtual rigid bolt tightening connection property between two parts.

Click the Virtual Bolt Tightening Connection Property icon .

The Virtual Bolt Tightening Connection Property dialog box appears. A symbol representing the virtual bolt tightening connection property appears on the corresponding faces, and a Virtual Bolt Tightening Connection Property object appears in the specification tree under the Properties objects set.
You can change the identifier of the virtual bolt tightening connection property by editing the Name field.
In the specification tree, select an assembly constraint created previously in the Assembly Design workbench or a general analysis connection created previously in Nonlinear Structural Analysis.

The Supports field is updated to reflect your selection.
If necessary, modify the default values of the force parameter. Tightening is represented by a positive force. A virtual bolt tightening connection property can exert only a positive force; a negative force is interpreted as zero.
Click OK in the Virtual Bolt Tightening Connection Property dialog box.

Creating Virtual Spring Bolt Tightening Connection Properties

A virtual spring bolt tightening connection property is nearly identical to a virtual rigid bolt tightening connection property. The main difference is that a virtual spring bolt tightening connection property accounts for elastic deformation of the bolt and the assembly, whereas a rigid bolt tightening connection property accounts for deformation of the assembly but not of the bolt. Both properties take into account pretension in a bolt-tightened assembly in which the bolt is virtual—not modeled explicitly with a part.

The computation is carried out according to a two-step approach. In the first General Static Step of the analysis the model is submitted to tension forces due to bolt tightening by applying opposite forces on the two surfaces representing the assembly constraint. In general, the first step in your simulation history will not contain other loads, so the bolt tightening connection property can be evaluated and used as a precondition for the rest of the analysis. Then in the second General Static Step of the computation the relative displacement of the two bolt surfaces (obtained in the first step) is fixed while further loading is applied to the model. During these two steps the relative motions of both surfaces and the translations perpendicular to the coincidence constraint axis are linked. Since bodies can be meshed independently, virtual spring bolt tightening connection properties are designed to handle incompatible meshes.

A virtual spring bolt tightening connection property is defined in terms of the two surfaces that may interact. These surfaces are indicated through the definition of an assembly constraint or an analysis connection. You can use an assembly constraint defined in the Assembly Design workbench to define the contact surface pairing between the bolt thread and the bolt support tapping. Alternatively, you can use a general analysis connection defined in Nonlinear Structural Analysis to define the contact surface pairing. Table 6–9 summarizes the constraints that can be used to define a virtual rigid bolt tightening connection property in Nonlinear Structural Analysis.

Table 6–9 Virtual spring bolt tightening connection properties.

Assembly Design Workbench		Nonlinear Structural Analysis
Coincidence Constraint	Contact Constraint	General Analysis Connection

This task shows you how to create a virtual spring bolt tightening connection property between two parts.

Click the Virtual Spring Bolt Tightening Connection Property icon .

The Virtual Spring Bolt Tightening Connection Property dialog box appears. A symbol representing the virtual spring bolt tightening connection property appears on the corresponding faces, and a Virtual Spring Bolt Tightening Connection Property object appears in the specification tree under the Properties objects set.
You can change the identifier of the virtual spring bolt tightening connection property by editing the Name field.
In the specification tree, select an assembly constraint created previously in the Assembly Design workbench or a general analysis connection created previously in Nonlinear Structural Analysis.

The Supports field is updated to reflect your selection.
If necessary, modify the default values of the force parameter. Tightening is represented by a positive force. A virtual spring bolt tightening connection property can exert only a positive force; a negative force is interpreted as zero.
Enter the translational and rotational stiffness values for the virtual spring.

The virtual spring is modeled as a general spring; the spring stiffness may be different for each linear and torsional direction in which the spring acts.
Click OK in the Virtual Spring Bolt Tightening Connection Property dialog box.