This function allows the user to create and/or modify the constraints. The Constraints dialog box is illustrated in Figure 10.11.6.

SHOW CONSTRAINT

Toggle checkbox on/off to show/hide display of selected Constraint set.

SHOW FORCE

Toggle checkbox on/off to show/hide load force.

SHOW ALL

Toggle checkbox on/off to show/hide all Constraints.

ADVANCED OPTIONS

Toggle checkbox on to access the advanced options for constraint definition. If this option is not toggled on, only the basic constraint types will be displayed, including Fixed, Hinged and Guide/Pin.

           Create LCS

Click this button to create LCS.

           Set Current LCS

Define the created LCS as the current LCS, that is, the constrained LCS.

Figure 10.11.6  Constraints dialog box

1.        CREATE CONSTRAINT

          Select a type of constraint. In eta/DYNAFORM, each node is associated with eight degree of freedom as listed below:

1.        Fixed: include the DOF for three translations and three rotations.

2.        Hinged: hinged constraint, only constrain the three translation DOF of node.

3.        Guided Pin: only constrain the DOF of node in XY-Plane, namely, X-translation and Y-translation.

4.        X-translation

5.        Y-translation

6.        Z-translation

7.        XZ: constrain the node so that it is symmetric along XZ-Plane, which means to translate along Y-Axis and rotate along X-Axis and Z-Axis.

8.        YZ: constrain the node so that it is symmetric along YZ-Plane, which means to translate along X-Axis and rotate along Y-axis and Z-Axis.

The following drop down menu as illustrated in Figure 10.11.7 provides the basic and advanced approaches for definition of constraints.

     

(a)  Basic                           (b)  Advanced

Figure 10.11.7  Type of Constraint

        Click Create.

        Enter the Constraint Set ID Number in the displayed dialog box.

        Select nodes to apply constraints.

2.        DELETE CONSTRAINT

          Select a constraint set from the list.

          Click Delete.

          Select Yes to remove the constraint set from the eta/DYNAFORM Question dialog box as illustrated in Figure 10.11.8.

Figure 10.11.8  eta/DYNAFORM Question dialog box

3.        DEFINE CONSTRAINT

         Select a set from the list.

         Select type of constraint.

         Click Define.

          Select nodes. Nodes with the selected degree of freedom will be added to the highlighted constraint set.

4.        RELEASE CONSTRAINT

Remove some nodes from the selected constraint set.

5.        CLEAR CONSTRAINT

Remove all nodes from a selected constraint set.  An eta/DYNAFORM Question dialog box as illustrated in Figure 10.11.9 is displayed.

Figure 10.11.9  eta/DYNAFORM Question dialog box

Select Yes to remove all constraints.

Select No to reject the choice.

Note: The DOF of constraints are all in the current coordinate system.