A Line Constraint is used to model transitions where two incompatible meshes meet along a line, for example where a finer mesh on one side of the line has elements half as wide as elements in the coarser mesh on the other side. The Line Constraint does not impose rigid behavior on the model. Rather, the deformation along the line is determined by the coarser of the two meshes.
Along the line, define one constraint for each of the larger elements. Assign to each constraint the joints of the large element; these are called the master joints. Also assign to the constraint all joints from the smaller elements on the other side of the line that are between the two master joints; these are called the slave joints. The displacements of the slave joints will be linearly interpolated from the displacements of the master joints. You may select which degrees of freedom you want to be interpolated.
The order in which you assign the constraint to the joints is not important. The program will automatically select the two joints farthest from the centroid of the selection to be used as the masters.
The constraint must apply to at least three joints to have any effect on the model. They should lie along a straight, or nearly straight, line.
Use the following areas on the Line Constraints form to make the appropriate entries:
Constraint Name edit box. Use the default, or enter a unique name for the constraint being defined.
Coordinate System drop-down list. Choose the coordinate system in which the constrained degrees of freedom (below) are being defined. If all degrees of freedom are being used, the choice of coordinate system has no effect on the constraint.
Constrained DOFs options. Choose the degrees of freedom being constrained.
If the Define menu > Joint Constraints command was used to access the Line Constraints form, the defined constraint must be assigned to the joints.
See Also
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Access the Line Constraints form as follows:
Click the Define menu > Joint Constraints command to display he Define Constraints form or select the joints to be constrained and click the Assign menu > Joint > Constraints command to display the Define/Assign Constraints form. Then do one of the following:
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