Polybeams

A polybeam is a series of beams that connects a series of points.

1. From the Project Browser, select the system to which the polybeam entity is to be added.
2. Right-click on a system in the Project Browser and select Add > Force Entity > PolyBeam from the context menu.
   OR
   Right-click on a Polybeam folder in the Project Browser and select Add PolyBeam from the context menu.
   OR
   Right-click the PolyBeam button on the Force toolbar.
   The Add PolyBeam dialog is displayed.
3. Specify a label for the polybeam.
4. Specify a variable name for the polybeam.
   By default, variables names of entities in MotionView follow a certain convention. For example, all polybeam entities have a variable name starting with “pbm_”. This is the recommended convention to follow when building models in MotionView since it has many advantages in model editing and model manipulation.
5. Click OK to close the window or Apply to continue creating entities.
   Once a polybeam entity has been added to the model, the panel for the polybeam will automatically be displayed in the panel area.

A polybeam has circular cross sections throughout its length. The mass of the polybeam is distributed across dummy bodies that are located at each point in the polybeam. A polybeam is defined by specifying the cross-sectional properties of the beam and the locations of the points in the beam. MotionView automatically generates the actual beam elements and dummy bodies.

1. If the Polybeams panel is not currently displayed, select the desired polybeam by clicking on it in the Project Browser or in the modeling window.
   The Polybeams panel is automatically displayed.
2. From the Point Connectivity tab, click the Point collectors and select the points that describe the polybeam from the modeling window, or double-click the collectors to open the Model Tree (from which the desired points can be selected).
   Tip:

   • To add points to the end of the table, enter the number of points in the text box and click Append.
   • Select the check box next to any point and click Insert to add a new point above the point selected.
   • Delete points by selecting their respective check boxes and clicking Delete.
3. Click the Beam Properties tab.
   By default, the polybeam has a circular cross section.
4. Enter a value for the mass density (Rho) of the material of the beam.
5. Enter the values for the Young’s Modulus (E) and Shear Modulus (G) in the corresponding fields.
6. Enter the values of the Outer (OD) and Inner Diameters (ID) of the polybeam cross section.
7. Enter a value for the correction factor (AS) for the shear deflection.
8. Enter a value for the stiffness to damping matrix ratio (CRatio).
   The damping matrix for the polybeam is computed by multiplying the stiffness matrix by the C ratio.
9. If needed, click the Point Coordinates tab and edit the coordinates of points in the X, Y, and Z directions.