Bushings

Use the Bushings tool to create bushings and edit their connectivity, properties, and orientation rules.

Create Bushings

  1. From the Browser, select the system to which the bushing is to be added.
  2. From the Model ribbon, click the Bushings icon.
    A guide bar for entity creation appears.
  3. Optional: Activate the Pair check box to create a pair entity.
    A bushing entity, like most of the entities that are created in HyperWorks, can be a single entity or a pair entity. Pair entities help to create models that are symmetric about the Z-X plane of the model. Their properties can also be symmetric about the Z-X plane (in other words, the Y property is mirrored). Asymmetry or symmetry of the joint can be decided or specified when editing the created joint.
  4. Select the first body reference (Body 1).
    • Select a body in the modeling window.

      OR

    • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
    Note: When defining a pair bushing, use pair entities for Body, Origin, etc.
  5. Select the second body reference (Body 2).
    • Select a body in the modeling window.

      OR

    • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
  6. Select an origin reference.
    • Select a point in the modeling window.

      OR

    • On the guide bar, click the Advanced Selector and make your selection in the Model Tree.
  7. Optional: Click to reset the entity selections and select new entities.
  8. Once the reference selections are made, create the joint using one of the following methods:
    • Click on the guide bar. Next, use the microdialog to select the desired joint type from the drop-down menu and edit/orient the joint.

      OR

    • Click the button that appears at the mouse location in the modeling window. Next, use the microdialog to select the desired joint type from the drop-down menu and edit/orient the joint.

      OR

    • Click to create the entity and exit the selections for this joint.
    Note: If the selected bushing is a pair entity, use the microdialog to distinguish between the Left and Right and then edit its properties.
    Once the bushing has been added to the model, the corresponding bushing will automatically be displayed in the browser area.
    Note: By default, variables names of entities in MotionView follow a certain convention. For example, all bushing entities have a variable name starting with 'bsh_'. This is the recommended convention to follow when building models in MotionView since it has many advantages in model editing and model manipulation.
Tip: A new bushing can be created from the Project Browser by right-clicking on the Model label (or any system/analysis of your choice) and selecting Add > Force Entity > Bushing or by right-clicking Bushings and selecting Add Joint.

Edit Bushings

Define the Connectivity of Bushings

The connectivity and orientation information of a joint and bushing are identical. A joint places a combination of rigid constraints between two bodies, and a bushing places compliant constraints between bodies.

  1. If the Bushings panel is not currently displayed, select the desired bushing by clicking on it in the Project Browser or in the modeling window.
    The Bushings panel is automatically displayed.
  2. Click the Body 1 collector and pick a body from the modeling window, or double-click the collector to open the Model Tree (from which the desired body can be selected).
    Note: If the selected bushing is a pair entity, first distinguish between the Left and Right tabs in the panel, and then edit the properties. When defining a pair bushing, use pair entities for Body, Point, etc.
    Tip: Check the Symmetric properties option to make the bushing properties symmetric. Once this option is activated, MotionView will ask you which side of the values of the pair entity (left or right) is to be used. Selecting any one side will make values of that side as “leader” and the values of the other side ("follower") will gray out and follow the values on the leader side.
  3. Similarly, click Body 2 and select the desired body from the modeling window (or use the Model Tree).
  4. Click the Point collector (under Origin) and select a point from the modeling window, or double click the Point collector to open the Model Tree (from which the desired point can be selected).
  5. Use the orientation options to orient the coordinate system.

Define the Stiffness and Damping of Bushings

The Trans Stiffness and Rot Stiffness tabs allow you to define the stiffness properties of a compliant joint or a bushing. Trans Damping and Rot Damping tabs allows you to define the damping properties of a compliant joint or bushing. Both stiffness and damping can be linear or non-linear.

  1. Click the Trans Stiffness tab.
  2. Define the translational stiffness properties of the bushing by selecting an option from the drop down menu in each direction.
    If Linear is chosen, enter a translational stiffness coefficient in the local direction
    If Curve is chosen, define the force transmitted through the bushing, expressed in the form of a force vs displacement curve that is a function of independent variables.
    1. Select AKIMA, CUBIC, LINEAR , or QUINTIC under Interpolation as the method of interpolation of between two data points on the curve.
    2. Enter a value under Independent variable.
    3. Resolve the curve by double-clicking the Curve collector and selecting a curve from the Select a Curve dialog.
      Note: To use a curve, you first need to define a curve (using the Curves panel) which represents the behavior of the bushing.
    If Spline3D is chosen:
    1. Select AKIMA, CUBIC, LINEAR , or QUINTIC under as the method of interpolation of values between 2 data points in XY plane.
    2. Resolve the 3D spline by double-clicking on the Spline3D collector and selecting a Spline3D entity from the Select a Spline3D dialog.
      Note: To use a Spline3D entity, you first need to define a spline using the Spline3D panel.
    3. Specify an expression for Independent variable X and Independent variable Z.
    If Expression is chosen, define the force transmitted through the bushing in the form of a function expression.
  3. Click the Rot Stiffness tab.
  4. Repeat the same process in order to define rotational stiffness/torque.
  5. Define the damping properties of the bushing by clicking the Trans Damping and Rot Damping tabs and making your selections in a similar manner.

Define the Preload of Bushings

The Preload tab allows you to define initial translational and rotational force preloads for compliant joints or bushings.

  1. Click the Preload tab.
  2. Enter values for the initial translational preloads (Fx, Fy, Fz) in the local x, y, and z directions.
  3. Enter values for the initial torque preloads (Tx, Ty, Tz) in the local x, y, and z directions.

Use User-Defined Properties for a Bushing

If desired, define the bushing using the User-Defined tab, which will allow you to specify the properties of the bushing using user subroutines.

  1. From the Connectivity tab, click the User-defined properties check box.
    The Stiffness, Damping, and Preload tabs are removed.
  2. Click the newly added User-Defined tab.
  3. Define the user subroutine.
    1. Provide an expression with the USER solver function with parameters being passed to the user subroutine.
    2. Alternatively, activate the Use local file and function name check box to specify a local file where the subroutine code can be accessed by the solver.
      If this option is not specified, MotionSolve will search for a subroutine following its user subroutine loading rules.
    3. Select a function type from the drop-down menu.
    4. Select the local file for the subroutine.
      The type of file to be specified will depend on the selected function type. For example, if DLL/SO is selected, you can specify a file with a .dll extension (for Windows) or an .so extension (for Linux).
    5. Specify the function name in the subroutine that defines the entity, or accept the default name provided by HyperWorks.