Unknown force

Use Unknown Force to calculate, for a set of given positions, the required force, torque, or jack to keep a mechanism in static equilibrium. All the external influences are considered (gravity, spring, external or joint forces, and so on). The mechanism must have a single degrees of mobility .

You can study a succession of positions by driving a degree of freedom of one of the mechanism joints and by giving the number of positions.

  1. On the ribbon, click Dynamic Simulation tab Results panel Unknown Force .
  2. Select the appropriate force type: Force, Torque, or Jack.
  3. For a force or torque, do the following:
    • Click Location and then click a point on a part in the graphics window.
    • Click direction and then click an available entity on the second joint component in the graphics window to give the direction of the force or torque by orienting the vector drawn in the graphics window. Select an available entity, such as a linear edge, a cylindrical face, or a sketch line.

      A yellow vector appears in the graphics window to show the direction of the force or torque.

      The vector is oriented in the graphics window. You can switch its direction and fix it during all the calculations.

    • If necessary, click Invert Direction to flip the direction of the force or torque and, therefore, the yellow vector.
    • Click Fixed Load Direction if you want to lock the direction of the force or torque.
    • Alternatively, click Associative Load Direction if you want to associate the direction with the part that has the application point and then make it mobile.
  4. For a jack, do the following:
    • Click Location one and then click an available entity on a part in the graphics window.
    • Click Location two and then click an available entity on a part in the graphics window to select the second application point and give the director of the force vector. The line P1-P2 defines the direction of the jack unknown force.

      A yellow vector representing the force appears in the graphics window.

  5. In the Kinematics box, select one of the mechanism's joints in the pull-down list.
  6. If the selected joint has two or more degrees of freedom, select the one that is driven in the Degree of freedom box.

    The Initial position box shows the initial position of the selected degree of freedom. You cannot change this value.

  7. Enter the final position in the Final position text box.
  8. If necessary, adjust the number of intermediary positions in the # of steps box.

    The default is 100 steps.

  9. Click More to show parameters related to appearance of the force, torque, or jack vector in the graphics window.
    • If you want to show the vector in the graphics window and to enable the Scale and Color fields, click Display.
    • If you want to scale the force, torque, or jack vector so you can see the entire vector in the graphics window, enter the factor in the Scale field.

      The default is 0.01.

    • If you want to select a color for the vector in the graphics window, click the color box to open the Microsoft Color dialog box.
  10. Click OK.

    The Output Grapher opens automatically and shows the variable fr'?' or mm'?' (for the force or torque searched) under the Unknown Force directory.

Note:
Parent topic: Simulations