Defining a Time Curve

To define a time curve:

  1. In the PropertyManager of a load or restraint in a transient thermal or nonlinear study, under Variation with time,
    1. Do one of the following:
      • Click Linear to use the default linear curve of load vs. time. If you select this option, go directly to step 7.
      • Click Curve to specify your own variation of load versus time. If you select this option, continue with the next step.
    2. Click Edit.
  2. In the Time Curve dialog box:
    1. In the Curve information box, do the following:
      • In the Name box, type a name for the time curve.
      • Set the Shape to one of the following:
        Option Description
        User defined  
        Loading

        The load multiplier (Y value) increases from 0 at time 0 to 1 at time tend where tend is the end time for the nonlinear analysis or the total time for the transient thermal analysis.

        Unloading

        The load multiplier (Y value) decreases from 1 at time 0 to 0 at time tend where tend is the end time for the nonlinear analysis or the total time for the transient thermal analysis.

        Loading unloading

        The load multiplier (Y value) increases from 0 at time 0 to 1 at time tend/2 and then decreases to 0 at time tend where tend is the end time for the nonlinear analysis or the total time for the transient thermal analysis.

        Harmonic

        You can define a harmonic loading as a combination of sine and cosine wave forms with the option of an exponential rise or decay.

        where:

        • As = Sine curve amplitude
        • ωs = Sine curve frequency
        • φs = Sine curve phase
        • Ac = Cosine curve amplitude
        • ωc = Cosine curve frequency
        • φc = Cosine curve phase
        • c = Exponential coefficient
        • t = time
    2. In the Curve data box, do the following:
      • Set the Units for the X (Time) column.
      • The Y values are dimensionless multipliers to the quantity specified in the PropertyManager for the associated load/restraint.
      • Edit the curve data as desired (Available only when Shape is set to User defined. To get the curve from an external file, click Get curve to open the Function Curves dialog box.
        The X-Y columns show the default values based on the selected shape. You can edit the values in the cells as desired. To add a row, double-click in any cell in the Points column. To delete selected rows, right-click the selection and select Delete.
      • To save the curve for subsequent use, click Save Curve, specify a name and a destination folder for the curve file and click Save.

        The program adds the extension .cwcur to the filename. The specified curve can be used in other documents.

    3. Click OK.
  3. In the Load/fixture PropertyManager, to view the actual values of the specified load/restraint, under Variation with time click View.
  4. Close the graph window.
    • In a nonlinear study, if you do not define a time curve for a load or a restraint, the program uses the default linear time curve.
    • You can release a prescribed displacement in a nonlinear study. Click the down arrow in the Y column cell and select Off. If you enter a 0 value in the Y column cell at a particular time step, the selected dofs are considered fixed.