Mechanical APDL Basic Analysis Guide

• TVAR - changes the meaning of variable 1 from time to cumulative iteration number.


• VARNAM - assigns a name (32 character max.) to a variable.


• RESET - removes all variables and resets all specifications to initial defaults.

8.4. Processing Your Variables to Develop Calculated Data

Often, the specific analysis data you obtain in your results file can be processed to yield additional
variable sets that provide valuable information. For example, by defining a displacement variable in a
transient analysis, you can calculate the velocity and acceleration by taking derivatives with respect to
time. Doing so will yield an entirely new variable that you may wish to analyze in conjunction with your
other analysis data.

8.4.1. Interactive

The variable viewer provides an intuitive calculator interface for performing calculations. All of the
command capability can be accessed from the calculator area. The calculator can be displayed or hidden
by clicking on the bar above the calculator area.

Follow these steps to process your time history data using the variable viewer:

1. Specify a variable in the variable name input area. This must be a unique name, otherwise you will
   be prompted to overwrite the existing variable of that name.


2. Define the desired variable expression by clicking on the appropriate keys, or selecting time-history
   variables or APDL parameters from the drop down lists.

Result: The appropriate operators, APDL parameters or other variable names appear in the Ex-

pression Input Area.

3. Click the “Enter” button on the calculator portion of the Variable viewer

Result: The data is calculated and the resultant variable name appears in the variable list area.

The expression will be available in the variable viewer for the variable name until the variable

viewer is closed.

Notes:

• To find the derivative of a variable “UYBLOCK” with respect to another variable

VBLOCK = deriv ({UYBLOCK} , {TIME})

• To find the amplitude of a complex time-history variable “PRESMID”

AMPL_MID = abs ({PRESMID})

OR,

AMPL_MID = sqrt (real ({PRESMID}) ^2 + imag ({PRESMID}) ^2)

• To find the phase angle of a complex time-history variable “UYFANTIP”

PHAS_TIP = atan ({UYFANTIP}) * 180/pi

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The Time-History Postprocessor (POST26)