You can specify a time or spatially-varying load by entering a mathematical function.
Specifying a Load with a Mathematical Function
To define a function load:
In the Details pane, click Magnitude (or Displacement) and select from the fly-out menu.
Enter a function, such as =1000*sin(10*time). Note that the values you are evaluating can exceed the final time value by as much as one time step.
Mechanical displays the function you entered as follows:
The Graph window plots the variation of the magnitude with time.
Annotations in the Geometry window display the current time in the Graph window along with the magnitude value at that time.
The Tabular Data window displays the read-only values of the function's magnitude per solution step. You can Activate and/or Deactivate a function value at a solution load step.
Supported Mathematical Functions
The following functions are supported.
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For more information about how to specify these functions, see Mathematical Expressions.
Note: When you specify a Magnitude as a , the integer Modulus (%) operator is not supported.
Spatial Load and Displacement Function Data
When using spatial varying loads or displacements, selecting Function as the input option in the Details pane presents an editable function field. Enter a mathematical expression in this field. Expressions have the following requirements:
For a Pressure load, the Define By option must be set to Normal To.
For a Line Pressure load, the Define By option must be set to Tangential.
You can use the spatial variation independent variables x, y, or z, and time (entered in lowercase) in the definition of the function.
For Line Pressure loads in a 3D analysis or Pressure loads in a 2D analysis, you can also use the variable s. This allows you to define pressure as a function of the distance along a path whose length is denoted by s. When defining a path length, valid primary variables you can enter are s alone or s combined with time, for example, s*time, or s*sin(time/s). Load values are sent to the solver for each element on the defined path based on a first-order approximation.
Define only one direction, x, y, or z, or path length, s. After entering a direction or path length, the Graph Controls category (see above) displays.
Properties of Mathematical Function Loads
When the Details pane property Magnitude is set to Function, the following categories automatically display.
- Function
Read-only properties include:
Unit System: The unit system for the function.
Angular Measure: The unit of angular measure that is used to evaluate trigonometric functions.
Note: The application uses the Unit System and Angular Measure that were selected when you specified the Function option for the Magnitude. These settings do not change even if you manually change the Unit System and/or Angular Measure via the Units of Measure pane in the status bar.
- Graph Controls
Properties include:
X-Axis: Displays time or the spatial independent variable in the graph. When set to Time, you can activate and deactivate the load at a solution step.
Alternate Value: If the function combines time and a spatial independent variable, one of these values (alternate) must be fixed to evaluate the function for the two dimensional graph.
Range Minimum: If the X-Axis property is set to a spatial independent variable, this is the minimum range of the graph. For time, this value defaults to 0.0 and cannot be modified.
Range Maximum: If the X-Axis property is set to a spatial independent variable, this is the maximum range of the graph. For time this defaults to the analysis end time and can’t be modified.
Number of Segments: The function is graphed with a default value of two hundred line segments. This value may be changed to better visualize the function. The function can be graphed with up to 100,000 segments.
Caution: Specifying a large number of points may slow the response time of Mechanical.