Step Controls

Step Controls play an important role in static and transient dynamic analyses. Step controls are used to perform two distinct functions:

  1. Define Steps.

  2. Specify the Analysis Settings for each step.

Defining Steps

See the procedure, Specifying Analysis Settings for Multiple Steps located in the Establish Analysis Settings section.

Specifying Analysis Settings for Each Step

The following items can be changed on a per step basis:

Step Controls

The selections available in the Details view for Step Controls group are described below.

Activation/Deactivation of Loads

You can activate (include) or deactivate (delete) a load from being used in the analysis within the time span of a step. For most loads (for example, pressure or force) deleting the load is the same as setting the load value to zero. But for certain loads such as specified displacement this is not the case. Activation and deactivation of loads is not available to the Samcef or ABAQUS solver.

Note:  Changing the method of how a multiple-step load value is specified (such as Tabular to Constant), the Activation/Deactivation state of all steps resets to the default, Active.

To activate or deactivate a load in a stepped analysis:

  1. Highlight the load within a step in the Graph or a specific step in the Tabular Data window.

  2. Click the right mouse button and choose Activate/Deactivate at this step!.

Note:  For displacements and remote displacements, it is possible to deactivate only one degree of freedom within a step.

For Imported loads and Temperature, Thermal Condition, Heat Generation, Voltage, and Current loads, the following rules apply when multiple load objects of the same type exist on common geometry selections:

Note:  For each load step, if both Imported Loads and user-specified loads are applied on common geometry selections, the Imported Loads take precedence. See respective Imported Load for more details.

  • For imported loads specified as tables, with the exception of imported displacement and temperature loads, a value of zero is applied in the table where the load is deactivated, and commands are sent to the solver only at the first active load step. Hence these reactivated/deactivated imported loads with tabular loading do not overwrite other unchanged or reactivated/deactivated loads that exist higher (previously added) in the tree.

  • For imported loads specified as tables, the data is available outside the range of specified analysis times/frequencies. If the solve time/frequency for a step/sub-step falls outside the specified Analysis Time/Frequency, then the load value at the nearest specified analysis time is used.

Note:  The tabular data view provides the equation for the calculation of values through piecewise linear interpolation at steps where data is not specified.

Some scenarios where load deactivation is useful are:

Example: Springback of a cantilever beam after a plasticity analysis

In this case a Y displacement of -2.00 inch is applied in the first Step. In the second step this load is deactivated (deleted). Deactivated portions of a load are shown in gray in the Graph and also have a red stop bars indicating the deactivation. The corresponding cells in the data grid are also shown in gray.

In this example the second step has a displacement value of -1.5. However since the load is deactivated this will not have any effect until the third step. In the third step a displacement of -1.5 will be step applied from the sprung-back location.

Release 16.2 - © SAS IP, Inc. All rights reserved.