The Nlgeom setting for a step determines whether Abaqus will account for geometric nonlinearity in that step. The Nlgeom setting is turned on by default for Abaqus/Explicit steps and turned off by default for Abaqus/Standard steps.
The sequence of steps and the current Nlgeom setting determine whether you can change the Nlgeom setting in a particular step. For example, if Abaqus is already accounting for geometric nonlinearity, the Nlgeom setting is toggled on for all subsequent steps, and you cannot toggle it off. Similarly, you cannot change the Nlgeom setting during a linear perturbation step. For more information, see “Linear and nonlinear procedures,” Section 14.3.2.
Note: When you create a step, you can click the Basic tab in the Step Editor and select On or Off as the Nlgeom setting.
To change the Nlgeom setting for an existing step:
To display the Edit Nlgeom dialog box and to change the setting where applicable, do one of the following:
From the main menu bar, select Step
Nlgeom.
From the main menu bar, select StepEditstep name.
The Step Editor appears. From the Nlgeom field on the Basic tabbed page, click 
.
From the main menu bar, select StepManager.
The Step manager appears. From the buttons along the bottom of the manager, click Nlgeom.
From the Edit Nlgeom dialog box, click the step name of interest to turn Nlgeom on or off for that step.
If Nlgeom is turned on for a step, a check mark appears in the Nlgeom column. If Nlgeom is turned off for a step, no tickmark appears.
Click OK to close the Edit Nlgeom dialog box.
