Geometric Nonlinearity
In most cases, the parts in a multibody analysis will translate and rotate significantly during the analysis. This means that the analysis must be considered as geometrically nonlinear.
You enable a geometrically nonlinear analysis for a certain study step by selecting the Include geometric nonlinearity checkbox in the Study Settings section of a study step.
If any active feature in the model requires the analysis to be geometrically nonlinear, the Include geometric nonlinearity checkbox is selected automatically, and it cannot be cleared. For Stationary or Time Dependent study steps, the following physics features will force the use of geometric nonlinearity:
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When any Joint is used.
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When a nonzero rotation is prescribed in a Prescribed Displacement/Rotation subnode of Rigid Material.
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When a nonzero rotation is prescribed in a Prescribed Displacement/Rotation subnode of any Gear.
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When a nonzero rotation is prescribed for a Rigid Connector.
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When a Cam–Follower node is used.
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When a Rigid Body Contact node is used.
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When a Contact node is used.
Note that Contact node will force the use of geometric nonlinearity for all study types.
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Modeling Geometric Nonlinearity
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Joints
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Contact Modeling
For other study step types, you can choose whether to include the effect of geometric nonlinearity. For example, when computing the eigenfrequencies of a structure using an Eigenfrequency study step, the problem is geometrically linear, but in the case of a prestressed eigenfrequency analysis, effects of geometric nonlinearity have to be included.