Nonlinear analyses (Abaqus)

In the Abaqus environment, in a General solution step in a General Analysis type of solution, an analysis can be either linear or nonlinear, depending on whether you include the effects of any nonlinearities present in the model in the analysis.

There are three sources of nonlinearity that you can include in a nonlinear stress analysis:

• Material nonlinearity

• Boundary nonlinearity

• Geometric nonlinearity

Note:

Abaqus handles both material and boundary nonlinearities automatically.

Material nonlinearity

Material nonlinearity occurs when materials exhibit nonlinear stress-strain relationships. Some examples of material nonlinearity include:

• Elasto-plastic and hyperelastic materials (examples of nonlinear constitutive response).

• Temperature-dependent, time-dependent, and strain rate-dependent materials, such as viscoelastic or creep materials.

• Material failure, such as crushing and cracking.

Boundary nonlinearity

In a general analysis, certain types of boundary conditions, such as contact, can be sources of nonlinearity. Friction, nonlinear elastic springs, and multipoint constraints are other examples of sources of boundary nonlinearity.

Geometric nonlinearity

Geometric nonlinearity refers to the nonlinear stiffness variations that are caused by large deformations or rotations. In Abaqus, setting the NLGEOM option for a step determines whether Abaqus accounts for geometric nonlinearity in that step.

If you expect geometrically nonlinear behavior to occur in a particular step, you should use the large-displacement formulation (*STEP, NLGEOM=YES). In the Abaqus environment, you control the setting of the NLGEOM option using the NLGEOM check box in the Solution Step dialog box:

• Select the NLGEOM check box to indicate that Abaqus should account for geometric nonlinearity (nonlinear effects of large displacements and deformations) during the current step and all subsequent steps in the solution.Note: After you select the NLGEOM check box, the setting applies to all subsequent steps in the solution.

• Clear the NLGEOM check box to perform a geometrically linear analysis during the current step.

Learn more

Axisymmetric analysis (Abaqus)

Dynamic explicit analysis (Abaqus)

Modal steady-state dynamic analysis (Abaqus)

Modeling cohesive behavior in Abaqus contact analyses

Modeling abstractions (Abaqus)

User-defined progressive failure analysis (Abaqus)

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