- Geometric nonlinearity
- Incorporating the effects of geometric nonlinearity in an analysis
requires only minor changes to an
Abaqus/Standard
model. You need to make sure the step definition considers geometrically
nonlinear effects. This is the default setting in
Abaqus/Explicit.
You also need to set time incrementation parameters as discussed in
Automatic incrementation control in Abaqus/Standard.
- Local directions
- In a geometrically nonlinear analysis the local material
directions may rotate with the deformation in each element. For shell, beam,
and truss elements the local material directions always rotate with the
deformation. For solid elements the local material directions rotate with the
deformation only if the elements refer to nondefault local material directions;
otherwise, the default local material directions remain constant throughout the
analysis.
Local directions defined at nodes remain fixed throughout the
analysis; they do not rotate with the deformation. See
Transformed Coordinate Systems
for further details.
- Effect on subsequent steps
- Once you include geometric nonlinearity in a step, it is
considered in all subsequent steps. If nonlinear geometric effects are not
requested in a subsequent step,
Abaqus
will issue a warning stating that they are being included in the step anyway.
- Other geometrically nonlinear effects
- The large deformations in a model are not the only important
effects that are considered when geometric nonlinearity is activated.
Abaqus/Standard
also includes terms in the element stiffness calculations that are caused by
the applied loads, the so-called load stiffness. These terms improve
convergence behavior. In addition, the membrane loads in shells and the axial
loads in cables and beams contribute much of the stiffness of these structures
in response to transverse loads. By including geometric nonlinearity, the
membrane stiffness in response to transverse loads is considered as well.
- Material nonlinearity
- The addition of material nonlinearity to an
Abaqus
model is discussed in
Materials.
- Boundary nonlinearity
- The introduction of boundary nonlinearity is discussed in
Contact.
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