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There are three sources of nonlinearity in structural problems:
material, geometric, and boundary (contact). Any combination of these may be
present in an
Abaqus
analysis.
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Geometric nonlinearity occurs whenever the magnitude of the
displacements affects the response of the structure. It includes the effects of
large displacements and rotations, snap through, and load stiffening.
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In
Abaqus/Standard
nonlinear problems are solved iteratively using the Newton-Raphson method. A
nonlinear problem will require many times the computer resources required by a
linear problem.
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Abaqus/Explicit
does not need to iterate to obtain a solution; however, the computational cost
may be affected by reductions in the stable time increment due to large changes
in geometry.
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A nonlinear analysis step is split into a number of increments.
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Abaqus/Standard
iterates to find the approximate static equilibrium obtained at the end of each
new load increment.
Abaqus/Standard
controls the load incrementation by using convergence controls throughout the
simulation.
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Abaqus/Explicit
determines a solution by advancing the kinematic state from one increment to
the next, using a smaller time increment than what is commonly used in implicit
analyses. The size of the increment is limited by the stable time increment. By
default, time incrementation is completely automated in
Abaqus/Explicit.
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The Job Monitor dialog box allows the progress of
an analysis to be monitored while it is running. The Job
Diagnostics dialog box contains the details of the load
incrementation and iterations.
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Results can be saved at the end of each increment so that the evolution
of the structure's response can be seen in
the Visualization module.
Results can also be plotted in the form of X–Y
graphs.