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.
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.
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.
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.
A nonlinear analysis step is split into a number of increments.
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.
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.
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.
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.