Residuals

Residuals represent the difference between the internal and external forces acting on a model. If the residuals are small, Abaqus accepts the iteration as converged. The tolerances used to determine whether a solution is converged are very important. The tolerances must be small enough to provide an accurate solution but large enough to achieve the solution within a reasonable number of iterations. Before accepting an iteration as converged, Abaqus further requires that corrections to the primary solution variables and constraint equation compatibility errors must also be small.

When the equilibrium iterations do not converge, the node where the maximum residual occurs during the final iterations is usually the best place to begin searching for the problem. There are many conditions that may prevent the equilibrium iterations from converging; diagnosing the source of the problem requires a certain amount of experience.

Residual information, including the maximum residual value in each iteration, is summarized in tabular form for each attempt that contains residual diagnostics. Your selections in the Equations and Variables fields control the data in the table. You can plot columns from the table by selecting Plot selected column. When you have located a problematic iteration, select it in the Job History tree. Then you can select items from the Residuals page for the iteration and click Highlight selections in viewport to view the regions in the current viewport.