Instead, here are general links to Knowledge Base articles which may be helpful for common convergence problems in severe discontinuity and equilibrium iterations:
|Debugging Abaqus/Standard divergence with too many cutbacks in the last attempted increment||QA00000008780|
|Hints for obtaining a converged contact solution in Abaqus/Standard||QA00000008797|
|Understanding Abaqus/Standard negative eigenvalue messages||QA00000009389|
|What do zero pivot warnings in the message file of my Abaqus/Standard analysis mean?||QA00000008866|
|What might cause Abaqus/Standard to diverge with numerical singularity warnings?||QA00000008894|
|What do warnings that the current strain increment exceeds the strain to first yield mean?||QA00000008867|
This plot shows the converged step time increment, ΔTime, vs Step Time. The nonlinear implicit solver will automatically increase ΔTime when convergence comes quickly. If difficulties are encountered then multiple Attempts will be made with cutbacks to ΔTime until convergence is achieved. Any cutbacks will be clearly visibile below and provide an overview of step times when these convergence difficulties occured. Click on a point to jump to more detailed information in the Table of Iterations below.
This plot shows the maximum change of results affecting the time integration accuracy. The solver monitors these results of converged Attempts. If the maximum change exceeds a user-specified tolerance then the solver will make a new Attempt with a cutback Increment ΔTime.
The plot(s) below show the evolution of each average equilibrium "flux" (force, moment, heat, etc.) vs Step Time for converged increments. This provides some indication of how the load distribution is changing due to nonlinearities in the model and may be correlated with ΔTime cutbacks or other issues.
This is a plot of the monitored nodal degree of freedom vs step time. It shows the linearity of response and can provide indication of approaching buckling load.
These warnings indicate poor conditions for the equation solver and are often produced in static steps with unconstrained rigid body motion in the indicated degree of freedom. Additional information is available in QA00000008894.
This table is a chronological summary of all the solver iterations reported in the .msg file. The Result column describes the first failed check, if any, followed by corresponding nodal data. The Value should generally decrease for each iteration within an Attempt if the nonlinear solution is converging. Here you can review the rate of convergence and any causes of difficulties. Unsuccessful Attempts are colored red.
This section summarizes the convergence measures of Iterations within the last Attempt. Choose another Attempt by clicking its Plot button in the Table of Iterations above. Curves may be suppressed by clicking their name in the legend.
This plot shows how the contact is changing within the Attempt. Contact changes are classified as "severe discontinuities" because they significantly alter the load path through the mesh. The number of contact changes should reduce as the solver iterates to resolve the contact state.
The following plots summarize the evolution of equilibrium within the Attempt. Convergence is accepted when all of the checks of these parameters satisfy criteria as described in the manual. Generally, the residuals and corrections should be approaching zero as the solver iterates. The default convergence criteria work well for most problems and should not normally need adjustment.
Contact pairs in this section are sorted according to the number of times they failed convergence checks in all Iterations of all Attempts. This doesn't necessarily indicate any problem with the model but can be helpful to identify interfaces that are the most challenging for the solver. If a contact pair is failing significantly more often then you may want to review its contact definitions and behaviors. Common reasons include indeterminate friction, reversed slave/master, overly stiff penalty or direct enforcement.
This model has symptoms of contact chatter which contributed to failed convergence of some Attempts. Detailed contact diagnostics will help identify the contact pairs most involved in chatter by including all nodal contact changes in the plot below. However, the size of the .msg file and time to process it may grow substantially. Request detailed contact diagnostics for a Step under the Output→Diagnostic print... menu of Abaqus CAE or with the keyword *PRINT, CONTACT=YES
Nodes in this section are sorted according to the number of times they failed convergence checks in all Iterations of all Attempts. If a few nodes occur significantly more often than others you should review the model or results to see what might be the cause. Common reasons include hourglassing, overly coarse mesh, distortion or underconstraint. The most repeated nodes are assigned a symbol to help with identification throughout this report.
This model has symptoms of contact chatter which contributed to failed convergence of some Attempts. Detailed contact diagnostics will help identify the nodes most involved in chatter by including them in the summary below. However, the size of the .msg file and time to process it may grow substantially. Request detailed contact diagnostics for a Step under the Output→Diagnostic print... menu of Abaqus CAE or with the keyword *PRINT, CONTACT=YES
The following table shows each failed convergence check grouped by node. The Failed Check column will help differentiate contact or equilibrium issues. Review of the Step, Increment, and Attempt will help identify whether the node is a continuous problem.
|Node||Step||Increment||Attempt||Iteration||Failed Check||DOF||Value||Contact Pair|