Step Cycling

For some analyses it is desirable to repeat a step or series of steps over a large number of cycles. Common examples include battery aging, wear, erosion, and material fatigue analyses. Explicitly redefining the same steps to simulate a large number of cycles is cumbersome and inefficient. The step cycling capability provides a more convenient and efficient means to define cycling behavior.

You can define a step or a series of steps to be repeated within a step cycling sequence. Abaqus/Standard repeats the steps according to the number of cycles you specify as part of the step cycling sequence definition. Steps outside of a step cycling sequence definition are executed only once. If you begin a step cycling sequence definition but do not specify an end to the sequence, Abaqus/Standard cycles all steps following the start of the cycling sequence.

You can assign a name to a step cycling sequence. Abaqus/Standard prepends this name to the step name written to the output databases for steps within the step cycling sequence.

STEP CYCLING, START, NAME=name
number of cycles

STEP CYCLING, END

If you use the step controls mechanism (Controlling the Analysis Based on the Simulation State in Abaqus/Standard) to end an intermediate step of a step cycling sequence, Abaqus/Standard will proceed to the next step in the step cycle definition. Some applications might also require terminating a cycling sequence. You can use the step cycling control mechanism to end a cycling sequence before the specified number of cycles is reached. It is recommended that you end a cycling sequence during the last step of the sequence. However, if your application requires ending a cycling sequence in any intermediate step within the cycle and there are other steps following the cycling sequence, your model definitions must ensure that any subsequent changes to loads and boundary conditions are meaningful and correct.

STEP CYCLING CONTROL, NAME=name, ACTION=END CYCLING

By default, Abaqus/Standard writes results to the output databases for all cycles within a step cycling sequence. This can result in a significant amount of data if the number of cycles is large. You can reduce the size of the output databases by restricting output to a specific cycle frequency as part of the step cycling sequence definition. Abaqus/Standard always writes output in the last cycle of a step cycling sequence.

STEP CYCLING, START, NAME=name
number of cycles, frequency at which to write output

By default, Abaqus/Standard writes all results for a step cycling sequence to the same output database. However, for analyses consisting of a series of steps not part of a cycling sequence followed by only a single step cycling sequence, Abaqus/Standard can distribute the results to multiple output files. You can specify a cycle frequency at which Abaqus/Standard directs output to new output databases.

The names of the new output databases will include an integer suffix indicating the index of the last cycle written to the file. For example, if an analysis consists of 1000 cycles and you specify a cycle frequency of 200, Abaqus/Standard writes six output databases. The name of the first output database is jobName_1.odb, and it contains the first cycle only. The names of the subsequent output databases are of the form jobName_N.odb, where N is 200, 400, 600, 800, and 1000.

STEP CYCLING, START, NAME=name
number of cycles, frequency at which to write output, frequency at which to create a new output database

To optimize performance, Abaqus/Standard stores only the final state of the steps comprising a step cycling sequence on the analysis database. Therefore, subsequent continuation analyses (Analysis Continuation Techniques) should use the step id of the continuation step without regard to a specific cycle. For example, if you perform a restart from an analysis consisting of two steps repeated through N cycles, in a subsequent restart analysis you would specify either Step 1 or Step 2 as the step from which to continue the analysis.

In contrast, Abaqus/Standard writes results to the output databases for each cycle of a step cycling sequence, in accordance with the user's output requests. Therefore, step ids on the output databases are sequential across all steps of the analysis. If you import results into a subsequent analysis, such as for initial conditions (Initial Conditions) or external fields (General Capability for Importing External Fields), you should use the step id consistent with the step ids present on the output databases. For example, if an analysis consists of two steps repeated through 50 cycles, the step ids available for importing results would lie in the range 1 to 100.

Step cycling is subject to the following limitations:

• Perturbation procedures cannot be included in a step cycling sequence.
• Restart can be performed only from the last cycle of a step cycling sequence (Restarting an Analysis).
• Import cannot be performed between two analyses if either analysis includes a step cycling sequence (About Transferring Results between Abaqus Analyses).

In addition, a step cycling sequence cannot include the following features:

• Adaptive meshing (ALE Adaptive Meshing and Remapping in Abaqus/Standard)
• Adjoint design sensitivities (Adjoint Design Sensitivity Analysis)
• Parametric modeling (Parametric Modeling)
• Element progressive activation (Progressive Element Activation)
• Extended finite element method (Modeling Discontinuities as an Enriched Feature Using the Extended Finite Element Method)
• Multiple nonlinear load cases (Multiple Nonlinear Load Case Analysis)