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This behavior becomes less puzzling when one realizes how the gradual changes to the Bisection feature have given the term `Bisection` an evolving meaning in ANSYS. Over the years, heuristic improvements to automatic nonlinear solution controls have expanded the meaning of `Bisection` in the ANSYS program, so that one could say that `Bisection` now means `automatic restart with automatically changed solution controls.` Timestep size is just one solution control that the program can change automatically in such a restart. The objective in the current program design is to try to achieve the most rapid solution possible, by automatically striving for a balance between reliable convergence and maximum timestep size.
In the output that you sent, after TIME = 39.8846, a non-converged solution `Bisected,` or was automatically restarted, with a changed solution control: the Predictor automatically turned off. No other solution control changes took place in this restart -- including the time step size, which remained unchanged. This automatically restarted solution converged, but had a plastic strain increment slightly above the limit of 15%, so another `Bisection` took place, in which the timestep size was reduced slightly, from0.15928E-01 to 0.15359E-01. The time-step size reduction in this instance was based on the ratio of maximum plastic strain increment to the plastic stain increment limit.
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