Convergence Ratios |
 
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Convergence Ratios |
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If an analysis fails to converge successfully, the program outputs the convergence ratio for each unsuccessful iteration – this is presented at the end of the input data echo section of the main output file (with the file extension OUT). Refer to Solution Convergence for further information on convergence ratios. There are typically 15 iterations (depending on the analysis type, and the time-stepping procedure if applicable), and the table will show whether or not the analysis was approaching the convergence tolerance. It will also allow you to identify the critical degrees of freedom. If the analysis was approaching convergence, then you could possibly try increasing the maximum number of iterations permitted. In the case of static analyses, you could try reducing the load increment. In the case of dynamic analyses, you could try varying the time stepping or solution parameters, as discussed in the following sections. If the convergence ratios suggest that the analysis is highly unlikely to converge, for example if the critical ratios are alternating between two or three identical values at successive iterations, this is generally indicative of shortcomings in the model specification, and you may want to review the input specification (the advice presented in Nonlinear Properties may be important in this context).
•*TOLERANCE is used to define the analysis convergence tolerance measure and related data.