Fatigue Wizard (unlike the Autodesk Simulation software) is a 32-bit application. Because Fatigue Wizard is a 32-bit application, it is limited on the size of files it can consider. Since this program reads the Autodesk Simulation binary stress output file, this file cannot be read completely if larger than 2GB in size. For a linear static stress analysis, this file has the *.nso file extension. For MES, this file has the *.aso file extension.
There is also another limitation within the Fatigue Wizard in that only models having 250,000 nodes or less can be considered.
Both of these limitations may be extended if one is using Autodesk Simulation Mechanical/Multiphysics 2013 software on a 64-bit computer having more than 4 GB RAM. This may allow stress result files up to 3 GB in size.
The work-around to these limitations is to either identify the "area of interest" from the originally analyzed model, then create a new model containing a much coarser mesh one the whole of the model, and use mesh refinement in the "Area of Interest". This technique would be used to reduce the total number of nodes in the model and it can be used for both linear static stress and MES analyses. The new model would then be re-analyzed, then one would choose to run the Fatigue Wizard.
If the model size has less than 250,000 nodes, but the total *.aso file is larger than 2 GB (3GB on 64-bit computer), and if the analysis is an MES analysis, then one can reanalyze the model so that less time steps are produced in the results file.
For example, if the MES analysis produced 60 time steps and the *.aso file was 4 GB in size, then re-analyzing the model so that only 30 time steps are produced will create an *.aso file that is only 2 GB in size.
Finally, there are alternative techniques available where a new "sub-model" is created such that only the "area of interest" is represented. Using the 2013 software release, one can interpolate deflection results from the original model results to the new "sub-model". One would then run the stress utility manually for the "sub-model", from which the Fatigue Analysis can then be performed. It should be noted this last option is available for linear static stress analyses only. This last option is only summarized, since it is not supported through the interface and requires running commands from the DOS prompt. Please let me know if you have further questions.
Pat Tessaro, P.E.
Premium Support Specialist – Simulation
Autodesk, Inc.
6425 Living Place
Suite 100
Pittsburgh, PA 15206
