When the action is set to Full Analysis and the user presses the Apply button the following occurs:
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The job begins the submission process by checking to see if an existing job of the same name exists. If it does, overwrite permission will be requested.•
All of the information requested in the main setup form and the subordinate solution parameter, materials, and loading information forms are written to a MSC.Fatigue input file called jobname.finand includes 90% of the fatigue input parameters. It is an ASCII unformatted file whose text lines consist of “Parameter = Value”. The other 10%of the fatigue input information is retained in the database and consists of the region application information (nodes or elements) for the material and surface
finish/treatment combinations and, in most cases, the FE results. If any information is not complete, the user will be notified and the submission process will terminate.
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Information is extracted from the database such as the region or group data and results via the PAT3FAT or FATTRANS translator. MSC.Fatigue Pre&Post or MSC.Patran is suspended while the translation is in progress. Ajobname.fesfile results from this translation. This is the fatigue analysis input file and is binary in nature. It can be translated to ASCII form and edited if desired.•
A UNIX shell script, (p. 313), is invoked from which the actual fatigue analysis begins.The analysis goes through two or three basic steps. The fatigue input file is
preprocessed via the FEFAT module. This consists of reading thejobname.fesfile, superpositioning of load cases, rainflow cycle counting, among other things. The result of this operation is a file calledjobname.fpp(jobname.tcy for crack growth analyses).
(This submit script is actually a C program on Windows platforms.)
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The next phase consists of performing the actual fatigue calculations using the module FEFAT (or PCRACK for crack growth). The results of this operation is a file calledjobname.fef(orjobname.crgfor crack growth analyses).
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If additional calculations are requested such as a Factor-of-Safety analysis have been requested, they are executed next.•
If MSC’s Analysis Manager is installed and licensed, the job as described above will be submitted via the Analysis Manager as opposed to a UNIX shell script (although the script is still executed). It is important that this module be configured properly for proper execution. SeeAnalysis Manager(p. 70) for details.When the job has been completed the results can be read into the database under the Results form. SeePostprocessing Results(p. 72). For more information about the files created from a MSC.Fatigue analysis and the actual operation of the MSC.Fatigue modules, seeTotal Life and Crack Initiation(Ch. 5) orCrack Growth(Ch. 7). Also seeThe MSC.Fatigue Jobname(p. 24).
The following files are generated during a Crack Initiation or Total Life (S-N) analysis:
The following files are generated during a Crack Growth analysis:
Filename Description
jobname.fin Fatigue job parameter data.
jobname.fes FE stress and fatigue input file.
jobname.fpp Fatigue preprocessing results file.
jobname.fef Fatigue results file.
jobname.fos Stress factor-of-safety results file.
jobname.msg Message file.
jobname.sta Job status file.
jobnamenn.cyh Cycle distribution at node/element nn.
jobnamenn.dhh Damage distribution at node/element nn.
Filename Description
jobname.fin Fatigue Input Data.
jobname.fes FE stress and fatigue input file.
jobname.tcy Crack growth analysis time history input.
jobname.crg Crack growth results file.
jobname.msg Message file.
jobname.sta Job status file.
Main Index
Fast Analysis. A special option called Fast Analysis (FASTAN) is also available when
performing a full analysis. This option is activated when the Simplified Analysis toggle is set to ON. The purpose of a Fast Analysis is to speed up the identification of the critical areas of a model. This option is especially useful for large models with complex loading. The operation is done by extracting the peaks and valleys from the time histories (shortening the time histories but keeping the damage content) and then running a fatigue analysis which will identify the critical locations. These locations are then used in a full analysis with the full length time histories. This is the operation performed for multiple load cases.
If only a single load case is used, the peak valley extraction method is not used. Instead the time history is cycle counted and then the subsequent rainflow matrix is used for the remainder of the analysis. For a single load case, only the Simplified Analysis toggle needs to be turned on, but for multiple load cases, the settings of the other widgets on the Job Control form are taken into account. A description of all the parameters for multiple load cases follows:
Parameter Description
Type This specifies how the peak/valley extraction is to be performed. Three methods are available. The first is to specify a percentage gate of the total stress/strain range of the signal. The second is to specify the number of points to be retained in the time history. The third is to specify a percentage reduction of the total signal. Type is ignored for single load cases. Instead a rainflow matrix is created from the time history.
Percentage Gate
A percentage gate can be specified which is a percentage of the maximum stress/strain range of the time history. For example if the largest range is 1000MPa and the gate is set to 50 (percent), then any cycles encountered with ranges below 500 MPa will be ignored. This parameter is ignored for a single load case.
Number of Points
The total number of points to be retained in the time history can be specified. This number cannot be less than two nor can it be less than the number of points that a 99% gate would calculate. The program will automatically compensate if the user has specified an unacceptable number of points to retain. This parameter is ignored for a single load case.
Reduction Factor
This is the percent reduction factor by which to reduce the time history signals. For example if the signals have 1000 points, and you specify 50%, the signal will be reduced to 500 points. Again the same limits apply to this as apply when specifying the number of points to retain. This parameter is ignored for a single load case.
Number of FE Entities
Finally, you have the ability to specify how many of the most critical locations should be retained in the final analysis. If you specify 50 points, then the 50 points with the most damage from the analysis using the reduced time histories will be used in the full analysis with the full signals.
Only these nodes will be reported back. (Although you may look at the results from the fast analysis which are calledjobname_short.*and may be manually viewed and/or imported into the database.) This parameter is ignored for single load cases.