Cycle Counting Analysis (Mode 2) |
 
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Cycle Counting Analysis (Mode 2) |
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The three steps in performing a general cycle counting analysis with LifeTime are as follows:
Perform a Flexcom random sea analysis for each fatigue seastate. In setting up each analysis, you must store time histories of the variable(s) of interest. Unlike full fatigue analysis runs, cycle counting requires that these parameters be stored via timetrace output – database output is not sufficient. Obviously for meaningful cycle counting the same variables should be nominated in all of the Flexcom runs.
Specify the fatigue analysis input data. This would typically include the following information:
•The names of the Flexcom random sea analyses, and tabulate the percentage occurrences of the corresponding seastates
•The variables (or “channels”) of the Flexcom timetrace output which you want cycle counted. Channel in this context refers to an individual variable in a Flexcom timetrace output file.
•The divisions (or “bins”) for the histogram output
Run LifeTime. When running, the program loops over all seastates and all of the relevant channels, and performs the cycle counting. Further details are provided in Program Outputs.
•Numerous keywords are contained in the $LOAD CASE section, including data such as environmental parameters (e.g. current and waves).
o*TIMETRACE is used to request the storage of results for timetrace postprocessing (this is mainly used in the area of time domain fatigue analysis).
•Numerous keywords are contained in the $LIFETIME CYCLE section, which corresponds to LifeTime Mode 2.
o*BINS is used to specify bins or divisions for histogram output.
o*CHANNELS is used to specify channels for cycle counting.
o*SEASTATE FILES is used to specify all of the Flexcom random sea analyses on which the LifeTime calculations are to be based, and to tabulate the percentage occurrences of the corresponding seastates.
•*HISTOGRAM OUTPUT is used to specify data relating to histogram output.