I/O Options and Subcase Information Entry Used to request fatigue damage results output for all fatigue subcases or individual fatigue subcases, respectively.


RNFLOW (format, RTOP=rtop) = option


Argument Options Description
format <OPTI, blank>
Results are output in OptiStruct results format (.#.rnf file).
blank (Default)
Results are output only if OPTI format is activated using OUTPUT or FORMAT entries.
rtop <0.0 < Real < 1.0>

Default = blank 7

From the elements defined in FATDEF, the ones within the top “rtop” fraction based on the damage values are identified. Then the rainflow results for these elements are output.

Example: If rtop=0.3, then the elements in the top 30% damage are identified for rainflow output. There is no rainflow output for the rest of the elements.

option <YES, ALL, NO, NONE, SID>

Default = ALL

YES, ALL, blank
Results are output for all elements.
Results are not output.
If a set ID is specified, results are output only for elements listed in that set.


  1. Fatigue results via the RNFLOW entry are available only for OPTI format in the .rnf file. This is also supported for Random Response and Sine Sweep Fatigue Analysis.
  2. Multiple instances of this card are allowed. If instances are conflicting, the last instance dominates.
  3. This entry can be used to output the Rainflow Cycle count history for a particular fatigue subcase. The Cycle number, Stress Range, Mean Stress, and Damage, for each fatigue event for each element are output to <filename>.fatrf.<subcaseID>.rnf file.
  4. For Multiaxial Fatigue, only proportional multiaxial subcase is supported for RNFLOW output.
  5. For Random Response Fatigue, NBIN on FATPARM entry is required in order to print the Rainflow cycle count information. If DS on FATPARM entry is defined, Rainflow cycle count information will not be available.
  6. When a Set ID (SID) is specified, the rtop fraction of damaged elements will not be printed if the rtop fraction of damaged elements are not part of the elements in Set ID.
  7. If RTOP is not specified, then rainflow results are output for all elements defined in FATDEF (this can be considered equivalent to a RTOP value of 1.0).