EQSTSAMP

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

Format

EQSTSAMP (format, RTOP=rtop) = option

Definitions

Argument Options Description
format <OPTI, H3D, blank>
OPTI
Results are output in OptiStruct results format (.eqsts file).
H3D
Results are output in Hyper3D format (.h3d file).
blank (Default)
Equivalent Stress Results are output for all active output formats for which the result is available. 8
rtop < 0.0 < Real < 1.0 >

Default = blank 9

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

For example: If rtop=0.3, then the elements in the top 30% damage are identified for equivalent stress output. There is no equivalent stress output for the rest of the elements.
option <YES, ALL, NO, NONE, SID>

Default = ALL
YES, ALL, blank
Results are output for all elements.
NO, NONE
Results are not output.
SID
If a set ID is specified, results are output only for elements listed in that set.

Comments

  1. Equivalent Stress amplitude for each element represents the single constant value of stress that is equivalent to the stress that causes the same damage that occurs based on the multiple load cycles from rainflow counting. Equivalent Stress amplitude results via the EQSTSAMP entry are available only in H3D (.h3d) and OPTI (.eqsts) formats.
  2. This is currently only supported for SN and EN Static and Transient Fatigue Analysis.
  3. Multiple instances of this card are allowed; if instances are conflicting, the last instance dominates.
  4. This entry can be used to output the Equivalent Stress Amplitude for each element of fatigue subcases. The Equivalent number of Cycles, Equivalent Stress Amplitude, Critical Angle (only for Multiaxial Fatigue) and Damage value are output to <filename>.fat.<subcaseID>.eqsts file.
  5. The Angle output in Multiaxial Fatigue Analysis is the angle of the critical plane at which the damage value is output. As always, the worst damage between the tensile and shear critical plane searches is output along with the corresponding angle. The angle is calculated from the X-axis of the material coordinate system (this can be modified using PARAM,OMID).
  6. If the life value calculated is greater than the corresponding Fatigue Limit (FL), then the equivalent stress amplitude is reported as 0.0.
  7. 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.
  8. In the absence of specific format information on the result entry, and if an OUTPUT or FORMAT entry is not present, then the default output format (typically H3D) is considered as the active format. If an OUTPUT or FORMAT entry is specified, then the format chosen is considered active and the default is not applicable.
  9. If RTOP is not specified, then equivalent stress is output for all elements defined in FATDEF (this can be considered equivalent to a RTOP value of 1.0).
  10. EQSTSAMP is supported as an elemental vector plot in the H3D file.

    For example, in HyperView, a vector plot can be applied after selecting “Equivalent Stress Amplitudes” results type. The vector is located at the element center and its direction represents the ANGLE and its length represents the equivalent stress value.