_fat.#.eqsts file

An OptiStruct ASCII format results file.

File Creation

This file is created when the OPTI format is chosen in EQSTSAMP I/O Options Entry for Fatigue Analysis. The # is the corresponding Fatigue subcase ID and separate .eqsts files are created for multiple Fatigue Subcases (Refer to the I/O Options, EQSTSAMP, FORMAT and OUTPUT).

File Contents

This file contains Equivalent Stress Amplitude and corresponding Equivalent Number of Cycles for each Fatigue subcase. The information is printed as a single table for all/SID elements in the model (for EQSTSAMP(OPTI)=ALL/SID). The printed tables vary in content depending on the type of Fatigue solution being run. Currently, .eqsts file output is supported for SN and EN Static and Transient Fatigue analyses only.


The table format is similar for both Static and Transient Fatigue analysis. For Uniaxial Fatigue analysis, the Angle column is set to NA.

Figure 1.
The following data are printed in the table:
Elem ID
The header at the top of the table consists of the Element ID of consideration.
The value of damage for each element.
Eq. no. cycles
Indicates the equivalent number of cycles for each element.
Eq. stress amp.
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.
Angle (Deg.)
Indicates the angle in multiaxial fatigue analysis of the critical plane at which the damage value is output.