.#.rnf file

The .#.rnf is an OptiStruct ASCII format results file.

File Creation

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

File Contents

This file contains Rainflow Cycle count history for each Fatigue subcase. The information is printed as a separate table for each element in the model (for RNFLOW=ALL) or separate tables for each element in the selected element set (for RNFLOW=SID). The printed tables vary in content depending on the type of Fatigue solution being run. Currently, .rnf file output is supported for Static, Transient, Sine-Sweep, and Random Response Fatigue analyses.

Static Analysis

For Static Analysis, the printed tables are different depending on if SN or EN Fatigue is being conducted.



Figure 1. Example: Table for Static Analysis (SN)
For Static analysis SN, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Cycles
Number of Rainflow cycles detected for the current Element in the current FATEVNT.
Cycle ID
Rainflow Cycle ID
Stress Amplitude
Stress ampitude of the current Cycle
Mean Stress
Mean stress of the current Cycle
Damage
Damage value of the current Cycle
For each cycle, two points of the load time history are required to fully identify a complete cycle. For instance, one cycle is from TABFAT_pt1 → TABFAT_pt2 → TABFAT_pt1.
TABFAT_pt1
First point of the load time history for the current cycle
TABFAT_pt2
Second point of the load time history for the current cycle

Example: Table for Static Analysis (EN)

For EN Fatigue, the table printed varies depending on the damage model used.


Figure 2. EN Static Fatigue (SWT)
Figure 3. EN Static Fatigue (MORROW)

For Static analysis EN, the following data are printed in the table
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Cycles
Number of Rainflow cycles detected for the current Element in the current FATEVNT.
Cycle ID
Rainflow Cycle ID
Strain Amplitude
Strain ampitude of the current Cycle
Max Stress (SWT)
Max stress of the current Cycle
Mean Stress (MORROW)
Mean stress of the current Cycle
Damage
Damage value of the current Cycle
For each cycle, two points of the load time history are required to fully identify a complete cycle. For instance, one cycle is from TABFAT_pt1 → TABFAT_pt2 → TABFAT_pt1.
TABFAT_pt1
First point of the load time history for the current cycle
TABFAT_pt2
Second point of the load time history for the current cycle

Sine Sweep Fatigue Analysis

For Sine Sweep Fatigue Analysis, the printed tables are different depending on if SN or EN Fatigue is conducted.



Figure 4. Example: Table for Sine Sweep Fatigue Analysis (SN)
For Sine Sweep SN, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Frequencies
Number of Frequencies in Sine Sweep Fatigue Analysis for the current subcase.
Freq ID
Number/ID of the current frequency of interest in the table
Number of Cycles
Number of cycles of the particular frequency of interest
Stress Amplitude
Stress ampitude of each Cycle at the current frequency
Mean Stress
Mean stress of each Cycle at the current frequency
Damage
Cumulative damage value of the current Cycle at the current frequency

Example: Table for Sine Sweep Fatigue Analysis (EN)

For EN Fatigue, the table printed varies depending on the damage model used.


Figure 5. EN Sine Sweep Fatigue (SWT)


Figure 6. EN Sine Sweep Fatigue (MORROW)
For Sine Sweep EN, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Frequencies
Number of Frequencies in Sine Sweep Fatigue Analysis for the current subcase.
Freq ID
Number/ID of the current frequency of interest in the table
Number of Cycles
Number of cycles of the particular frequency of interest
Strain Amplitude
Strain ampitude of each Cycle at the current frequency
Max Stress (SWT)
Max stress among all Cycles at the current frequency
Mean Stress (MORROW)
Mean stress of all Cycle at the current frequency
Damage
Damage value of the worst damage Cycle at the current frequency

Random Response Fatigue Analysis

For Random Response Fatigue Analysis, the printed tables are different depending on if SN or EN Fatigue is conducted.



Figure 7. Example: Table for Random Response Fatigue Analysis (SN)
Note: For all Damage models, the printed value in the Prob. Column is the actual Probability value (not the Probability Density Function value).
For Random Response SN, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Stress Amplitudes
Number of Stress Amplitudues in Random Response fatigue analysis for the current subcase.
DIRLIK/LALANNE/NARROW/THREE
Random Response Damage model used
Stress ID
Number/ID of the current stress amplitude of interest in the table
Prob
Probability of occurrence of the corresponding stress amplitude
Number of Cycles
Number of cycles of the particular stress amplitude
Mean Stress
Mean stress of each Cycle at the current stress amplitude
Damage
Cumulative damage value of all Cycles at the current stress amplitude

Example: Table for Random Response Fatigue Analysis (EN)

For EN Fatigue, the table printed varies depending on the damage model used.


Figure 8. EN Random Response Fatigue (SWT)


Figure 9. EN Random Response Fatigue (MORROW)
For Random Response EN, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Strain Amplitudes
Number of Strain Amplitudues in Random Response fatigue analysis for the current subcase.
DIRLIK/LALANNE/NARROW/THREE
Random Response Damage model used
Strain ID
Number/ID of the current strain amplitude of interest in the table
Prob
Probability of occurrence of the corresponding strain amplitude
Number of Cycles
Number of cycles of the particular strain amplitude
Mean Stress (SWT)
Mean stress of each Cycle at the current strain amplitude
Max Stress (MORROW)
Max stress of each Cycle at the current strain amplitude
Damage
Cumulative damage value of all Cycles at the current strain amplitude

Multiaxial Fatigue Analysis

For Multiaxial Analysis, the printed tables are different depending on if SN or EN Fatigue is being conducted.

Example: Table for Static Analysis (SN)

For Multiaxial Fatigue, the Damage model also influences the type of table printed in the .rnf file.


Figure 10. Goodman Damage Model
For Static analysis SN, with Goodman damage model, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Cycles
Number of Rainflow cycles detected for the current Element in the current FATEVNT.
Cycle ID
Rainflow Cycle ID
Normal Stress Amplitude
Stress ampitude of Normal Stress for the current Cycle
Mean Stress
Mean stress of the current Cycle
Damage
Damage value of the current Cycle. For multiaxial fatigue, the reported damage is the worst damage out of all damages calculated for planes rotated by 10 degrees. The plane with maximum damage at each location is called the critical plane and this is reported.
Damage Model
Damage model being used for this Cycle, and additionally also lists the critical plane determined to have the maximum damage (possible planes are T0, A0, A45, B45).


Figure 11. Findley Damage Model
For Static analysis SN, with Findley damage model, the following data are printed in the table.
Element ID
The header at the top of the table consists of the Element ID of consideration.
Event ID
The first line under Element header indicates the ID of the FATEVNT Bulk Data Entry and in parentheses lists the counter of the current FATEVNT under consideration out of the total number of FATEVNT entries).
Number of Cycles
Number of Rainflow cycles detected for the current Element in the current FATEVNT.
Cycle ID
Rainflow Cycle ID
Shear Stress Amplitude
Stress ampitude of Normal Stress for the current Cycle
Normal Stress
Normal stress for the current Cycle
Damage
Damage value of the current Cycle. For multiaxial fatigue, the reported damage is the worst damage out of all damages calculated for planes rotated by 10 degrees. The plane with maximum damage at each location is called the critical plane and this is reported.
Damage Model
Damage model being used for this Cycle, and additionally also lists the critical plane determined to have the maximum damage (possible planes are T0, A0, A45, B45).

Comments

  1. The I/O Option RESULTS controls the frequency of output for analytical results during an optimization.