FATLOAD
Bulk Data Entry Defines fatigue loading parameters.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
FATLOAD | ID | TID | LCID | LDM | Scale | Offset | LHFORMAT | CHANNEL | |
SWEEP | SR | SRUNIT | |||||||
HARMO | Fi | MAGi | |||||||
LDHIST | BGNSTP | ENDSTP |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
ID | Each
FATLOAD card must have a unique
ID. This identifier may be referenced by a FATEVNT
definition. No default (Integer > 0) |
|
TID | TABFAT or
TABLEDi entry identification
number. References TABFAT ID: If LCID references a Linear static subcase, TID should be a positive integer (Integer > 0) or blank. It can only be blank when SQNTL field is set on the FATEVNT entry. If LCID references Transient or Random Response subcase, TID should be blank. References TID on ASSIGN,DAC or ASSIGN,RPC: If LCID references a Linear static subcase, TID should be a positive integer (Integer > 0). This TID should match the TID on ASSIGN,DAC or ASSIGN,RPC entries. If both TABFAT and ASSIGN,DAC have same TID, then the load history from TABFAT is not used, and is just ignored. References TABLEDi ID: If LCID references a Frequency Response subcase, then, TID references a TABLEDi table which defines a magnification load table. If TID is left blank for Sine Sweep Fatigue analysis, then a scale factor of 1.0 is applied automatically to the Frequency Response output used for Sine Sweep calculations. (Integer > 0 or blank) |
|
LCID | Subcase identification number of a Linear Static, Transient, Frequency Response,
Random Response, or Multibody Dynamics (MBD) subcase. 3 No default (Integer > 0) |
|
LDM | The
magnitude of the FEA load in
the same units as those for the time history. It
is ignored in fatigue analyses based on a
transient analysis subcase. 2 Default = 1.0 (Real) |
|
Scale | Scale factor applied to the load or time history.
It is ignored in fatigue analyses based on a
transient analysis subcase. Default = 1.0 (Real) |
|
Offset | Offset applied to the load or time history. It is
ignored in fatigue analyses based on a transient
analysis subcase. Default = 0.0 (Real) |
|
LHFORMAT | Identifies the format of the load history
information defined via TID
field.
|
|
CHANNEL | Identifies the channel which is used for the load
history definition for the RPC
format. This field is mandatory, if the
LHFORMAT field is set to
RPC. Default = blank (Integer > 0) |
|
SWEEP | Flag indicating that the options for Sweep test are to follow. | |
SR | Sweep rate. 4 No default (Real ≥ 0.0) |
|
SRUNIT | Unit
of sweep rate.
No default |
|
HARMO | Continuation line indicating the sine tone properties for Sine-on-Random Fatigue Analysis or fatigue calculation from Multiple Sine Tones Fatigue Analysis. | |
Fi | Sine
tone frequencies. No default (Real) |
|
MAGi | Magnification factor to frequency response stress
at the specified frequency
(Fi). If 0.0, the sine load at this frequency is ignored. Default = 1.0 (Real) |
|
LDHSIT | Continuation line indicating the first output time step and the last output time step of a stabilized cycle in the underlying nonlinear analysis. | |
BGNSTP | The first output time step of a
stabilized cycle in the underlying nonlinear analysis. Default = 1 (Integer) |
|
ENDSTP | The last output time step of a
stabilized cycle in the underlying nonlinear analysis. Default = blank (The last output time step) |
Comments
- This magnitude is used as a scale factor to normalize the finite element stresses/strains to obtain the stress/strain distribution due to a unit loading.
- The equation below depicts
how LDM, Scale and Offset values
work together to scale the FEA stress tensor at time
:
If SQNTL flag on FATEVNT is blank (default), all FATLOADs referenced on a particular FATEVNT are applied simultaneously.
The stress tensors at each time from each FATLOAD, for the entire fatigue event are calculated as:Subsequently, Rainflow counting is conducted using to calculate the equivalent stress amplitude and mean stress. This is used to calculate damage and life for this fatigue event.
If SQNTL flag on FATEVNT is set, all FATLOADs referenced on a particular FATEVNT are applied sequentially, instead of simultaneously.
The stress tensors at each time from each FATLOAD are calculated as:(1) Where,- Superposed stress tensor for the entire fatigue event, as a function of time .
- Stress tensor for the fatigue load, as a function of time .
- Stress tensor from static analysis for a FATLOAD entry, (TID referencing a TABFAT entry is only used for Static subcases. TID should be blank for Transient Analysis-based Fatigue Analysis).
- , , , and
- Corresponding LDM, TABFAT, Scale, and Offset field values for each FATLOAD entry, .
- A referenced MBD subcase allows Fatigue Optimization using the ESL method. Fatigue Analysis is not supported for this solution, only optimization is supported.
- If SR=0.0, then sweep does not occur. In this case, the damage at the first frequency (from FREQi entries) is calculated. Final damage is reported after being multiplied by T# in FATSEQ. Similarly, for the case of a single loading frequency being used in the FRF subcase, the damage is calculated at that frequency and the final damage is reported after multiplying by T# in FATSEQ.
- When time history of underlying nonlinear analysis result is directly used as a load history in fatigue analysis, load history between BGNSTP and ENDSTP is only used in fatigue analysis. This feature can be used to choose stabilized cycle or to remove setup load of the nonlinear analysis.
- This card is represented as a load collector in HyperMesh.