Product Information
Fatigue Analysis
LUSAS performs fatigue calculations
on the results of a linear finite element stress analysis using the
total life approach. The fatigue life may be expressed in terms of
the damage that is done to the structure by a prescribed loading
sequence or as the number of repeats of the sequence that will cause
failure of the structure. Contour plots illustrating the fatigue
life of every part of the structure can be generated. |
Fatigue Calculations
Fatigue calculations of the life of a
structure or component are defined and calculated using the following
data:
-
 S-N
Curves
The S-N curve is used to calculate the number of cycles to failure for
each loadcase. Miner’s rule is used to combine the damage for each
loadcase to give the total damage to the structure for the specified
loading sequence. Log values are used because of the large variation
in magnitude of the input data. The curve is considered linear in the
log-log domain.
- Fatigue Spectra
A loading spectrum defining the loading sequence in terms of a
series of loadcases, each of which has an associated load
factor and number of cycles.
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Fatigue Results
Results from the fatigue
calculations may be viewed using any of the standard LUSAS results
processing methods. Fatigue results come from any chosen component of
stress, as specified in the Fatigue loadcase.
Results may be visualised in
two ways:
- Loglife
This is the log10 of the
life expectancy of the structure subject to the level of loading
measured in the number of cycles to failure.
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Damage
The amount of damage that a material sustains under fatigue loading. A
value of unity represents failure.
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