How does FatiguePro work?
 For
Stress-Based
Fatigue, the technological breakthrough in this development was the use of
"Green's Functions" for the transient, thermal analysis. This approach requires
that a detailed, finite element analysis be conducted for each monitored location only
once. The Green's Function consists of thermal stress results of this analysis, for a unit
step change in boundary temperature. By using the Green's Function in
FatiguePro, on-line
finite element analysis is not required. Thus, analysis for an hour of data for several
locations can typically be completed in less than a minute using a personal computer.
In many cases, the local temperature, pressure or flow at a specific location is not
readily available as a specific instrument reading and must be determined based on other
instrument data. Predictions of the various stress components at a location are termed
"transfer functions." SI has developed extensive expertise in this area to
predict realistic stresses. This technology has been modernized to consider such effects
as thermal stratification cycling.
In the Automated Cycle-Counting module, plant transients
are identified mechanistically through a set of rules. These rules involve the definition
of the events per the Technical Specification as well as benchmarking of real plant data.
The ACC module automatically records pertinent parameters associated with the event, such
as temperatures, pressures and maximum heatup/cooldown rates. This information can be used
for the basis of computing partial cycles in the Cycle-Based Fatigue
module.
The Crack Growth module computes the through-wall stresses for a
section and performs a fatigue crack growth calculation based on a cubic polynomial stress
distribution.
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