The ovarall speed of the fatigue calculation is often limited by disk access – consequently it is important that the disk access speed is as fast as possible. All available processor cores are used, to process load cases concurrently. To help you manage this, you can estimate the calculation time, and fatigue analyses can be run in batch mode. The calculation stage of a fatigue analysis can take a long time, especially a rainflow analysis with a lot of load cases.
These data are held separately from other OrcaFlex data, and saved in a separate file.
Open the fatigue analysis tool and set up the fatigue analysis data.plt output files to represent your VIV load cases. Alternatively, for a SHEAR7 analysis, create a set of SHEAR7. With the normal OrcaFlex facilities, set up and run simulations modelling the various load cases the line will experience.The steps involved in performing a fatigue analysis are: Instead, this method performs rainflow cycle counting and collates these cycles into histograms, to be used as inputs to subsequent post-processing – for instance to perform an engineering criticality assessment (ECA). The histograms method does not involve damage at all. OrcaFlex then collates the damage from a number of SHEAR7 load cases. stochastic irregular wave fatigue analysis using spectral methodsĪnother calculation method is SHEAR7, under which damage is calculated by SHEAR7 rather than by OrcaFlex.deterministic irregular wave fatigue analysis using the rainflow cycle counting method.deterministic regular wave fatigue analysis.The damage, having been calculated, is summed by one of the following analysis types: Mooring line fatigue calculates damage from effective tension ranges using T-N curves.Various S-N curve methods recover stress using homogeneous pipe stress (for metal risers), stress factors (for umbilicals and flexibles), or externally calculated stress (suitable for bespoke applications), then calculate damage based on the specified S-N curve.The tool is accessed from the Results | Fatigue analysis menu item.įatigue damage can be calculated in a number of ways, depending on the application: The fatigue analysis tool is essentially a self-contained sub-program within OrcaFlex, with its own menus, data and results.
Fatigue damage is collated and summed for specified load cases and then presented in graphs or tables. The OrcaFlex fatigue analysis tool is a post-processor which calculates fatigue damage using a variety of methods.
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