LIFE
The LIFE module is used to calculate fatigue Life in a FEM (acting as a 'Digital Twin' of a real structure) with a broad palette of Strain based and Stress based approaches.
The GUI is very intuitive and the analysis process is straightforward.
When both FEM and internal stresses are imported, a 'surface-stress-resolving' technique is employed in order to handle, during the calculation, the plane stress tensors which occur at the component surface (in case of shell modelled components this is not done as stresses are naturally planar on the top-bottom faces).
In the LIFING database only stresses occurring at the surfaces are stored.
Stresses at the surface, if no pressure is applied, are in fact plane stress by definition.
From a numerical standpoint this is not true, as FEM stresses are calculated at Gauss points (internal) and stresses at the surfaces (element nodal stresses) are extrapolated.
LIFE will ignore stress tensor components which are not the plane stress component ones.
This approach implies that a 'good' mesh refinement is required for a good Fatigue Life estimation.
Other than just analysing, the LIFE module can be used for stress tensor time history extraction at selected locations with Virtual Strain Gauge and related Multiaxial Assessments.
The analyst can put on any FEM location (on the surface), a strain gauge and can orient it.
For the selected element
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the sequence of stress tensors can be visualized and dumped in ASCII files
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Mohr Circles at defined instant can be visualized
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Multiaxial Assessment can be performed (scatter plots for showing Maximum Principal direction variation over the time as well as Biaxiality ratio variation over the time.
Time histories can be exported and/or handled as following:
This module allows to perform the following tasks.
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Filter sequence. The following methods are included:
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Non-turning points filtering (always active)
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Racetrack filtering
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Modified. The following options are available:
Scaling (entire sequence or a portion)
Offsetting (entire sequence or a portion)
Negative values scaling
Clipping
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Cycle counted. The Range-Pair method is implemented as per the ASTM STP1006 standard. The output cycles sequence is dumped in a ASCII file. The option to dump the counted sequence in AFGROW format is available.
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Exceedence plots and Range-Mean Hystograms can be visualized
Element stress tensor sequences can be also filtered with the Multiaxial Racetrack Filter.