Update all FE data

A new feature has been added in Fatlab 1.98: in the Setup model window, the user can now press the Update all button to read all FE data again (model + all FE stress files).

This is very useful during an iterative design validation process, when the FE model has been updated e.g. with a new reinforcement or some detail change. Both the mesh and the stress distribution may change and the Fatlab analysis must therefore be updated.


Extraction of the model and FE stress files from ANSYS can be achieved using a batch file calling ANSYS in batch mode and executing the macro fatlab.mac (both files are included in most examples).

Thus following a FE model update, only the following few steps are necessary to obtain an updated fatigue assessment:

  1. Execute extract.bat.
  2. Open the Setup model window and press Update all and then OK.
  3. Open the Run analysis and press OK.

The effect of an update in the FE model on a running Fatlab model can thus be evaluated in approximately 7 mouse clicks total.

Additional support for nonlinear FE models

Fatlab 1.71 now features a much more advanced handling of nonlinear FE models.



Previously, it was only possible to select either a linear or bilinear load-stress relationship, now however both 1D and 2D interpolation routines have been implemented. It is thus possible to setup some quite advanced models and significantly reduce the error from using superposition with nonlinear models.

An example using all above load-stress relationships will be provided.

Comparison of cycle counting techniques


A comparison of the 3 implemented cycle counting techniques in Fatlab is now available.

Fatlab supports Reservoir counting and two different implementations of Rainflow counting, on counting half cycles and one counting full cycles.

Apparently, there is quite some difference in the results when counting cycles in very short time series, whereas the difference evens out for longer more random time series.


Please refer to the Theory reference for details and recommendations.


Welcome to fatiguetoolbox.org, the home of Fatlab – a free open source fatigue analysis software developed in Matlab.

Fatlab works by postprocessing results from FE analyses and combining these with load-time series in order to perform a detailed fatigue assessment of a component. It handles both multiaxiality (through the critical plane method) and non-linear FE models.

Fatlab was developed at Aalborg University by M. M. Pedersen in collaboration with R&D A/S. It is part of the project “Wind load simulator for function and durability test of wind turbine drive-trains” and has been partly sponsored by the Danish Energy Technology Development and Demonstration Programme (EUDP) .