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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) .

Parallel execution option available

As mentioned, the standalone version will be discontinued and only the source will be provided for running under Matlab. This is because the deployed version behaved slightly different than the source version, and ran much slower. So, going forward, development will not be halted by limitations of the deploytool.

One of the limiting issues of the deployed version was in parallel execution of the code. It ran fine in Matlab, but not when deployed. So now this feature has been re-implemented, as of Fatlab 2.022. It uses the Parallel Computing Toolbox. Fatlab will detect whether the toolbox is installed and enable it accordingly. The user can then select a number of cores for the execution under Run Analysis.

Special thanks to Martin Dahl Kilt for helping with this feature and performance issues.

Support for shell elements

As of version 2.008 Fatlab will support also support the following ANSYS shell elements; SHELL63,  SHELL181 and SHELL281. Additionally, the wireframe display now works for both plane and shell elements as well as solid elements of course.



Fatlab 2.006 available

Fatlab 2.006 is now available (source only, the standalone version will not be updated for the time being). The source code has been moved to SourceForge and is now under SVN version control, thus the change in version numbering. The commit log is now public.

The new version includes support for 2D ANSYS elements; PLANE42, PLANE82, PLANE182 and PLANE183. Like all other elements, only the corner nodes are read, so the will be limited difference between the Q4 and Q8 elements in Fatlab.



  • In some cases, the extraction of peaks/valleys from the stress signal were faulty. The extraction routine could not detect a peak consisting of two identical values, but it can now. The problem would occur e.g. for a sine load with an unfortunate number of sample points
  • For very long lives Fatlab would report infinite utilization under some circumstances. This was due to the use of single precision format in some of the calculations, which maxes out at approximately 10^38. Now using double precision, this is no longer an issue.
  • There were some problems using Matlab 2016a & b (graphics only) which have now been fixed, so Fatlab will run equally well in any Matlab version from 2015aSP1 and forward.

New example added

A new example have been added, which shows how to setup a model with a bolted joint including pretension. The model is also subjected to “bi-linear loading” due to two hinged actuators which are either pulling or pushing, leading to very different stress responses depending on the loading direction.


Improved user interface

The newest version of Fatlab (1.41) contains a number of improvement in the user interface:

  • Individual parts of the FE model can now be turned on/off, both visually and in the calculations. Parts are now also highlighted when selected.
  • Most view modifying control elements have been moved to the toolbar
  • Toggling eg. coordinate system etc. on/off does now not reset the current plot
  • Element borders can now be hidden/shown
  • 3D connexion pointing devices are now supported
  • Many bugfixes and speed improvements, e.g. on loading


Matlab HG2 supported

Fatlab 1.119 and onwards now support the Matlab Handle Graphics 2 engine (HG2) which was implemented in Matlab 2014b.

This means significantly improved performance for 3D visualization, e.g. during rotation of the model, and also includes antialiasing of the edges, so things look a lot nicer.


Programmatically, the main difference is that handles are now objects rather than numbers. This change means that when exploiting the advantages of HG2, previous Matlab versions will no longer be supported, i.e. future versions of Fatlab will require Matlab 2014b as a minimum.


Fatlab 1.109

New release: Fatlab 1.109


  • Now showing utilization as default contour plot after finalizing a run. Also selects the node displaying the highest utilization under the graph-plot.
  • Edge detection speed significantly increased during model import.
  • Implemented several “load-reduction” techniques under load-setup for calculation speed-up.
  • Added option to “run visible nodes only”, i.e. disregarding all hidden nodes during calculation.
  • Bugfixes in window resize function and “show parts”.


Fatlab 1.102

Fatlab 1.102 is now available for download. In addition to several bugfixes, the following new features have been implemented.

Lightning can  now be applied, making it easier to perceive the depth of the model. The light is currently fixed to the model front, i.e. the back of the model will be shaded, also when rotating. This will be improved eventually.

Additionally, an option to rotate the camera view instead of the model is now available. This is activated using the new slightly bluish Rotate 3D button in the toolbar. The old one is still available, because they work in slightly different ways. Most notable, the new one allows continuous rotation of the elevation angle, which is limited to +/-90 degrees for the old.




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.