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

Changes

- 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:

- Execute
*extract.bat*. - Open the
*Setup model*window and press*Update all*and then*OK.* - 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

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) .