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FEBio 1.5 Release

David Rawlins's picture

We are excited to announce the arrival of version 1.5 of FEBio (Finite Elements for Biomechanics). This new version can be downloaded at FEBio is an open-source finite element package, specifically designed for solving problems in the field of computational biomechanics. This new version includes some major changes and contains a number of new and exciting features. Some of the noteworthy changes and additions are listed below.

- Multiple solutes.  FEBio has been updated to allow different solutes to be used in different regions of a model.  For example, adjacent regions of biphasic-solute materials need not have the same solute.  A solute table must now be provided in the input file, which lists all the solutes appearing in a particular analysis.  Each region that contains solutes must provide the solute id's corresponding to the entries in the solute table.  For biphasic-solute materials, backward compatibility is maintained with the FEBio 1.4 file format, though only one solute may be used throughout an analysis in the old format.

- Triphasic materials.  Triphasic materials have been implemented in this version.  A triphasic material consists of a solid, a solvent, and two solute species that are monovalent counter-ions.  The solid matrix may carry an electric charge (the fixed-charge density), in which case the triphasic material will undergo swelling due to Donnan osmotic pressure.  Electric potential and current density are evaluated in all triphasic analyses.

- Cell growth.  A cell growth material has been implemented, which describes the growth of cells as driven by osmotic forces, due to the increasing (or decreasing) content of intracellular solid and membrane-impermeant solute.

- Relative boundary conditions.  Relative boundary conditions have been implemented for all nodal degrees of freedom of displacement, fluid pressure, and solute concentration.  Relative boundary conditions are meaningful only in multi-step analyses.  When a nodal degree of freedom is specified to be relative at a particular step, the value prescribed for that node is superposed over the value of that degree of freedom at the end of the preceding step.

All documentation has been updated and can be downloaded from  The release notes have been updated and can also be downloaded separately from the Documentation tab of the software page.  The svn logs have been added to the Help directory of the download.  These can be useful for developers who want to know which files in the source code were effected by particular changes.  Online versions of the manuals are also available at

FEBio's supporting software, PreView and PostView, have also undergone some major improvements, making it easier than ever to create, define and analyze finite element models with FEBio. These packages can also be downloaded from

We encourage you to report any problems or questions on the Software Forum:

We also would like to take this opportunity to thank our ever-growing user base for helping us make FEBio a great tool for computational biomechanics. As always, we would really appreciate any feedback that you may have to help us improve FEBio.

Kind Regards,

The FEBio Software Team

     Steve Maas
     Dave Rawlins
     Gerard Ateshian
     Jeff Weiss
     Ben Ellis

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