fcFEM - FEA from start to finish

About the development of the FEM module/workbench.

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bernd
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Re: fcFEM - FEA from start to finish

Postby bernd » Thu Feb 14, 2019 7:02 am

:shock: :)
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HarryvL
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Re: fcFEM - FEA from start to finish

Postby HarryvL » Fri Feb 15, 2019 12:56 am

Got the interface elements working. Identifying the interface elements from FC mesh data and extracting the relevant information was the greatest challenge. The actual finite element implementation is a matter of a few hours.

Example of a sliced block with interface normal stiffness high and shear stiffness zero. The top face is pushed down and restrained in lateral directions, as is the bottom face.


Sliced_Block_1.jpg
Sliced_Block_1.jpg (36.1 KiB) Viewed 118 times

out.gif
out.gif (315.21 KiB) Viewed 118 times


The blocks are assembled in a compound and the Coherence Mesh parameter for the GMSH object is set to FALSE to make sure that two sets of nodes are generated at the interface.
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HarryvL
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Re: fcFEM - FEA from start to finish

Postby HarryvL » Fri Feb 15, 2019 2:30 pm

And it exports well to VTK / ParaView:


Sliced_Cube_1.png
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thschrader
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Re: fcFEM - FEA from start to finish

Postby thschrader » Fri Feb 15, 2019 10:19 pm

Harry, give us a break. :)
Can you explain what you are doing?
No math, just words..
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HarryvL
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Re: fcFEM - FEA from start to finish

Postby HarryvL » Fri Feb 15, 2019 11:47 pm

Hi Thomas,

General/motivation; there are quite a few practical and interesting engineering problems that are hard to do or even impossible with the current FreeCAD/Calculix combination and I don’t think adding more external solvers or waiting for their developer(s) is the answer. For example: mixed meshes (sandwich panels, soil/structure interaction, pre-stressed concrete, bridges), analysis beyond limit points (plastic collapse of frames, plates and soil bodies, non-linear buckling of structures, etc.)

Specific: I built a macro that takes FC mesh and material data and performs the basic tasks of a finite element program. Now I am adding functionality that allows me to do the analyses that were previously out of reach. Zero-thickness elasto-plastic interface elements were high on the list for me as they are a simple and robust alternative for (small deformation) contact problems and can be used in mixed meshes to model the interaction (e.g. cohesive or frictional slip) between 1D/2D structural elements and the surrounding 3D matrix (eg concrete reinforcement, soil anchors, tunnel linings, foundation plates, piles).

Status: basic linear elastic solver framework and curved 2D interface elements work, although I am still running into trouble with more complex contact geometries. This is work in progress.

Next steps: 1) calculate and export stress results (note: interface elements are really handy to visualize contact stresses); 2) extend the solver framework to handle plasticity and collapse (simplest example being the slip and pull-out of structural elements along elasto-plastic interfaces); 3) include simple, traditional, beams and shell elements; 4) include general material and geometric non-linearity for 1D, 2D and 3D elements; 5) Add essential QT5 GUI functionality to provide specific input; 6) Make available for testing.
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Pauvres_honteux
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Re: fcFEM - FEA from start to finish

Postby Pauvres_honteux » Sat Feb 16, 2019 3:11 am

HarryvL wrote:
Fri Feb 15, 2019 11:47 pm
...handle plasticity and collapse (and buckling?) (simplest example being the slip and pull-out of structural elements along elasto-plastic interfaces);

3) include simple, traditional, beams (idealized fasteners) and shell elements (isotropic and non isotropic).
4) include general material and geometric non-linearity for 1D, 2D and 3D elements (fiber reinforced sandwiched material).
5) Add essential QT5 GUI functionality to provide specific input (lots of automagical stuff =Ob ).
....
This is where my salivating glands got into high gear! I interpret this as crash simulations are within reach? Please say yes! :)
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HarryvL
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Re: fcFEM - FEA from start to finish

Postby HarryvL » Sat Feb 16, 2019 8:06 am

I plan to provide basic finite element functionality and bolt on features if and when needed for a specific design challenge. As this will be FOSS at some point, others can do the same.