I have just finished following on the ANSYS Interface lesson and i think I did everything as its suggested. However, when I ran the “convert to APDL” command,the command prompt says" No valid licence has been found, Press any key to exit". Could anyone know why this happened?
I copied the licence as you advised.I think that took care of that. One final problem, the xml file. When I “run application” for the clavicle example, I get the error message that “The output data file does not exist and cannot be created.” Is it a problem with the working directory or is there an xml template that one should use?
I created a folder titled “output” in the “model” folder and ran the application again but the problem still persists. I still get the error message that “The output data file does not exist and cannot be created.” but the inverse dynamic analysis is still performed.
I imported the stl file of the L4 vertebrae from Anybody using local coordinates and used this geometry in Ansys.
I then read the boundary condition files in Ansys and I got some “spikes” coming out of the L4 vertebrae. I don’t know if it’s because of the APDL template because I only changed the db file name following the example in the tutorials for the clavicle.
I have attached an image of how the vertebrae looks like after reading the load files from AnyBody.
Could you know what is the cause of this? I also noticed some forced are not on the surface of the vertebrae as I expected.
Sometimes muscles attachments are defined closer to their line of action than surfaces or to the locations, where they attach to the soft tissues bands. This creates such representations. At the same time you could be seeing some of the via points that are not necessary on the surface, but follow the muscle action lines. For example, the intervertebral joint nodes, where the IV joint reaction forces are computed are also not on the surface. This is why you see “spikes”, and in case of vertebra this is actually a good picture.
I have one last question(s). The output force from Anybody, it is a point force, right? Is there a way to make it into a uniformly distributed force? or does one have to simply sum the forces by themselves and apply them to a specific selection of nodes instead of directly importing the load step files into ANSYS?
The final APDL script is adjustable - if you have some ideas, please modify the template and make it usable for yourself.
There is no out-of-the-box option for doing what you want. But it would depend very much what you are trying to do. If you want to combine all forces into one - you could it inside of AnyBody and export forces as a CSV file, which can be further read in ANSYS.
But if you want to group many different muscles into many different groups - it could be quite complex.
Thank you for your explanation.
I would just like to apply the forces acting on, say the L4 and L5 vertebrae and analyze the stress distribution on the intervertebral disc between them. As you know, the AnyBody model lacks the Intervertebral discs. However, since I am using different L4, L5 and Intervertebral disc models in Ansys, I have not been able to effectively transfer these forces directly using the output files from AnyBody.
This is why I was checking if summing these forces by myself from AnyBody and applying them on the endplates would alter the results by much. I think this approach is covered in the first lesson in FE analysis with AnyBody.
How does one sum the forces in AnyBody into a CSV file?
As I see it - i would create “central” nodes (that you could also use in FEA) on the endplates of adjacent vertebral bodies and recompute relevant joint reaction forces in these ref. frames on both sides. You could use AnyForceMomentMeasure2 class for doing that.
You can then apply these forces to, say, rigid surfaces of the endplates, if your task is to look at the discs.
I think it might be easier to construct a special output (AnyFileOutput) for you than go through the normal converter.
‘‘I have just finished following on the ANSYS Interface lesson and i think I did everything as its suggested. However, when I ran the “convert to APDL” command,the command prompt says" No valid licence has been found, Press any key to exit". Could anyone know why this happened?’’