Learning Forum

[Kyle Villalobos]

Hi,

I believe I have made a post on here before. I am trying to use ANSYS LS-DYNA's simulation capabilities to simulate concussions and other brain injuries. At this stage, the model can be quite crude. I just want to gain a basis level of understanding to build off of that allows me to see how the brain might move in the skull based on a given impact. I believe the brin has a high coeffcient of restitution, so even a little change in the angle or amount of force applied can affect the ways the brain moves or makes contact with the skull. These slight changes can create huge chnages in terms of patient symptoms of injury. I can use average brain sizes/volumes and average skull sizes/volumes to do this; I am not concerned about the effects of the neck at this time. Essentially, I want to see how a smaller spheroid with a very soft gelatin-like texture/strcuture material moves inside a larger spheroid that is far more rigid. The gap between these two surrogate spheroids is known anatomically as the sub-arachnoid space, and is about 1/4 inches. I was hoping to apply the force somewhat simply, using arrows or some type of vector, in a drag-and-pull sort of way. A good example of what I mean can be found here: https://phet.colorado.edu/sims/html/collision-lab/latest/collision-lab_all.html

 

I like this simulation, but it doesn't allow me to reflect 3D-motion or put the objects inside one another. But the method of applying force is quite simple and is analogous to what I'm looking for.

 

Now onto the ANSYS relevance... I have downloaded the own LS-DYNA package and the ANSYS Workbench which contains an LS DYNA mechanical module??? I am just really confused and overwhelmed by the capabilities of ANSYS and its intracacies. I see there's an ANSYS Mechanical LS-DYNA as a part of the workbench, and a separate Pre-Post LS DYNA package along with a powershell. It's just a lot. Could anyone help guide me on how to proceed in creating my model of the brain and skull-- which can and should be crude in their geometrical design, though the consistency of the materials can hopefully be quite accurate-- and how to simply apply force to this model. 

Also, I see that LS DYNA, the individual package NOT the mechanical module as a part of the workbench, has a head impact positioning feature. But it seems you may need to upload a model from somewhere else. I created two sphereoid objects in Pre-Post, but don't know how to upload these into the head impact positioning feature, or if I even can/should do that.

 

Just really confused on how to proceed, I'm only 16. If anyone knows of any other simpler software that may be better for my purposes, I'm open to that. I just heard that LS DYNA has the ability to reflect biological tissues, like brain and bone, and the way the respond to force stimuli. 

[Kyle Villalobos]

Sorry, just to clarify, I would like to state that the brain is encased in cerebrospinal fluid which fills in the aforementioned subarachnoid space. The cerebrospinal fluid be assumed to be water and have all the same properties, as it is 99% water.

 

If it is much simpler to not account for the brain's 'floating' in this fluid then I won't. It could be just assumed to be an empty space/gap between the the skull and brain (AKA to spheroid objects). I have attached sceenshot photos that help explain the above post further. 

 

https://www.youtube.com/watch?v=gT5IqJsr6N8

https://www.youtube.com/watch?app=desktop&v=IM5CPxkELQU

These videos contain head models, though I'm not sure if they contain a brain. Am I able to access these models publically and easily or do I have to create them myself? In either case, would I do so in the LS DYNA Pre-Post or the ANSYS LS DYNA Mechanical module as a part of the general workbench?

 

Other things worth mentioning, if not able to simply apply force/velocity/accerleration vectors like I am able to in the post's linked simulation, I could make the force come from making the head come into contact with a wall, another head, or just a cube, all being solid, rigid bodies. Injurous brain movement/concussions normally occur at around 60-100 Gs of force, for reference. 

 

I don't need to see in-depth analysis of the brain's injury to neurons or anything like that, just a way to gain a basis of understanding for how the brain might move in the skull in high-force collisions/impacts, on a MACRO-level. I'm hoping to create graphs of the brain's movement, and/or force (acceleration and velocity graphs) from the data I collect. I believe ANSYS can create these graphs but I'm not sure how to do so.

 

Thank you for your time!

[Alex Rycman]

Hi Kyle, 

It's amazing to see that you are taking interested in the brain injury biomechanics, the topic that you would like to explore more is Finite Element Human Body Models (FE HBM). Please search and you will find good books talking about FE HBMs.

Before you are going to start generating your own model, you can look at available free models HBMs e.g., THUMS models. Alternatively, you can start your journey with dummy models. You can download them from here: https://lsdyna.ansys.com/lstc-dummy-models-overview/

User: user

Password: computer

I think for now it would be easier to run LS-DYNA via LS-RUN and pre-post analysis using LS-PrePost. Here you can find a presentation regarding LS-PrePost   https://ftp.lstc.com/anonymous/outgoing/lsprepost/Training/Intro/LS-PrePost_Intro.pdf

Lastly, have a look at the examples available at https://lsdyna.ansys.com/knowledge-base/simple-examples/

Good luck, 
Alex.

[Kyle Villalobos]

Alex, 

Thank you so, so much. I really do need all the help I can get. I am looking at the dummy models right now, and they're excellent. However, I'd also like to look at the HBMs and THUMS models you mentioned. Would you be able to provide me a link or source to those? I'm not sure how to find them.

 

In addition, I was able to import the dummy models. How would I import these HBMs/THUMS models?

 

Lastly, what is the process of applying force to these models? It seems to be a complicated process in LS-DYNA. Do I need to have a wall or some other contact surface, am I able to apply "free force" (analogous to the PHET simulation linked in my original post)?

 

Thank you sincerely,

Kyle

 

[Alex Rycman]

 

Hello, 

I would recommend searching for THUMS model in your search engine and I am confident that you will find appropriate links. 

To open k, key or dyn files you can use LS-PrePost you can download it from here:

https://ftp.lstc.com/user/lsprepost

user: user

password: computer

Simulating a HBM is quite complicated. I strongly recommend that you will take a look at the examples here https://lsdyna.ansys.com/knowledge-base/simple-examples/examples-manual/load/

Thanks,
Alex