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# How to simulate muscle material properties?

## How to simulate muscle material properties?

(OP)
Hi! I'm a beginner in the Solidworks world. I'm trying to simulate the strains suffered by the rectus femoris muscle. I already created the morphological model which contains the muscle itself and the two tendons. I have come across some doubts/problems when trying to figure out which material and properties should I use. My doubts are the following:

1. I have read a lot of information on the internet and several papers, trying to find out which kind of material (and its properties) should I use to fit the muscle properties. That is quite hard since most of the studies are not done with Solidworks (I know that maybe it is not the best software available for this purpose) but I have to use it and I have to figure out how to do it as soon as possible. But going back to the question, since the muscle is non-linear. anisotropic, almost incompressible and viscoelastic; I have come to the idea that the best way to simulate it is using a non-linear study and an hyperelastic material with a Mooney-Rivlin model for the muscle. The problem is that I am not really sure about that, and in case that I am right, I am quite lost about the parameters I need to use for defining it. So I hope you can give me advice about if it is correct and if it is, about the parameters that I need to use.

2. This muscle is bipennate, which means that on one side its fibres are oriented with 10 degrees of pennation angle and the other side is oriented with -10 degrees of pennation angle. The pennation angle is the angle formed by the fibres and the line of action of the muscle (You can get a better idea of what I am trying to explain with the following image).

This means that the muscle is very resistant to the strains in both angles. Is there any way to specify this? I mean, to tell that the material resists the strains along an axis with 10 degrees and not along its longitudinal axis? I thought about an orthotropic material, but I think it does not really fit my needs. So I would appreciate it if you could help me to find out how to specify this if there is any way of doing it.

Thank you so much in advance!

### RE: How to simulate muscle material properties?

I have not been successful trying to get Solidworks to work with "flexible" or "stretchable" materials. I will be interested to see if any of the experts on here come up with good suggestions for you.

### RE: How to simulate muscle material properties?

First of all you would not be able to do a simulation like that with standard solidworks or even solidworks premium. You would need a higher end package (at least Simulation Premium. Something that provides access to defining materials with non-linear orthotropic properties. For the Dipennet type geometry you may wish to use shells and create one half of the muscle and then use symmetry in the simulation software.

Standard Solidworks only give you limited Linear static analysis on parts only.
Premium Solidworks gives you Linear Static analysis on Assemblies and parts and much more.
Solidworks Simulation Premium gives you non-linear capabilities.

You would need to define all of the aspects of the material though and for that I cannot help. I believe that you would need to use orthotropic properties as I believe that there are differences depending on how the material is oriented to the loads.

Regards,
Jon

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