Load at a Cross Section

[Hossein Mokhtarzadeh]

Hello all,

Is there a simple method to report loading (moments and forces) at a cross section of e.g. tibia from OpenSim?

Cheers,
Hossein

[jimmy d]

Depends on your definition of 'simple'. You can calculate Joint Reaction Loads between bodies, so you could split the tibia into multiple bodies, each with a weld joint between, and perform a joint reaction analysis to find the forces at each weld joint.

[Hossein Mokhtarzadeh]

Thanks a lot James!

Splitting the tibia is a great idea. I was thinking if we can define e.g. a plane (crossing the tibia, & muscles) and then parametrically change it (its height from e.g. ankle joint) and get forces (or JRF) at any point this plane crosses the tibia so that I can avoid splitting the tibia into multiple bodies. I doubt this can be done easily. Am I right?

I gave the example of tibia as it is quite simple, however, if we consider e.g. spinal joints then having multiple bodies and changing muscles' origin and insertion could be quite challenging when splitting the vertebrae into multiple bodies.

I wish to do what we perform theoretically using Free Body Diagram and crossing the bodies at any point (e.g. using a plane). Then I can have muscle forces at that level, and calculate the forces and moments acting on the bodies at that cross section. I wonder if you may have any ideas. Thank you.
Cheers,
Hossein

[jimmy d]

I doubt this can be done easily. Am I right?

You are right, that cannot be done.