inertia relief

Main Forum
1

I hunger for someone’s help.
I emplyed GaitFullBody model and exported muscle forces calculated in AnyBody and applied as boundary conditions to femur generated for Abaqus. I am confused about the function of “inertia relief”(pictures show).

How can I utilize it in Abaqus? I submitted the job and I found the femur was out of the shape. What kind of mistakes I have make?
I will preciate if some can help me. Thanks!!!

2

Dear Yao Tommy,

I am sorry for answering so late.

Our loads are supposed to keep the body in rest, however, for one or another reason it might happen that the residual generate some motion to the bone.
Inertia Relief is an option that allows to remove such motion.

The deflection seems to be a little extreme - this may happen due to several reasons:

  1. just visual - please check that the results are not being scaled for the Abaqus visualization
  2. Material properties of the bone are not correct - for example, the Young’s modulus is not representing the elasticity of the cortical bone.
  3. Error in the simulation - what is the maximum magnitude of the muscle forces? Do you use just the standard GaitFullBody model and corresponding bones? or is it a custom model?

Regards,
Pavel

3

Thank you for your answer.
I think it is attributed to the deformation scale in abaqus visulation. I changed the value of deformation scale factor from “247” into “1” and the extreme deflection disappeared. Is that correct?

4

Yes, i think it is. FE packages typically exaggerate deflection by default to highlight minor deformations.

Regards,
Pavel