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Thread: How to load a model in different speeds?

  1. #1
    Join Date
    Nov 2016
    Posts
    3

    Default How to load a model in different speeds?

    Hi,

    I had built a model of a human heel trying to simulate human gait.
    I'm loading the model through displacement of another part (plate- which simulates the ground) toward the lower part of the heel. The contact condition between the plate and the lower part of the heel is 'sliding'.

    I?m looking for a way to mimic the velocity of the gait by loading the heel in different speeds.
    I was trying to change the curve graph of the plate displacement by using the curve editor, but I got the same results every time I change the curve regardless of the curve I had selected.

    I would like to know if there is a different way of doing this?

    Thank you for your time and help.

    Hadar

  2. #2
    Join Date
    Nov 2016
    Posts
    3

    Default

    I would highly appreciate someone's help with this.

    I tried to run a dynamic simulation instead of static but it seems like the sliding contact does not work yet for dynamic problems.

  3. #3
    Join Date
    Nov 2007
    Location
    Salt Lake City, UTAH
    Posts
    1,664

    Default

    Hi Hadar,

    Regarding your first post, in a (quasi-) static analysis, there are no inertial effects. If in addition your materials are all elastic, then the results will indeed not depend on the velocity at which you are loading the heel. This would explain why you don't see any change in the results when you alter the speed of the plate.

    Regarding your second post, FEBio's contact algorithm should in principle work with dynamic analysis, however, they are not guaranteed to preserve energy, and as a result, we advice caution when using contact in dynamic analysis. I recommend using a very small time step so the contact can be resolved accurately, but even then, there will be no guarantee that energy is conserved.

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

  4. #4
    Join Date
    Nov 2016
    Posts
    3

    Default

    Hi Steve,

    Thank you very much for your response.

    I am curious to know if there is a different way to run these kinds of simulation in FEbio when there are basically two parts that come into contact with each other, and one activates load over the other? (while taking into account the speed of the loading)
    By the way, I'm using hyper-elastic materials (Neo-Hookean and Ogden) for some of the materials in the model and Isotropic-elastic for the rest.

    Hadar

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