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Thread: Spring Tied interface

  1. #1
    Join Date
    Apr 2014

    Default Spring Tied interface


    I am trying to use the spring tied interface contact to connect 2 objects. Essentially I have 2 tubes (one inside the other) I want the inner and outer tubes to be forced to move together even though they are not in direct contact as pressure is applied. I thought using a spring contact would be great for this but I can't seem to get it to work. I created the preview file and it gives the error "unrecognized tag 'spring' ". I attached my files below, but any help with how to use this type of contact or if there is a better way to ensure 2 objects that are not touching move together would be helpful.

    Attached Files Attached Files

  2. #2
    Join Date
    Dec 2007


    Hi Andrew,

    I am not sure that I understand what you want to do exactly. The tubes are not touching but you want them to move together: Do you mean that only the inner surface of the outer tube and the outer surface of the inner tube must move together? Is each tube allowed to deform along any direction? In any case, you may choose to enforce linear constraints in FEBio, e.g., constrain the displacement degrees of freedom of nodes on the outer tube to match that of nodes on the inner tube. You can also consider using a tied contact interface (that would be my first try): It behaves as though you tied two surfaces with very stiff springs.



  3. #3


    Hey Andrew,

    I don't know if you solved this already, but I can explain that error. In FEBio spec version 2.0, springs are placed within the Contact section in the .feb file automatically when exported from Preview, but need to be within a Discrete section in order for FEBio to run the file. I made this change to TubesTied.feb and it ran without any errors.


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