kjoint2 problems

lambefr
lambefr New Altair Community Member
edited October 2020 in Community Q&A

Long story and potentially many questions in the same post but all related to the same issue and I ned help!  I can't seem to understand how my kjoint2 spherical connection between 2 RBODY is behaving.  What I am trying to model is a suspension ball joint in Radioss and I want the rotation to be limited to a certain maximum angle in ANY direction from vertical (creating a conical shaped limit envelop). I created a simple problem to resolve my issues but it doesn't seem to work.

 

I cerated 2 node reference systems in such a way that they move together and that their Z axis is always coaxial.  I then limited my kjoint2 in Saz- and Saz+ to ±1 rad but it does not behave as desired.  When I plot my TH/spring, I can see that RZ of my spring DOES respect the 1 rad angle limit.  But this does not make sense with the visual behavior and the true angle that I can plot in Hyperview that cleary goes over 1 rad.  Also Rx and Ry are showing rotation which again does not make sence with the visual behavior.

 

Any help to resolve this is appreciated!

Thanks

 

All my simple model files:

 

<?xml version="1.0" encoding="UTF-8"?>Radioss_BJ_angle_V19_2.thumb.png.a87d96ea37cae68bf85097446dd55472.png

 

Radioss_BJ_angle_V19_5frames.gif.140abfaeee206521cd727a29e65e37b2.gif


 

 

Unable to find an attachment - read this blog

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2017

    Hi,

    We are working on your query and will update you very soon.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2017

    Hi,

    I feel this is the intended behavior of the spring. For spherical joints it will be free to rotate in all directions.

    You can try with  negative and positive stopping displacement in all directions and see.

    <?xml version="1.0" encoding="UTF-8"?>joint.PNG

  • lambefr
    lambefr New Altair Community Member
    edited July 2017

    Hi, thanks for the answer but it does not answer my question.  I know how a sperical joint is suppose to behave... all rotations are free!  No need to explain that to me.

     

    What I am pointing out is that I want to limit the angular articulation of my srping in a certain way and although the moving skew /MOV that I created are visually moving correctly (i.e. their Z axis are always coaxial - see gif image above), the spring does not seem to follow my skews correctly.

     

    Why is my kjoint2 not behaving as I would expect?