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RBE2 Application

User: "Altair Forum User"
Altair Employee
Updated by Altair Forum User

Dear All,

I want to ask about RBE2 application, please see my picture below.

I have a simple plate, and I want to give constraint on 2 holes on top, and forces (160kN on both hole or 80kN each hole) on 2 holes on bottom

Why my simulation result (stress & deformation) totally different?, because in my opinion, case on the problem 1 and problem 2 are same....

Am I miss something?

Best regards,

Iron_Man

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

<?xml version="1.0" encoding="UTF-8"?>Problem_1.PNG

<?xml version="1.0" encoding="UTF-8"?>Problem_2.PNG

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    User: "Rahul Rajan_21763"
    New Altair Community Member
    Updated by Rahul Rajan_21763

    To me it should give different results.Point of load (distance)is varying.Any specific reason for using only specific nodes for creating RBE2/why not selecting all nodes of hole?

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    @Rahul R,

    Thank you for your response, you said 'To me it should give different results.Point of load (distance)is varying' could you telling me more detail about it? or you have reference documents to understand about it?

     

    'Any specific reason for using only specific nodes for creating RBE2/why not selecting all nodes of hole? '

    I use RBE2 on half of hole to describe shaft contact area.

     

    Thank you,

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi @Iron_Man59

     

    I think in second case you will see a moment around the SPC point and your displacement results will be huge compared to first one. 

     

    Instead leave SPCs as in case one and apply force/load as in case 2. Your results should match. 

     

    User: "tinh"
    Altair Community Member
    Updated by tinh

    No no, I think it is due to another reason...

    assume X is horizontal direction

    in case 1, 2 holes with force can have X deformation 

    but in case 2, they are impossible. rbe2 is similar to a rigid bar which constrained x deformation. so result of 2 cases will be different. could you check case 2 deflection is lower than case 1?

     

    SPC and Force are same, but structure stiffness are different

     

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Dear All,

    Thank you for your response,

    @Prakash Pagadala,

    'I think in second case you will see a moment around the SPC point and your displacement results will be huge compared to first one.'

    No, the displacement on problem 1 is bigger than problem 2, please see my picture below.

     

    'Instead leave SPCs as in case one and apply force/load as in case 2. Your results should match.'

    What the problems that should be compared to your statement above? Problem 1 VS Your statement or Problem 2 VS Your statement?

     

    @tinh,

    'could you check case 2 deflection is lower than case 1?'

    As what I mention above, YES, the displacement on problem  is lower than problem 1

     

    All,

    Please see my actual problem below, maybe you could give better solution how to model it on hyperworks,

     

    Thank you,

    <?xml version="1.0" encoding="UTF-8"?>assy_problem_sketch.png

     

     

     

     

    <?xml version="1.0" encoding="UTF-8"?>Problem1 VS Problem 2_Displacement.PNG

    <?xml version="1.0" encoding="UTF-8"?>Problem1 VS Problem 2_VMStress.PNG

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Here are my three cases: 

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

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    @Prakash Pagadala,

    I see that the result on problem 1 (left picture (biggest one)) is similar with the result on problem 2 (right picture(top)), my question, which is better to use?

    if you have reference to study about that problem above please share to us.

    thank you

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    My case here is different. But I think in case 2 there is some local stiffness due to rigids. 

    User: "tinh"
    Altair Community Member
    Updated by tinh

    Hi.

    Just use RBE2 at SPC positions

    with LOAD positions => use RBE3 to eliminate over-stiffness

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    @Iron_Man59

     

    Few questions:

     

    1) Why only half of the hole is constrained and loaded?

    2) Can you use RBE3 for loading?

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi @tinh,

    I never used RBE3 before, please give me guidance to use it (what is RBE3?, what is the differences with RBE2?, when to use it?, etc)

    Thank you

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    I never used RBE3 before, please give me guidance to use it (what is RBE3?, what is the differences with RBE2?, when to use it?, etc)

     

    In short,  RBE3 does not add stiffness like RBE2

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    @Prakash Pagadala,

    Yes, I know about it, BUT I need the information how to use RBE3 correctly!!!

    Any reference?

    Thank you

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi,

    Please go through this webinar on using RBE's with examples. Hope this will be helpful.

     

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi @George P Johnson,

    Thank you for sharing the video, but unfortunately the video is broken.

    I can not play it.

    Please share another link.

    Thank you,

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi,

    This video is working fine at my end. I just played the same in GOM player. Once the file starts click the video player screen and it will start.

    Please try and update

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi @George P Johnson,

    I've update my windows media player and re-download your video, but the video is still error to play.

     

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

    User: "Altair Forum User"
    Altair Employee
    OP
    Updated by Altair Forum User

    Hi,

    This seems very strange!!!...The same worked for me in Windows Media Player.

    I'm reattaching the file once again. This is in .swf format. Recommend you to download GOM player and try playing the same.

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

    Unable to find an attachment - read this blog