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Displacements in a DTRAN Solution

User: "mpvnaresh"
Altair Community Member
Updated by mpvnaresh

Hi all 

 In a Direct Transient solution i have given a acceleration load with certain frequency and amplitude.

When  icheck displacements in the location where acceleration is applied, The Displacement curve is a not oscillationg one.Instead it is keep on going.

Can any one help me in getting the oscillating displacements.

I have tried by changing all options of FORM(1) in Displacement output request.but no use.

Please help me in this .

 

 

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

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

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

    Did you specify damping in your model?

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Yes Sir ,

    I specified

     

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    This is not only the model , for all DTRAN analysis i am facing the same problem.

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

    Could you please share the .fem and .out file of the run of any simplified model with this issue?

     

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh
    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Sir

    Kindly let me know if any other  information is needed.

     

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

     sir ..any update ?  

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

    Can you give a try with time Vs disp instead of time Vs accel? 

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Sir 

     

    with displacements as input load it is oscillating .But the question remains same.

    If i convert it into displacements obviously it oscilates as we are giving displacement directly.

    But my load case is in acceleration i need to apply it in accelerations only.

     

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

    Could you please consider initial velocity for the base setup where you have time Vs accel.Transient initial conditions are defined using a TIC Bulk Data Entry. Initial displacements and initial velocities can be defined. This should help you to avoid drift in the displacement plot and get oscillating plot.

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Thanks For the response .

    I will try this and update you .

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Sir 

     

    I am not able to give Input of Initial conditions . Can you please help in how to do this?

    How to create TIC Bulk data entry. And also i have no data for initial displacements and initial velocities then how to get those values. 

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

    I got help from my colleague to calculate the initial velocity based on the given acceleration curve.I remember we provided initial velocity of -624.0 and with that we got proper oscillating plot.Attached is the fem file.

    <?xml version="1.0" encoding="UTF-8"?>Oscillating plot.JPG

    Unable to find an attachment - read this blog

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Sir

     

    I really Appreciate this.

    Thanks a lot for your time.

    I think this is solved. 

    But when try to integrate the acceleration curve to get celocity i am gettion a Zero velocity. Please help me in the methodology for getting velocity.and also how did you created TIC (V).

    When i go go to load type page Velocity type is Blank.

     

    Thanks again for the support sir.

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

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

    TIC V you can create from constraints panel & set the load type to TIC V.Sorry i cant provide you right now the hand calculation which we did to calculate Intial velocity,  as i am away from office desk.However,I do have the math we performed in HyperGraph to crosscheck.PFA mvw file for same,

    <?xml version="1.0" encoding="UTF-8"?>TIC V.JPG

    Unable to find an attachment - read this blog

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Thanks Sir

     

    User: "mpvnaresh"
    Altair Community Member
    OP
    Updated by mpvnaresh

    Sir

     

    I calculated Initial Velocity and applied as TIC(V).

    But after the compltio of acceleration cycle displacements are cumulative.

    (which mathematically  may true, As Acceleration=0,  Velocity which is integral of Acceleration = constant , Then Displacement is a straight line which is cumulative )

    How can we make the  velocity, displacement to be zero after the load (Acceleration)is removed . 

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