Query on PBUSHT defined with KN line having non-linear force vs displacement graph

Gopal SinghRathore
Gopal SinghRathore New Altair Community Member
edited August 2022 in Community Q&A

Hi,

I took a single spring element defined with CBUSH and assigned it a non-linear force vs displacement graph. When I apply one of the force values to it and check for displacement in spring, I am not able to correlate it with force vs displacement data given as input.

Please check.

File is attached here for further reference.

Thank you

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Answers

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited August 2022

    Your Force x Disp curve looks wrong.

    As the elongation gets negative, your force increases positively.

    image

     

    I would expect something like this:

    image

    https://www.coursehero.com/study-guides/boundless-physics/hookes-law/

  • Gopal SinghRathore
    Gopal SinghRathore New Altair Community Member
    edited August 2022
    Adriano A. Koga_21884 said:

    Your Force x Disp curve looks wrong.

    As the elongation gets negative, your force increases positively.

    image

     

    I would expect something like this:

    image

    https://www.coursehero.com/study-guides/boundless-physics/hookes-law/

    Hi,

    Thank you for your reply.

    I am attaching the scenario where my spring is in function . 
    Can you let me know how this can be plotted to represent the force -deflection curve in optistruct.

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited August 2022
    Gopal SinghRathore said:

    Hi,

    Thank you for your reply.

    I am attaching the scenario where my spring is in function . 
    Can you let me know how this can be plotted to represent the force -deflection curve in optistruct.

    you curve should be input in OS as a function of Force x Deflection for your spring. Similarly to what I've shared before.

    In the right hand side you will have spring elongation, and at the left hand side, compression.

    Yours is defined flipped.

     

    image

  • Gopal SinghRathore
    Gopal SinghRathore New Altair Community Member
    edited August 2022

    Hi,

    After flipping the curve (Image attached below), solver seems to give results as per force vs deflection table defined.

    One question here is that in my case, there is a preload assigned to spring element and my force values would not be coming negative but as spring element force can be positive or negative based on applied load direction. So in this case, when spring element takes negative value, solver seems to follow the last two points slope .

    Is there a way to apply force vs deflection graph with pre-load as in my table.

    I can see that in PGAP property but cannot see force vs defection curve assigning to it.

    Thank you for your support.

    image

     

     

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