viscoelastic material simulation in radioss

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi everyone, I need an urgent help from all of you. I am doing a viscoelastic material simulation in radioss using kelvin maxwell law. i have the material data in storage modulus vs frequency so i changed my data into g(t) vs t. now when i go for curve fitting the value of prony term gi is coming greater than one.. As i have read in abaqus manual that value of gi should be less than 1 ,, so my question is this theory applied with radioss also or I can use my prony term coefficient which are coming greater than one.Please clear my concepts regarding this or also as per radios can i take the no of prny term more than 5 during curve fitting,, clear my concpts regarding this

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2015

    i mannu,

    There is no mention of this condition for the Kelvin Maxwell Law in RADIOSS

    Is there a reason specified why this has to be less than 1 elsewhere?

    See in help - Altair RADIOSS > Reference Guide > Starter Input > Starter Keywords > /MAT:
    /MAT/LAW40 (KELVINMAX)

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2015

    The linear viscoelastic model in Abaqus is defined in the shear relaxation modulus as:

    G(t) = Go{ 1 - Sum series (i=1, I=n) gi exp(-t/Taui)}

    As you know Go is the instantaneous shear modulus which is the highest modulus value of the prony series at time = 0.0. After that all moduli should be reduced less numbers than G0 till they go to G-Infiniti and this occurs at t goes to infiniti. Therefore,
    G-infiniti is called the long term modulus at t = inifinit defined by

    G_infinit = Go { 1 - Sum series (gi)}

    There is no way in above equation that gi will exceed 1

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2018

    @Prakash Pagadala I have also some questions regarding this MATLAW.

    I have a constitutive model for a polymer material that I want to test its compression in radios but I do not know how to put my data into radios.

    can you help me to do so?

    thanks  

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2018

    Hi @SamuelIshak

     

    Sorry for a late reply.

     

    You can use LAW65 and if you are using solid elements try LAW 33

     

     

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