Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: How to use stress relaxation curve data in modeling viscoelastic material in Ansys v.

  1. #1

    How to use stress relaxation curve data in modeling viscoelastic material in Ansys v.

    Hi every one

    I have the tensile test stress -relaxation data from literature and the function of curve fitting on them .
    But I dont know how to use them in modeling viscoleastic material
    in Ansys v.10
    beacause the predefined viscoelastic models in Ansys needs the shear and Bulk module vs time or shift function ,volumetric response coefficients .

    Thanks a lot

  2. #2
    Join Date
    2000-02
    Location
    Boston, USA
    Posts
    3,328
    I don't know what material you are working with, but the assumption that most people make is that the material is almost incompressible and hence the shear relaxation modulus can be approximated from the uniaxial relaxation modulus divided by 3.

    -Jorgen
    Jorgen Bergstrom, Ph.D.
    PolymerFEM Administrator

  3. #3
    thanks for your advise
    so how can I use the stress relaxation data to obtain bulk module or shear
    module vs time?
    would you mind help me more
    thanks

  4. #4
    Join Date
    2000-02
    Location
    Boston, USA
    Posts
    3,328
    I don't know what polymer that you are working with, but you can probably assume that the bulk modulus is 50 times the Young's modulus, and that the shear modulus is equal to the Young's modulus divided by 3.

    -Jorgen
    Jorgen Bergstrom, Ph.D.
    PolymerFEM Administrator

  5. #5
    Join Date
    2008-06
    Location
    BANGALORE
    Posts
    25

    Ansys

    hi
    once you used the curve fitting technique in ANSYS for different model with experimental data, one of the model will closely matches with experimental data, that material model can be used for further analysis.
    Regards-
    Nandish R.V
    Sr. Lecturer
    Dept. of Mechanical Engineering,
    The Oxford College of Engineering,
    Bengaluru - 068

  6. #6
    For using the fitting data option in Ansys I need to have the shear module and
    bulk module data vs. time

  7. #7
    Join Date
    2008-06
    Location
    BANGALORE
    Posts
    25

    curve fitting

    no. only strain vs. stress data (experimental data) is required for curve fitting. later for further analysis you may need youngs' modulus and poisons ratio.
    Regards-
    Nandish R.V
    Sr. Lecturer
    Dept. of Mechanical Engineering,
    The Oxford College of Engineering,
    Bengaluru - 068

  8. #8

    Viscoelastic Ansys

    Hi nandish.rv

    So wat is the procedure for converting the stress strain curve into bulk modulus VS TIME or shear modulus Vs TIME. so that we can input using the curve fitting tab in ANSYS.

    Plz can you explain the procedure clearly.

    Thanks

  9. #9

    stress relaxation

    dear all,

    I am new user to this family and ABAQUS as well. I tried to model my viscoelastic materials during the uniaxial compression. The stress relaxation data was used to get prony parameters in ABAQUS.

    To check if the model is ok, I ran a stress relaxation simulation. However, no stress decay at all ! The shape of force vs. time (displacement) during loading looks reasonable. BUT I really do not understand why the force did not decay during holding in my simulation. I checked the time scale, they are correct.

    It is greatly appreciated if you could please gvie me some advice.

    Great thanks,

    Vicky

  10. #10

    shear modulus and bulk modulus versus Young's modulus

    . . . what jorgen said concerning shear and bulk modulus in relation to Young’s modulus is right. But in case of rubbery materials there may be an additional complication, because for very small time intervalls (. . . at the beginning of the relaxation proccess) the material may be in the glassy state and therefore exhibit a smaller Poisson Ratio (smaller that 0.5). How this can be incorporated is for example shown in the attached report.

    regards
    Manfred
    Last edited by manfred; 2009-10-14 at 13:18.

Similar Threads

  1. ANSYS viscoelastic curve fitting
    By juan in forum Finite Element Modeling
    Replies: 5
    Last Post: 2010-04-26, 10:19
  2. Need help with modelling viscoelastic material in ANSYS
    By Waqas Khan in forum Constitutive Models
    Replies: 7
    Last Post: 2008-07-11, 13:47
  3. Modeling Stress Relaxation in ABAQUS
    By rm447 in forum Constitutive Models
    Replies: 4
    Last Post: 2008-05-29, 15:24
  4. Relaxation curve vs. creep
    By Waqas Khan in forum Constitutive Models
    Replies: 1
    Last Post: 2008-05-26, 19:13
  5. how can the cooling process change the stress relaxation?
    By benutella in forum Finite Element Modeling
    Replies: 1
    Last Post: 2004-09-01, 19:21

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •