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Shell element transverse shear stresses in ABAQUS

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  • Shell element transverse shear stresses in ABAQUS

    Hi Dr. Jorgen,

    I've couple of quick questions:

    1) I am planning to use ABAQUS 2D shell formulation (S4R) to estimate 3D state of stress. I've read several articles to estimate the transverse shear stresses once the in-plane stresses are known by integrating the 3D equilibrium equations. This is, of course, easily done, if we have closed form solutions for in-plane stresses:

    sigma_xz,z = - (sigma_xx,x + sigma_xy,y)
    sigma_yz,z = - (sigma_xy,x + sigma_yy,y)

    How do I estimate transverse shear stresses using ABAUAS VUMAT, when I only know the in-plane stresses at one integration point in the element (in case of S4R) in VUMAT?

    2) In my analysis, I will use progressive failure analysis, where transverse stiffness cannot be kept constant in the analysis (I read in ABAQUS manual, we cannot change the transverse stiffness. Is there any possibility to vary transverse stiffness in case of shell elements?

    Thank you for your help,
    Nagesh

  • #2
    1) You are right, you cannot take a spatial derivative within a VUMAT. I am not clear, however, why you need to know the transverse shear stresses within the VUMAT?

    2) What happens if you use a constant transverse stiffness in your progressive failure model?

    -Jorgen
    Jorgen Bergstrom, Ph.D. PolymerFEM Administrator

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    • #3
      Hi Dr. Jorgen

      Thank you for your reply.

      1) To reduce the computational cost, I wanted to use 2-D shell elements. Only in-plane components are available in VUMAT for shell elements. In composites (for which I am modeling ), transverse shear stresses contribute to critical failure modes such as delamination, which is why I wanted to estimate some how, but by retaining the less computational cost.

      2) In progressive failure analysis, user reduces the transverse stiffnesses once the transverse failure occurs. Is there any possibility to change the transverse stiffness of shell elements during the analysis.

      Thanks,
      Nagesh

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      • #4
        Good points - I agree.
        Hmm, I cannot think of a way to change the transverse stiffnes during an analysis :(

        -Jorgen
        Jorgen Bergstrom, Ph.D. PolymerFEM Administrator

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        • #5
          Hi Nagesh and Dr. Jorgen,

          I am also modelling a similiar damage problem in composites using shell elements in which I need to update the value of transverse shear stiffness as the damage variable evolves. There doesn´t seem to be a straightforward way to do this in Abaqus VUMAT. In case you have figured out a solution, I would be glad if you could share it.

          Thanks,
          Udit

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