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Element Formulation Switch for Implicit


Under-integrated elements are widely popular in the explicit field for their robustness and computational efficiency. However, their use in Implicit without appropriate stabilization methods can cause singularities and may result in poor convergence behavior. LS-DYNA offers parameters such as ISHELL, ISOLID, and IBEAM in the keyword *CONTROL_IMLPICIT_EIGENVALUE which can be used to switch to an alternate element formulation during an Implicit solution. All necessary mapping of element history variables is automatically treated before and after the switch. The switching of element formulation, when defined, is applied for all implicit solutions types such as eigenvalue extraction, implicit static linear, implicit static non-linear, and implicit dynamic.

  • Abhiram R Devesh says:

    Hello Mr.Bala
    I have few questions regarding these implicit element formulations.

    a. What are the properties or specialties of these implicit element formulations?
    b. Why the explicit element formulations can cause singularites?

    Thanks in advance
    Regards
    Abhiram R D

  • Suri Bala says:

    Abhiram,

    Implicit element formulations are for small deformations while explicit is for finite displacements and rotations. Most explicit formulations can be used for Implicit calculations when using the correct hourglass controls although a fully intergrated or selective-intergrated formulation would be recommended.

    Suri

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