/PROP/TYPE11 (SH_SANDW)

This property is compatible with XFEM (crack propagation) using /FAIL/JOHNSON, /FAIL/TAB1 and /FAIL/TBUTCHER.

Format

Definition

Comments

1. I_shell, I_sh3n – 4-node and 3-node shell formulation flag
   • I_shell=1,2,3,4 (Q4): original 4 nodes Radioss shell with hourglass perturbation stabilization.
   • I_shell=24 (QEPH): formulation with hourglass physical stabilization for general use (istotropic + LAW25 shells only).
   • I_shell=12 (QBAT): modified BATOZ Q4γ24 shell with four Gauss integration points and reduced integration for in-plane shear. No hourglass control is needed for this shell.
   • I_sh3n=30 (DKT18): BATOZ DKT18 thin shell with three Hammer integration points.
2. I_smstr- Small strain formulation
   • Small strain formulation is activated from time t = 0, if I_smstr =1 or 3. It may be used for a faster preliminary analysis, but the accuracy of results is not ensured. Any shell for which can be switched to a small strain formulation by Radioss Engine option /DT/SHELL/CST, except if I_smstr =4.
   • If I_smstr =1 or 3, the strains and stresses which are given in material laws are engineering strains and stresses; otherwise they are true strains and stresses.
3. h_m, h_f, and h_r - Hourglass coefficients
   • h_m, h_f, and h_r are only used for Q4 shells. They must have a value between 0 and 0.05.
   • For I_shell=3, default values of h_m and h_r are 0.1 with larger values possible.
4. d_n - Shell numerical damping coefficient
   • d_n is only used for I_shell = 12 and 24.
     • for I_shell = 24, d_n is used for hourglass stress calculation
     • for I_shell= 12 (QBAT), d_n is used for all stress terms, except transverse shear
     • for I_sh3n=30 (DKT18), d_n is only used for membrane
5. I_thick- Shell resultant stresses calculation flag
   • If I_thick=1, the small strain option is automatically deactivated in the corresponding type of element.
6. I_plas- Shell plane stress plasticity flag
   • It is recommended to use I_plas =1, if I_thick =1.
   • I_plas=1 is available for Material Law 27.
   • If I_plas=1, the small strain option is automatically deactivated in the corresponding type of element.
7. I_dril - Drilling degree of freedom stiffness flag
   • Drilling DOF stiffness is recommended for implicit solutions especially for Riks method and bending dominated problems.
   • I_dril is available for QEPH, QBAT (I_shell =12, 24), and standard triangle (C0) shell elements (I_sh3n = 1, 2).
8. Anisotropy direction definition.
   The reference vector $V$ is defined as following according flag I_P:

   • If I_P=0 and skew_ID = 0, the reference vector $V$ is defined with VX, VY and VZ.
   • If I_P=0 and skew_ID ≠ 0, the reference vector $V$ is the first direction (local X) of the local coordinate system skew_ID.
   • If I_P = 20, the reference vector $V$ is defined with the node N1 and N2 of the shell elements.
   • If I_P = 22, the reference vector $V$ is the first direction (local X) of the local coordinate system skew_ID. Vector components VX, VY and VZ are ignored.
   • If I_P = 23, the reference vector $V$ is defined with VX, VY and VZ. Local coordinate system skew_ID is ignored.
   The reference vector $V$ is projected on the shell element plane and becomes the vector $V^{\prime }$ . Then for each layer, the 1^st material direction (m1) is vector $V^{\prime }$ turned ${\varphi }_i$ degrees (turns positive direction around shell normal $n$ ).

   
   
   Figure 2.

   The hierarchy order to define the reference vector $V$ is:

   • initial state card (/INISHE/ORTHO)
   • shell property

   In case of reference metrics, the orientation for directions of anisotropy must be defined with the reference geometry, not the initial one.

   The 2^nd material direction m2 derived from direction m1 rotated 90 degrees (orthotropic).

9. I_pos – Layer position
   • I_pos = 0: layer positions are calculated automatically with "Thick".
     If $Thick\ne {\displaystyle \sum _i^N{t}_i}$

     • A warning message is displayed.
     • And individual layer thickness will be adjusted to new layer thickness $t_i^{new}$ with:
       (1)

       $$Thick={\displaystyle \sum _i^N{t}_i^{new}}$$
       Here "Thick" and are the shell thickness and layer thickness which specified in input.

       
       
       Figure 3.

   • I_pos = 1: all layer positions in the element thickness are user-defined (with $t_i$ and $Z_i$ ).
     • “Thick” is not checked, as it does not need to be equal to the sum of layer thickness.
     • Multiple layers are allowed to have the same space position.

     For more details, refer to “Layer thickness and layer position calculation” in the Property and Elements FAQs.

10. Mat_ID_i- Material for each layer
    • Each layer as well as the corresponding part must use the same material law type. But may have different material properties, hence material IDs. Radioss checks for this condition and errors out if it is not met.
    • Global material properties (membrane stiffness, bending stiffness, mass, and inertia) are calculated based on the material properties and layer (thicknesses …). They are used for stability, mass and interface stiffness.
    • A material is still required at part definition level but, is only used for pre- and post- (visualization “by material”) and its physical characteristics are ignored.
    • The previous formulation where stiffness and mass were calculated from the material associated to the part is still used if the version number of the input file is V13 or earlier.
11. P_thick_fail parameter is not compatible with failure defined within the material law itself, such as plastic failure strain in LAW36.
12. Element suppression rules used with /FAIL models:
    • Each single layer is turned OFF when all in-plane Gauss integration points in the layer are deleted.
    • The whole shell element is deleted when the following criterion is met:(2)
      $${\displaystyle {\sum }_{i}Thic{k}_i\cdot F\_weigh{t}_i}\ge P\_thic{k}_{fail}$$
      with (3)
      $$i=1,N_{layers}$$

      Where, Thick_i is relative thickness of failed layer i

    • When Ifail_sh parameters are defined locally in failure models associated to each layer material, the P_thick_fail value is used by default and local parameter settings are ignored. Local failure model settings are only used when P_thick_fail is not defined in the property which allows for backward compatibility with old models.