/PROP/TYPE9 (SH_ORTH)

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 node Radioss shell with hourglass perturbation stabilization.
   • I_shell =24 (QEPH): formulation with hourglass physical stabilization for general use.
   • 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.
   • Flag I_shell =2 is incompatible with one integration point for shell element.
2. I_sh3n - Small strain formulation
   • Small strain formulation is activated from time t= 0, if I_smstr = 1, 3 or 11. It may be used for a faster preliminary analysis, but the accuracy of results is not ensured. Any shell for which $\Delta \text{t<}\Delta {\text{t}}_{\text{min}}$ can be switched to a small strain formulation by Radioss Engine option /DT/SHELL/CST, except if I_smstr = 4 or 11.
   • If I_smstr =1, 3 or 11, the strains and stresses which are given in material laws are engineering strains and stresses; otherwise, they are true strains and stresses.
   • I_smstr =11 has been developed to improve the robustness for Airbag models; actually, it is only compatible with Law 19 and with all quadrilateral shells and standard C0 tria. For Q4 shell using reference state coordinates, when I_smstr = 1, it will be set automatically to I_smstr = 11.
3. h_m, h_f, and h_r - Hourglass coefficients
   • h_m, h_f, and h_r are only used for Q4 shells (I_shell=1,2,3,4). 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_m and d_n - Shell membrane damping and numerical damping coefficient
   • Default d_m

     	LAW19	LAW25	LAW32	LAW36
     Ishell =1,2,3,4 (Q4)	0.25	0.05	0.0	0.0
     Ishell =12	0.25	0.05	0.0	0.0
     Ishell =24	0.015	0.015	0.015	0.015

   • d_n is only used for I_shell =12 and 24 and I_sh3n=30:
     • 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 transvers shear
     • for I_sh3n=30 (DKT18) d_n is only used for membrane
5. I_thick - Shell resultant stresses calculation flag
   • Flag I_thick is automatically set to 1 for /MAT/LAW32 (HILL).
   • 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.
   • 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 and 24), and standard triangle (C0) shell elements (I_sh3n = 1 and 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.
   • If I_P = 24 and skew_ID = 0, the 1^st material direction (m1) is defined with the node N1 and N2 of the shell elements of the shell seatbelt (only with /MAT/LAW119).

     Figure 2.

   • If I_P = 24 and skew_ID ≠ 0, the first direction of the local coordinate system is used to define the transversal direction of the shell seatbelt (only with /MAT/LAW119), the 2^nd material direction m2. The skew (/SKEW/MOV or /SKEW/MOV2 only) must be defined with two nodes of the same seatbelt shell element. The third node can be chosen arbitrarily. The given orientation is propagated to all connected seatbelt elements.

     Figure 3.

   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 4.

   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 is derived from direction m1 rotated 90 degrees (orthotropic).

9. P_thick_fail parameter is not compatible with failure defined within the material law itself, such as plastic failure strain in LAW36.
10. Element deletion rules used with /FAIL models:
    • Under-integrated elements (Belytchko, QEPH, DKT18):
      • If more than one failure model is applied to the shell material, or P_thick_fail=0 (blank), the value of P_thick_fail is calculated individually from each failure model settings.
        Example:

        Ifail_sh = 1

        One integration point failure sufficient to delete element, then P_thick_fail= 1.0 e-6

        Ifail_sh = 2

        All integration points failure is necessary to delete the element, thenP_thick_fail= 1.0

      • If only one failure model is applied to the material, the P_thick_fail value from the property is taken by default and overwrites local Ifail_sh settings from the failure model.
    • Fully integrated shells (Batoz, DKT_S3):
      • The rule described for under-integrated shells applies to each Gauss point separately. P_thick_fail ratio is checked for all integration points in thickness for each in-plane Gauss point. The element is deleted only when all Gauss points reach P_thick_fail ratio criteria.