/PROP/TYPE9 (SH_ORTH)

Format

Definitions

Example

There are 3 integration points through the shell thickness. Material direction m1 (fiber direction) defined with vector $V$ and angle $\varphi$ .

Figure 1.

#RADIOSS STARTER
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#-  1. LOCAL_UNIT_SYSTEM:
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/UNIT/2
unit for prop
#              MUNIT               LUNIT               TUNIT
                  kg                  mm                  ms
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#-  2. GEOMETRICAL SETS:
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/PROP/SH_ORTH/2/2
SH_ORTH example
#   Ishell    Ismstr     Ish3n    Idrill                             Pthick_fail
        12         0         0         1                                       0
#                 hm                  hf                  hr                  dm                  dn
                   0                   0                   0                  .1                  .1
#        N                         Thick              Ashear   skew_ID    Ithick     Iplas
         3                           1.8                   0         0         1         1
#                 Vx                  Vy                  Vz                 Phi                  Ip
                   1                   0                   1                  45                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
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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.
   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 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.