Generalized Shell Export

The ABD properties are exported to the FEM using PSHELL entries along with associated MAT2 entries for the 3x3 membrane (A), membrane-bending coupling (B), and bending (D) matrices. The MAT2 entries also contain the thermal coefficients.

The Nastran PSHELL ABD formulation factors out the shell thickness as a separate user input. This is different than the ABD terms found in classical lamination theory (CLT) where the shell thickness is modeled directly in the ABD terms. HyperSizer follows the CLT convention by setting the PSHELL thickness to 1 unit (see the 3^rd field below). The PSHELL entry also contains a "bending moment of inertia ratio" field defined as 12I/T³. In the same way as the shell thickness, the bending moment of inertia I is already modeled in the D matrix. Therefore, this field is always set to 12 units (T =1 unit, I = 1 unit⁴).

Listed below is a PSHELL entry for component 64 which points to three different MAT2 entries. The MAT2 entry 640 contains the 3x3 membrane stiffness matrix A as well as the membrane thermal expansion coefficients. The MAT2 entries 639 and 637 contain the bending D and bending-coupling B terms respectively. Also note that the PSHELL thickness is 1 and the bending moment of inertia ratio is 12 (these values hold for all unit systems).

$

$ Structural Component ID =       64          material properties = TENSION   

PSHELL*               64             640             1.0            639

*                   12.0                                 .4680427790E-04*

*                                                    637

MAT2*                640  .216362035E+07  .348738516E+06 -.181898940E-10*      

*         .131543634E+07  .367435860E-09  .410734503E+06                *      

*         .316926664E-05  .748853548E-06 -.259254383E-21  .700000000E+02

MAT2*                639  .602760870E+07  .635808845E+03  .231525114E+02*      

*         .237766844E+04  .231525114E+02  .267053518E+06                *      

*         .489963249E-05  .240954625E-05 -.578532834E-09  .700000000E+02

MAT2*                637  .221413007E+07  .577538334E+04  .113686838E-11*      

*         .186302688E+05  .113686838E-11  .121608701E+06                *      

*         .490000000E-05  .490000000E-05 -.853752119E-22  .700000000E+02$

Notes:

• The mass of the panel is modeled using the "Non-Structural Mass" (NSM) parameter (i.e. mass per unit area).
• The thickness of the PSHELL entry is always one unit as in classical lamination theory.
• Z1 and Z2 fiber distances for stress calculations are exported according to the outermost regions of the panel section.

The Shell General Sections option is used to export the section properties.The ABD stiffness terms are defined directly in the section definition as shown below. Below each section definition is the element set containing all the elements assigned to that section.

Important: All shell sections must be defined using the *SHELL GENERAL SECTION option, not *SHELL SECTION.

** Structural Component ID = 1 material properties = COMPRESSION

*Shell General Section, Elset=PSHELL_DIST_1, Orientation=ORI_HS, Density= .592198758E-04

** A11, A12, A22, A13, A23, A33,-B11,-B12

** -B13, D11,-B12,-B22,-B23, D12, D22,-B13

** -B23,-B33, D13, D23, D33

.261155507E+07,  .555149837E+06,  .164488841E+07,  .000000000E+00,  .000000000E+00, .584415584E+06, -.125211795E+07, -.139613361E+05

.000000000E+00,  .201468859E+07, -.139613361E+05, -.413669219E+05,  .000000000E+00, .135201967E+04, .400598421E+04, .000000000E+00

.000000000E+00, -.168311688E+05,  .000000000E+00,  .000000000E+00,  .157445766E+04

The ABD stiffness terms are defined using the GENS preintegrated shell section type.

! Structural Component 5: Upper Wing Skin

SECTYPE,5,GENS,,Upper_Wing_Skin

SSPA, 2.08324500e+006, 4.82671906e+005, 0.00000000e+000, 1.83297400e+006, 1.84815097e-009, 5.35660875e+005

SSPB, 9.94687000e+005, 3.03106299e+003, 0.00000000e+000, 8.66018066e+003, 0.00000000e+000, 6.33101211e+004

SSPD, 2.20499700e+006, 1.93676196e+003, 5.01369095e+001, 8.40326270e+003, 5.01369095e+001, 1.40657594e+005

SSPE, 5.35660875e+007, 0.00000000e+000, 5.35660875e+007

SSMT, 1.11575996e+001, 3.34375311e+000, -4.54863971e-004

SSBT, 1.23353122e+001, 1.39628606e-001, -3.61031857e-004

SSPM, 4.61436035e-005