*SHELL SECTION
DENSITY
Set this parameter equal to a mass per unit surface area ofthe shell.
If this parameter is used, the mass of the shell includes a contribution from this para meter in
addition to any contribution from the material definition.
NODAL THICKNESS
Include this parameter to indicate that the shell thickness should not be re ad from the data lines but
should be interpolated from the thickness specified at the node s with the *NODAL THICKNESS
option. For composite sec tions the total thickness is interpolated from the nodes and the thicknesse s
of the layers specified on the data lines are scaled proportionall y. This parameter is ignored for
continuum shells.
OFFSET
Include this parameter to define the distance (as a fraction of theshell thickness) from the shell
midsurface to the reference surface (containingthe nodes of the element). This parameter accepts
positive or negative values or the labels SPOS or SNEG.
Positive values of the offset are in the positive normal direction (see “Shell elements:
overview,” Section 23.6.1 of the ABAQUS Analysis User’s Manual). When OFFSET=0.5 (or
SPOS), the top surface of the shell is the reference surface. When OFFSET=−0.5 (or SNEG), the
bottom surface of the shellis the reference surface. Thedefault is OFFSET=0, which indicates that
the middle surface of the shell is the reference surface. This parameter is ignored for continuum
shells.
ORIENTATION
Set this parameter equal to the name of an orientation definition (“Orientations,” Section 2.2.5of
the ABAQUS Analysis User’s Manual) to be used with mate rial calculations in this definition of
shell section behavior. This orientation will be used for material calculations and stress output in
the individual layers, forthe section forces output, and for the transverse shear stiffness.
It is possible to use a different orientation definition for material calculations in the individual
layers of a composite shell by referencing an orientation definition or giving an orientationangle
(in degrees, positivecounterclockwise relative to the shell local directions) on each layer definition
data line. Any layer definition line that does not have an orientation reference or an angle specified
will use the orientation defined here.
POISSON
Include this parameter to define the shell thickness direction behavior.
Set this parameter equal to a nonzerovalue to cause the thickness direction strain under plane
stress conditions to be a linear function of the membrane strains. The value of the POISSON
parameter must be between −1.0 and 0.5.
Set POISSON=ELASTIC to automatically select this parameter value based on the initial
elastic part of the material definition.
Set POISSON=MATERIALin an ABAQUS/Explicit analysis to cause the thickness direction
strainunde r plane stress conditions to be a function of the membrane strains and the i n-plane material
properties.
18.15–2
ABAQUS Version 6.1 Module: ID:
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