4.18 PLATE NO.18 WITH 6 NODES
This is a curvilinear Serendipity Reissner- Mindlin plate
element with square shape functions. The transformation is isoparametric.
The integration is carried out numerically in both axises according
to Gauss- Legendre. Consequently, the integration order can be
selected in Z88I1.TXT in the material information lines. The order
3 (= 3 points) is mostly sufficient (reduced integration). This
element calculates both displacements and stresses quite good.
The integration order can be chosen again for the stress calculation.
The stresses are calculated in the corner nodes (good for an overview)
or calculated in the Gauss points (substantially more exactly).
Area loads are defined in the appropriate material lines, file
Z88I1.TXT, instead of Second moment of
inertia RIYY. For this element you need to set the plate flag
IPFLAG to 1. Attention: In contrary to the usual rules of the
classic mechanics Z88 defines ThetaX the rotation around the X-
axis and ThetaY the rotation around the Y- axis.
This element type is implemented for use with automeshers e.g.
Pro/MESH for the 3D CAD system Pro/ENGINEER by Parametric Technology.
Thus, a mesh generation with Z88N is not possible, because this
will make no sense. Use plates No.20
for the mesher Z88N.
Because plates No.20 compute both the deflections and the stresses
more exactly than the curvilinear triangle plates No.18, you should
prefer always plates No.20.
CAD : 1-4-2-5-3-6-1 ,
ref. chap. 2.7.2
> KFLAG for cartesian (0) or cylindrical coordinates (1)
> set plate flag IPFLAG to 1 (or 2, if you want to reduce the shear influence)
> 3 degrees of freedom for each node (w, ThetaX, ThetaY )
> Element type is 18
> 6 nodes per element
> Cross-section parameter QPARA is the element thickness
> "Second moment of inertia RIYY" is the area load
> Integration order INTORD per each mat info line. 3 is usually good. Possible is: 3 for 3 Gauss points, 7 for 7 Gauss points and 13 for 13 Gausspoints. For easy use with plate element No.20 (e.g. with Pro/ENGINEER), function SPLA88 of Z88 uses internally these values:
integration order 1 or 2 in Z88I1.TXT: 3 Gauss points
integration order 4 in Z88I1.TXT: 7 Gauss points
Example: Z88I1.TXT uses an entry of 2 for INTORD: Thus, plate
elements No.20 use 2*2 = 4 Gauss points and plate elements No.18
use 3 Gauss points for integration.
> Integration order INTORD: Basically, it is a good
idea to use the same value as chosen in Z88I1.TXT , but different
values are permitted
0 = Calculation of the stresses in the corner nodes
1, 7, 13 = Calculation of the stresses in the Gauss points (e.g. 7 Gauss points) See note
for Z88I1.TXT.
> KFLAG has no meaning
> Reduced stress flag ISFLAG:
0 = no calculation of reduced stresses
1 = von Mises stresses computed for the Gauss points (INTORD
not 0 ! )
Results:
Displacements in Z (i.e. w) and rotations ThetaX around
X- axis and ThetaY around the Y- axis.
Stresses: The stresses are calculated in the corner nodes or Gauss points and printed along with their locations. The following results will be presented:
Optional von Mises stresses
Nodal forces in X and Y for each element and each node.