4.7
PLANE STRESS ELEMENT NO.7 WITH 8 NODES
This is a curvilinear Serendipity
plane stress 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 is mostly sufficient. This
element
calculates both displacements and stresses very exactly. 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). Pay attention to edge loads when using
forces,
cf. chapter 3.4. It is easier to enter edge
loads via
the surface and pressure loads file Z88I5.TXT.
You may
combine this element with elements no.3 (not recommended) or elements no.14 (good).
Plane Stress Elements No.7
can be generated by the mesh generator Z88N
from super elements Plane Stress Elements No.7
or No.11. Thus, the Plane Stress Element
No.7 is well suited as super element.
Plane Stress Element
No.7 is recommended for all sort of plane stress computation. This element is well-balanced in
respect to the precision of displacement and stress calculation as well
as to
its needs for memory and computing power.
Input:
CAD (see chapter 2.7.2): 1-5-2-6-3-7-4-8-1
Z88I1.TXT
> KFLAG for cartesian (0) or polar
coordinates (1)
> IQFLAG=1 if edge loads for this element are filed in Z88I5.TXT
> 2 degrees of freedom for each node
> Element type is 7
> 8 nodes per element
> Cross-section parameter QPARA is
the element thickness
> Integration order INTORD per each
mat info line. 3 is usually good.
Z88I3.TXT
> 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
1,2,3,4 = Calculation of the stresses in the Gauss points
> KFLAG = 0: Calculation of SIGXX, SIGYY
and TAUXY
> KFLAG = 1: Additional calculation of SIGRR, SIGTT and TAURT
> Reduced stress flag
ISFLAG:
0 = no calculation of reduced
stresses
1 = von Mises stresses in the Gauss points ( INTORD not 0 !)
2 = principal stresses in the Gauss points (INTORD not 0!)
3 = Tresca stresses in the Gauss
points (INTORD not 0!)
Z88I5.TXT
This file is
optional and only used if in addition to nodal forces edge loads
applied onto
element no.7:
>
Element number with surface and pressure
load [Long]
>
Pressure, positive if poiting towards the
edge [Double]
>
Tangential shear, positive in local r
direction [Double]
> 2
corner nodes and one mid node of the
loaded surface [3 x Long]
The local r
direction is defined by the nodes
1-2. The local nodes 1, 2, 3 may differ from the local nodes 1, 2, 3
used for
the coincidence.
Results:
Displacements ino X and Y.
Stresses: The stresses are calculated in the corner nodes or
Gauss
points and printed along with their locations. For KFLAG = 1 the radial
stresses SIGRR, the tangential stresses SIGTT and the accompanying
shear
stresses SIGRT are computed additionally (makes only sense if a
rotational-symmetric
structure is available). For easier orientation the respective radiuses
and
angles of the nodes/points are printed. Optional von Mises stresses
Nodal forces in X and Y for each element and each node.