4.14
PLANE STRESS ELEMENT NO.14 WITH 6 NODES
This is a curvilinear Serendipity
plane stress element with square shape functions. The transformation is
isoparametric. The integration is carried out numerically according to
Gauss-
Legendre. Consequently, the integration order can be selected in Z88I1.TXT in the material information lines.
The order 7 (=7 Gauss points) 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.
This element type is
implemented for use with automeshers e.g. Pro/MECHANICA
for the 3D CAD system Pro/ENGINEER
by Parametric Technology. Thus, a
mesh generation with Z88N is not
possible. Use plane stress elements
No.7 for Z88N.
Use plane stress
element No.7
whenever possible. It is substantially more precise than this
isoparametric triangle.
Input:
CAD (see chapter 2.7.2): 1-4-2-5-3-6-1
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 14
> 6 nodes per element
> Cross-section parameter QPARA is the element thickness
> Integration order INTORD per each mat info line. 7 is usually
good.
Possible is: 3 for 3 Gauss points, 7 for 7 Gauss points and 13 for 13
Gausspoints. For easy use with plane stress element No.7 (e.g. with
Pro/ENGINEER), function ISOD88 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, plane stress elements No.7 use 2*2 = 4 Gauss points and plane
stress elements No.14 use 3 Gauss points for integration.
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, 7, 13 = Calculation of the stresses in the Gauss points (e.g. 7
Gauss
points) See note for Z88I1.TXT.
> 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!)
This file is
optional and only used if in addition
to nodal forces edge loads applied onto element no.14:
>
Element number with surface and pressure
load
>
Pressure, positive if poiting towards the
edge
>
Tangential shear, positive in local r
direction
> 2
corner nodes and one mid node of the loaded
surface
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.