4.17
TETRAHEDRON NO.17 WITH 4 NODES
This is a volume element
with linear shape functions. The transformation is isoparametric. The
integration is carried out numerically according to Gauss- Legendre.
Thus, the
integration order can be selected in Z88I1.TXT
in the material information lines.
The order 1 is good.
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
and a DXF data exchange with Z88X is not
possible, because this will make no
sense.
Hexahedron No.17 also
applies well for thick plate elements, if the plate's thickness is not
too
small compared to the other dimensions.
Basically, this element
calculates deflections and stresses very bad i.e. inaccurate. One needs
very
fine meshes to obtain usefull results. Its one and only reason is the
data
exchange with 3D CAD systems. Use tetrahedrons No.16, hexahedrons No.1 and (best choice) hexahedrons
No.10.
Tetrahedron No.17 cannot be
generated by the net generator Z88N. A DXF data
exchange with Z88X is not implemented because
tetrahedrons due to their strange geometry are very difficult to
arrange in
space. This element's main purpose is the use with automeshers from
third-party
suppliers. Caution: Sometimes the automeshers of CAD systems
produce
very bad element and nodal numbering resulting in an useless large
amount of
memory needs of Z88F. In this case, renumber especially the nodes.
Input:
Z88I1.TXT
> KFLAG for cartesian (0) or
cylindrical coordinates (1)
> IQFLAG=1 if pressure loads for
this element are filed in Z88I5.TXT
> 3 degrees of freedom for each node
> Element type is 17
> 4 nodes per element
> Cross-section parameter QPARA is 0 or any value, has no
influence
> Integration order INTORD for each mat info line. 1 is usually
good.
Allowed are 1 for 1 Gauss point, 4 for 4 Gauss points and 5 for 5 Gauss
points.
Z88I3.TXT
> Integration order INTORD for stress calculation: Can be
different
from INTORD in Z88I1.TXT.
0 = Calculation of stresses in the corner nodes
1, 4, 5 = Calculation of stresses in the Gauss points (e.g. 4 = 4 Gauss
points)
> KFLAG , any, has no influence
> 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 pressure loads applied onto element no.17:
>
Element number with pressure load
>
Pressure, positive if poiting towards the
edge
> 3
corner nodes of the loaded surface
The local
nodes 1 to 3 may differ from the
local nodes 1 to 3 used for the coincidence.
Results:
Displacements in X, Y and Z
Stresses: SIGXX, SIGYY, SIGZZ, TAUXY, TAUYZ, TAUZX, respectively
for corner
nodes or Gauss points. Optional von Mises stresses.
Nodal forces in X, Y and Z for each element and each node.