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!)

Z88I5.TXT

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.