3

3.3 MESH GENERATOR INPUT FILE Z88NI.TXT

The layout of Z88NI.TXT is very similar to the layout of Z88I1.TXT, the input file for the FE processor: Only the &- labeled data is required in addition. Cause: Z88NI.TXT can serve the plot program Z88P. Moreover, Z88NI.TXT can be copied to the name Z88I1.TXT and therefore be used to feed the FE processor with a very rough structure for very first checks and results. Mind the following formats:

[Long] = 4 bytes integer number
[Double] = 8 bytes floating point number, alternatively with or without point
[Character] = A letter

1st input group, i. e. first line, contains:

Dimension of the structure (2 or 3)
Number of nodes of the super structure
Number of super-elements
Number of degrees of freedom
Number of material information lines
Coordinate flag KFLAG (0 or 1)
Beam flag (must be 0 here !)
Plate flag (0 or 1)
& Trap radius flag NIFLAG (0 or 1)

Write all numbers into a line, separate at least by one blank respectively. All numbers here of the type [Long].

Explanation KFLAG:

At input of 0 the coordinates are expected cartesian while at input of 1 polar or cylindrical coordinates are expected. The latter are then converted into cartesian coordinates and thereupon stored in this form in Z88I1.TXT. Caution: The axially symmetric elements No.8 and 12 positively expect cylindrical coordinates, set KFLAG to 0 here !

Explanation IPFLAG:

If Plates No.20 appear in the structure, then set plate flag IPFLAG to 1, otherwise it must be 0.

Explanation NIFLAG:

In order to identify already defined nodes the mesh generator needs a trap radius. The defaults are 0.01 for for EPSX, EPSY and EPSZ if NIFLAG is 0. These values can be modified at extremely small or large structures. To initiate this change, set NIFLAG to 1. The new trap radiuses of EPSX, EPSY and EPSZ are then defined in Z88NI.TXT as the 6th input group.

Example: Super-structure 2-dimensional with 37 nodes, 7 super elements, 74 degrees of freedom, one material information line. Cartesian coordinates, no beams (anyway forbidden in the mesh generator file), trap radius default value. Thus

2 37 7 74 1 0 0 0 0

2nd input group, starting in line 2, contains:

Coordinates, one line per node.

Node number, strictly increasing [Long]
Number of the degrees of freedom for this node [Long]
X-coordinate or, if KFLAG is 1, R- coordinate [Double]
Y-coordinate or, if KFLAG is 1, PHI-coordinate [Double]
Z-coordinate or, if KFLAG is 1, Z-coordinate [Double]

The Z coordinate can be skipped at 2-dimensional structures. Enter angles PHI in radian.

Write all numbers into a line, separate at least by one blank respectively.

Example: The node no.8 has 3 degrees of freedom and the coordinates X = 112.45, Y = 0. , Z = 56.75. Thus: 8 3 112.45 0. 56.75

3rd input group, starting after last node, contains:

Coincidence, two lines for every finite element

1st line:

Element number, strictly ascending
Super-element type (7,8,10,11,12,20) [Long]

Write all numbers into a line, separate at least by one blank respectively. All numbers here of the type [Long].

2nd line: Depending on element type

1st node number for coincidence
2nd node number for coincidence
.....
20th node number for coincidence

Write all numbers into a line, separate at least by one blank respectively. All numbers here of the type [Long].

Example: An Isoparametric Serendipity Plane Stress Element No.7 has element number 23. The coincidence has the global nodes 14, 8, 17, 20, 38, 51, 55, 34 (locally these are the nodes 1-2-3-4-5-6-7-8, see chapter 4.7) . Thus resulting in two lines:

23 7
14 8 17 20 38 51 55 34

4th input group, starting after last element, contains:

Material information, one line for each material information.

This material information line starts with super-element no. inclusively [Long]
This material information line ends with super-element no. inclusively [Long]
Youngs's Modulus [Double]
Poisson's Ratio [Double]
Integration order (1, 2, 3 or 4) [Long]
Cross section value QPARA [Double]

... And if plates are defined in addition:
area load

Write all numbers into a line, separate at least by one blank respectively. Beams and cams are forbidden in Z88NI.TXT.

Explanation cross section value QPARA:

QPARA is element type-dependent, e.g. for hexahedrons 0, for trusses the cross-sectional area, and for plane stress elements the thickness. Here are the mesh generator-suitable elements:

Element No.1: Isoparametric Hexahedrons 8 nodes

Element No.7: Isoparametric Serendipity Plane Stress Element 8 nodes

Element No.8: Isoparametric SerendipityTorus 8 nodes

Element No.10: Isoparametric Serendipity Hexahedron 20 nodes

Element No.11: Isoparametric Serendipity Plane Stress Element 12 nodes

Element No.12: Isoparametric Serendipity Torus 12 nodes

Element No.20: Isoparametric Serendipity Plate 8 nodes

Example: The structure has 34 super elements No.7. The thicknesses are supposed to vary: Elements 1 to 11 thickness 10 mm, elements 12 to 28 15 mm and elements 29 to 34 now 18 mm. Material steel. Integration order shall be 2. Thus three material information lines:

1 | 1 | 11 | 206000 | 0.3 | 2 | 10.
2 | 12 | 28 | 206000 | 0.3 | 2 | 15.
3 | 29 | 34 | 206000 | 0.3 | 2 | 18.

& 5th input group, starting after last material information line, contains:

The descriptive details for the mesh generation process. 2 lines for every super element.

1st line:

Super element no. [Long]
Finite element type( types 1,7,8,10,19,20) to be generated [Long]

2nd line:

Number of finite elements in local x direction [Long]
Type of subdivision of CMODE x [Character]
Number of finite elements in local y direction [Long]
Type of the subdivision CMODE y [Character]
Number of finite elements in local z direction [Long]
Type of the subdivision of CMODE z [Character]

The two values for Z are skipped at 2-dimensional structures.

Explanations: CMODE can accept the following values:

- "E": Subdivision equidistant, "e" is also permitted
- "L": Subdivision increasing geometrically in local coordinate direction
- "l": Subdivision decreasing geometrically in local coordinate direction

The local x-, y and z axises are defined as follows:

- Local x axis points in direction of local nodes 1 and 2
- Local y axis points in direction of local nodes 1 and 4
- Local z axis points in direction of local nodes 1 and 5

See following sketch:

Example: Subdivide an Isoparametric Serendipity Plane Stress Element with 12 nodes (Element No.11) into finite elements of type Isoparametric Serendipity Plane Stress Element with 8 nodes (Element No.7). Subdivide in local x direction three times equidistantly and subdivide 5 times increasing geometrically in local y direction. The super element is supposed to have the number 31. Thus :

31 11
7 3 E 5 L (e or E for equidistant are equivalent)

& 6th input group, optionally after the end of input group 5 :

Input group 6 is required if NIFLAG was set to 1, i. e. the trap radiuses is upposed to be modified. 1 line :

Trap radius in global X direction EPSX [Double]
Trap radius in global Y direction EPSY [Double]
Trap radius in global Z directionEPSZ [Double]

Skip the Z detail for 2-dimensionalen structures.

Example: The trap radiuses shall be set to 0.0000003 for X, Y and Z respectively. Thus :

0.0000003 0.0000003 0.0000003

This is effective only if NIFLAG was set to 1 in the first input group!