5 EXAMPLES

5.0 OVERVIEW

You will find several examples in this chapter along with their respective input files B*.* on the Z88 CD or Internet distribution. The examples 4, 6, 7 and 9 can be calculated analytically by hand.

Work with the examples which resemble your own applications. Also look at the protocol files *.LOG produced by the Z88 modules. Plot the various examples and results. Vary the input files, especially the mesh generator-input files for the examples 1, 5 and 7. Doing so gives you a smart feeling for the howtos of Z88 very quick.

If examples won’t run, first search for memory problems. Are there any other programs in the computer's memory, especially those fat and greedy memory eaters like office packages? All examples were tested on various computer equipment and operating systems, and most examples do run even on oldfashioned computers. Nevertheless, Z88 is running very large structures on modern PCs without any problems, see example 5.10. The largest structure computed with Z88 up to now featured 4.5 Mio. DOF and was run on a 64 Bit PC with 64 Bit Windows Server 2003 and with 64 Bit LINUX, too. If necessary, adjust Z88.DYN. Investigate the *.LOG files: It is shown here if Z88 modules run out of memory. UNIX: Check file and directory permissions.

After you have investigated the ready-to-run examples, try to draw the examples in your CAD program. Export to DXF files and convert them into Z88 files. If the CAD converter does not convert your DXF files properly, then redo the steps 3 and 5 of chapter 2.7.2. Did you "snap" the points cleanly ? If nothing works try another CAD program.

If you’v got a 3D CAD program with an integrated automesher you may export FE meshes to COSMOS or NASTRAN files and read these files into Z88 with Z88G. Check the amount of needed memory and the quality of the nodal numbering by running Z88F in test mode. Renumber with the Cuthill McKee programm Z88H, if nessesary. Or, even better, use the iteration solver.

Example 1: Fork wrench. Plane stress problem with Serendipity Plane Stress No.7 and mesh generator use. Learning objectives: CAD and mesh generator use at curvilinear plane structures, displaying stresses in the plot program. This example is fixed on the Z88 CD or Internet distribution ready to run as the first introduction example with Z88X.DXF, Z88I2.TXT and Z88I3.TXT.

Example 2: Crane truss. Modelled with Trusses No.4. Learning objectives: Use of the different views and rotation possibilities in space within the plot program.

Example 3: Transmission cam. Cam with different diameters, forces and moments in different planes with cam elements No.5, statically overdefined. Learning objectives: Use of the cam elements, especially for the boundary conditions at finite elements with 6 degrees of freedom per node, use of the different views in the plot program.

Example 4: Beam in plane, repeatedly statically over-defined. On both sides firmly fixed Beam No.13. Learning objectives: Use of Beams No.13, choice of the boundary conditions and the interpretation of the results.

Example 5: Disk segment in cake form. General spatial problem with Hexahedrons No.10 (20 nodes) as super elements and mesh generation of Hexahedrons No.1 (8 nodes). Learning objectives: Use of the mesh generator at curvilinear spatial elements, showing stresses, different views and spatial rotation possibilities in the plot program. After running this example successfully it is a nice idea to make the mesh generator generating Hexahedrons No.10 instead of Hexahedrons No.1, what is just a breeze. But you must define new nodes for the boundary conditions.

Example 6: Pipe under inner pressure of 1,000 bar. Axially symmetric problem, solved as plane stress problem with Plane Stress Elements No.7. Learning objectives: Clever use of symmetry qualities of a structure and choice of the proper boundary conditions and surface loads, showing stresses in the plot program.

Example 7: Press fit. Axially symmetric problem with Tori No.8 and use of mesh generator. Learning objectives: Work with torus elements, use of the mesh generator with mesh compression, stress display in the plot program.

Example 8: Crankshaft. Space structure with Tetrahedrons No.16. Learning objectives: Starting with a COSMOS file from Pro/ENGINEER, we will use the 3D converter Z88G, the Cuthill-McKee program Z88H and both the solvers, i.e. the direct Cholesky solver Z88F and the sparse matrix iteration solver Z88I1/Z88I2. This is an example for a FEA structure imported from a CAD system.

Example 9: Rectangular plate with 16 nodes Lagrange plate elements No.19. Learning objectives: Starting with an AutoCAD drawing for a super structure with plates No.20, we'll export the DXF file to the CAD converter Z88X. Running the mesh generator Z88N will generate a mesh of plates No.19. The system will be solved by the sparse matrix iteration solver.

Example 10: Piston of a diesel engine with Tetrahedrons No.16. Learning objectives: Starting with a NASTRAN file from Pro/ENGINEER, we will use the 3D converter Z88G and the iteration solver Z88I1/Z88I2. This is an example for a FEA structure imported from a CAD system using the surface and pressure loads file Z88I5.TXT.

Notes:

- The input and output files are printed sometimes shortened to avoid useless pages. Only the essential is shown. You can start every example at any time.
- Remember that 0 (zero) never is real zero but is represented as an approximation to the floating point numbers in a computer. Input values entered in Z88I1.TXT as 0 can appear in output files like Z88O0.TXT as very small numbers which is caused by formattings of the operating system's runtime libraries. This is normal. Of course, this is also true for real calculated results, for example displacements in Z88O2.TXT, stresses in Z88O3.TXT and nodal forces in Z88O4.TXT. Such results have always to be seen in relation to other results: Is, for example, in Z88O2.TXT the biggest calculated displacement 0.1 mm, then consider another displacement, let's say 1.234E-006 mm, as defacto zero.