1.1. Basic information

1.1.1. How to perform a calculation and how to get started

Create an input file, e.g. problem.dat. The default input file is tochnog.dat, which will be used if no other input file is specified. Thus the command tochnog tochnog.dat yields output on the screen while tochnog tochnog.dat > tochnog.out redirects the output to a file.

So to get started do, for example, the following:

  • cd test/other

  • tochnog condif1.dat

Use the condif1.dat test to get started.

  • Copy condif1.dat to tochnog.dat.

  • Use your favorite editor to open the file tochnog.dat and study it.

  • Change echo to -yes.

  • Remove the parentheses (…) surrounding the control_print statement and save the file.

  • Run by typing tochnog or tochnog tochnog or tochnog tochnog.dat.

  • Study the output on the screen.

  • Study the tochnog.log file.

  • Study the tochnog.dbs file. It contains the database after the calculation, and is an input file itself!

Read at least once the start of the data part introduction section.

1.1.2. Pre- and postprocessing

You can use GID both for preprocessing (mesh generation) and post processing (plotting). GID is commercially available at the www.gidsimulation.com Internet page. A free demo version of is available for download.

Alternatively to GID You can use Mecway for preprocessing input_abaqus and post processing control_print_gmsh. Mecway is commercially available at the mecway.com Internet page. It is very affordable, and also has built in FE calculations (mostly for mechanical engineering). A free demo version of Mecway is available for download.

You can also use GMSH both for preprocessing and post processing. GMSH is freely available at www.gmsh.info.

Postprocessing files are written for the visualization program PARAVIEW. The PARAVIEW program is freely available at www.paraview.org .

Furthermore. postprocessing files are written for the visualization program TECPLOT. These TECPLOT files are less well maintained than the files for other postprocessing programs. With GNUPLOT you can plot les resulting from control_print_history and control_print_data_versus_data. Also any other x-y plotting program can be used for such files.

1.1.3. Space discretization and time discretization

The computational domain is divided into finite elements. The elements connect at nodes. Either one-dimensional (1D), two-dimensional (2D), three-dimensional (3D) or axi-symmetrical (2D) domains can be used.

Only first order in time equations are solved. Time derivatives are approximated with Euler backward time discretization.

1.1.4. Program capabilities

  • Input

    Format free input. Words and no ‘magic numbers’ in rigidly dened columns are used. Boundary conditions can be imposed onto at geometrical entities, as well as onto elements and nodes.

  • Output/plotting

    Output can be printed over user-specied geometrical objects (points, lines, quadrilaterals,…) as well as at nodes. The history of each variable, and for functions of variables, can be printed over user-specied geometrical objects as well as at nodes. Interface files for the GID pre- and post processor.

  • Finite elements

    1D, 2D and 3D. Tochnog mostly uses isoparametric elements. There are also springs, trusses, beams and contact-springs however. Linear and quadratic simplex elements (triangles, tetrahedrons). Linear and quadratic prism elements. A full family of first to fourth order bar, quadrilateral and brick elements.

  • Mesh generation/refining/etc.

    • Macro regions are automatically divided into finite elements. Local h-refinement

    • Global h-refinement (more elements).

    • Global p-refinement (polynomial refinement).

  • Differential equations (materials)

    • Convection-diffusion equation:

      • Temperature calculations.

    • Fluids:

      • Stokes and Navier-Stokes.

    • Solids:

      • Elasticity (isotropy and transverse isotropy).

      • Elasto-Plasticity (Von-Mises, Mohr-Coulomb, Gurson, etc.; plasticity surfaces can be arbitrarily combined).

      • Hypo-Plasticity (Von-Wolersdorff, Masin, cohesion, intergranular strains, pressure dependent initial void ratio).

      • Damage.

      • Thermal stresses.

      • Hypoelasticity.

      • Viscoelasticity.

      • Viscoplasticity.

      • Viscosity.

    • Ground water flow equation:

      • Storage equation - saturated and non-saturated - multiple phreatic levels - piping and lifting safety - fully coupled consolidation analysis.

      • Wave equation.

  • Interaction analysis

    • Automatic uid-solid interaction.

    • Temperature eects on uids, solids.

  • Contact analysis

    • Contact with and without friction.

    • Frictional heat generation.

  • Frames of description

    • Lagrangian and Eulerian

  • Types of analysis

    • Static, quasi-static and dynamic analysis.

  • Parallelization

    • Full shared memory parallelization node and element loops

  • Special features

    • Automatic time-stepping (large steps for good iteration behaviour, small steps for bad iteration behaviour).

    • Automatic distribution of tendon trusses over nite elements (automatic embedment).

    • Restart possibility.

    • Convection wiggle stabilization (both for low and high order elements).

1.1.5. Files used by Tochnog

  • Input file. For example condif1.dat. The input file consists of an initialization part (which dof’s should be solved, etc.) and a data part (elements, nodes, etc.).

  • Runtime input file. For example condif1.run. Use it to give Tochnog data records on the y (while it is running).

  • Plot files. For example condif1_flavia.msh and condif1_flavia.res.

  • Database file. For example, after the calculation with input file condif1.dat the database file condif1.dbs will be written. It contains everything (nodes, elements, solutions fields, etc.). On error exit for example condif1_error.dbs will be generated.

  • Scratch file tochnog_tmp.txt. Don’t use this name yourself.

  • Log file tochnog.log. Contains log messages of calculations.