---
name: "tochnog"
section: "1"
platform: "linux"
package: "tochnog"
version: "20010124-3.1"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/tochnog"
---

# tochnog(1)

simulate mechanics by the finite element method

## NAME

tochnog - simulate mechanics by the finite element method

## SYNOPSIS

**tochnog** \[ *input-file* \]

## DESCRIPTION

**tochnog** is a free finite-element program.

The *finite element method* is “a general discretization procedure of continuum problems posed by mathematically defined statements.” \[O.C. Zienkiewicz & R.L. Taylor. *Finite Element Method,* 5th ed, sect 1.1.  2000.\] **tochnog** implements one-, two- or three-dimensional, or axi-symmetrical computational domains, each consisting of finite elements connected at nodes; but (unlike as in common finite element programs) with all fields assumed to be continuous over the domain.  Such continuity gives a more diffuse but at the same time a more stable numerical scheme, with the further advantage that all fields are stored not in integration points but in the nodes themselves, leading to a relatively easy implementation of remeshing and refining techniques.  Only first order in time equations are solved; time derivatives are approximated with Euler backward time discretization.

**tochnog** accepts format-free input; reports results over points, lines, quadrilaterals, etc., as well as at nodes; outputs suitably for plotting; provides springs, trusses and 2D beams in addition to isoparametric elements; implements tools to generate and refine model meshes; reports accuracy by residue and error estimate; analyzes interactions between fluids and solids, and also contact with and without friction; frames Lagrangian, Eulerian and AEL calculations; simulates statically, quasi-statically or dynamically; and significantly parallelizes its calculations to take advantage of parallel processing when available.

For thermal analysis, **tochnog** evolves the energy balance equation.  For fluids, the Stokes and Navier-Stokes.  For solid elasticity, the isotropy and transverse isotropy.  For solid elastoplasticity, the von Mises, Mohr-Coulomb and Gurson.  For solid hypoplasticity, the von Wolfersdorf, cohesion, intergranular strain, and pressure-dependent initial void ratio.  Also for solids, the damage, thermal stress, hypoelasticity, viscoelasticity, viscoplasticity and viscosity.  For ground water flow, the storage equation.  For general wave phenomena, the wave equation.

**tochnog** is an extensive numerical free-software package whose operation extends far beyond that which a mere man page can document.  The *TOCHNOG User's Manual* and other documents found in */usr/share/doc/tochnog/* give complete instructions on **tochnog**'s use.

## INVOCATION

If the *input-file* name given on the command line contains no “.” dot, then the standard **tochnog** input filename extension “.dat” is implicitly appended to it (for example, “problem” is interpreted as “problem.dat”).  If omitted, *input-file* defaults to “tn.dat”.

It is usual to redirect **tochnog**'s output rather than to let it stream to the terminal.  For example,

-

  $ **tochnog tn.dat \>tn.out**

## OPTIONS

The instructions given in *input-file* control **tochnog**. The **tochnog** command itself accepts no command-line options.  See the documentation in */usr/share/doc/tochnog/* for further information.

## FILES

- *tn.dat*

  the default input file

- *tn.run*

  the runtime input file

- *tn.log*

  the calculation message log

- *tn.dat*, et al.

  output files in various formats, suitable for plotting

- *tn.dbs*

  the state database, containing full calculation state data, including nodes, elements, solution fields, etc.

- *tn.dvd*

  the step-by-step record of the evolution over time of the model's unknown variables

- *tn.tmp*

  a scratch file (do not use this name yourself)

- *tn.out*

  conventionally, the file to which **tochnog**'s *stdout* is redirected (but the user controls this as described under **INVOCATION** above)

- */usr/share/doc/tochnog/*

  reference documents including the *TOCHNOG User's Manual* (on a Debian system, found only when the *tochnog-doc* package is also installed)

## BUGS

Unknown.  (This man page is contributed by a user unaffiliated with **tochnog** development.)

## AUTHOR

Dennis Roddeman \<dennis.roddeman@feat.nl\>

As of January 2001, the author asks that any error reports, questions, wishes, etc., be e-mailed to him at the address given.

Thaddeus H. Black \<t@b-tk.org\> provided this man page.

## SEE ALSO

[**gnuplot**(1)](/gnuplot/1.md) (for plotting); [**gv**(1)](/gv/1.md) and [**lpr**(1)](/lpr/1.md) (for viewing and printing the .ps documents in */usr/share/doc/tochnog/*).