# mesh module stress

## Syntax

    stress stress_keywords stress_values

- zero or more stress_keyword/value pairs may be appended
- stress_keyword = reference_point, stress or wear

    reference_point values = rx ry rz
      rx, ry, rz = coordinates of reference point
    stress value = on or off
    wear value = finnie or off

## Examples

    fix cad all mesh/surface/stress file mesh.stl type 1 wear finnie

## Description

This mesh module computes the average normal and shear stresses that the particles in the fix group exert on each triangle of the mesh is evaluated (which costs a bit of performance). Also, the total force and torque on the particle is calculated (see output info). The per-element average normal stress can be dumped into VTK format using dump mesh/vtk.

With the optional stress keyword, stress tracking can be turned off if desired. The reference point for calculating the body torque can be controlled via the reference_point keyword. The optional wear keyword can activates a simple qualitative wear model (finnie) - for details on the model, see the seperate /doc/finnie-wear.pdf. The wear coefficient is divided by the mesh element area, therefore it is independent of mesh size. The finnie constant k in Eqn. (4.23) has to be specified as follows:

    fix id all property/global k_finnie peratomtypepair n_atomtypes value_11 value_12 .. value_21 value_22 .. .

    (value_ij=value for the finnie constant between atom type i and j; n_atomtypes is the number of atom types you want to use in your simulation)

This mesh module is a prerequisite for the following mesh modules

- `6dof`
- `binning`
- `contact`
- `deform`
- servo
- stress

## Restart, fix_modify, output, run start/stop, minimize info

This mesh module stores a global vector with 9 components for access by various output commands. The first 3 components are equal to the total force on the mesh, the next 3 components store the total torque on the body exerted by the particles. Finally, the last 3 components are the coordinates (moved, scaled, rotated) of the reference point. Other info see `fix mesh`.

## Related commands

fix mesh/surface fix wall/gran

## Default

reference_point = 0. 0. 0. stress = on wear = off