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### fix mesh/surface/stress command

Syntax:

    fix ID group-ID mesh/surface/stress file filename premesh_keywords premesh_values mesh_keywords mesh_values surface_keyword surface_values stress_keywords stress_values

- ID, is documented in fix command, the group-ID is ignored for this command.
- mesh/surface/stress = style name of this fix command
- file filename premesh_keywords premesh_values mesh_keywords mesh_values surface_keyword surface_values are documented in fix mesh/surface.
- zero or more stress_keyword/value pairs may be appended
- stress_keyword = stress or wear

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

Examples:

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

Description:

This fix is identical to fix mesh/surface but additionally the pressure and shear force 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 forces can be dumped into VTK format using dump mesh/vtk.

With the optional stress keyword, stress tracking can be turned off is desired. The reference point for calculating the body torque can be controlled via the referece_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 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)

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

This fix stores a global vector with 6 components for access by various output commands. The first 3 components are equal to the total force on the mesh, the last 3 components store the total torque on the body exerted by the particles. Other info see fix mesh.

Related commands:

fix mesh/surface fix wall/gran

Default:

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