cohesion model sjkr/temp

Purpose

Modelling material cohesion using a modified version of the simplified Johnson-Kendall-Roberts (SJKR) cohesion model.

Syntax

cohesion sjkr/temp [other model_type/model_name pairs as described here ] settings keyword values

zero or one keyword/value pairs may be appended after the keyword settings (after all models are specified)

tangential_reduce values = 'on' or 'off'
  on = tangential model does not see normal force computed by this model
  off = tangential model does see normal force computed by this model

Associated material properties

Material interaction properties

cohesionEnergyDensity ( $k$ ): cohesion energy density between the two materials [energy/length^3]. It is expressed as a function of the temperature and provided via lookup table.

Description

This model can be used as part of pair gran and fix wall/gran

The difference between this model and the SJKR is that the cohesion energy density is set to be a function of the contact temperature (interpolated from a lookup-table).

The contact temperature is calculate for a particle-particle contact as

$T_c = (T_i e_i + T_j e_j)/(e_i e_j)$

where $T_i$ and $T_j$ are the temperatures of the particles $i$ and $j$ in contact. The thermal effusivity $e$ is defined as

$e = \sqrt{k \rho c_p}$

where $k$ is the thermal conductivity, $\rho$ is the density and $c_p$ is the specific heat capacity.

For particle-wall contacts the contact temperature is the arithmetic mean value of particle and wall.

Note

The lookup table is a simple whitespace separated two column (Tc-cohEnergyDensity) file.

The optional keyword tangential_reduce specifies if the tangential force model should be affected by the additional normal force exerted by this model. If set to ‘off’ (which is default), then the tangential force model will take into account the extra normal force generated by this model; hence, the tangential force model will be able to transmit a larger amount of tangential force. If set to ‘on’, then the tangential model will not take the normal force from this model into account, typically leading to a lower value of tangential force (via the Coulomb friction limit).

Restrictions

The cohesion model has been derived for the Hertzian style, it may note be appropriate for the Hookean styles.

It is not available for atom_style superquadric

Coarse-graining information:

Using coarsegraining in combination with this command should lead to statistically equivalent dynamics and system state.

Default

tangential_reduce = ‘off’