tangential model history/powder

Purpose

This tangential model is equivalent to the tangential model history but can vary its coefficient of friction with compaction density.

Syntax

tangential history/powder [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)

heating_tangential_history values = 'on' or 'off'
  on = model contributes to surface heating in the frame of enable_surface_heating
  off = model does not contributes to surface heating
torsion values = 'on' or 'off'
  on = model calculates friction based on torsion
  off = model ignores rotation around the contact normal

Associated material properties

Material properties

youngsModulus ( $Y$ ): The Youngs Modulus of a material, i.e. its stiffness [pressure]
poissonsRatio ( $\nu$ ): The Poisson’s ratio, i.e. the ratio of transverse to axial strain [ $\cdot$ ]

Material interaction properties

coefficientRestitution ( $e$ ): The coefficient of restitution of two materials [ $\cdot$ ]
coefficientFriction ( $\mu$ ): The coefficient of friction acting between two materials (can be a file) [ $\cdot$ ]

Description

This model can be used in the tangential argument of both particle_contact_model and wall_contact_model.

This model calculates the tangential force between two particles in contact as done in the tangential model history.

The coefficient of friction in this version of the model depends on the compression density $\alpha$ that is computed by fix powder/update and thus requires that this fix is employed in the simulation. The coefficient of friction which is specified as a fix property/global can be a non-constant property, e.g. of type lookup, and is set according to

$\mu = \mu_0\frac{\alpha - \alpha_{min}}{1 - \alpha_{min}},$

i.e. as a function of the normalized compression density, which is 0 for uncompressed and 1 for compressed particles, respectively.

The remaining model is equivalent to the tangential model history.

Coarse-graining information:

Using coarsegraining in combination with this command might lead to different dynamics or system state and thus to inconsistencies. However, the influence of this model on the global dynamics or system state might be small so in some cases the results may be valid. This has to be reviewed by a specialist on a case-by-case basis.

Default

heating_tangential_history = ‘off’, torsion = ‘off’