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doc:user:elements:contact:laws

Contact materials

Description

For all contact materials, a penalty along the normal direction and a depth at which contact is detected are required. Contact can be:

  • positively unilateral (UNILATERAL_POSITIF), contact for $\mbox{gap} \geq 0$ (by default)
  • negatively unilateral (UNILATERAL_NEGATIF), contact for $\mbox{gap} \leq 0$
  • bilateral (BILATERAL), contact for both $\mbox{gap} \geq 0$ and $\mbox{gap}\leq 0$

Choice of depth at which contact is detected: If the contact matrix is made of circles, the depth must be smaller than the smallest radius. If it is planar, the depth is arbitrary, but a large depth leads to a slow contact detection, when if the depth is too small some contacts can be missed.

FrictionlessContactMaterial

Description

Contact without friction.

Parameters

Name Metafor Code Dependency Default
Penalty along normal direction PEN_NORMALE TM
Depth at which contact is detected PROF_CONT -
Type of contact TYPE_CONT - UNILATERAL_POSITIF

FrictionlessVariablePenaltyContactMaterial

Description

Contact without friction where penalty can depend on the gap.

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE GD

:!: No TM dependency here!

An evolution function must be associated to PEN_NORMALE (depending on generalized displacements GD).

StickingContactMaterial

Description

Sticking contact. A penalty along the tangential direction is added.

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Type of contact TYPE_CONT -

StickingVariablePenaltyContactMaterial

Description

Sticking contact where penalty can depend on the gap.

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE GD
Penalty along tangential direction PEN_TANGENT GD

:!: No TM dependency here!

An evolution function must be associated to PEN_NORMALE and/or PEN_TANGENT (depending on generalized displacements GD). These function can be different.

CoulombContactMaterial

Description

Coulomb's friction law. A tangential penalty, a coefficient of static friction (setting the maximal tangential force before sliding) and a coefficient of dynamic friction (setting the value of the sliding force) are required.

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Coefficient of static friction COEF_FROT_STA TM
Coefficient of dynamic friction COEF_FROT_DYN TM
Type of contact TYPE_CONT -

TrescaContactMaterial

Description

Tresca's friction law. Friction do not depend on pressure. It is computed using penalty method with sticking contact, and starts sliding once the tangential stress reaches a threshold entered by the user.

:!: This law requires the use of AREAINCONTACT = AIC_ONCEPERSTEP

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Static frictional shear factor TRESCA_STA_M TM
Dynamic frictional shear factor TRESCA_DYN_M TM
Initial shear yield stress TRESCA_K -
Type of contact TYPE_CONT -

The threshold is usually computed using $m\,\sigma_0\,/\sqrt{3}$ where m is Tresca's coefficient of friction and $\sigma_0$ is the tensile yield stress of the material.

TmFrictionlessContactMaterial

Thermomechanical contact without friction.

The heat flux $q_{N}$ normal to the contact interaction (going out of the slave surface) is given by

$$q_{N} = h_c \left(p_{N} \right) \left(T^{S} - T^{M}\left(\bf{\xi}^{S}\right)\right), $$

where

  • $p_{N}$ is the contact pressure,
  • $T^{S}$ is the temperature of the slave node,
  • $T^{M}\left(\bf{\xi}^{S}\right)$ is the temperature of a point on the master surface corresponding to the closest projection of the slave node on the master surface,
  • $h_c$ is the thermal resistance under conduction.

This thermal resistance under conduction $h_c$ is modeled as

$$h_c \left(p_{N} \right) = h_{c0} \left(\frac{p_{N}}{H_v}\right)^{w}, $$

where

  • $H_v$ Vickers's material hardness ,
  • $w$ is an exponent,
  • $h_{c0}$ is the nominal thermal resistance under conduction.

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Depth at which contact is detected PROF_CONT -
Nominal thermal resistance CTM_H_NOMINAL -
Exponent CTM_EXPONENT_E -
Material hardness CTM_HARDNESS -
Type of contact TYPE_CONT -

:!: Not tested in 3D :!:

TmStickingContactMaterial

Sticking thermomechanical contact

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Nominal thermal resistance CTM_H_NOMINAL -
Exponent CTM_EXPONENT_E -
Material hardness CTM_HARDNESS -
Type of contact TYPE_CONT -

:!: Not tested in 3D :!:

TmCoulombContactMaterial

Description

Thermomechanical contact using Coulomb's friction law

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Coefficient of static friction COEF_FROT_STA TM
Coefficient of dynamic friction COEF_FROT_DYN TM
Nominal thermal resistance CTM_H_NOMINAL -
Exponent CTM_EXPONENT_E -
Material hardness CTM_HARDNESS -
Type of contact TYPE_CONT -

:!: Not tested in 3D :!:

TmTrescaContactMaterial

Description

Thermomechanical contact using Tresca's friction law

Parameters

Name Metafor Code Dependency
Penalty along normal direction PEN_NORMALE TM
Penalty along tangential direction PEN_TANGENT TM
Depth at which contact is detected PROF_CONT -
Static frictional shear factor TRESCA_STA_M TM
Dynamic frictional shear factor TRESCA_DYN_M TM
Initial shear yield stress TRESCA_K -
Nominal thermal resistance CTM_H_NOMINAL -
Exponent CTM_EXPONENT_E -
Material hardness CTM_HARDNESS -
Type of contact TYPE_CONT -

The threshold is usually computed using $m\,\sigma_0\,/\sqrt{3}$ where m is Tresca's coefficient of friction and $\sigma_0$ is the tensile yield stress of the material.

:!: Not tested in 3D :!:

doc/user/elements/contact/laws.txt · Last modified: 2016/03/30 15:23 (external edit)