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/INTER/TYPE21/inter_ID/unit_ID

inter_title

surf_IDs

surf_IDm

Istf

Ithe

Igap

Iadm

Fscalegap

Gapmax

DEPTH

Pmax

Stmin

Stmax

Stfac

Fric

Gapmin

Tstart

Tstop

IBC

Inacti

VISS

Bumult

Ifric

Ifiltr

Xfreq

sens_ID

fct_IDF

AscaleF

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C1

C2

C3

C4

C5

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C6

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NRadm

Padm

Angladm

Kthe

fct_IDK

AscaleK

Tint

Ithe_form

Frad

Drad

Fheat

IDrby

IDref

Damp

Dampr

Gap is constant over the slave surface and along the time, equal to Gapmin. And a default value for Gapmin is computed as t/2, t being the average thickness of the slave shell elements.

In case of constant gap, Gapmax and Fscalegap will not be used.

If contact thickness of the part is not define in input /PART:

and will vary along the time according to the variation of shells and 3-node shells thickness, on the slave side.

If contact thickness of the part is define in input /PART:

Where,

, with t is thickness of the slave element for shell elements.

for brick elements.

If Igap = 1 or 2, the variable gap is always at most equal to Gapmax and default value for Gapmax will be set to 1030 and is always at least equal to Gapmin (but there is no default value for Gapmin).

If the contact occurs in a zone (master side) whose radius of curvature is lower than the element size (slave side), the element on the slave side will be divided (if not yet at maximum level).

If the contact occurs in a zone (master side) whose radius of curvature is lower than NRadm times the element size (slave side), the element on the slave side will be divided (if not yet at maximum level).

If the contact occurs in a zone (master side) where the angles between the normals are greater than Angladm, and the percentage of penetration is greater than Padm, the element on the slave side will be divided (if not yet at maximum level).

A default value for DEPTH is computed as the maximum of:

If the input value is not equal to 0, DEPTH will be raised up to the upper value of the gap (at time 0) among all nodes.

Too large DEPTH will decrease the performances of search algorithms for contact.

Inacti = 5 or Inacti = 6, the gap is initially reduced and recovers its computed value as the slave node depenetrates.

Inacti = 6 is recommended instead of Inacti =5, to avoid high frequency effects into the interface.

with is Coulomb Friction coefficient.

Fric is Coulomb friction

Fric becomes a scale factor of Coulomb friction coefficient which depends on the temperature.

While,

is the interface temperature which is taken as the mean temperature of slave and master:

Where,

p is the pressure of the normal force on the master segment

V is the tangential velocity of the slave node.

14.	Currently, the coefficients C1 ~ C6 are used (if Ifric = 0) and C6 is not used (if Ifric = 1) to define a variable friction coefficient for new friction formulations.

The following formulations are available:

 if

 if

 if

Where,

•	First critical velocity must be different to 0 ().

•	First critical velocity must be lower than the second critical velocity ().

•	The static friction coefficient and the dynamic friction coefficient , must be lower than the maximum friction ( and ).

•	The minimum friction coefficient , must be lower than the static friction coefficient and the dynamic friction coefficient ( and ).

While and adhesion force is computed as follows:

with

Where,

Vt is the tangential relative velocity of the slave node with the master segment

If Ifiltr ≠ 0 , the tangential forces are smoothed using a filter:

Where coefficient is calculated from:

•	If Ifiltr = 1 , simple numerical filter

•	If Ifiltr = 2 , standard -3dB filter, with , and T is filtering period

•	If Ifiltr = 3 , standard -3dB filter, with Xfreq is cutting frequency

The filtering coefficient Xfreq should have a value between 0 and 1.

By Ithe= 1 (heat transfer activated) to consider heat exchange and heat friction in contact.

Tint is used only when Ithe_form= 0. In this case. The temperature of master side assumed to be constant (equal to Tint). If Ithe_form= 1 then Tint is not take into account. So the nodal temperature of master side will be considered

If Ithe = 2, Heat transfer is computed using thermal conductance Kthe only for the slave side. The temperature of the master side is not assumed to be a constant but is calculated from the temperature field defined on each master node. These nodal temperatures can vary over time and space which are defined using /IMPTEMP.

Thermal conduction

Ithe = 1 needs the material of the slave side to be a thermal material using finite element formulation for heat transfer (/HEAT/MAP).

Thermal conduction is computed when the slave node falls into gap:

Heat exchange coefficient

While fK is function of fct_IDK

Radiation is considered in contact if and the distance, d, of the slave node to the master segment is:

While Drad is the Maximum distance for radiation computation. The default value for Drad is computed as the maximum of:

It is recommended not to set the value too high for Drad, which may reduce the performance of RADIOSS Engine.

A radiant heat transfer conductance is computed as:

with

Where, is the Stefan Boltzman constant, is the emissivity of slave surface, and is the emissivity of master surface.

A damping force (resp. torque) is applied to the tool:

(resp.)

With resp.

Where,

C is a percentage of the critical damping with the tool mass Mass (resp. inertia I)

K is the total interface stiffness (resp. rotational stiffness Kr).

(resp. ) is the translational (resp. rotational) velocity of the tool, if IDref is equal to 0; otherwise, it is the relative velocity with respect to tool of interface IDref.