/INTER/TYPE7

Block Format Keyword

/INTER/TYPE7 - Interface Type 7

Description

Interface TYPE7 is a multi-usage impact interface, modeling contact between a master surface and a group of slave nodes. It is also possible to consider heat transfer and heat friction. All limitations that were encountered with interfaces TYPE3, TYPE4 and TYPE5 are solved with this interface:

•	A node can at the same time be a slave and a master node.

•	Each slave node can impact each master segment; except if it is connected to this segment.

•	A node can impact on more than one segment.

•	A node can impact on the two sides, on the edges and on the corners of each segments.

•	It is a fast search algorithm without limitations.

The main limitations of this interface are:

•	Time step is reduced in case of high impact speed or contacts with small gap;

•	It does not work properly if used with a rigid body at high impact speed or rigid body with small gap.

•	It does not solve edge to edge contact (to solve this, /INTER/TYPE11 should be used along with TYPE7).

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/INTER/TYPE7/inter_ID/unit_ID
inter_title
grnd_IDs	surf_IDm	Istf	Ithe	Igap		Ibag	Idel	Icurv	Iadm
Fscalegap		Gapmax		Fpenmax
Stmin		Stmax		%mesh_size		dtmin		Irem_gap	Irem_i2

Insert if Icurv = 1 or 2

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
node_ID1	node_ID2

Required Fields

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
Stfac		Fric		Gapmin		Tstart		Tstop
IBC			Inacti	VISS		VISF		Bumult
Ifric	Ifiltr	Xfreq		Iform	sens_ID	fct_IDF	AscaleF

If Ifric > 0

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
C1		C2		C3		C4		C5

If Ifric > 1

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
C6

If Iadm = 2

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
NRadm	Padm		Angladm

If Ithe = 1

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
Kthe		fct_IDK		Tint		Ithe_form	AscaleK
Frad		Drad		Fheats		Fheatm

Field	Contents	SI Unit Example
inter_ID	Interface identifier (Integer, maximum 10 digits)
unit_ID	Optional unit identifier (Integer, maximum 10 digits)
inter_title	Interface title (Character, maximum 100 characters)
grnd_IDs	Slave nodes group identifier (Integer)
surf_IDm	Master surface identifier (Integer)
Istf	Interface stiffness definition flag (Comment 3). For SPH, only Istf =0, 1 and 1000 are available. (Integer) = 0:default, set to value defined in /DEFAULT/INTER/TYPE7 = 1: Stfac is a constant stiffness value = 2, 3, 4 and 5: Stfac is a stiffness scale factor and the interface stiffness is computed from both master and slave characteristics = 1000: Stfac is a stiffness scale factor and interface stiffness is computed based only on the master side characteristics (default if /DEFAULT/INTER/TYPE7 is not defined)
Ithe	Heat contact flag (Integer) = 0: no heat transfer or heat friction = 1: heat transfer or heat friction activated
Igap	Gap/element option flag (Comment 11) (Integer) = 0: default, set to value defined in /DEFAULT/INTER/TYPE7 = 1: variable gap varies according to the characteristics of the impacted master surface and the impacting slave node = 2: variable gap + gap scale correction of the computed gap = 3: variable gap + gap scale correction of the computed gap + size of the mesh taken into account to avoid initial penetrations. = 1000: constant gap; equal to the minimum gap Gapmin (default if /DEFAULT/INTER/TYPE7 is not defined)
Ibag	Airbag vent holes closure flag in case of contact. This flag is also used to activate Sol2SPH particles, if the corresponding solid element is in contact. (Integer) = 0: default, set to value defined in /DEFAULT/INTER/TYPE7 = 1: closure = 2: no closure (default if /DEFAULT/INTER/TYPE7 is not defined)
Idel	Node and segment deletion flag (Integer) = 0: default, set to the value defined in /DEFAULT/INTER/TYPE7 = 1: when all the elements (4-node shells, 3-node shells, solids) associated to one segment are deleted, the segment is removed from the master side of the interface. It is also removed in case of explicit deletion using RADIOSS Engine keyword /DEL in the Engine file. Additionally, non-connected nodes are removed from the slave side of the interface. = 2: when a 4-node shell, a 3-node shell or a solid element is deleted, the corresponding segment is removed from the master side of the interface. It is also removed in case of explicit deletion using RADIOSS Engine keyword /DEL in the Engine file. Additionally, non-connected nodes are removed from the slave side of the interface. = 1000: no deletion (default if /DEFAULT/INTER/TYPE7 is not defined) = -1: same as = 1, except non-connected nodes are not removed from the slave side of the interface. = -2: same as =2, except non-connected nodes are not removed from the slave side of the interface. Note: Idel = 1 and -1 has a higher CPU cost when compared with Idel = 2 and -2.
Igap	Gap envelope with curvature (Comment 5) (Integer) = 0: no curvature = 1: spherical curvature = 2: cylindrical curvature = 3: automatic bicubic surface
Iadm	Computing local curvature flag for adaptive meshing (Comments 6 through 8) (Integer) = 0: not activated (default) = 1: interface update according mesh size = 2: interface update according mesh size, penetration and angle
Fscalegap	Gap scale factor (used only when Igap = 2 and 3) Default = 1.0 (Real)
Gapmax	Maximum gap (used only when Igap = 2 and 3) (Real)
Fpenmax	Maximum fraction of initial penetration (Comment 13) (Real)
Stmin	Minimum stiffness (used only when Istf > 1) (Real)
Stmax	Maximum stiffness (used only when Istf > 1) Default = 1030 (Real)
%mesh_size	Percentage of mesh size (used only when Igap = 3) Default = 0.4 (Real)
dtmin	Limiting nodal time step (Comment 26) (Real)
Irem_gap	Flag for deactivating slave nodes if element size < gap value, in case of self-impact contact (Comment 14) (Integer) = 0: default, set to the value defined in /DEFAULT/INTER/TYPE7 = 1: no deactivation of slave nodes. Default if /DEFAULT/INTER/TYPE7 is not defined. = 2: deactivation of slave nodes
Irem_i2	Flag for deactivating the slave node, if the same contact pair (nodes) has been defined in interface TYPE2. = 0: default, set to the value defined in /DEFAULT/INTER/TYPE7 = 1: with deactivating default if /DEFAULT/INTER/TYPE7 is not defined, implicit solution (if /IMPLICIT is defined) = 3: without deactivating (default if /DEFAULT/INTER/TYPE7 is not defined, for explicit solution)
node_ID1	First node identifier (Integer)
node_ID2	Second node identifier (ignored when Igap = 1) (Integer)
Stfac	Stiffness scale factor for the interface (if Istf ≠ 1) Default = 1.0 (Real) Interface stiffness (if Istf = 1) Default = 0.0 (Real)
Fric	Coulomb friction (if fct_IDF = 0) Default = 0.0 (Real) Coulomb friction scale factor (if fct_IDF ≠ 0) Default = 1.0 (Real) (Comment 20)
Gapmin	Minimum gap for impact activation (Real)
Tstart	Start time (Real)
Tstop	Time for temporary deactivation (Real)
IBC	Deactivation flag of boundary conditions at impact (Boolean)
Inacti	Deactivation flag of stiffness in case of initial penetrations (Comment 13) (Integer) = 0: default, set to the value defined in /DEFAULT/INTER/TYPE7 = 1: deactivation of stiffness on nodes = 2: deactivation of stiffness on elements = 3: change node coordinates to avoid initial penetrations = 5: gap is variable with time and initial gap is adjusted as follows: , where P0 is the initial penetration = 6: gap is variable with time but initial gap is adjusted as follows (the node is slightly depenetrated): = 1000: no action (default if /DEFAULT/INTER/TYPE7 is not defined)
VISS	Critical damping coefficient on interface stiffness Default set to 0.05 (Real)
VISF	Critical damping coefficient on interface friction (Comment 22) Default set to 1.0 (Real)
Bumult	Sorting factor ( Comments 15 and 16) Default set to 0.20 (Real)
Ifric	Friction formulation flag (Comments 19 and 20) (Integer) = 0: static Coulomb friction law = 1: generalized viscous friction law = 2: Darmstad friction law = 3: Renard friction law
Ifiltr	Friction filtering flag (Comment 21) (Integer) = 0: no filter is used = 1: simple numerical filter = 2: standard -3dB filter with filtering period = 3: standard -3dB filter with cutting frequency
Xfreq	Filtering coefficient This coefficient should have a value between 0 and 1. Default = 1.0 (Real)
Iform	Friction penalty formulation type (Comment 22) (Integer) = 0: default, set to the value defined in /DEFAULT/INTER/TYPE7 = 1: viscous (total) formulation (default if /DEFAULT/INTER/TYPE7 is not defined) = 2: stiffness (incremental) formulation
sens_ID	Sensor identifier to Activate/Deactivate the interface (Comment 26) (Integer) If an identifier sensor is defined, the activation/deactivation of interface is based on sensor and not on Tstart or Tstop.
fct_IDF	Friction coefficient with temperature function identifier Default = 0 (Integer)
AscaleF	Abscissa scale factor on fct_IDF Default = 1.0 (Real)
C1	Friction law coefficient (Real)
C2	Friction law coefficient (Real)
C3	Friction law coefficient (Real)
C4	Friction law coefficient (Real)
C5	Friction law coefficient (Real)
C6	Friction law coefficient (Real)
Kthe	Heat exchange coefficient (if fct_IDK = 0) Default = 0.0 Heat exchange coefficient (if fct_IDK ≠ 0) Default = 1.0 (Comment 23) (Real)
fct_IDK	Function identifier for thermal heat exchange definition with contact pressure. Default = 0 (Integer)
AscaleK	Abscissa scale factor on fct_IDK Default = 1.0 (Real)
Tint	Interface temperature (Comment 23) (Real)
Ithe_form	Heat contact formulation flag (Integer) = 0: exchange only between interface (constant temperature) and shells (slave side) (default) = 1: heat exchange between all pieces in contact
NRadm	Number of elements through a 90 degrees radius (Integer)
Padm	Criteria on the percentage of penetration Default = 1.0 (Real)
Angladm	Angle criteria (Real)
Frad	Radiation factor (Real)
Drad	Maximum distance for radiation computation (Real)
Fheats	Frictional heating factor on salve side (Comment 24) (Real)
Fheatm	Frictional heating factor on master side (Comment 24) (Real)

(1)-1	(1)-2	(1)-3	(1)-4	(1)-5	(1)-6	(1)-7	(1)-8
					IBCX	IBCY	IBCZ

Field	Contents	SI Unit Example
IBCX	= 1: Deactivation flag of X boundary condition at impact (Boolean)
IBCY	= 1: Deactivation flag of Y boundary condition at impact (Boolean)
IBCZ	= 1: Deactivation flag of Z boundary condition at impact (Boolean)

1.	In case of SPMD, each master segment defined by surf_IDm must be associated to an element (possibly to a void element).

2.	For the flag Ibag, refer to the monitored volume option (/MONVOL).

3.	Contact stiffness computed as:

For Istf =1000, stiffness:

For Istf > 1 and Istf < 1000, stiffness:

Where, Kn is computed from both master segment stiffness Km and slave node stiffness Ks:

Where, Km is master segment stiffness and computed as follows:

when the master segment lies on a shell or is shared by shell and solid:

when the master segment lies on a solid:

Where, S is the segment area; V is the volume of the solid, and B is the Bulk Modulus.

Where, Ks is an equivalent nodal stiffness considered for interface TYPE7, and computed as:

when the node is connected to a shell element:

when the node is connected to a solid element:

There is no limitation to the value of stiffness factor (but, a value greater than 1.0 can reduce the initial time step).

4.	Istf = 2, 3, 4, or 5 are not compatible with SPH formulation.

5.	If Icurv = 1, a spherical curvature is defined for the gap with node_ID1 (center of the sphere).

If Icurv = 2, a cylindrical curvature is defined for the gap with node_ID1 and node_ID2 (on the axis of the cylinder).

If Icurv = 3, the master surface shape is obtained with a bicubic interpolation, respecting continuity of the coordinates and the normal from one segment to the other. In case of a fast and large change in curvature, this formulation might become unstable (will be improved in future version).

inter_type7_Icurv

6.	In case of adaptive meshing and Iadm = 1:

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).

inter_type7_Iadm

7.	In case of adaptive meshing and Iadm = 2:

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).

inter_type7_angladm

8.	The coefficients NRadm, Padm, and Angladm are used only if adaptive meshing and Iadm = 2.

9.	If Gapmax = 0, there is no maximum value for the gap.

10.	If Gapmin is not specified or set to zero, a default value is computed as the minimum of:

•	t is the average thickness of the master shell elements;

•	, lmin being the smallest side length of all master segments (shell or brick).

If all of the master segments are brick, Gapmin is defined by:

•	, lmin being the smallest side of all master brick segments.

11.	Variable gap:

If Igap =1, variable gap is computed as:

If Igap =2, variable gap is computed as:

If Igap =3, variable gap is computed as:

Where,

•	gm: master element gap:

gm = , where t is the thickness of the master element for shell elements

gm = 0 for brick elements

•	gs: slave node gap:

gs = 0 if the slave node is not connected to any element or is only connected to brick or spring elements.

, where t is the largest thickness of the shell elements connected to the slave node.

for truss and beam elements, with S being the cross section of the element.

•	gs_1: length of the smaller edge of element.

•	gs_1: length of the smaller edge of elements connected to the slave node.

If the slave node is connected to multiple shells and/or beams or trusses, the largest computed slave gap is used.

The variable gap is always at least equal to Gapmin.

12.	Deactivation of the boundary condition is applied to slave nodes group (grnd_IDs).

13.	Inacti = 3 may create initial energy if the node belongs to a spring element.

Inacti = 5 is recommended for airbag simulation deployment.

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

Inacti_flag_6

If Fpenmax is not equal to zero, nodes stiffness is deactivated if:

whatever the value of Inacti.

14.	With Irem_gap = 2, it allows to have the element size smaller than gap values:

inter_type7_master_seg

For self-impact contact, when Curvilinear Distance (from a node of the master segment to a slave node) is smaller than (in initial configuration), this slave node will not be taken into account by this master segment, and it will not be deleted from the contact for the other master segments.

15.	The sorting factor, Bumult is used to speed up the sorting algorithm.

16.	The sorting factor Bumult is machine dependent.

17.	One node can belong to the two surfaces at the same time.

18.	There is no limitation value to the stiffness factor (but a value greater than 1.0 can reduce the initial time step).

19.	For friction formulation:

If the friction flag Ifric = 0 (default), the old static friction formulation is used:

with is Coulomb friction coefficient

•	If fct_IDF = 0: Fric is Coulomb friction.

•	If fct_IDF ≠ 0: Fric becomes a scale factor of Coulomb friction coefficient which depends on the temperature.

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

For flag Ifric > 0, new friction models are introduced. In this case, the friction coefficient is set by a function (),

Where, p is the pressure of the normal force on the master segment and V is the tangential velocity of the slave node.

20.	Currently, the coefficients C1 through C6 are used to define a variable friction coefficient for new friction formulations.

The following formulations are available:

•	Ifric = 1 (generalized viscous friction law):

•	Ifric = 2 (Darmstad law):

•	Ifric = 3 (Renard law):

where,

First critical velocity must be different to 0 ().

First critical velocity must be less than the second critical velocity .

The static friction coefficient C1 and the dynamic friction coefficient C2, must be less than the maximum friction C3 ( and ).

The minimum friction coefficient C4 must be less than the static friction coefficient C1 and the dynamic friction coefficient C2 ( and ).

21.	Friction filtering:

If Ifiltr flag ≠ 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 the filtering period

if Ifiltr = 3 , standard -3dB filter, with Xfreq = cutting frequency

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

22.	Friction penalty formulation Iform:

If Iform = 1 (default) viscous formulation, the friction forces are:

While an adhesion force is computed as:

with

If Iform = 2, stiffness formulation), the friction forces are:

While an adhesion is computed as:

with

Where, Vt is the contact tangential velocity.

Iform = 2 is recommended for implicit and low speed impact explicit analysis.

23.	Heat exchange:

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

•	If Ithe_form = 0, then heat exchange is between shell and constant temperature contact Tint.

•	If Ithe_form = 1, then heat exchange is between all contact pieces.

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.

Heat exchange coefficient

•	If fct_IDK = 0, then Kthe is heat exchange coefficient and heat exchange depends only on heat exchange surface.

•	If fct_IDK ≠ 0, Kthe is a scale factor and heat exchange depends on contact pressure:

While fK is the function of fct_IDK.

24.	Heat Friction

•	Frictional energy is converted into heat when Ithe > 0 for interface.

•	Fheats and Fheatm are defined as the fraction of frictional energy and distributed respectively to the slave side and master side. So generally:

When both Fheats and Fheatm are equal to 0, the conversion of the frictional sliding energy to heat is not activated.

•	The frictional heat QFric is defined:

o	If Iform= 2 (a stiffness formulation): Slave side: Master side: (Ithe_form= 1)

o	If Iform= 1 (a penalty formulation): Slave side: Master side: (Ithe_form= 1)

25.

Radiation

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:

•	upper value of the Gap (at time 0) among all nodes

•	smallest side length of slave element

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.

26.	Slave segment is deactivated from the contact when the segment kinematic time step calculated for this contact becomes smaller than dtmin.

27.	When sens_ID is defined for activation/deactivation of the interface, Tstart and Tstop are not taken into account.