/INTER/TYPE20

Block Format Keyword

/INTER/TYPE20 - Interface Type 20

Description

This is a general single surface or surface to surface contact interface. Edge to Edge contact is also possible. Penalty stiffness is constant and therefore the time step is not affected (for standard penalty stiffness). This contact interface can replace interface TYPE3, TYPE5, TYPE7, TYPE11 or TYPE19. The interface is basically defined in terms of one or two surfaces. If only one surface is used, this surface is self-impacting. If two surfaces are defined, nodes of surface two impact surface one. A symmetric treatment can be activated. Edges of surface one and two can be taken into account for the contact. Nodes can be added to surface.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/INTER/TYPE20/inter_ID/unit_ID
inter_title
surf_ID1	surf_ID1	Isym	Iedge	grnd_ID	line_ID1	line_ID1		edge_angle
				Igap		Ibag	Idel
				Fpenmax
Blank Format

Required Fields

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
Stfac		Fric		Gap0		Tstart		Tstop
IBC			Inacti	VISS		VISF
Ifric	Ifiltr	Xfreq		Iform

Read this input only if Ifric > 0 (Optional)

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

Read this input only if Ifric > 1 (Optional)

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

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)
surf_ID1	First surface identifier (Integer)
surf_ID2	Optional second surface identifier (Integer) = 0: First surface is self-impacting (except if Isym = 2)
Isym	Symmetric contact treatment flag (Integer) = 0: Set to 1 = 1: Nodes from surfaces 1 and 2 and nodes from grnd_ID impact surfaces 1 and 2 = 2: Nodes from surface 2 and nodes from grnd_ID impact surface 1
Iedge	Edge definition flag (Integer) = 0: No edge generation from surf_ID1 and surf_ID2 = 1: Only external border edges from surf_ID1 and surf_ID2 are generated = 2: All segment edges from surf_ID1 and surf_ID2 are generated = 3: Same as 1 + sharp edges between segments
grnd_ID	Optional nodes group identifier used to add nodes to surface nodes (Integer)
line_ID1	Optional first line identifier (Integer)
line_ID2	Optional second line identifier (Integer)
edge_angle	Edges angle Default = 91 (Real) Use only if Iedge = 3 If angle between two edges is smaller than edge_angle, the edge is considered.
Igap	Gap/element option flag (Integer) = 0: gap is constant and equal to Gap0 (Comment 6) = 1: gap varies (in space, not in time) according to the characteristics of the impacted surfaces and nodes (Comment 7).
Ibag	Airbag vent holes closure flag in case of contact Default = 0 (Integer) = 0: no closure = 1: closure
Idel	Node and segment deletion flag (Comment 5) Default = 0 (Integer) = 0: no deletion = 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. = -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.
Fpenmax	Maximum initial penetration factor (0 < Fpenmax < 1) (Comment 10) Default = 1.0 (Real)
Stfac	Interface stiffness scale factor Default = 1 (Real)
Fric	Coulomb friction (Real)
Gap0	Minimum gap for impact activation (Comment 6) If Igap = 0 default is: (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 9) (Integer) = 0: no action = 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 but initial penetration is computed as follows (the node is slightly depenetrated):
VISS	Critical damping coefficient on interface stiffness Default set to 0.05 (Real)
VISF	Critical damping coefficient on interface friction Default set to 1.0 (Real)
Ifric	Friction formulation flag (Comments 13 and 14) Default = 0 (Integer) = 0: static Coulomb friction law = 1: generalized viscous friction law = 2: Darmstad friction law = 3: Renard friction law
Ifiltr	Friction filtering flag (Comment 15) (Integer) = 0: no filter is used (Default) = 1: simple numerical filter = 2: standard -3dB filter with filtering period = 3: standard -3dB filter with cutting frequency
Xfreq	Filtering coefficient (Real)
Iform	Friction penalty formulation type Default = 2 (Integer) = 1: viscous (total) formulation = 2: stiffness (incremental) formulation
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)

(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	Deactivation flag of X boundary condition at impact (Boolean) =0: free DOF =1: fixed DOF
IBCY	Deactivation flag of Y boundary condition at impact (Boolean) =0: free DOF =1: fixed DOF
IBCZ	Deactivation flag of Z boundary condition at impact (Boolean) =0: free DOF =1: fixed DOF

1.	The simplest input is to enter only one self-impacting surface surf_ID1.

2.	To emulate an interface TYPE7 or TYPE11 input:

TYPE20 to emulate TYPE7 input

TYPE20 to emulate TYPE11 input

(TYPE20) surf_ID1 = surf_IDm (TYPE7)

(TYPE20) grnd_ID = grnd_IDs (TYPE7)

(TYPE20) line_ID1 = line_IDs (TYPE11)

(TYPE20) line_ID2 = line_IDm (TYPE11)

(TYPE20) line_ID1 = 0

(TYPE20) line_ID2 = 0

(TYPE20) surf_ID1 = 0

(TYPE20) grnd_ID = 0

(TYPE20) surf_ID2 = 0

(TYPE20) Isym = 2

(TYPE20) Iedge = 0

(TYPE20) surf_ID2 = 0

(TYPE20) Isym = 0

(TYPE20) Iedge = 0

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

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

5.	Flag Idel = 1 has a CPU cost higher than Idel = 2.

6.	If Igap = 0, a default value used for Gap0, which is computed as:

With,

•	t: average thickness of the master shell elements;

•	l: average side length of the master brick elements;

•	lmin: smallest side length of all master segments (shell or brick)

7.	If Igap = 1, the gap is computed for each impact as:

With,

•	gm: master element gap:

, with 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.

, with 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.

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

If the free edge of a shell element is in contact, then Igap can shift the gap of the free edges border shells, as shown below:

inter_type2_Igap

8.	Deactivation of the boundary condition is applied to slave nodes group (surf_IDs).

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

Inacti = 5: see figure below

Inacti_flag

10.	Maximum penetration value is set as a fraction of the actual gap (including variable gap):

If the initial penetration of a slave node is greater than the calculated maximum value (Fpenmax), the node will be deactivated from the interface (node stiffness deactivation).

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

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

13.	For Friction Formulation

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

with ( is Coulomb friction coefficient)

•	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

V is the tangential velocity of the slave node.

14.	Currently, the coefficients C1 ~ 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 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 ).

15.	Friction filtering

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 a 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.

16.	Friction penalty formulation Iform

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

While an adhesion force is computed as follows:

with

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

While an adhesion force is computed as follows:

with

Where,

Vt is contact tangential velocity

/INTER/TYPE20

/INTER/TYPE20

/INTER/TYPE20

Format

See Also: