/INTER/LAGDT/TYPE7

Block Format Keyword

/INTER/LAGDT/TYPE7 - Interface Type 7 with Constant Minimum Time Step

Description

Describes the interface TYPE7 with constant minimum time step. Which means same behavior as interface TYPE7 with possible switch to Lagrange multiplier formulation, if minimum time step defined with /DT/INTER/CST is reached. The main limitations are:

•	Same limitation as interface TYPE7 with Lagrange multiplier formulation.

•	Friction is not working after switching into Lagrange multiplier formulation.

•	Not yet compatible with SPMD.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/INTER/LAGDT/TYPE7/inter_ID/unit_ID
inter_title
grnd_IDs	surf_IDm	Istf		Igap		Ibag	Idel
Fscalegap		Gapmax
Stmin		Stmax
Stfac		Fric		Gapmin		Tstart		Tstop
IBC			Inacti	VISS		VISF		Bumult
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)
grnd_IDs	Slave nodes group identifier (Integer)
surf_IDm	Master surface identifier (Integer)
Istf	Stiffness definition flag (Comment 4) (Integer) = 0: Stfac is a stiffness scale factor and the stiffness is computed according to the master side characteristics = 1: Stfac is a stiffness value = 2, 3, 4 and 5: Stfac and the stiffness is computed from both master and slave characteristics
Igap	Gap/element option flag (Integer) = 0: gap is constant and equal to the minimum gap = 1: gap varies accordingly to the characteristics of the impacted master surface and the impacting slave node = 2: variable gap + gap scale correction of the computed gap
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 2) 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.
Fscalegap	Gap scale factor Default = 1.0 (Real)
Gap_max	Maximum gap = 0: there is no maximum value for the gap. (Real)
Stmin	Minimum stiffness (Real)
Stmax	Maximum stiffness Default = 1030 (Real)
Stfac	Interface stiffness, if Istf = 1 Default set to 0.0 (Real)
Stfac	Stiffness scale factor for the interface, if Istf = 0; Default set to 1.0 (Real)
Fric	Coulomb friction (Real)
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 8) (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 and initial gap is computed as follows: , with being the initial penetration = 6: 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 (Comment 16) Default set to 1.0 (Real)
Bumult	Sorting factor (Comments 11 and 12) Default set to 0.20 (Real)
Ifric	Friction formulation flag (Comment 15) 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 16) (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 Should have a value between 0 and 1. (Real)
Iform	Friction penalty formulation type Default = 1 (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
IBCX	Deactivation flag of X boundary condition at impact =0: free DOF =1: fixed DOF (Boolean)
IBCY	Deactivation flag of Y boundary condition at impact =0: free DOF =1: fixed DOF (Boolean)
IBCZ	Deactivation flag of Z boundary condition at impact =0: free DOF =1: fixed DOF (Boolean)

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

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

3.	If Igap = 2, the variable gap is computed as:

The values given in Line 4 are ignored if Igap ≠ 2.

4.	Contact stiffness computed as:

➢	For Istf = 0, stiffness

➢	For Istf > 1 , stiffness

Where,

•	Kn is computed from both master segment stiffness Km and slave node stiffness Ks

Istf = 2,

Istf = 3,

Istf = 4,

Istf = 5,

•	Km is master segment stiffness and computed as follows:

When master segment lies on a shell or is shared by shell and solid

When master segment lies on a solid:

Where,

S is the segment area,

V is the volume of the solid,

B is the Bulk Modulus

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

When node is connected to a shell element:

When node is connected to a solid element:

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

5.	The values given in Line 5 are ignored if Istf < 1.

6.	A default value for Gapmin is computed as the minimum of:

While,

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

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

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

7.	The gap is computed for each impact as:

Where,

•	gm: master element gap:

with t: 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: 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.

The variable gap is always at least equal to Gapmin.

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

9.	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.

starter_inter_type7_Inacti

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

11.	The default value for Bumult is automatically increased to 0.30 for models which have more than 1.5 million nodes and to 0.40 for models with more than 2.5 million of nodes.

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

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

14.	For Friction Formulation

➢	If the friction flag Ifric = 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.

15.	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 coefficient ( and ).

16.	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 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.

17.	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