PCNTX24

Bulk Data Entry

PCNTX24 – Extended CONTACT Property type 24 for Geometric Nonlinear Analysis

Description

Defines properties type 24 of a CONTACT interface for geometric nonlinear analysis.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
PCNTX24	PID
	ISTF
						GAPMAXs	GAPMAXm
	STMIN	STMAX	IGAP0	IPEN0	IPENMAX	IPENMIN
	STFAC	FRIC		TSTART	TEND
	IBC			INACTI	VISS
	IFRIC	IFILT	FFAC		SENSID
	FRICDAT	C1	C2	C3	C4	C5	C6

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
PCONT	34
PCNTX24	34

Field	Contents
PID	Property identification number of the corresponding PCONT entry. No default (Integer > 0)
ISTF	Stiffness definition flag (See comment 5). Default as defined by CONTPRM (Integer = 0, …, 5) 0 - The stiffness is computed according to the master side characteristics. 2, 3, 4 and 5 - The interface stiffness is computed from both master and slave characteristics.
GAPMAXs	Slave maximum gaps. (Real)
GAPMAXm	Master maximum gaps. (Real)
STMIN	Minimum stiffness (Only with ISTF > 1). Default as defined by CONTPRM (Real > 0)
STMAX	Maximum stiffness (Only with ISTF > 1). Default as defined by CONTPRM (Real > 0)
IGAP0	Gap modification flag for slave shell nodes on the free edges. (Integer) 0 - No change 1 - Set gap to zero for the slave shell nodes
IPEN0	Initial penetration detection flag (Integer) 0 - default method. Excludes the initial auto-impacts in the same part (shell and solid elements only). IPEN0 = 1 takes into account the initial auto-impacts in the same part, but in some complex situations, wrong initial penetrations might be given. 1 - method 1 (including auto-impact in each part)
IPENMAX	Maximum initial penetration: Penetration higher than this value will not be taken into account. (Real)
IPENMIN	Minimum initial penetration: Penetration higher than this value will be taken into account. (Real)
STFAC	Interface stiffness scale factor. Default as defined by CONTPRM (Real > 0)
FRIC	Coulomb friction. Default as defined by CONTPRM (Real > 0)
TSTART	Start time Default = 0.0 (Real > 0)
TEND	Time for temporary deactivation. Default = 1030 (Real > 0)
IBC	Flag for deactivation of boundary conditions at impact applied to the slave grid set. Default as defined by CONTPRM (Character = X, Y, Z, XY, XZ, YZ, or XYZ)
INACTI	Handling of initial penetrations flag. Default as defined by CONTPRM (Integer = 0, 1, -1, or 5) 0 - only tiny initial penetrations (1.0e-08) will be taken into account. Ignores the initial penetrations, but the contacts are not deleted, new contact will be well detected once the penetrations are disappeared 1 - all initial penetrations will be ignored. -1 - all initial penetrations will be taken into account. 5 - Similar to the one of interface type 7, but once the initial penetration is gone, the new contact will be detected using not-adjusted gap (P0 is reset to zero)GAP is variable with time and initial gap is adjusted as follows: gap0 = gap - P0, where P0 is the initial penetration
VISS	Critical damping coefficient on interface stiffness. Default as defined by CONTPRM (Real > 0)
IFRIC	Friction formulation flag (See comment 8). Default as defined by CONTPRM (Character = COUL, GEN, DARM, or REN) COUL - Static Coulomb friction law. GEN - Generalized viscous friction law. DARM - Darmstad friction law. REN - Renard friction law.
IFILT	Friction filtering flag (See comment 9). Default as defined by CONTPRM (Character = NO, SIMP, PER, or CUTF) NO - No filter is used. SIMP - Simple numerical filter. PER - Standard -3dB filter with filtering period. CUTF - Standard -3dB filter with cutting frequency.
FFAC	Friction filtering factor. Default as defined by CONTPRM
SENSID	Sensor identifier to Activate/Deactivate the interface (See comment 12) No default (Integer) If a sensor identifier is defined, the activation/deactivation of interface is based on the sensor and not on Tstart or Tstop.
FRICDAT	Indicates that additional information for IFRIC will follow. Only available when IFRIC = GEN, DARM or REN.
C1, C2, C3, C4, C5, C6	Coefficients to define variable friction coefficient in IFRIC = GEN, DARM, or REN. Default as defined by CONTPRM (Real > 0)

Comments

1.	The property identification number must be that of an existing PCONT bulk data entry. Only one PCNTX24 property extension can be associated with a particular PCONT.

2.	PCNTX24 is only supported for geometric nonlinear explicit dynamic analysis subcase defined by ANALYSIS = EXPDYN. It is ignored for all other subcases.

3.	If FRIC is not explicitly defined on the PCONTX/PCNTX# entries, the MU1 value on the CONTACT or PCONT entry is used for FRIC in the /INTER entries for Geometric Nonlinear Analysis. Otherwise, FRIC on PCONTX/PCNTX# overwrites the MU1 value on CONTACT/PCONT.

4.	In implicit analysis, different contact formulations are used for contact where slave and master set do not overlap and where they overlap (self-contact).

In the case of self-contact, the gap cannot be zero and a constant gap is used. For small initial gaps, the convergence will be more stable and faster if GAP is larger than the initial gap.

In implicit analysis, sometimes a stiffness with scaling factor reduction (for example, STFAC = 0.01) or reduction in impacted thickness (if rigid one) might reduce unbalanced forces and improve convergence, particularly in shell structures under bending where the effective stiffness is much lower than membrane stiffness; but it should be noted that too low of a value could also lead to divergence.

5.	If ISTF ≠ 1, the interface stiffness K is computed from the master segment stiffness Km and/or the slave segment stiffness Ks.

The master stiffness is computed from Km = STFAC * B * S * S/V for solids, Km = 0.5 * STFAC * E * t for shells.

The slave stiffness is an equivalent nodal stiffness computed as Ks = STFAC * B * V-3 for solids, Ks = 0.5 * STFAC * E * t for shells.

In these equations, B is the Bulk Modulus, S is the segment area, and V is the volume of a solid. There is no limitation to the value of stiffness factor (but a value larger than 1.0 can reduce the initial time step).

The interface stiffness is K = max (STMIN, min (STMAX, K1)) with:

•	ISTF = 0, K1 = Km

•	ISTF = 2, K1 = 0.5 * (Km + Ks)

•	ISTF = 3, K1 = max (Km, Ks)

•	ISTF = 4, K1 = min (Km, Ks)

•	ISTF = 5, K1 = Km * Ks / (Km + Ks)

6.	The gap is computed automatically (similar with IGAP = VAR on PCNTX7) for each impact as gs + gm;

with:

•	gm - master element gap, with:

gm = t/2, t: thickness of the master element for shell elements.

gm = 0 for solid elements.

•	gs - slave node gap:

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

gs = t/2, t - largest thickness of the shell elements connected to the slave node.

gs = 1/2√S for truss and beam elements, with S being the cross section of the element.

gm and gs are limited separately by GAPMAXm and GAPMAXs before the gap computation.

7.	The coefficients C1 - C6 are used to define a variable friction coefficient .

8.	IFRIC defines the friction model.

IFRIC = COUL – Coulomb friction with FT < FRIC * FN.

For IFRIC > 0 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.

The following formulations are available:

•	IFRIC = GEN - Generalized viscous friction law

FRIC + C1 * p + C2 * V + C3 * p * v + C4 * p2 + C5 * v2

•	IFRIC = DARM - Darmstad law

= C1 * e(C2V) * p2 + C3 * e(C4V) * p + C5 * e(C6V)

•	IFRIC = REN - Renard law

	0 < V < C5
	C5 < V < C6
	C6 < V

where:

renard4

•	The first critical velocity Vcr1 must not be 0 (C5 ≠ 0). It also must be lower than the second critical velocity Vcr2 (C5 < C6).

•	The static friction coefficient C1 and the dynamic friction coefficient C2, must be lower than or equal to the maximum friction C3 (C1 < C3 and C2 < C3).

•	The minimum friction coefficient C4, must be lower than or equal to the static friction coefficient C1 and the dynamic friction coefficient C2 (C4 < C1 and C4 < C2).

9.	IFILT defines the method for computing the friction filtering coefficient. If IFILT ≠ NO, the tangential friction forces are smoothed using a filter:

FT = α * F'T + (1 - α) * F'T-1

where,

FT is the tangential force

F'T is the tangential force at time t

F'T-1 is the tangential force at time t-1

α is the filtering coefficient

IFILT = SIMP – α = FFAC

IFILT = PER – α = 2dt/FFAC, where dt/T = FFAC, T is the filtering period

IFILT = CUTF – α = 2 * FFAC * dt, where FFAC is the cutting frequency

10.	IFORM selects two types of contact friction penalty formulation.

The viscous (total) formulation (IFORM = VISC) computes an adhesive force as:

Fadh = VISF * √(2KM) * VT

FT = min (µFN, Fadh)

The stiffness (incremental) formulation (IFORM = STIFF) computes an adhesive force as:

Fadh = FTold + ΔFT

ΔFT = K * VT * dt

FTnew = min (µFN, Fadh)

11.	When SENSID is defined for activation/deactivation of the interface, TSTART and TSTOP are not taken into account.

12.	When the contact type is the symmetric surface to surface, the output normal contact forces in TH file are correctly calculated if the two surfaces are well separated.

13.	For implicit test: Interface type24 is now only available with SMP. The default of ISTF will be set to 4. The default INACTI will be set to -1.

14.	This card is represented as an extension to a PCONT property in HyperMesh.