PCNTX5

Format

Example

Definitions

Comments

1. The property identification number must be that of an existing PCONT Bulk Data Entry. Only one PCNTX5 property extension can be associated with a particular PCONT.
2. PCNTX5 is only applied in geometric nonlinear analysis subcases which are defined by ANALYSIS = NLGEOM or IMPDYN. 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. INACTI = 3 or 4 are only recommended for small initial penetrations and should be used with caution because:
   • the coordinate change is irreversible
   • it may create other initial penetrations if several surface layers are defined in the interfaces
   • it may create initial energy if the node belongs to a spring element
6. IFRIC defines the friction model.

   IFRIC = COUL - Coulomb friction with F_T ≤ FRIC * F_N.

   For IFRIC > 0 the friction coefficient is set by a function ( $\mu$ = $\mu$ (p, V)), 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 = 1 - Generalized viscous friction law(1)
     $$\mu =\text{FRIC}+\text{C}1*\text{p}+\text{C}2*\text{V}+\text{C}3*\text{p}*\text{v}+\text{C}4*{\text{p}}^2+\text{C}5*{\text{v}}^2$$
   • IFRIC = 2 - Darmstad law(2)
     $$\mu ={\text{C}}_1*{\text{e}}^{(\text{C}{\hspace{0.17em}}_2\text{V})}*{\text{p}}^2+{\text{C}}_3*{\text{e}}^{(\text{C}{\hspace{0.17em}}_4\text{V})}*\text{p}+{\text{C}}_5*{\text{e}}^{(\text{C}{\hspace{0.17em}}_6\text{V})}$$
   • IFRIC = 3 - Renard law

     $\mu =C_1+\left(C_3-C_1\right)\cdot \frac{V}{C_5}\cdot \left(2-\frac{V}{C_5}\right)$	0 ≤ V ≤ C5
     $\mu =C_3-\left(\left(C_3-C_4\right)\cdot {\left(\frac{V-C_5}{C_6-C_5}\right)}^2\cdot \left(3-2\cdot \frac{V-C_5}{C_6-C_5}\right)\right)$	C5 ≤ V ≤ C6
     $\mu =C_2-\frac{1}{\frac{1}{C_2-C_4}+{\left(V-C_6\right)}^2}$	C6 ≤ V

     Where:(3)

     $$\begin{array}{l}{C}_1=C1={\mu }_s,C_2=C2={\mu }_d\hfill \\ C_3=C3={\mu }_{\text{max}},C_4=C4={\mu }_{\text{min}}\hfill \\ C_5=C5=V_{cr1},C_6=C6=V_{cr2}\hfill \end{array}$$
   • The first critical velocity V_cr1 must not be 0 (C5 ≠ 0). It also must be lower than the second critical velocity V_cr2 (C5 < C6).
   • The static friction coefficient C1 and the dynamic friction coefficient C2, must be lower than the maximum friction C3 (C1 < C3 and C2 < C3).
   • The minimum friction coefficient C4, must be lower than the static friction coefficient C1 and the dynamic friction coefficient C2 (C4 ≤ C1 and C4 ≤ C2).
7. IFILTR defines the method for computing the friction filtering coefficient. If IFILTR ≠ NO, the tangential friction forces are smoothed using a filter:(4)
   $${\text{F}}_{\text{T}}=\alpha *{\text{F}\prime }_{\text{T}}+(1-\alpha )*{\text{F}\prime }_{\text{T}-1}$$
   Where,

   F_T

   Tangential force

   F'_T

   Tangential force at time t

   F'_T-1

   Tangential force at time t-1

   α

   Filtering coefficient

   • IFILTR = SIMP - α = FFAC
   • IFILTR = PER - α = 2πdt/FFAC, where dt/T = FFAC, T is the filtering period
   • IFILTR = CUTF - α = 2π * FFAC * dt, where FFAC is the cutting frequency
8. This card is represented as an extension to a PCONT property in HyperMesh.