Iform = 10

Block Format Keyword Able to handle up to four materials: Three elasto-plastic materials (solid, liquid, or gas), and one high explosive material (JWL EOS).

The material law is based on a diffusive interface technique. For sharper interfaces between submaterial zone, refer to /ALE/MUSCL.

It is not recommended to use this law with Radioss single precision engine.

LAW51 is based on equilibrium between each material present inside the element. Radioss computes and outputs a relative pressure ΔPΔP . At each cycle:(1)
ΔP=ΔP1=ΔP2=ΔP=3ΔP4ΔP=ΔP1=ΔP2=ΔP3=ΔP4
Total pressure can be calculated with external pressure:(2)
P=ΔP+PextP=ΔP+Pext
Where,
P
Positive for a compression and negative for traction.
Hydrostatic stresses are computed from Polynomial EOS:(3)
σm=ΔP=C0+C1μ+C'2μ2+C'3μ3+(C4+C5μ)E(μ)
(4)
dEint=δW+δQ=(ΔP+Pext)dV+δQ

Where, E=Eint/V0,C'2=C2δμ0andC'3=C3δμ0 mean that the EOS is linear for an expansion and cubic for a compression.

By default, the process is adiabatic δQ=0 . To enable thermal computation, refer to 6.

Deviatoric stresses are computed with a Johnson-Cook model:(5)
σdev={GεifσVMα(α+bεpn)(1+cln˙ε˙ε0)(1(TT0TmeltT0)m)ifσVM>α
High explosive material is modeled with linear EOS if unreacted and JWL EOS for detonation products:(6)
ΔP={C0+C1μifT<TdetA(1ωR1V)eR1V+B(1ωR2V)eR2V+ωEVifσVM>α

Where, V is relative volume: V=Volume/V0 and E is the internal energy per unit initial volume: E=Eint/V0 . 9 to 13

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/MAT/LAW51/mat_ID/unit_ID
mat_title
Blank
Iform                  
#Global Parameters
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Pext ν νvol        
#Material1 Parameters
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
αmat_10 ρmat_10 Emat_10 ΔPmat_1min Cmat_10
Cmat_11 Cmat_12 Cmat_13 Cmat_14 Cmat_15
Gmat_11 amat_1 bmat_1 nmat_1    
cmat_1 ˙εmat_10            
mmat_1 Tmat_10 Tmat_1melt Tmat_1lim ρCmat_1v
εmat_1p,max σmat_1max Kmat_1A Kmat_1B    
#Material2 Parameters
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
αmat_20 ρmat_20 Emat_20 ΔPmat_2min Cmat_20
Cmat_21 Cmat_22 Cmat_23 Cmat_24 Cmat_25
Gmat_21 amat_2 bmat_2 nmat_2    
cmat_2 ˙εmat_20            
mmat_2 Tmat_20 Tmat_2melt Tmat_2lim ρCmat_2v
εmat_2p,max σmat_2max Kmat_2A Kmat_2B    
#Material3 Parameters
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
αmat_30 ρmat_30 Emat_30 ΔPmat_3min Cmat_30
Cmat_31 Cmat_32 Cmat_33 Cmat_34 Cmat_35
Gmat_31 amat_3 bmat_3 nmat_3    
cmat_3 ˙εmat_30            
mmat_3 Tmat_30 Tmat_3melt Tmat_3lim ρCmat_3v
εmat_3p,max σmat_3max Kmat_3A Kmat_3B    
#Material4 Parameters (Explosive)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
αmat_40 ρmat_40 Emat_40 ΔPmat_4min Cmat_40
A B R1 R2 ω
D PCJ Cmat_41     IBFRAC  

Definitions

Field Contents SI Unit Example
mat_ID Material identifier.

(Integer, maximum 10 digits)

 
unit_ID Unit Identifier

(Integer, maximum 10 digits)

 
mat_title Material title.

(Character, maximum 100 characters)

 
Iform Formulation flag.

(Integer)

 
Pext External pressure. 2

Default = 0 (Real)

[Pa]
ν Kinematic viscosity shear ν=μ/ρ . 3

Default = 0 (Real)

[m2s]
νvol Kinematic viscosity (volumetric), νvol=3λ+2μρ which corresponds to Stokes Hypothesis. 3

Default = 0 (Real)

[m2s]
αmat_i0 Initial volumetric fraction. 4

(Real)

 
ρmat_i0 Initial density.

(Real)

[kgm3]
Emat_i0 Initial energy per unit volume.

(Real)

[Jm3]
ΔPmat_imin Hydrodynamic cavitation pressure. 5

If fluid material ( Gmat_i1=0 ), then default = -Pext

If solid material ( Gmat_i10 ), then default = -1e30.

(Real)

[Pa]
Cmat_i0 Initial pressure.

(Real)

[Pa]
Cmat_i1 Hydrodynamic coefficient.

(Real)

[Pa]
Cmat_i2 Hydrodynamic coefficient.

(Real)

[Pa]
Cmat_i3 Hydrodynamic coefficient.

(Real)

[Pa]
Cmat_i4 Hydrodynamic coefficient. 9

(Real)

[Pa]
Cmat_i5 Hydrodynamic coefficient.

(Real)

 
Gmat_i1 Elasticity shear modulus.
= 0 (Default)
Fluid material

(Real)

[Pa]
amat_i Plasticity yield stress.

(Real)

[Pa]
bmat_i Plasticity hardening parameter.

(Real)

[Pa]
nmat_i Plasticity hardening exponent.

Default = 1.0 (Real)

 
cmat_i Strain rate coefficient.
= 0
No strain rate effect

Default = 0.00 (Real)

 
˙εmat_i0 Reference strain rate.

If ˙ε˙εmat_i0 , no strain rate effect

(Real)

[1s]
mmat_i Temperature exponent.

Default = 1.00 (Real)

 
Tmat_i0 Initial temperature.

Default = 300 K (Real)

[K]
Tmat_imelt Melting temperature.
= 0
No temperature effect

Default = 1030 (Real)

[K]
Tmat_ilim Maximum temperature.

Default = 1030 (Real)

[K]
ρCmat_iv Specific heat per unit of volume. 7

(Real)

[Jm3K]
εmat_ip,max Failure plastic strain.

Default = 1030 (Real)

 
σmat_imax Plasticity maximum stress.

Default = 1030 (Real)

[Pa]
Kmat_iA Thermal conductivity coefficient 1. 8

(Real)

[WmK]
Kmat_iB Thermal conductivity coefficient 2. 8

(Real)

[WmK2]
αmat_40 Initial volumetric fraction of unreacted explosive. 4

(Real)

 
ρmat_40 Initial density of unreacted. explosive

(Real)

[kgm3]
Emat_40 Detonation energy.

(Real)

[Jm3]
ΔPmat_4min Minimum pressure. 5

Default = Pext

(Real)

[Pa]
Cmat_40 Initial pressure of unreacted explosive.

(Real)

[Pa]
A JWL EOS coefficient.

(Real)

[Pa]
B JWL EOS coefficient.

(Real)

[Pa]
R1 JWL EOS coefficient.

(Real)

 
R2 JWL EOS coefficient.

(Real)

 
ω JWL EOS coefficient.

(Real)

 
D Detonation velocity. [ms]
PCJ Chapman-Jouget pressure.

(Real)

[Pa]
Cmat_41 Hydrodynamic coefficient for unreacted explosive. 9

(Real)

[Pa]
IBFRAC Burn Fraction Calculation flag. 11
= 0
Volumetric Compression + Burning Time
= 1
Volumetric Compression only
= 2
Burning Time only

(Integer)

 

Example

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/LAW51/99
99.99% Water + 0.01% Air-MULTIMAT:AIR+WATER+TNT,units{kg,m,s,Pa}
#(output is total pressure:Pext=0)
#--------------------------------------------------------------------------------------------------#
#                    Material Law No 51. MULTI-MATERIAL SOLID LIQUID GAS -ALE-CFD-SPH               
#--------------------------------------------------------------------------------------------------#
#     Blank format

#    IFORM
        10
#---Global parameters------------------------------------------------------------------------------#
#              P_EXT                  NU               LAMDA
                   0                   0                   0
#---Material#1:AIR(PerfectGas)---------------------------------------------------------------------#
#            ALPHA_1             RHO_0_1               E_0_1             P_MIN_1               C_0_1
              0.0001                 1.2             2.5E+05                   0                   0
#              C_1_1               C_2_1               C_3_1               C_4_1               C_5_1
                   0                   0                   0                 0.4                 0.4
#                G_1           SIGMA_Y_1                BB_1                 N_1
                   0                   0                   0                   0
#               CC_1     EPSILON_DOT_0_1
                   0                   0
#               CM_1                T_10             T_1MELT            T_1LIMIT             RHOCV_1
                   0                   0                   0                   0                   0
#      EPSILON_MAX_1         SIGMA_MAX_1               K_A_1               K_B_1
                   0                   0                   0                   0
#---Material#2:WATER(Linear_Incompressible)--------------------------------------------------------#
#            ALPHA_2             RHO_0_2               E_0_2             P_MIN_2               C_0_2
              0.9999              1000.0                   0                   0                1E+5 
#              C_1_2               C_2_2               C_3_2               C_4_2               C_5_2
             2.25E+9                   0                   0                   0                   0
#                G_2           SIGMA_Y_2                BB_2                 N_2
                   0                   0                   0                   0
#               CC_2     EPSILON_DOT_0_2
                   0                   0
#               CM_2                T_20             T_2MELT            T_2LIMIT             RHOCV_2
                   0                   0                   0                   0                   0
#      EPSILON_MAX_2         SIGMA_MAX_2               K_A_2               K_B_2
                   0                   0                   0                   0
#---Material#3:not defined Plastic material with Johnson-Cook Yield criteria-----------------------#
#            ALPHA_3             RHO_0_3               E_0_3             P_MIN_3               C_0_3
                 0.0                   0                   0                   0                   0
#              C_1_3               C_2_3               C_3_3               C_4_3               C_5_3
                   0                   0                   0                   0                   0
#                G_3           SIGMA_Y_3                BB_3                 N_3
                   0                   0                   0                   0
#               CC_3     EPSILON_DOT_0_3
                   0                   0
#               CM_3                T_30             T_3MELT            T_3LIMIT             RHOCV_3
                   0                   0                   0                   0                   0
#      EPSILON_MAX_3         SIGMA_MAX_3               K_A_3               K_B_3
                   0                   0                   0                   0
#---Material#4:TNT(JWL)----------------------------------------------------------------------------#
#            ALPHA_4             RHO_0_4               E_0_4             P_MIN_4               C_0_4
                 0.0                1590              7.0E+9               1E-30             1.0E+05
#                B_1                 B_2                 R_1                 R_2                   W
           371.20E+9            3.231E+9                4.15              0.9499                 0.3
#                  D                P_CJ                C_14                       I_BFRAC
              6930.0             2.1E+10             22.5E+5                             0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

  1. Numerical diffusion can be improved using the second order method for volume fraction convection, /ALE/MUSCL. The previous /UPWIND used to limit diffusion is now obsolete.
  2. Radioss computes and outputs a relative pressure ΔP .(7)
    ΔP=max{ΔPmin,C0+C1μ+C'2μ2+C'3μ3+(C4+C5μ)E(μ)}

    However, total pressure is essential for energy integration ( dEint=PdV ). It can be computed with the external pressure flag Pext.

    P=ΔP+Pext leads to dEint=(Pext+ΔP)dV .

    This means if Pext = 0, the computed pressure ΔP is also the total pressure ΔP=P .

  3. Kinematic viscosities are global and is not specific to each material. It allows computing viscous stress tensor:(8)
    τ=μ[(V)+t(V)]+λ(V)I
    Where,
    ν=μ/ρ
    Kinematic shear viscosity flag
    νvol=3(λ+2μ3)ρ
    Kinematic volumetric viscosity flag
  4. Volumetric fractions enable the sharing of elementary volume within the three different materials.

    For each material αmat_i0 must be defined between 0 and 1.

    Sum of initial volumetric fractions 3i=1αmat_i0 must be equal to 1.

    For automatic initial fraction of the volume, refer to the /INIVOL card.

  5. ΔPmat_imin flag is the minimum value for the computed pressure ΔP . It means that total pressure is also bounded to:(9)
    Pmat_imin=ΔPmat_imin+Pext

    For fluid materials and detonation products, Pmat_imin must remain positive to avoid any tensile strength so ΔPmat_imin must be set to Pext .

    For solid materials, default value ΔPmat_imin = 1e-30 is suitable but may be modified.

  6. By default, the process is adiabatic: δQ=0 . Heat contribution is computed only if the thermal card is associated to the material law (/HEAT/MAT).
    In this case, δQ=ρCVVdT and the parameters for thermal diffusion are read for each material:(10)
    ρCmat_iV,Kmat_iA,Kmat_iBandTmat_i0

    For solids and liquids, CνCp for perfect gas: γ=Cp/Cν

  7. The temperature evolution in the Johnson-Cook model is computed with the flag ρCmat_iV , even if the thermal card (/HEAT/MAT) is not defined.
  8. Thermal conductivity, K , is linearly dependent on the temperature:(11)
    K(T)=KA+KBT
  9.  Cmat_41 can be estimated 1 with (12)
    Cmat_41= ρ0mat_4 (cunreacted0)2

    Where, cunreacted0 is the speed of sound in the unreacted explosive and an estimation for TNT is 2000 m/s.

  10. Explosive material ignition is made with detonator cards, /DFS/DETPOINT or /DFS/DETPLAN.
  11. Detonation Velocity (D) and Chapman Jouget Pressure (PCJ) are used to compute the burn fraction calculation ( Bfrac[0,1] ). It controls the release of detonation energy and corresponds to a factor which multiplies JWL pressure.

    For a given time: P(V,E)=BfracPjwl(V,E) .

    A detonation time Tdet is computed by the Starter from the detonation velocity. During the simulation the burn fraction is computed as:(13)
    Bfrac=min(1,max(Bf1,Bf2))
    Where, the burn fraction calculation from burning time is:(14)
    Bf1=1V1VCJ=ρ0 D2PCJ(1V)
    and the burn fraction calculation from volumetric compression is:(15)
    Bf2={0,x<0TTdet1.5Δx,x0

    It can take several cycles for the burn fraction to reach its maximum value of 1.00.

    Burn fraction calculation can be changed defining the IBFRAC flag:

    IBFRAC = 1: Bfrac=min(1,Bf1)

    IBFRAC = 2: Bfrac=min(1,Bf2)

  12. As of version 11.0.240, Time Histories for Detonation time and burn fraction are available through /TH/BRIC with BFRAC keyword. This allows to output a function f whose first value is detonation time (with opposite sign) and positive values corresponds to the burn fraction evolution.(16)
    Tdet=f(0)Bfrac(t)={0,f(t)<0f(t),f(t)0
  13. Detonation times can be written in the Starter output file for each JWL element. The printout flag (Ipri) must be greater than or equal to 3 (/IOFLAG).
  14. Material tracking is possible through animation files:

    /ANIM/BRICK/VFRAC (volumetric fractions for all materials)

1
Hayes, B. "Fourth Symposium (International) on Detonation." Proceedings, Office of Naval Research, Department of the Navy, Washington, DC (1965): 595-601