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/EOS/COMPACTION

Block Format Keyword Describes pressure for a porous media such as soil or foam which can be compacted and unloaded.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/EOS/COMPACTION/mat_ID/unit_ID
eos_title
C0 C1 C2 C3   Iform
μmin μmax B    
Psh        

Definition

Field Contents SI Unit Example
mat_ID Material identifier.

(Integer, maximum 10 digits)

 
unit_ID Unit Identifier.

(Integer, maximum 10 digits)

 
eos_title EOS title.

(Character, maximum 100 characters)

 
C0 EOS parameter.

(Real)

 
C1 EOS parameter.

(Real)

 
C2 EOS parameter.

(Real)

 
C3 EOS parameter.

(Real)

 
Iform Flag formulation for unloading behavior. 5
0
Default is 1
1 (Default)
Constant unloading slope
2
Linear unloading slope

(Integer)

 
μmin Elastic limit.

No compaction below μ<μmin .

Pe=C0+C1μmin+C2μmin2+C3μmin3

Default = 0.0 (Real)

 
μmax Maximum compaction.

Default = 1020 (Real)

 
B Unloading bulk modulus.

(Real)

[Pa]
Psh Pressure shift.

(Real)

[Pa]

Example

Comments

  1. This equation of state is used to model pressure in porous media such as soil or foam. The compaction has an elastic response when it is less than the elastic limit μ=μmin .


    Figure 1.
  2. Plastic compaction is along path defined by curve:(1)
    P=C0+C1μ+C2μ2+C3μ3
    Where,
    P
    Pressure in material
    μ
    Volumetric strain with μ=ρρ01
    Unloading and reloading are made along straight line whose slope is B.
    Psh
    Pressure shift value used to model the relative pressure formulation.


    Figure 2. Pressure versus Volumetric Strain
  3. In versions prior to 2019.1, this equation of state was embedded in /MAT/LAW10 with a fixed elastic limit, μmin=0 .
  4. Equations of state are used by Radioss to compute the hydrodynamic pressure and are compatible with the material laws:
    • /MAT/LAW3 (HYDPLA)
    • /MAT/LAW4 (HYD_JCOOK)
    • /MAT/LAW6 (HYDRO or HYD_VISC)
    • /MAT/LAW10 (DPRAG1)
    • /MAT/LAW12 (3D_COMP)
    • /MAT/LAW49 (STEINB)
    • /MAT/LAW102 (DPRAG2)
    • /MAT/LAW103 (HENSEL-SPITTEL)
  5. The unloading path runs along a constant slope B by default. You can define a variable slope which increases with the compaction using Iform=2. The slope will then evolve from C1 at µmin to B at μmax .
    Figure 3. Iform=1 Unloading along a constant slope B
    Figure 4. Iform=2 Unloading slope evolves from C1 to B in [µmin,µmax]