/MAT/LAW75 (POROUS)

Block Format Keyword

/MAT/LAW75 - P- Porous Material Model

Description

Describes the P- porous material model. This material describes ductile Porous material with Herrmann model. It only works with 8-node brick element and is not compatible with ALE.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW75/mat_ID/unit_ID or /MAT/POROUS/mat_ID/unit_ID
mat_title

E
mat_IDs	Iflag1	Iflag2	itemax
PE		Ps		n
tol

Field	Contents	SI Unit Example
mat_ID	Material identifier (Integer, maximum 10 digits)
unit_ID	Optional unit identifier (Integer, maximum 10 digits)
mat_title	Material title (Character, maximum 100 characters)
	Initial density for porous material (Real)
E	Young’s modulus (Real)
	Poisson’s ratio (Real)
mat_IDs	Material identifier of the solid (fully compacted) material (Integer)
Iflag1	Pressure formulation flag Default = 1 (Integer) = 1: Herrmann [1] = 2: Modified Herrmann [2]
Iflag2	Deviatoric stresses formulation flag Default = 1 (Integer) = 1: Hydrodynamic = 2: Elastic
itemax	Maximum number of iterations on a calculation Default = 5 (Integer)
PE	Elastic compact pressure (elastic limit) (Comment 3) (Real)
Ps	Solid (matrix) compact pressure (Comment 3) (Real)
n	Exponent used for fitting the experiment data (Comment 3) Default = 2 (Real)
tol	Convergence tolerance on a calculation Default = 10-8 (Real)

#RADIOSS STARTER

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/UNIT/1

unit for mat

g cm mus

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#- 2. MATERIALS:

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/MAT/LAW75/1/1

porous soil

# RHO_I

1.70

# E NU

3 .300

# mat_IDs Iflag_1 Iflag_2 ite_MAX

2 1 2 0

# PE PS n

.01 .05 0

# TOL

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/MAT/HYD_JCOOK/2/1

soil

# RHO_I RHO_O

1.76000004 0

# E NU

3.5999999 .300000012

# a b n EPS_max SIGMA_max

10000 0 0 0 0

# C0 C1 C2 C3

0 0 0 0

# P_min Psh

0 0

# C4 C5 E0

0 0 0

# c EPS_0 m Tmelt Tmax

0 0 0 0 0

# RHOCP

/EOS/POLYNOMIAL/2/1

EOS for soil

# C0 C1 C2 C3

0 2.81999993 2 -1.37

# C4 C5 E0 Psh

1.53999996 1.53999996

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#ENDDATAS

/END

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

1.	The porosity is defined as:

Note that > 1 (s > )

where, s is the density of the solid (full compacted matrix) material and is the density of the porous material.

2.	If the EOS of the solid (matrix) material is:

Then the EOS of the porous material is:

for Herrmann formulation.

for modified Herrmann formulation.

Where, (e) is the internal energy per unit mass. It is same in porous material and in the solid (matrix) material.

3.	If P < PE the behavior is elastic, and if P > PE describes plastic region.

In the elastic region, the change of porosity with pressure P is reversible.

In the plastic region, the porosity is assumed to depend on pressure as described below:

mat_law75_eq6

Where,

P is the porosity where pressure reach the elastic compact pressure PE.

=1, the pressure reaches the solid (matrix) compact pressure Ps.

0 is the initial porosity.

mat_law75_porosity

[1] “Constitutive equation for the dynamic compaction of ductile porous materials”, Herrmann W., J. Applied Physics 40, 1969

[2] “Static and dynamic pore collapse relations for ductile porous materials”, Carroll M.M., Holt A.C., J. Applied Physics 43, 1972

/MAT/LAW75 (POROUS)

/MAT/LAW75 (POROUS)

/MAT/LAW75 (POROUS)

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