/MAT/LAW79 (JOHN

Block Format Keyword

/MAT/LAW79 - Johnson-Holmquist Model [1][]

Description

This material law describes the behavior of brittle materials, such as ceramics and glass. The implementation is the second Johnson Holmquist model: JH-2

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW79/mat_ID/unit_ID
mat_title

G
a		b		m		n
c
T		HEL		PHEL
D1		D2
K1		K2		K3

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 (Real)
	Reference density used in E.O.S (equation of state) Default = (Real)
G	Shear modulus (Real)
a	Intact normalized strength constant (Comment 1) (Real)
b	Fractured normalized strength constant (Comment 1) (Real)
m	Fractured strength pressure exponent (Comment 1) (Real)
n	Intact strength pressure exponent (Comment 1) (Real)
c	Strain rate coefficient = 0: no strain rate effect (default) (Real)
	Reference strain rate Usually = 1 (Real)
	Maximum normalized fractured strength Default = 1030 (Real)
T	Maximum pressure tensile strength Default = 1030 (Real)
HEL	Hugoniot elastic limit (Real)
PHEL	Pressure at Hugoniot elastic limit (Real)
D1	Damage constant (Comment 2) (Real)
D2	Damage exponent (Comment 2) (Real)
K1	Bulk modulus (Real)
K2	Pressure coefficient (Comment 3) (Real)
K3	Pressure coefficient (Comment 3) (Real)
	Bulking pressure coefficient (Real)

	B4C [2]	Al2O3 [1]
	2510	3700
G	197	90
a	0.927	0.93
b	0.70	0.31
m	0.85	0.6
n	0.67	0.6
c	0.005	0
	0.2	-
T	0.26	0.2
HEL	19.0	2.8
PHEL	8.71	1.46
D1	0.001	0.005
D2	0.5	1
K1	233	131
K2	-593	0
K3	2800	0
	1	1

#RADIOSS STARTER

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

/UNIT/1

unit for mat

g mm ms

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

#- 2. MATERIALS:

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

/MAT/LAW79/1/1

concrete

# RHO_I RHO_0

.0037 0

# G

90160

# a b m n

.93 0 0 .6

# c EPS0 SIGMA_FMAX

0 .001 1E-30

# T HEL PHEL

200 2790 1460

# D1 D2

0 0

# K1 K2 K3 BETA

130950 0 0 1

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

#ENDDATA

/END

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

1.	The equation describing the normalized equivalent stress is:

with the equivalent stress of the intact material:

and the equivalent stress of the failed material:

Stress are normalized to the stress at the Hugoniot elastic limit:

and pressure are normalized to PHEL:

2.	The accumulated damage is:

where, the plastic strain to failure is:

3.	The Equation of state is:

where, the bulking pressure is computed as a function of the elastic energy loss converted into potential hydrostatic energy:

4.	Time history available output:

USR3: Damage D

USR4: Bulking Pressure

USR5: Yield Stress

[1] An improved computational constitutive model for brittle materials, G.R. Johnson, T.J.Holmquist, American Institute of Physics, 1994.

[2] Response of boron carbide subjected to large strains, high strain rates, and high pressures G.R.Johnson, T.J.Holmquist, Journal of Applied Physics, Volume 85, #12, June 1999.

/MAT/LAW79 (JOHN_HOLM)

/MAT/LAW79 (JOHN_HOLM)

/MAT/LAW79 (JOHN_HOLM)

[1] An improved computational constitutive model for brittle materials, G.R. Johnson, T.J.Holmquist, American Institute of Physics, 1994.

See Also: