/MAT/LAW81

Block Format Keyword

/MAT/LAW81 - Drücker-Prager Material Law with Cap

Description

This law is based on Drücker-Prager yield criteria with cap. It has a strain-hardening cap model based on the principles of Foster. Plasticity has an isotropic hardening. Failure surface is limited to the standard linear Drücker-Prager relation, with symmetry around the pressure axis. This law is LAG, ALE and EULER compatible.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW81/mat_ID/unit_ID
mat_title

K0		G0

		Eps_max
fct_IDK	fct_IDG	fct_IDC	fct_IDPb	Isoft

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)
K0	Scale factor for bulk modulus (Real)
G0	Scale factor for shear modulus (Real)
	Friction angle (Real)
	Plastic flow angle (Real)
	Ratio pa/pb Default = 0.5 (Real)
Eps_max	Maximum dilatancy (negative number limiting ) Default - 1030 (Real)
	Initial value of the plastic volumetric strain (Comment 3) (Real)
fct_IDK	Function identifier defining the evolution of bulk modulus vs the plastic volumetric strain (Comment 3). (Integer)
fct_IDG	Function identifier defining the evolution of shear modulus vs the plastic volumetric strain (Comment 3). (Integer)
fct_IDC	Function identifier defining C vs the equivalent plastic strain (Integer)
fct_IDPb	Function identifier defining Pb vs the volumetric plastic strain (Integer)
Isoft	Cap softening flag (Integer) = 0 (default): cap softening is allowed. = 1: imposes that and Pb cannot decrease.

#RADIOSS STARTER

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/UNIT/1

unit for mat

kg m s

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#- 2. MATERIALS:

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/MAT/LAW81/1/1

LAW81

# RHO_I

1700

# K0 G0

1150000000 800000000

# BETA PSI

15 0

# ALPHA EPS_MAX EPS_0

.5 .02 .002

# fct_IDK fct_IDG fct_IDc fct_IDPb Isoft

0 0 3 4 1

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#- 3. FUNCTIONS:

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/FUNCT/3

Yield Hardening

# X Y

0 2000

.1 2002000

1 2002000

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/FUNCT/4

Cap Hardening

# X Y

-1 1000

0 1000

.001 30000

.0022 70000

.0024 80000

.004 100000

.0056 200000

.0078 800000

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#ENDDATA

/END

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1.	The yield surface is defined as:

Where:

rc(p) = 1 if p < pa

if pa < p < pb

While, p is the pressure, q is the von Mises stress and c is the material cohesion.

P0 is the pressure, where and pb is the cap limit pressure.

mat_law81

2.	Plastic flow is governed by the non-associated flow potential G, as defined below:

if p ≤ pa

if pa < p ≤ p0

G = F if p > p0, the flow becomes associated on the cap

3.	If cap softening is allowed, can decrease, therefore it is recommended to define the following curves on a relevant range. For example, if , negative values.

If fct_IDK = 0 then, K = K0

If fct_IDK ≠ 0 then, K = K0 * fct_IDK ()

If fct_IDG = 0 then, G = G0

If fct_IDG ≠ 0 then, G = G0 * fct_IDK()

4.	The following user variables are available for post-treatment:

USR1 is the equivalent plastic strain EPSPD

USR2 is the plastic volumetric strain EPSPV

USR3 is the cohesion c

USR4 is the cap limit pressure Pb