/MAT/LAW70 (FOAM

Block Format Keyword

/MAT/LAW70 - Visco-elastic Foam Tabulated Material

Description

This law describes the visco-elastic foam tabulated material. This material law can be used only with solid elements.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW70/mat_ID/unit_ID or /MAT/FOAM_TAB/mat_ID/unit_ID
mat_title

E0				Emax				Itens
Fcut		Ismooth	NL	NunL	Iflag	Shape		Hys

If NL ≠ 0

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
fct_IDL			FscaleL

If NunL ≠ 0

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
fct_IDunL			FscaleunL

If Itens = 1

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
fct_IDT	FscaleT

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)
E0	Initial Young’s modulus (Comment 3) (Real)
	Poisson’s ratio (Real)
Emax	Maximum Young's modulus (Comment 3) =0: Emax is equal to E0 (default ) (Real)
	Reference strain value for the maximum Young's modulus usage Default = 1 (Real)
Itens	Flag to activate different behavior between tensile and compression (Integer) = 0: same behavior between the compression tensile (default) = 1: different behavior between compression tensile. The tensile behavior is the compression curve multiply by Scale factor, which is defined in fct_IDT.
Fcut	Cutoff frequency for strain rate filtering Default = 1030 (Real)
Ismooth	Smooth strain rate option flag (Integer) = 0: no strain rate smoothing (default) = 1: strain rate smoothing active
NL	Number of loading functions (Comment 2) (Integer)
NunL	Number of unloading functions (Comment 2) (Integer)
Iflag	Flag to control the unloading response (Comment 2) Default = 0 (Integer) = 0: The material behavior follows NL loading curves and NunL unloading curves. = 1: The material behavior follows NL loading curves (only first curve is used for quasi-static) and NunL loading curves. For unloading the deviatoric stress is reduced by using the quasi-static unloading curve with = 2: The material behavior follows NL loading curves (only first curve used for quasi-static) and NunL unloading curves. For unloading the tensor stress is reduced by using the quasi-static unloading curve with, = 3: The loading curves are used for both loading and unloading behavior. The deviatoric unloading stress is reduced by: with = 4: The loading curves are used for both loading and unloading behavior and the tensor unloading tensor stress is reduced by: with
Shape	Shape factor Default = 1.0 (Real)
Hys	Hysteresis unloading factor Default = 1.0 (Real)
fct_IDL	Load function (in compression) identifier (Integer)
	Strain rate for load function (Real)
FscaleL	Load function scale factor (Real)
fct_IDunL	Unload function (in compression) identifier (Integer)
	Strain rate for unload function (Real)
FscaleunL	Unload function scale factor (Real)
fct_IDT	Scale factor function between tensile and compression according strain (Integer)
FscaleT	Ordinate scale (Real)

#RADIOSS STARTER

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

/UNIT/1

unit for mat

kg 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/LAW70/1/1

Foam

# RHO_I

5E-8

# EO NU E_max EPS_max Itens

.01 0 10 .8 0

# F_cut F_smooth N_L N_unl Iflag Shape Hys

.1 1 4 0 4 2 1E-20

# fctID_L Eps_._L Fscale_L

1 0 .001

2 .01 .0015

3 .1 .002

3 1 .003

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

#- 3. FUNCTIONS:

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

/FUNCT/1

Foam

# X Y

0 0

.03 .002

.04 .003

.14 .005

.46 .008

.63 .01

.82 .07

.83 .08

.93 1.4

.94 2.0

.95 3.0

.96 6

.97 10

.98 35

.99 300

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

/FUNCT/2

Foam

# X Y

0 0

.03 .002

.04 .003

.14 .005

.46 .008

.63 .01

.82 .07

.83 .08

.93 1.4

.94 2.0

.95 3.0

.96 6

.97 10

.98 35

.99 300

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

/FUNCT/3

Foam

# X Y

0 0

.03 .002

.04 .003

.14 .005

.46 .008

.63 .01

.82 .07

.83 .08

.93 1.4

.94 2.0

.95 3.0

.96 6

.97 10

.98 35

.99 300

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

#ENDDATA

/END

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

1.	This material is available for the following parameters in the solid property:

For Hexas:

Element	Isolid	Ismstr	Iframe
Hexa	1	1	1
	1	1	2
	1	11	1
	1	11	2
	17	11	1
	17	11	2
	14	11	2

Choice of formulation depends on particular load case. It is advised to use Isolid= 1, Ismstr=11 and Iframe= 1 or 2. When hourglass appears, then fully-integrated solid elements with Isolid= 17 or 14, Ismstr= 11, Iframe= 1 or 2 can be used.

For Tetras:

Element	Isolid	Ismstr	Iframe
Tetra	1	1	1
Tetra	1	11	1

2.	Flag to control the unloading response Iflag.

➢	If Iflag = 0, then NL and NunL must be greater than 0 (NL > 1 and NunL > 1).

➢	If Iflag = 1 or 2:

•	NL and NunL must be greater than 0 (NL > 1 and NunL > 1)

•	The first loading curve used for quasi-static

•	D is computed as below:

Where, and are the current stresses computed, respectively.

•	P is the pressure

➢	If Iflag = 3 or 4:

•	NunL could be 0, because unloading curves are not used.

•	D is computed as:

Where, Wcurv and Wmax are current and maximum energy.

3.	When is reached, Emax is used whatever the curve definition is.

E0 and Emax used to calculate the current time step. According to current value of strain, RADIOSS interpolates Young’s modulus between E0 and Emax linearly, where E0 is also used to calculate contact stiffness. RADIOSS automatically modifies E0 if it is less than the initial value according to the input stress/strain curves tangents.

•	If E0 is not specified, use maximal initial slope of all stress strain loading curves as E0.

•	If Emax is not specified (or set default), use Emax as E0. Specified value of Emax should be greater than E0, otherwise also take = E0 as Emax.

•	If is not specified (or set default), take the strain where, Emax is reached for the first time on one of the loading curves.

•	If both and Emax are specified, take where, Emax is reached for the first time on one of the loading curves.

4.	For stresses above the last load function, the behavior is extrapolated by using the two last load functions. Then, in order to avoid huge stress values, it is recommended to repeat the last load function.

5.	All curves need to be defined as positive abscissa and ordinate.

Function fct_IDT is used to scale specified stress strain curve in compression. Product of this function and specified stress strain function in compression gives the stress strain function in tension. Note that stress strain function in compression can be specified only until strain is equal to 1, which corresponds to full contraction of the foam. Therefore the stress strain function in tension can be defined only until the tensile strain of 1.

7.	In order to recover the stress and strain the initial state file, the following options have to be saved in the ASCII Output File (STY-File):

•	/OUTP/STRESS/FULL

•	/OUTP/STRAIN/FULL

•	/OUTP/USERS/FULL

8.	Specific material output variables:

•	USR1: Equivalent strain* ( )

•	USR2: Max of internal energy

•	USR3: Current Young modulus

•	USR4: Equivalent strain

•	USR5: Status (1=loading; -1=unloading)

•	USR6: Stress

•	USR7: Strain rate

•	USR8: Internal energy

/MAT/LAW70 (FOAM_TAB)

/MAT/LAW70 (FOAM_TAB)

/MAT/LAW70 (FOAM_TAB)