HyperWorks Solvers

/MAT/LAW4 (HYD_JCOOK)

/MAT/LAW4 (HYD_JCOOK)

 Previous topic Next topic Expand/collapse all hidden text  

/MAT/LAW4 (HYD_JCOOK)

 Previous topic Next topic JavaScript is required for expanding text JavaScript is required for the print function  

Block Format Keyword

/MAT/LAW4 - Hydrodynamic Johnson-Cook Material

Description

This law represents an isotropic elasto-plastic material using the Johnson-Cook material model. This model expresses material stress as a function of strain, strain rate and temperature. This material may account for the nonlinear dependence between pressure and volumetric strain when corresponding equation of state is specified. A built-in failure criterion based on the maximum plastic strain is available. This material law is compatible with solid elements only.

Format

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

/MAT/LAW4/mat_ID/unit_ID or /MAT/HYD_JCOOK/mat_ID/unit_ID

mat_title

 

 

 

 

 

 

E

 

 

 

 

 

 

a

b

n

Pmin

 

 

 

 

 

 

 

 

c

m

Tmelt

Tmax

 

 

 

 

 

 

 

 
hmtoggle_plus1Flag Definition

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)

E

Young’s modulus

(Real)

Poisson’s ratio

(Real)

 

a

Yield stress

(Real)

b

Plastic hardening parameter

(Real)

n

Plastic hardening exponent

Default = 1.0  (Real)

 

Failure plastic strain

Default = 1030  (Real)

 

Maximum stress

Default = 1030  (Real)

Pmin

Pressure cutoff ( < 0 )

Default = -1030  (Real)

c

Strain rate coefficient

Default = 0.00  (Real)

= 0: no strain rate effect

 

Reference strain rate

(Real)

If , no strain rate effect

m

Temperature exponent

Default = 1.00  (Real)

 

Tmelt

Melting temperature

Default = 1030  (Real)

= 0: no temperature affect

Tmax

for T > Tmax: m = 1 is used

Default = 1030  (Real)

Specific heat per unit volume

(Real)

hmtoggle_plus1Example (Steel)

#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/HYD_JCOOK/1/1

Aluminum

#              RHO_I               RHO_0

                 2.8                   0

#                 E                   nu

                .734                 .33

#                  A                   B                   n              epsmax              sigmax

               .0024               .0042                  .8                   0               .0068

#               Pmin

              -.0223

#                  C           EPS_DOT_0                   M               Tmelt               Tmax

                .062                1E-6                   1                1220                   0

#              RHOCP

             2.59E-5

/EOS/TILLOTSON/1/1

Aluminum

#                 C1                  C2                   A                   B

                .752                 .65                  .5                1.63

#                 ER                  ES                  VS                  E0               RHO_0

                .135                .081                 1.1                   0                   0

#              ALPHA                BETA

                   5                   5

/FAIL/JOHNSON/3

#                 D1                  D2                  D3                  D4                  D5

                .112                .123                -1.5                .007                   0

#              EPS_0  Ifail_sh  Ifail_so                                    Dadv               Ixfem

                1E-6         0         1                                       0                   0

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

#ENDDATA

/END

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
hmtoggle_plus1Comments
1.In this model, the material behaves as a linear-elastic material when the equivalent stress is lower than the plastic yield stress. For higher stress values, the material behavior is plastic and the stress is calculated as shown:

Where,

Where, is the plastic strain, is the strain rate, T is the temperature, T0 is the ambient temperature, Tmelt is the melting temperature and T0 = 300K.

clip0067

2.The plastic yield stress should always be greater than zero. To model pure elastic behavior, the plastic yield stress will be set to 1030.
3.When reaches the value of (for tension, compression or shear), in one integration point, the deviatoric stress of the corresponding integration point is permanently set to 0, however, the solid element is not deleted.
4.The plastic hardening exponent, n, must be less than or equal to 1.
5.To eliminate the effect of the strain rate, either set the value of c equal to 0 or set the reference strain rate () equal to 1030. There is no effect of strain rate when is less than .
6.By default, the hydrostatic pressure is linearly proportional to volumetric strain:

Where, is the bulk modulus and is the volumetric strain.

An additional Equation of State (/EOS) card can refer to this material in order to incorporate a nonlinear dependency between hydrostatic pressure and volumetric strain.

See Also:

Material Compatibility

Law Compatibility with Failure Model

/MAT/LAW4 in Theory Manual

Material/Failure in FAQ

Example 46 - TNT Cylinder Expansion