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/FAIL/JOHNSON - Johnson-Cook Failure Model

Description

Describes the failure criteria by Johnson-Cook failure model.

Format

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/FAIL/JOHNSON/mat_ID/unit_ID

D1

D2

D3

D4

D5

Ifail_sh

Ifail_so

 

 

Dadv

 

Ixfem

 

Optional line:

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

fail_ID

 

 

 

 

 
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)

 

D1

1st parameter

(Real)

 

D2

2nd parameter

(Real)

 

D3

3rd parameter

(Real)

 

D4

4th parameter

(Real)

 

D5

5th parameter

(Real)

 

Reference strain rate

(Real)

fail_johnson

Ifail_sh

Shell failure flag

(Integer)

If Ixfem =0: failure – element deleted

If Ixfem =1: failure – element cracked (Comment 2)

= 1: (Default) Shell is deleted or cracked.

If clip0236 for one integration point or layer.

= 2: For each integration point, the stress tensor is set to zero.

If clip0236 and shell is deleted or cracked.

If clip0236 for all integration points or layers.

 

Ifail_so

Solid failure flag

(Integer)

= 1: (Default) Solid element is deleted, if clip0236 for one integration point.

= 2: For each integration point, the deviatoric stress tensor vanishes, if clip0236

 

Dadv

Criterion for the crack advancement (Only active if with Ixfem =1) (Comment 4)

(Real between 0 and 1)

= 1: (Default)

If Dadv > 1, then Dadv = 1 (max accumulation damage value D, used for crack initiation)

 

Ixfem

XFEM flag (for /PROP/SHELL, /PROP/SH_SANDW, and /PROP/TYPE51 properties only)

Default = 0 (Integer)

= 1: XFEM formulation (Comment 2)

= 0: Without XFEM

 

fail_ID

(Optional) Failure criteria identifier (Comment 3)

(Integer, maximum 10 digits)

 

Examples

In these two simple examples, strain rate and temperature are not considered. The stress-strain relationship could be simplified, as below:

With three typical loadings (example: pure tension, pure shear or pure compression) material parameter D1, D2 and D3 could be determined using the above simplified stress-stain relationship.

fail_johnson_example

Example 1: use Ixfem=0, if the element deleted reaches the rupture criteria.

Example 2: use Ixfem=1, if the element cracked reaches the crack criteria.

hmtoggle_plus1Example (Steel)

#RADIOSS STARTER

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

/UNIT/1

unit for mat

#              MUNIT               LUNIT               TUNIT

                  Mg                  mm                   s

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

#-  1. MATERIALS:

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

/MAT/PLAS_JOHNS/1/1

Steel

#              RHO_I

              7.8E-9

#                  E                  NU

              210000                  .3

#                  a                   b                   n           EPS_p_max            SIG_max0

                 270                 450                  .6                   0                   0

#                  c           EPS_DOT_0       ICC   Fsmooth               F_cut               Chard

                   0                   0         0         0                   0                   0

#                  m              T_melt              rhoC_p                 T_r

                   0                   0                   0                   0

/FAIL/JOHNSON/1/1

#                 D1                  D2                  D3                  D4                  D5

                0.11                0.08                -1.5                   0                   0

#              EPS_0  Ifail_sh  Ifail_so                                    Dadv               Ixfem

                   1         1         1                                       0                   0

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

#enddata

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
hmtoggle_plus1Example (Steel)

#RADIOSS STARTER

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

/UNIT/1

unit for mat

#              MUNIT               LUNIT               TUNIT

                  Mg                  mm                   s

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

#-  1. MATERIALS:

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

/MAT/PLAS_JOHNS/1/1

Steel

#              RHO_I

              7.8E-9

#                  E                  NU

              210000                  .3

#                  a                   b                   n           EPS_p_max            SIG_max0

                 270                 450                  .6                   0                   0

#                  c           EPS_DOT_0       ICC   Fsmooth               F_cut               Chard

                   0                   0         0         0                   0                   0

#                  m              T_melt              rhoC_p                 T_r

                   0                   0                   0                   0

/FAIL/JOHNSON/1/1

#                 D1                  D2                  D3                  D4                  D5

                0.11                0.08                -1.5                   0                   0

#              EPS_0  Ifail_sh  Ifail_so                                    Dadv               Ixfem

                   1         1         1                                     0.5                   1

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

#enddata

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
hmtoggle_plus1Comments
1.The parameters are used in stress-strain relationship:

Where,

( is the stress triaxiality)

T* is computed in the material law, if this one is thermo plastic, like /MAT/HYD_JCOOK (LAW4).

2.XFEM formulation (Ixfem=1) is only compatible with Belytchko (Ishell=1 or 2), Ishell=3 or 4 and QEPH (Ishell=24) shell elements. If XFEM is activated (Ixfem=1), the failure criteria will lead to element cracking instead of element or layer deletion.

Two XFEM options are available: mono-layer and multi-layer. The XFEM option depends on the property type associated to the failure criterion applied to the material identifier:

a)If /PROP/SHELL (TYPE1) is used, then mono-layer XFEM will be applied.

In this case, the whole element thickness is considered as a single layer. The failure criterion is calculated in each integration point, but only one single crack can appear in this element. This approach is compatible with all values of the shell flag (Ifail_sh=1 or 2). The crack direction is determined by the principal constraints in the last failed integration point.

b)If /PROP/SH_SANDW (TYPE11) is used, then multi-layer XFEM will be applied.

In this case, each integration point over thickness is considered as a distinct layer. The failure criterion is calculated separately and the crack direction may be different in each layer. Crack direction in each layer will independently propagate from one element to another. Multi-layer XFEM is not compatible with Ifail_sh=1. Its value will be automatically set to Ifail_sh=2 in this case.

c) If /PROP/TYPE51 is used, then multi-layer XFEM will be applied and the separate cracks may appear in each layer and propagate independently from one element to another. Thus, crack directions and patterns will be different in each layer. The failure criterion is calculated separately in each integration point and crack will propagate when all the integration points fail within a layer. Multi-layer XFEM is not compatible with Ifail_sh=1. Its value will be automatically set to Ifail_sh=2.

Warning:Mono-layer and multi-layer XFEM formulations cannot be mixed in the same model, yet. The choice between them must be made for the whole model.
3.The fail_ID is used with /STATE/BRICK/FAIL and /INIBRI/FAIL. There is no default value. If the line is blank, no value will be output for failure model variables in the /INIBRI/FAIL (written in .sta file with /STATE/BRICK/FAIL option).
4.Two different failure (rupture or crack) are introduced in this failure model. The failure criteria is calculated, as follows:
•Element rupture (Ixfem=0):

- Element rupture (deleted) if D > Dfail with Dfail=1

•Element crack (Ixfem=1):

- Element cracked, if:

D > Dfail  with Dfail=1, if this element has no failed neighbors.

So in this case use Dfail=1 for new crack initialization.

D > Dadv if this element has failed neighbors. Dadv will be used if existing crack arrives to a boundary of an element.

So in this case use Dadv for crack advancement.

- Element deleted, if a second crack arrives to the same element

where,

Dadv should always be less than 1 (Dfail =1) (Dadv < Dfail=1). If not, then Dadv is set to 1 (Dadv=Dfail=1).

See Also:

Failure to Element/Material Compatibility

Example 26 - Ruptured Plate

Example 45 - Multi-Domain

Johnson-Cook Failure in Theory Manual

Failure /FAIL/JOHNSON and /FAIL/TAB1