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/FAIL/TAB1 - Strain Failure Model with dependence on Lode Angle

Description

Describes the strain failure model based on damage accumulation using user-defined functions.

Format

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(10)

/FAIL/TAB1/mat_ID/unit_ID

Ifail_sh

Ifail_so

 

 

P_thickfail

P_thinfail

 

Ixfem

 

Card 2 - Damage accumulation parameters

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(2)

(3)

(4)

(5)

(6)

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(10)

Dcrit

D

n

Dadv

fct_IDd

 

 

Card 3 - Failure strain table dependent on stress triaxiality and Lode angle parameter

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(2)

(3)

(4)

(5)

(6)

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(8)

(9)

(10)

table1_ID

Xscale1

Xscale2

table2_ID

Xscale3

Xscale4

 

Card 4 - Element size scale function

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(2)

(3)

(4)

(5)

(6)

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(8)

(9)

(10)

fct_IDel

Fscaleel

El_ref

Inst_start

Fad_exp

 

 

Card 5 - Temperature scale function

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(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

fct_IDT

FscaleT

 

 

 

 

 

 

 

 

Card 6 - Optional line:

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(2)

(3)

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(5)

(6)

(7)

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(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)

 

Ifail_sh

Shell failure flag.

If Ixfem =0: failure – element deleted (Comment 1)

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

(Integer)

= 1: Shell is deleted/cracked, if the damage criterion is satisfied in one integration point or layer.

= 2: Shell is deleted/cracked, if the damage criterion is satisfied in all shell layers. For a single layer shell, the stress tensor is set to zero.

= 3: Shell is deleted/cracked, if the damage criterion is satisfied in all layers. Stress tensor is not modified in broken layers until the complete element is ruptured.

 

Ifail_so

Solid failure flag

(Integer)

= 1: Solid is deleted, if the damage criterion is satisfied in one integration point.

= 2: Deviatoric stress components are set to zero for the integration points where criteria is satisfied.

 

Ixfem

XFEM flag (for /SHELL and /SH_SANDW properties only)

Default = 0 (Integer)

= 1: XFEM formulation (Comment 2)

= 0: Without XFEM

 

P_thickfail

Ratio of thickness failure limit (shells only)

(Real)

If Ixfem =1: see Comments 2, 5, and 6

 

P_thinfail

Ratio of thickness reduction before failure (shells only and only active for Ifail_sh > 1)

(Real)

 

Dcrit

Critical accumulated damage value (failure criteria)

Default = 0.999  (Real)

 

D

Damage accumulation parameter D

Default = 1.0  (Real)

 

n

Damage accumulation parameter n

Default = 1.0  (Real)

 

Dadv

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

(Real, between 0 and 1)

Default = 0 means Dadv = Dcrit (Comment 4)

 

fct_IDd

Damage function identifier (Comment 4)

Default = 0  (Integer)

 

table1_ID

Failure strain table identifier (Comment 7)

(Integer)

 

Xscale1

Scale factor for the first variable of table1 (failure strain)

Default = 1.0 (Real)

symbol_Pa

Xscale2

Scale factor for the second variable table1 (strain rate)

Default = 1.0 (Real)

fail_johnson

table2_ID

Instability strain table identifier (Comment 9)

(Integer)

 

Xscale3

Scale factor for the first variable of table2 (strain rate)

Default = 1.0

 

Xscale4

Scale factor for the second variable of table2 (instability strain)

Default = 1.0

 

fct_IDel

Element size factor function identifier

(Integer)

 

Fscaleel

Element size function scale factor

Default = 1.0  (Real)

symbol_m

El_ref

Reference element size

Default = 1.0  (Real)

symbol_m

Inst_start

Instability strain (Only active if table2_ID is not defined)

Default = value of parameter D (Real)

 

Fad_exp

Fading exponent (Comment 10)

> 0: Fading exponent (Real)

< 0: Fading exponent is a function identifier (Integer)

Default = 0 (Real)

 

fct_IDT

Temperature factor function identifier

(Integer)

 

FscaleT

Temperature function scale factor

Default = 1.0  (Real)

fail_tab_temp

fail_ID

(Optional) Failure criteria identifier (Comment 8)

(Integer, maximum 10 digits)

 
hmtoggle_plus1Example (Steel)

#RADIOSS STARTER

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

/UNIT/1

unit for mat

#              MUNIT               LUNIT               TUNIT

                  kg                  mm                  ms

#---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

              7.9E-6

#                  E                  NU     Iflag

                 210                  .3         0

#                  a                   b                   n           EPS_p_max            SIG_max0

                 .05                 .52                  .1                   0                   0

#                  c           EPS_DOT_0       ICC   Fsmooth               F_cut               Chard

                .022                .001         0         1                   1                   0

#                  m              T_melt              rhoC_p                 T_r

                1.03                1796                3.91                 300

/FAIL/TAB1/1/1

# Ifail_sh  Ifail_so                             P_THICKFAIL          P_THINFAIL              I_Xfem

         1         1                                       1                   0                   0

#              DCRIT                   D                   N                Dadv   fct_IDd

                   1                   1                   1                   0         0

#Table1_ID             Xscale1             Xscale2 Table2_ID             Xscale3             Xscale4

      4711                   1                   1         0                   0                   0

#fct_ID_EL           Fscale_EL              EI_REF          INST_START             FAD_EXP

        21                   1                   1                   0                   0

# fct_ID_T            Fscale_T

        22                   1

#  fail_ID

         1

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

#-  3. FUNCTIONS:

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

/TABLE/1/4711

curve_list Failure Function vs. strain rates

#DIMENSION

        3

#   fct_ID                   strain_rate          Lode_angle

      3000                          1E-4                  -1

      3001                          1E-4                   0

      3002                          1E-4                   1

      3003                             1                  -1

      3004                             1                   0

      3005                             1                   1

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

/FUNCT/3000

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/3001

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/3002

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/3003

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/3004

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/3005

fail strain vs triaxiality

#        fail strain         triaxiality

#                  X                   Y

                   0                  .5                                                          

                   1                  .5                                                          

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

/FUNCT/21

Element length regularization

#                  X                   Y

                   0                   1                                                          

                  10                   1                                                          

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

/FUNCT/22

Temperature scale function

#                  X                   Y

                   0                   1                                                          

                1000                   1                                                          

#---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.Using Ixfem=0, failure leads to element or layer deletion. In this case, if Ifail_sh=1, then P_thickfail has to be set to zero for proper working failure criteria.
2.Using Ixfem=1 (XFEM formulation), failure leads to element crack:

XFEM formulation is only compatible with Belytchko (Ishell=1 or 2), Ishell=3 or 4 and QEPH (Ishell=24) shell elements.

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 shell flag options (Ifail_sh=1, 2 or 3), as well as P_Thickfail values. 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 for 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 and P_thickfail>0. Their values will be automatically set to Ifail_sh=2 and P_thickfail=0.

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.Failure strain value is found from interpolation between defined functions for actual strain rate.

The first function from table1_ID is used for strain rate values from 0 to its corresponding strain rate.

For strain rates above the last defined function, failure strain value is extrapolated using the last two curves and their corresponding strain rates.

4.Two different failures (rupture or crack) are introduced in this failure model. The failure criteria is calculated as:

Element rupture (Ixfem=0):

•Element rupture (deleted), if .  Dcrit is the only rupture criterion used when Ixfem=0.

Element crack (Ixfem=1):

•Element cracked, if:
o in case no failed neighbors for this element. Dcrit is used for new crack initialization.
oin case there is failed neighbors for this element. Dadv is used for crack advancement.
oElement deleted, if a second crack arrives to the same element.

Note:  Dadv should always be less than Dcrit (Dadv < Dcrit ). If not, then Dadv is set to Dcrit (Dadv=Dcrit)

And, damage, is computed in RADIOSS as:

If fct_IDd = 0:

If fct_IDd ≠ 0:

is plastic strain increment.

is described in table1_ID

fail_tab_eq3   is stress triaxiality

Where, is hydrostatic stress and is von Mises stress.

factorT = FscaleT * fct_IDT (Tstart )

Temperature Tstart is computed for material laws supporting thermo-plasticity.

Example: /MAT/HYD_JCOOK (LAW4).

5.P_thickfail is only compatible with shell elements (except, shells with property TYPE11 (SH_SANDW)), and is only used when Ifail_sh = 2 or Ifail_sh = 3. With Ixfem=1, P_thickfail is only compatible with mono-layer XFEM formulation (Comment 1).
6.When P_thickfail is used, the shell complete rupture occurs when the thickness of broken layers is greater than the ratio of shell total thickness.

Only adjacent layers that fail consecutively are accounted for the thickness sum (usually from one of external skin to the mid-surface).

7.The first variable of table1 is stress triaxiality , the second variable is strain rate and the third is the Lode angle parameter symbol_plastic_strain.

For shell, only 2D tables are available (no dependency of Lode angle).

8.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).
9.The first variable of table2 is triaxiality, the second is strain rate. It is only for shell.
10.Fading starts with instability. Recommend value is 5 to 10. If value is < 0, then fading exponent is a function_ID: Fading_exp as function of element length.

See Also:

Failure /FAIL/JOHNSON and /FAIL/TAB1