/FAIL/TBUTCHER
Block Format Keyword Describes a Tuler-Butcher failure model.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/FAIL/TBUTCHER/mat_ID/unit_ID | |||||||||
K | Ifail_sh | Ifail_so | Iduct | Ixfem | |||||
a | b | Dadv |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
fail_ID |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
mat_ID | Material
identifier. (Integer, maximum 10 digits) |
|
unit_ID | Unit Identifier. (Integer, maximum 10 digits) |
|
Exponent. (Positive real) |
||
K | Critical damage
integral. (Real) |
|
Fracture
stress. (Real) |
||
Ifail_sh | Shell failure flag.
If Ixfem =0: failure - element deleted If Ixfem =1: failure - element cracked. 2 (Integer) |
|
Ifail_so | Solid failure flag.
(Integer) |
|
Iduct | Ductile-brittle materials
flag (Only active if Ixfem=1
(shell only)).
(Integer) |
|
Ixfem | XFEM flag
(for /PROP/SHELL, /PROP/SH_SANDW, and
/PROP/TYPE51 properties only).
(Integer) |
|
a | Brittle rupture material
parameter (exponent). (Real) |
|
b | Brittle rupture material
parameter (exponent). (Real) |
|
Dadv | Criterion for the crack
advancement (Only active if Ixfem=1). 4 (Real, between 0 and 1) Default = 0.85 (for backward compatibility) |
|
fail_ID | Failure criteria identifier. 3 (Integer, maximum 10 digits) |
Example (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 + ductile failure model
# RHO_I
7.8E-9 0
# 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/TBUTCHER/1/1
# LAMDA K SIGMA_R Ifail_sh Ifail_so I_DUCT Ixfem
2 0.3e+8 150 0 1 0 0
# A B Dadv
0 0 0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
Comments
- An element
fails once the Tuler-Butcher cumulative damage parameter is greater than specified
critical damage value K. The damage parameter accumulation is
calculated differently for ductile and brittle materials
(Iduct = 1
or 2). For solids, only the ductile rupture is available,
Iduct flag has no effect.For ductile materials, the cumulative damage parameter is:
(1) Where,- Initial fracture stress
- Maximum principal stress
- Mmaterial constant (positive real value)
- t
- Time when the element cracks
- D
- Damage integral
- K
- Critical value of the damage integral
For brittle materials (shells only), the damage parameter is:
- 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 flag 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 criteria applied to the material identifier:
- 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 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.
- 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.
- 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. - If /PROP/SHELL (TYPE1) is used, then mono-layer
XFEM will be applied.
- 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).
- The failure criteria is
calculated as:
The cumulative damage parameter, D is only rupture criterion used when Ixfem=0.
When Ixfem=1, both D and Dadv can be used, respectively for crack initialization and advancement. If an element has no failed neighbors, D is used to initialize a new crack, if satisfied. Otherwise, if an existing crack occurs to a boundary of an element, the crack advancement criterion, Dadv will be used, instead of D. Eventually, if a second crack arrives at the same element, it will be deleted.