/FAIL/XFEM_TBUTC (Obsolete)
Block Format Keyword Describes a XFEM (eXtended Finite Element Method) failure model.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/FAIL/XFEM_TBUTC/mat_ID/unit_ID  
$\gamma $  K  $\sigma $ _{r}  I_{fail_sh}  I_{duct}  
a  b 
Optional Line
(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) 

$\gamma $  Exponent (Real) 

K  Critical damage
integral Default = 10^{30} (Real) 

$\sigma $ _{r}  Fracture stress Default = 10^{30} (Real) 
$\left[\text{Pa}\right]$ 
I_{fail_sh}  Shell failure flag
(Integer) 

I_{duct}  Ductilebrittle materials flag
(Integer) 

a  Material parameter
(exponent) (Real) 

b  Material parameter
(exponent) (Real) 

fail_ID  (Optional) Failure
criteria identifier 5 (Integer, maximum 10 digits) 
Comments
 This failure model is available for Shell only.
 An element fails once
the TulerButcher cumulative damage parameter is greater than the stated critical
damage value, K. The damage parameter accumulation is calculated
differently for ductile and brittle materials
(I_{duct} = 1
or 2).For ductile materials, the cumulative damage parameter is:
(1) $$\text{D}=\underset{0}{\overset{\text{t}}{\int}}{\text{(}\sigma {\sigma}_{r}\text{)}}^{\lambda}\text{dt}$$Where, $\sigma $ _{r}
 Fracture stress
 $\sigma $
 Maximum principal stress
 $\lambda $
 Material constant
 t
 Time when shell cracks for initiation of a new crack within the structure
 D
 Damage integral, another material constant
 For brittle
materials, the damage parameter is:
(2) $$\dot{D}=\frac{1}{K}{\left(\sigma {\sigma}_{r}\right)}^{a}$$(3) $${\sigma}_{r}={\sigma}_{0}{\left(1D\right)}^{b}$$(4) $$D=D+\dot{D}\text{\Delta}t$$  Current known
limitations are:
 /PARITH/ON does not ensure results repeatability, if SPMD > 1; it works in SMP parallel mode only.
 XFEM is currently NOT compatible with either /ANIM/VECT or with /PARITH/OFF.
 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).