(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

In this example, use /FAIL/TBUTCHER to simulate ductile failure. Depending on exponent, damage integral could be impulse criteria (  =1), energy (or work) criteria ( =2), or constant stress criteria. This could get by fitting the experiment data. In this example, use exponent =2.0.

#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

#                  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----|

For ductile materials, the cumulative damage parameter is:

Where,

is the initial fracture stress

is the maximum principal stress

is material constant (positive real value)

t is the time when the element cracks

D is damage integral

K is the critical value of the damage integral

For brittle materials (shells only), the damage parameter is:

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:

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.

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.

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.