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/FAIL/NXT

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/FAIL/NXT - Forming Limit Diagram based on Stresses

Description

Describes the forming limit based on stresses.

Format

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/FAIL/NXT/mat_ID/unit_ID

fct_ID1

fct_ID2

Ifail_sh

 

 

 

 

 

 

 

Optional line:

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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)

 

fct_ID1

Function identifier of lower limit for fracture (S-R mode)

(Integer)

 

fct_ID2

Function identifier of upper limit for fracture (3D mode)

(Integer)

 

Ifail_sh

Shell failure flag

(Integer)

= 0: Shell is not deleted (default)

= 1: Shell is deleted, if there is one layer in failure zone.

= 2: Shell is deleted, only if all layers are in the failure zone.

 

fail_ID

(Optional) Failure criteria identifier (Comment 6)

(Integer, maximum 10 digits)

 

hmtoggle_plus1Example (Steel)

In this example material LAW32 with /FAIL/NXT is used. The curve of upper limit for fracture (3D mode) is scaled with /MOVE_FUNCT.

 

#RADIOSS STARTER

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

/UNIT/1

unit for mat

                 Mg                  mm                   s

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

#-  2. MATERIALS:

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

/MAT/HILL/1/1

void_steel

#              RHO_I

              7.8E-9

#                  E                  NU

              210000                  .3

#                  A           EPSILON_0                   n             EPS_max           SIGMA_max

                 582               0.009                .258                   0                   0

#          EPS_DOT_0                   m

                   0                   0

#                r00                 r45                 r90                       Iyield0

                 1.0                 1.0                 1.0                             0

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

/FAIL/NXT/1/1

#  fct_ID1   fct_ID2  Ifail_sh

       100       101         1

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

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

/FUNCT/100

SR-mode

#                  X                   Y

                -1.2                 1.2

                  -1                 1.3

                -0.8                1.36

                -0.6                1.42

                -0.4                1.47

                 0.2                 1.5

                 0.4                1.45

                 0.6                1.33

                   1                 1.5

                 1.5                1.85

                   2                2.25

                 2.5                2.55

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

/FUNCT/101

3D-mode

#                  X                   Y

                -1.3                1.35

                -1.1                 1.6

                -0.9                 1.9

                -0.7                 2.2

                -0.5                2.55

                -0.3                2.85

                -0.1                3.15

                   0                 3.2

                 0.3                3.15

                 0.7                2.95

                 1.1                 2.7

                 1.3                2.65

                 1.5                 2.7

                 1.9                 2.8

                 2.3                2.95

                 2.7                 3.1

                 3.1                 3.2

/MOVE_FUNCT/101

scale for 3D-mode

#            Ascalex             Fscaley             Ashiftx             Fshifty

                   0                 2.0                   0                   0

#---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.This failure model is available for Shell only.
2.A method to predict the fracture limit during a metal forming process based on the localized bifurcation theory and the instability theory for elastoplastic material.
3.The forming limit diagram as presented in the following figure is represented in the symbol/h plane where, symbol is the stress and h is the current work-hardening modulus. The limit curves, SR and 3D represent the Stören-Rice’s mode (S-R) limit and the 3-dimensional localized mode limit respectively. The SR limit can be regarded as the lower limit and the 3D limit and the upper limit for fracture. The fracture should occur when the stress level reaches the 3D limit.

fail_nxt

4.To determine the failure zone, an instability factor is defined as:

According to the value of symbol_expf , the status for fracture is:

Free: if 0 < symbol_expf < 1

Warning: if 1 < symbol_expf < 2

Danger: if symbol_expf > 2. In this case, the element failed. In this case, symbol_expf is set equal to 2.

5.When this failure model is defined, it automatically generates animation files containing three new outputs which are the instability fracture symbol_expf (NXT failure factor), (SIGMA1/h), and (SIGMA2/h).

where, and are the two current principal stresses.

6.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).
7.Available laws with this criterion are LAW2, LAW32, LAW36, LAW43, LAW73, and LAW78.