/FAIL/GENE1

Block Format Keyword Multiple failure models with different combinations with strain rate, thermal or mesh size dependency.

Format

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/FAIL/GENE1/`mat_ID`/`unit_ID`
`P`_min		`P`_max	`SigP1_max`		`Time_max`	`dtmin`
`fct_ID`_sm		`Eps_dot_sm`	`Sig_max`		`Sigr`	`K`
`fct_ID`_ps		`Eps_dot_ps`	`Eps_max`		`Eps_eff`	`Eps_vol`
`Eps_min`		`Shear`	`fct_ID`_g12	`fct_ID`_g13	`fct_ID`_e1c
`tab_ID`_fld	`Itab`	`Eps_dot_fld`	`Nstep`	`I`_smooth	`I`_strain	`Thinning`
`Volfrac`		`P_thick`_fail	`NCS`		`T`_max
`fct_ID`_el		`Fscale`_el	`El_ref`

Optional line

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`fail_ID`

Definition

Field	Contents	SI Unit Example
`mat_ID`	Material identifier. (Integer, maximum 10 digits)
`unit_ID`	(Optional) Unit identifier. (Integer, maximum 10 digits)
`P`_min	Minimum pressure (positive in compression). (Real)	$[Pa]$ $[Pa]$
`P`_max	Maximum pressure (positive in compression). (Real)	$[Pa]$ $[Pa]$
`SigP1_max`	Maximum principal stress. < 0.0 Restricted to positive stress triaxiality. > 0.0 Unrestricted. (Real)	$[Pa]$ $[Pa]$
`Time_max`	Failure time. Default = 1E+20 (Real)	$[s]$ $[s]$
`dtmin`	Minimum time step. (Real)	$[s]$ $[s]$
`fct_ID`_sm	Function identifier of the maximum equivalent stress versus strain rate. (Integer)
`Eps_dot_sm`	Reference strain rate value for `fct_ID`_sm Default = 1 (Real)	$[\frac{1}{s}]$ $[\frac{1}{s}]$
`Sig_max`	Ordinate scale factor for `fct_ID`_sm or maximum equivalent stress if `fct_ID`_sm is not defined. Default = 1, if `fct_ID`_sm is defined (Real)	$[Pa]$ $[Pa]$
`Sigr`	Initial fracture stress for Tuler-Butcher criterion. (Real)	$[Pa]$ $[Pa]$
`K`	Critical value of the damage integral for Tuler-Butcher criterion. (Real)	$[P a^{2} \cdot s]$ $[P a^{2} \cdot s]$
`fct_ID`_ps	Maximum principal strain versus strain rate function identifier. (Integer)
`Eps_dot_ps`	Reference strain rate value for `fct_ID`_ps. Default = 1 (Real)	$[\frac{1}{s}]$ $[\frac{1}{s}]$
`Eps_max`	Ordinate scale factor for `fct_ID`_ps or maximum principal strain if `fct_ID`_ps is not defined. Default = 1, if `fct_ID`_ps is defined (Real)
`Eps_eff`	Maximum effective strain. (Real)
`Eps_vol`	Maximum volumetric strain. (Real)
`Eps_min`	Minimum principal strain. (Real)
`Shear`	Tensorial shear strain ( $\frac{γ_{max}}{2}$ $\frac{γ_{\max}}{2}$ ). Where, $γ_{max}$ $γ_{\max}$ is the engineering shear strain at failure. (Real)
`fct_ID`_g12	Maximum in-plane shear strain $γ_{12}$ $γ_{12}$ versus element size function identifier. (Real)
`fct_ID`_g13	Maximum transversal shear strain $γ_{13}$ $γ_{13}$ versus element size function identifier. (Real)
`fct_ID`_e1c	Maximum in-plane major strain $ε_{1}^{c}$ $ε_{1}^{c}$ versus element size function identifier. (Real)
`tab_ID`_fld	Table or function identifier of the Forming Limit Diagram. (Integer)
`Itab`	Table dependency type (used only if `tab_ID`_fld is a table). = 1 (Default) Table is the Forming Limit Diagram versus strain rate. = 2 Table is the Forming Limit Diagram versus element size. (Integer)
`Eps_dot_fld`	Reference strain rate value for `tab_ID`_fld. Default = 1 (Real)	$[\frac{1}{s}]$ $[\frac{1}{s}]$
`Nstep`	Number of cycles for the stress reduction. Default = 10 (Integer)
`I`_smooth	Interpolation type (in case of tabulated yield function). = 1 (Default) Linear interpolation. = 2 Logarithmic interpolation base 10. = 3 Logarithmic interpolation base n. (Integer)
`I`_strain	Engineering / True input strain flag. = 0 (Default) FLD curve defined in terms of true strain. = 1 FLD curve defined in terms of engineering strain. (Integer)
`Thinning`	Thinning failure value. (Real)
`Volfrac`	Damaged volume fraction to reach before the element is deleted (fully-integrated and higher order elements only). Default = 0.5 (Real)
`P_thick`_fail	Ratio of through thickness integration points that must fail before the under-integrated element is deleted. 0.0≤ `P_thick`_fail ≤1.0 Default = 1.0 (Real)
`NCS`	Number of conditions to reach before the element is deleted. Default = 1 (Integer)
`T`_max	Maximum temperature. (Real)	$[K]$ $[K]$
`fct_ID`_el	Element size scale factor function identifier for the criterias `P`_min, `P`_max, `SigP1_max`, `Sig_max`, `Sigr`, `K`, `EpsPS_max`, `Eps_eff`, `Eps_vol`, `Eps_min`, `Shear`, `tab_ID`_fld and `Thinning`. (Integer)
`Fscale`_el	Element size function scale factor for `fct_ID`_el, `tab_ID`_fld (`Itab`=2), `fct_ID`_g12, `fct_ID`_g23, `fct_ID`_g13 and `fct_ID`_e1c. Default = 1.0 (Real)
`El_ref`	Reference element size for `fct_ID`_el, `tab_ID`_fld (`Itab`=2), `fct_ID`_g12, `fct_ID`_g23, `fct_ID`_g13 and `fct_ID`_e1c. Default = 1.0 (Real)	$[m]$ $[m]$
`fail_ID`	(Optional) Failure criteria identifier.

Comments

Failure criteria is used only if the value is different from 0.
Failure models including:
- Minimum hydrostatic pressure based failure criteria:
  $P \leq - | P_{min} |$ $P \leq - | P_{\min} |$
- Maximum hydrostatic pressure based failure criteria:
  $P \geq | P_{max} |$ $P \geq | P_{\max} |$
  
  Where, hydrostatic pressure is computed as:
  
  $P = - \frac{σ_{x x} + σ_{y y} + σ_{z z}}{3}$ $P = - \frac{σ_{x x} + σ_{y y} + σ_{z z}}{3}$
  
  Note: Hydrostatic pressure is positive in compression.
- Maximum principal stress:
  $σ 1 \geq SigP1_max$ $σ 1 \geq SigP1_max$ if $SigP1_max>0$ $SigP1_max>0$
  
  $σ 1 \geq | SigP1_max |$ $σ 1 \geq |SigP1_max|$ if $SigP1_max<0$ $SigP1_max<0$ and positive stress triaxiality value $η = \frac{- P}{σ_{V O N M}}$ $η = \frac{- P}{σ_{V O N M}}$
- Maximum time ≥ Time_max
- Minimum elementary time step ≤ dtmin (not available with /DT/NODA option).
- Equivalent stress:
  $σ_{e q} \geq S i g_m a x \cdot f c t_I D_{s m} (\frac{˙ ε}{{˙ ε}_{s m}})$ $σ_{e q} \geq S i g_m a x \cdot f c t_I D_{s m} (\frac{\dot{ε}}{{\dot{ε}}_{s m}})$
- Tuler-Butcher model:
  ${\int_{0}^{t} [max (0, σ 1 - S i g r)]}^{2} d t \geq K$ ${\int_{0}^{t} [\max (0, σ 1 - S i g r)]}^{2} d t \geq K$
  
  Where, $σ 1$ $σ 1$ is the principal stress.
- Maximum principal strain:
  $ε 1 \geq E p s P S_m a x \cdot f c t_I D_{p s} (\frac{˙ ε}{{˙ ε}_{p s}})$ $ε 1 \geq E p s P S_m a x \cdot f c t_I D_{p s} (\frac{\dot{ε}}{{\dot{ε}}_{p s}})$
- Effective strain:
  $\sqrt{\frac{2}{3}} ε_{i j}^{'} ε_{i j}^{'} \geq E p s_e f f$
  
  Where, $ε_{i j}^{'}$ is the deviatoric strain.
- Volumetric strain:
  $ε_{v o l} = ε_{11} + ε_{22} + ε_{33} \geq E p s_v o l$
- Minimum principal strain:
  $ε_{3} \leq - | E p s_m i n |$
- Maximum tensorial shear strain:
  $γ_{1} = \frac{(ε_{1} - ε_{3})}{2} \geq S h e a r$
- Mixed-mode fracture criterion:
  - $γ_{12} = \frac{(ε_{1} - ε_{2})}{2} \geq f c t_I D_{g 12} (\frac{S i z e_{e l}}{E l_r e f})$ if $- 2 \leq (\frac{ε_{2}}{ε_{1}}) \leq - 0.5$
  - $γ_{13} = \frac{(ε_{1} - ε_{3})}{2} \geq f c t_I D_{g 13} (\frac{S i z e_{e l}}{E l_r e f})$ if $- 0.5 \leq (\frac{ε_{2}}{ε_{1}}) \leq 1$
  - $ε_{1} \geq f c t_I D_{e 1 c} (\frac{S i z e_{e l}}{E l_r e f})$ if $- 0.5 \leq (\frac{ε_{2}}{ε_{1}}) \leq 1$
    Where,
    
    $ε_{1}$ and $ε_{2}$
    
    In-plane major and minor strains
    
    $ε_{3}$
    
    Through thickness strain
    
    $S i z e_{e l}$
    
    Characteristic element size
- Forming Limit Diagram (FLD):
  - If Itab=1: $(ε_{1}, ε_{2}) \geq T a b_I D_{f l d} (\frac{\dot{ε}}{E p s_d o t_f l d})$
  - If Itab=2: $(ε_{1}, ε_{2}) \geq T a b_I D_{f l d} (\frac{S i z e_{e l}}{E l_r e f})$
    Where,
    
    $ε_{1}$ and $ε_{2}$
    
    In-plane major and minor strains
    
    $S i z e_{e l}$
    
    Characteristic element size
- The stresses are reduced during Nstep cycles before the element deletion
- Minimum thinning based criterion:
  - if Thinning > 0, shell element is deleted, if the thickness integration point thinning ≤ -|Thinning|,
  - if Thinning < 0, shell element is deleted, if the average thickness thinning ≤ -|Thinning|.
  - For solids, element is deleted, if $ε_{z z}$ ≤ -|Thinning|.
- Maximum element temperature ≥ Tmax
Volfrac is used for fully-integrated and higher order solids and shells. It represents the damaged volume fraction (for example, the sum of damaged integration points of associated volumes) value to reach to trigger the element deletion.
For under-integrated linear shell elements, deletion is based on the value of P_thick_fail. If P_thick_fail > 0, the element fails and is deleted when the ratio of through thickness failed integration points equals or exceeds P_thick_fail. P_thick_fail defined in the failure model overwrite the value defined in the shell property.
The integration point failure begins when NCS conditions are reached. Then the stresses in the integration points are reduced to zero in Nstep cycles.
Element size dependency using the following factors:(1)
$f a c t o r_{e l} = F s c a l e_{e l} \cdot f c t_I D_{e l} (\frac{S i z e_{e l}}{E l_r e f})$

Where, $S i z e_{e l}$ is the characteristic element size.
For post-processing results in ANIM of H3D files, you can use the variable field DAMA. For /FAIL/GENE1, the damage variable is computed with the following ratio.(2)
$D = \frac{N c r i t}{N C S}$

Where,

$N c r i t$

Number of specified criteria reached by the integration point.

$N C S$

Number of criteria to reach to trigger integration point failure.

For instance, if 3 criteria are specified in the input and NCS = 3, if an integration point reaches 2 of them, its damage variable value will be $D$ = 0.667.