/FAIL/TENSSTRAIN

Block Format Keyword Describes a strain-based failure model that is compatible with shell and solids elements.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/FAIL/TENSSTRAIN/mat_ID/unit_ID
ε t 1 ε t 2 fct_ID ε f 1 ε f 2 S-Flag
Optional lines if S-Flag: 2 or 3
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
fct_IDel Fscaleel Elref          
fct_IDT FscaleT            
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)

 
ε t 1 Equivalent strain when damage begins, if S-Flag=1 or 2.

Maximum principal tensile strain when damage begins, if S-Flag=3.

Default = 1.E30 (Real)

 
ε t 2 Equivalent strain when the element is deleted, if S-Flag=1 or 2.

Maximum principal tensile strain when the element is deleted, if S-Flag=3.

Default = 2.E30 (Real)

 
fct_ID Strain rate scale function identifier to scale ε t 1 and ε t 2 depending on the strain rate.

(Integer)

 
ε f 1 First principal strain for failure and element deletion. Only used with S-Flag =1. 3

(Real)

 
ε f 2 Second principal strain for failure and element deletion. Only used with S-Flag =1. 3

(Real)

 
S-Flag Options failure flag.
=1 (Default)
Equivalent strain input only. No additional input lines, except for Failure_ID. 2
=2
Equivalent strain input with element length and temperature scale factor functions. 4
=3
Maximum principal tensile strain input with element length and temperature scale factor functions. 4

(Integer)

 
fct_IDel Element size scale factor function identifier. 4

(Integer)

 
Fscaleel Element size function scale factor.

Default = 1.0 (Real)

 
El_ref Reference element size.

Default = 1.0 (Real)

[ m ]
fct_IDT Temperature scale factor function identifier.

(Integer)

 
FscaleT Temperature function scale factor.

Default = 1.0 (Real)

 
fail_ID Failure criteria identifier. 6

(Integer, maximum 10 digits)

 

Example (Aluminum)

In this example, set ε t 2 = 0.1 . Using fct_ID, different principal strain ( ε t 1 and ε t 2 ) actually used by computation, according to different test strain rate.
#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----|
/MAT/PLAS_TAB/1/1
Aluminium
#              RHO_I
         2.788714E-9                   0
#                  E                  Nu           Eps_p_max               Eps_t               Eps_m
               68000                  .3                   0                   0                   0
#  N_funct  F_smooth              C_hard               F_cut               Eps_f
         1         0                   0                   0                   0
#  fct_IDp              Fscale   Fct_IDE                EInf                  CE
         0                   1         0                   0                   0
# func_ID1  func_ID2  func_ID3  func_ID4  func_ID5
         2
#           Fscale_1            Fscale_2            Fscale_3            Fscale_4            Fscale_5
                   0
#          Eps_dot_1           Eps_dot_2           Eps_dot_3           Eps_dot_4           Eps_dot_5
                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FAIL/TENSSTRAIN/1
#             EPS_t1              EPS_t2  funct_ID              EPS_f1              EPS_f2    S-FLAG
                 .05                  .1        16                 .02                 .06         0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/16
scale factor for Eps_t1 and Eps_t2
#        strain rate        scale factor
#                  X                   Y
                   0                   1                                                            
                  50                  .5                                                            
               10000                  .5                                                            
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/2
True Stress-True plastic strain
#                  X                   Y
                   0                 124                                                            
                 .01                 150                                                            
                 .02                 165                                                                                                                
                 .04                 184                                                                                                                     
                 .06                 196                                                                                                                    
                 .08                 203                                                                                                                   
                  .1                 206                                                                                                                    
                 .12                 210                                                                                                                  
                 .14                 213                                                                                                                    
                 .16                 217                                                                                                                      
                 .18                 220                                                                                                                    
                  .5                 240                                                         
                1000                 240                                                            
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Example with Element Size Regularization

#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----|
/MAT/PLAS_TAB/1/1
Aluminium
#              RHO_I
         2.788714E-9                   0
#                  E                  Nu           Eps_p_max               Eps_t               Eps_m
               68000                  .3                   0                   0                   0
#  N_funct  F_smooth              C_hard               F_cut               Eps_f
         1         0                   0                   0                   0
#  fct_IDp              Fscale   Fct_IDE                EInf                  CE
         0                   1         0                   0                   0
# func_ID1  func_ID2  func_ID3  func_ID4  func_ID5
         2
#           Fscale_1            Fscale_2            Fscale_3            Fscale_4            Fscale_5
                   0
#          Eps_dot_1           Eps_dot_2           Eps_dot_3           Eps_dot_4           Eps_dot_5
                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FAIL/TENSSTRAIN/1
#             EPS_t1              EPS_t2  funct_ID              EPS_f1              EPS_f2    S-FLAG
                 .05                  .1        16                 .02                 .06         2
#FCT_ID_EL           FSCALE_EL              EI_REF
        21                   1                   1
# FCT_ID_T            FSCALE_T
        22                   1
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/21
Element length regularisation
#                  X                   Y
# relative ele. size        scale factor
                  .5                   1
                   1                   1				  
                   2                 0.8 
/FUNCT/22
Temperature scale function
#                  X                   Y
                   0                 1.0                                                            
                 350                 1.0  				   
				1000                 0.5  				   
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/16
scale factor for Eps_t1 and Eps_t2
#        strain rate        scale factor
#                  X                   Y
                   0                   1                                                            
                  50                  .5                                                            
               10000                  .5                                                            
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/2
True Stress-True plastic strain
#                  X                   Y
                   0                 124                                                            
                 .01                 150                                                            
                 .02                 165                                                                                                                
                 .04                 184                                                                                                                     
                 .06                 196                                                                                                                    
                 .08                 203                                                                                                                   
                  .1                 206                                                                                                                    
                 .12                 210                                                                                                                  
                 .14                 213                                                                                                                    
                 .16                 217                                                                                                                      
                 .18                 220                                                                                                                    
                  .5                 240                                                         
                1000                 240                                                            
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

  1. The failure criteria is based on the damage calculation:(1)
    D = ε ε t 1 ε t 2 ε t 1
    Where, ε is either the equivalent strain or maximum principal tensile strain depending on the S-Flag option. The stress is then reduced using the calculated damage value using this equation: (2)
    σ = ( 1 D ) σ

    The damage, D MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiraaaa@36C0@ , can be plotted using /ANIM/Eltype/DAMA or /H3D/Eltype/DAMA. The progressive damage value is calculated based on the ratio of total strain and the final calculated total strain limit. The highest value is retained until the element reaches the failure limit. There is no accumulation and no load path dependency.

  2. Equivalent strain is calculated using tensile strain equivalent of Rankine criterion:(3)
    ε T = 1 3 I 1 + 2 3 J 2 d cos θ MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaH1oqzda WgaaWcbaGaamivaaqabaGccqGH9aqpdaWcaaqaaiaaigdaaeaacaaI ZaaaaiaadMeadaWgaaWcbaGaaGymaaqabaGccqGHRaWkdaWcaaqaai aaikdaaeaadaGcaaqaaiaaiodaaSqabaaaaOWaaOaaaeaacaWGkbWa a0baaSqaaiaaikdaaeaacaWGKbaaaaqabaGcciGGJbGaai4Baiaaco hacqaH4oqCaaa@483F@
    Where,
    I 1 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGjbWaaS baaSqaaiaaigdaaeqaaaaa@391D@
    First invariant of strain tensor.
    J 2 d MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGkbWaa0 baaSqaaiaaikdaaeaacaWGKbaaaaaa@3A09@
    Second invariant of strain deviator.
    For 2D (shells) this definition is reduced to:(4)
    ε T = 1 2 ( ε xx + ε yy + ( ε xx ε yy ) 2 + ε xy 2 ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaH1oqzda WgaaWcbaGaamivaaqabaGccqGH9aqpdaWcaaqaaiaaigdaaeaacaqG YaaaamaabmaabaGaeqyTdu2aaSbaaSqaaiaadIhacaWG4baabeaaki abgUcaRiabew7aLnaaBaaaleaacaWG5bGaamyEaaqabaGccqGHRaWk daGcaaqaamaabmaabaGaeqyTdu2aaSbaaSqaaiaadIhacaWG4baabe aakiabgkHiTiabew7aLnaaBaaaleaacaWG5bGaamyEaaqabaaakiaa wIcacaGLPaaadaahaaWcbeqaaiaaikdaaaGccqGHRaWkcqaH1oqzda WgaaWcbaGaamiEaiaadMhaaeqaaOWaaWbaaSqabeaacaaIYaaaaaqa baaakiaawIcacaGLPaaaaaa@5877@
  3. When S-Flag=1, elements can be deleted when D MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiraaaa@36C0@ =1 for one integration point, the first pricinple strain ε 1 > ε f 1 , or the second principal strain ε 2 > ε f 2 is reached. Failure based on the principal tension strain for failure and element deletion, ε f 1 or ε f 2 , does not include damage and instead fails immediately.

    When S-Flag= 2 or 3, elements can be deleted when D MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiraaaa@36C0@ =1 for one integration point and ε f 1 or ε f 2 are not used.

  4. When S-Flag= 2 or 3, it is possible to scale the defined total failure strain values, ( ε f 1 or ε f 2 ) based on element size or temperature using the following factors:(5)
    f a c t o r e l = F s c a l e e l f e l ( S i z e e l E l _ r e f )
    Where,
    f e l
    Element size correction factor function defined via fct_IDel
    Sizeel
    Characteristic element size
    (6)
    f a c t o r T = F s c a l e T f T ( T * )
    Where, f T ( T * ) is the function, f c t _ I D T and Temperature T * is computed via:(7)
    T = T T i n i T m e l t T i n i

    It is recommended to use /HEAT/MAT to define the thermal parameters for material laws that support thermo-plasticity.

  5. When S-Flag =3, the strain calculation is based on 1st principal strain value. For material numbers < 28 with shell elements, damage is not applied and failure is immediate.
  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 the .sta file with /STATE/BRICK/FAIL option).