/FAIL/ALTER

Block Format Keyword An advanced nonlinear stress-based failure criteria for glass applications such as a windshield.

The failure stress is described by parameters defining micro-cracks and crack propagation speed. With the X-FEM approach, the stress is set to zero perpendicular to the crack direction.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/FAIL/ALTER/mat_ID/unit_ID
Exp_n V0 Vc Ncycles Irate   mode
Cr_foil Cr_air Cr_core Cr_edge grsh4N grsh3N
KIC KTH Rlen        
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)

  
Exp_n Crack growth exponent for subcritical crack growth.

Default = 16.0 (Real)

  
V0 Crack growth velocity for subcritical crack growth at KIC.

Default = 0.0 (Real)

 [ m s ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaada Wcaaqaaiaab2gaaeaacaqGZbaaaaGaay5waiaaw2faaaaa@39DE@
Vc Maximum crack propagation velocity glass.

Default = 0.0 (Real)

 [ m s ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaada Wcaaqaaiaab2gaaeaacaqGZbaaaaGaay5waiaaw2faaaaa@39DE@
Ncycles Stress filtering period in cycles. Only used when Irate=0. 2
= 1 (Default)
No filtering.

(Integer)

  
Irate Stress rate filtering method.
= 0
Exponential moving average using Ncycles.
= 1
Arithmetic average using the last 50 cycles.

(Integer)

  
mode Flag to switch failure propagation models between neighbor elements.
= 0 (Default)
No failure info propagation.
= 1
xfem failure propagation.
= 2
Isotropic frontwave propagation.
= 3
Directional propagation through element edges.
= 4
Directional propagation through edges and diagnosis.

(Integer)

  
Cr_foil Crack depth at bottom surface.

Default = 0.0 (Real)

 [ m ]
Cr_air Crack depth at top surface.

Default = 1.0 (Real)

 [ m ]
Cr_core Crack depth in between bottom and surface integration points.

Default = 1.0 (Real)

 [ m ]
Cr_edge Crack depth at the edge elements of windshield.

Default = 1.0 (Real)

 [ m ]
grsh4N (Optional) Group identifier for 4 node edge shell elements.

Default = 0 (Integer)

  
grsh3N (Optional) Group identifier for 3 node edge shell elements.

Default = 0 (Integer)

  
KIC Fracture toughness.

Default = 0.0 (Real)

 [ P a m ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeaaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaaca WGqbGaamyyamaakaaabaGaamyBaaWcbeaaaOGaay5waiaaw2faaaaa @3AB8@
KTH Fatique threshold.

Default = 0.0 (Real)

 [ P a m ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeaaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaaca WGqbGaamyyamaakaaabaGaamyBaaWcbeaaaOGaay5waiaaw2faaaaa @3AB8@
Rlen Reference length.

Default = 1.0 (Real)

 [ m ]
fail_ID Failure criteria identifier. 9

(Integer, maximum 10 digits)

  

Comments

  1. This failure criteria is using the maximum stress as failure criterion. It is computed based on the strength of the material determined by initial cracks and the crack propagation velocity. Depending on mode switch flag, different failure propagation models between neighbor elements may be used.
  2. When Irate=0, an exponential moving average filter is used, and the filtered stress is:(1)
    σ f ( t ) = α σ ( t ) + ( 1 − α ) σ ( t − Δ t ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Wdm3aaS baaSqaaiaadAgaaeqaaOWaaeWaaeaacaWG0baacaGLOaGaayzkaaGa eyypa0JaeqySdeMaeq4Wdm3aaeWaaeaacaWG0baacaGLOaGaayzkaa Gaey4kaSYaaeWaaeaacaaIXaGaeyOeI0IaeqySdegacaGLOaGaayzk aaGaeq4Wdm3aaeWaaeaacaWG0bGaeyOeI0IaeyiLdqKaamiDaaGaay jkaiaawMcaaaaa@4F8A@
    Where,
    σ f =filtered stress MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Wdm3aaS baaSqaaiaadAgaaeqaaOGaeyypa0JaaeOzaiaabMgacaqGSbGaaeiD aiaabwgacaqGYbGaaeyzaiaabsgacaqGGaGaae4CaiaabshacaqGYb GaaeyzaiaabohacaqGZbaaaa@47A0@
    α = 2 N c y c l e s + 1 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqySdeMaey ypa0ZaaSaaaeaacaaIYaaabaGaamOtamaaBaaaleaacaWGJbGaamyE aiaadogacaWGSbGaamyzaiaadohaaeqaaOGaey4kaSIaaGymaaaaaa a@41AE@
  3. This failure model is compatible only with under-integrated shell elements (Ishell =24 and Ish3n =2 are recommended) and not compatible fully integrated shells. Also, although there is no restriction of the shell property that can be used, it is only compatible with one layer shell models.
  4. The elements defined in the groups grsh4N and grsh3N should be along the edge of the windshield and will receive specific failure weakening.
  5. This failure model is applied to shell elements that sandwich a polyvinyl butyral (PVB) solid element layer using coincident nodes. The entire assembly models a windshield.


    Figure 1. Windshield Finite Element Model


    Figure 2. Windshield Model - Entire Assembly
  6. The shell elements using this failure model should be oriented so their normals point away the from the middle PVB.
  7. The shell elements should have an offset applied to correctly model bending. This can be done using /PROP/TYPE51 Ipos=4.
  8. The fracture limit depends on the location and the fracture state of surrounding elements. 1
  9. The fail_ID is used with /STATE/BRICK/FAIL and /INIBRI/FAIL and /PERTURB/FAIL/BIQUAD. 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 for brick and with /STATE/SHELL/FAIL for shell).
1 Alter, Christian, Stefan Kolling, and Jens Schneider. "An enhanced non–local failure criterion for laminated glass under low velocity impact." International Journal of Impact Engineering 109 (2017): 342-353.