RD-V: 0710 Fail BIQUAD

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Model Files

Model Descriptions

Units: Kg, mm, ms, GPa

The boundary conditions are represented.

Material Law Characteristics

• LAW36
  The elasto-plastic behavior is defined using the tabulated material LAW36. The True Stress versus Plastic True Strain curve is used as an input of LAW36. For more information about the LAW36 material, refer to RD-V: 0240 Tabulated Material (LAW36) in Verification Problems.

  
  
  

• /FAIL/BIQUAD
  This failure model uses a simplified nonlinear failure criterion based on plastic strain with linear damage accumulation. The failure strain is described by two parabolic functions, which are calculated by curve fitting from up to 5 failure strains entered by you represented below:

  c1

  Failure strain at uniaxial compression test

  where $\sigma *=-1/3$

  c2

  Failure strain at pure shear test

  where $\sigma *=0$

  c3

  Failure strain at uniaxial tension test

  where $\sigma *=1/3$

  c4

  Failure strain at plain strain tension test

  where σ∗=1/√3

  c5

  Failure strain at biaxial tension test

  where $\sigma *=2/3$

  The failure model used in this study is UHSS Steel, corresponding to Mflag=3.

  
  
  

  By default, a failure criterion approach with stress computation is used for /FAIL/BIQUAD. This means that damage evolution has no effect on stress computation until the element deletion triggered by $D=1$ . You may want to create a stress softening effect during damage evolution. To do so, the flag ICOUP must be a non-zero value to activate the stress/damage coupling. This introduces the following stress softening equation:

  $$\sigma ={\sigma }_{eff}\left(1-{\left(\frac{D-D_{crit}}{1-D_{crit}}\right)}^{EXP}\right)$$
  Where,

  $\sigma$

  Damaged stress tensor

  ${\sigma }_{eff}$

  Undamaged effective stress tensor

  $D_{crit}$

  Critical damage value that triggers stress softening

  $EXP$

  Exponent parameter

  Below are the /FAIL/BIQUAD parameters used for the different element’s formulation, except under “Effect of /FAIL/BIQUAD parameters on damage”:

  • M-Flag=3
  • S-Flag=3
  • Inst_start=0.05
  • DCRIT=0.5
  • EXP=2

Results