/FAIL/CONNECT

Format

Definition

Comments

1. This failure model is compatible only with the connection material, /MAT/LAW59 (CONNECT).
2. Failure criteria:
   From relative displacement:

   • I_fail=0: Uni-directional formulation (uncoupled failure formulation)
     $$Cs(t)=\max \left({\left|\frac{{\overline{u}}_N}{{\overline{u}}_{\max N}}\cdot {\alpha }_N\cdot {\mathrm{f}}_N\left({\dot{\overline{u}}}_N\right)\right|}^{{\exp }_N},{\left|\frac{{\overline{u}}_T}{{\overline{u}}_{\max T}}\cdot {\alpha }_T\cdot {\mathrm{f}}_T\left({\dot{\overline{u}}}_T\right)\right|}^{{\exp }_T}\right)>1$$
   • I_fail=1: Multi-directional formulation (coupled failure formulation)
     $$Cs(t)={\left|\frac{{\overline{u}}_N}{{\overline{u}}_{\max N}}\cdot {\alpha }_N\cdot {\mathrm{f}}_N\left({\dot{\overline{u}}}_N\right)\right|}^{{\exp }_N}+{\left|\frac{{\overline{u}}_T}{{\overline{u}}_{\max T}}\cdot {\alpha }_T\cdot {\mathrm{f}}_T\left({\dot{\overline{u}}}_T\right)\right|}^{{\exp }_T}>1$$

   From energy:

   $$Ce(t)=\max \left[{\left(\frac{En}{E{N}_{\max }}\right)}^{N_n}+{\left(\frac{Et}{E{T}_{\max }}\right)}^{N_t},\frac{EI}{E{I}_{max}}\right]>1$$
   Where,

   $EI$

   Internal energy per connection element area.

   $En$

   Internal energy in the normal direction per connection element area.

   $Et$

   Internal energy in the shear direction per connection element area.

3. A damage variable, $D$ is defined as maximum of the cumulative damage generated by relative displacement or energy:
   $$D_{\max }=\max \left[{\displaystyle {\int }_0^t\left({\mathrm{C}s(t)|}_{\mathrm{C}s(t)>1}\right)dt},{\displaystyle {\int }_0^t\left({\mathrm{C}e(t)|}_{\mathrm{C}e(t)>1}\right)dt}\right]$$

   The element is deleted (or stress in local integration point is set to zero), if:

   $$D_{\max }\ge T_{\max }$$

   If $T_{\max }$ is equal to default value, failure is immediate.

   Otherwise, when $T_{\max }>D_{\max }>0$ , softening is applied (for all directions) as:

   $$\sigma =\sigma {\left(1-\frac{D}{T_{\max }}\right)}^{N_{soft}}$$

4. fail_ID is used with /STATE/BRICK/FAIL and /INIBRI/FAIL. There is no default value. If the line is blank, no value is output for the failure model variables in the /INIBRI/FAIL (written in .sta file with /STATE/BRICK/FAIL option).
5. The following animation (/ANIM/BRICK) and time history (/TH/BRICK) outputs are available using USR (maximum value over integration points):

   	EImax (only)	ENmax or ETmax (only)	EImax and (ENmax or ETmax)
   USR1	$\frac{EI}{E{I}_{\max }}$		$\max \left[{\left(\frac{En}{E{N}_{\max }}\right)}^{N_n}+{\left(\frac{Et}{E{T}_{\max }}\right)}^{N_t},\frac{EI}{E{I}_{\max }}\right]$
   USR2		${\left(\frac{En}{E{N}_{\max }}\right)}^{N_n}+{\left(\frac{Et}{E{T}_{\max }}\right)}^{N_t}$	${\left(\frac{En}{E{N}_{\max }}\right)}^{N_n}+{\left(\frac{Et}{E{T}_{\max }}\right)}^{N_t}$

   Where,

   EI

   Internal energy per connection element area

   En

   Internal energy in the normal direction per connection element area

   Et

   Internal energy in the shear direction per connection element area

   	Ifail=0	Ifail=1
   USR3	$\max \left[{\mathrm{f}}_N\left({\dot{\epsilon }}_N\right)\cdot \frac{{\epsilon }_N}{{\epsilon }_{\max N}},{\mathrm{f}}_T\left({\dot{\epsilon }}_T\right)\cdot \frac{{\epsilon }_T}{{\epsilon }_{\max T}}\right]$	${\mathrm{f}}_N\left({\dot{\epsilon }}_N\right)\cdot \frac{{\epsilon }_N}{{\epsilon }_{\max N}}$
   USR4	${\mathrm{f}}_T\left({\dot{\epsilon }}_T\right)\cdot \frac{{\epsilon }_T}{{\epsilon }_{\max T}}$	$c4={\mathrm{f}}_T\left({\dot{\epsilon }}_T\right)\cdot \frac{{\epsilon }_T}{{\epsilon }_{\max T}}$
   USR5		${\left|\frac{{\epsilon }_N}{{\epsilon }_{\max N}}\cdot {\alpha }_N\cdot {\mathrm{f}}_N\left({\dot{\epsilon }}_N\right)\right|}^{{\exp }_N}\text{+}{\left|\frac{{\epsilon }_T}{{\epsilon }_{{\max }_T}}\cdot {\alpha }_T\cdot {\mathrm{f}}_T\left({\dot{\epsilon }}_T\right)\right|}^{{\exp }_T}>1$
   USR6	$SOFT={\left(1-\frac{D}{T_{\max }}\right)}^{N_{soft}}$	$SOFT={\left(1-\frac{D}{T_{\max }}\right)}^{N_{soft}}$

6. The area is calculated as the mean value of the upper and lower surface of the solid element. If the actual area reaches the value of initial area multiplied by AREA_scale factor, the whole element will be deleted. If the elements attached to the connect elements fail, this option can be used to prevent shooting nodes due to large deformation of the connect elements.
7. The different modes of failure can be plotted using /H3D/ELEM/FAILURE/ID=FAILID with the option MODE(=I or ALL):
   • MODE1: Normal direction displacement damage
     $$\left|\frac{{\overline{u}}_N}{{\overline{u}}_{max N}}·{\alpha }_N·f_N\left(\dot{{\overline{u}}_N}\right)\right|$$
   • MODE2: Shear plane displacement damage
     $$\left|\frac{{\overline{u}}_T}{{\overline{u}}_{max T}}·{\alpha }_T·f_T\left(\dot{{\overline{u}}_T}\right)\right|$$
   • MODE3: Displacement based damage
     $$max \left({\left|\frac{{\overline{u}}_N}{{\overline{u}}_{max N}}·{\alpha }_N·f_N\left(\dot{{\overline{u}}_N}\right)\right|}^{ex{p}_N} , {\left|\frac{{\overline{u}}_T}{{\overline{u}}_{max T}}·{\alpha }_T·f_T\left(\dot{{\overline{u}}_T}\right)\right|}^{ex{p}_T}\right)$$
     if Ifail = 0, otherwise,
     $${\left|\frac{{\overline{u}}_N}{{\overline{u}}_{max N}}·{\alpha }_N·f_N\left(\dot{{\overline{u}}_N}\right)\right|}^{ex{p}_N} + {\left|\frac{{\overline{u}}_T}{{\overline{u}}_{max T}}·{\alpha }_T·f_T\left(\dot{{\overline{u}}_T}\right)\right|}^{ex{p}_T}$$
   • MODE4: Normal direction energy damage
     $${\left(\frac{En}{E{N}_{max}}\right)}^{N_n}$$
   • MODE5: Shear plane energy damage
     $${\left(\frac{Et}{E{T}_{max}}\right)}^{N_t}$$
   • MODE6: Total energy damage
     $$\left(\frac{EI}{E{I}_{max}}\right)$$
   • MODE7: Energy damage
     $$max \left[{\left(\frac{En}{E{N}_{max}}\right)}^{N_n}+{\left(\frac{Et}{E{T}_{max}}\right)}^{N_t} , \frac{EI}{E{I}_{max}}\right]$$

     The global failure index can be displayed using /H3D/ELEM/FAILURE/ID=FAILID without the MODE option.