Materials/Failure

FAILURE LAYER # 11 ELEMENT # 1763 HASHIN MODE # 6 AT TIME #: 3.6405803218587E-0

For example, if 2x2 integration points in the plane and 8 layers through the thickness are selected. Then you have 2x2x8=32 integration points, which will be present in the output file 32 FAILURE LAYER.

• FAILURE LAYER # 1 ~ FAILURE LAYER # 8 means all integration points through layers in position of 1st integration point in plane
• FAILURE LAYER # 9 ~ FAILURE LAYER # 16 means all integration points through layers in position of 2nd integration point in plane.
• FAILURE LAYER # 17 ~ FAILURE LAYER # 24 means all integration points through layers in position of 3rd integration point in plane.
• FAILURE LAYER # 25 ~ FAILURE LAYER # 32 means all integration points through layers in position of 4th integration point in plane.

  
  
  Figure 1.

The minimum amount of data to use LAW24 can be obtained from:

• Density by weighing a specimen
• Young's modulus from a cylinder compression test
• Poisson coefficient is usually assumed to be near 0.2
• Compression strength, 'f_c' from a cube compression test

All other input values in LAW24 have defaults that are typical for concrete. But with the following additional tests, material LAW24 will be more accurate and better fit the failure envelope:

• Get ‘f_t’ from tensile test:

  ‘f_t’ is direct tensile strength. This test provides ‘f_t/f_c’ value for LAW24.

• Get couple of (f_st, H_t) from Splitting tensile test:

  This test is also called "Brazilian test".

  ‘f_st’ is splitting tensile strength in Splitting tensile test. It is asssumed that f_t=0.71f_st. Then you need to model this test to fit failure limit by validating ‘H_t’ value. I_solid=24 is also recommended for solid property for in Splitting tensile test.

• Get ‘f_b’ from Biaxial test and get (f₂,s₀) from confined test.

WARNING ID: 519
** WARNING IN SANDWICH SHELL INITIALIZATION
SHELL (ID=…) MASS (TYPE NUMBER …) 
SUM OF LAYER MASS DIFFER FROM TOTAL

WARNING ID: 520
** WARNING IN SANDWICH SHELL INITIALIZATION 
SHELL (ID=…) INERTIA (TYPE NUMBER …)
POTENTIAL INSTABILITY DUE TO LAYER INERTIA DISTRIBUTION

Indeed, mass me and inertia I of the element which will be distributed to the nodes of the shell are correctly computed from the characteristics of each layer:(1)

$$m_e=\left({\displaystyle \sum _{j=1,N}{p}_j{t}_j}\right)S$$

Where,

$S$

Area of shell element

$N$

Number of layers

$p_j$

Density of layer $j$

$t_j$

Thickness of layer $j$

$I={\displaystyle \sum _{j=1,N}{p}_j{t}_j}S\left(\frac{S+t_j{}^2}{12}+z_j{}^2\right)$

$z_j$

Distance to the middle plane of the shell element

When using LAW25, the following failure message can be written to the Engine output.

FAILURE-1

Criteria ${\epsilon }_{m1}$ for maximum tensile strain in first direction has been reached

FAILURE-2

Criteria ${\epsilon }_{m2}$ for maximum tensile strain in second direction has been reached

FAILURE-P

Criteria ${\text{W}}_p^{\max }$ (maximum plastic work for failure) has been reached

When the element is deleted (it depends on the failure of its different layers and on the flag I_off - Total Element Failure Criteria - into the global material associated to the PART), the following message is written:

RUPTURE OF SHELL ELEMENT …

The limitation to global integration include.

• Global integration (N=0) is only compatible with Material Laws 1, 2, 22, 36, 43 and 60.
• Failure models are not available with global integration for shells.
• Global integration is not compatible with saving stresses to state files using /STATE/DT which creates /INISHE and /INISH3N.

Workaround: Use material LAW2 with integration point and a huge value for the yield stress. As of V51, material LAW1 for shells uses global formulation, except if one integration point is asked for in the property, then a membrane only behavior occurs.

To define non-reflecting Eulerian boundary conditions, the following options can be used.

• /MAT/LAW51: I_form=6 for multi-material modeling.
• /MAT/LAW11 – I_form=3 or /EBCS (GRADP0,…) for mono-material modeling.