/MAT/LAW22 (DAMA)

Block Format Keyword This law is identical to Johnson-Cook material (/MAT/LAW2), except that the material undergoes damage if plastic strains reach a user-defined value ( εdam ). This law can be applied to both shell and solid elements.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/MAT/LAW22/mat_ID/unit_ID or /MAT/DAMA/mat_ID/unit_ID
mat_title
ρi                
E ν            
a b n εpmax σmax0
c ε˙0 ICC          
εdam Et            

Definition

Field Contents SI Unit Example
mat_ID Material identifier.

(Integer, maximum 10 digits)

 
unit_ID Unit Identifier.

(Integer, maximum 10 digits)

 
mat_title Material title.

(Character, maximum 100 characters)

 
ρi Initial density.

(Real)

[kgm3]
E Young's modulus.

(Real)

[Pa]
ν Poisson's ratio.

(Real)

 
a Yield stress - should be strictly positive.

(Real)

[Pa]
b Hardening parameter.

(Real)

[Pa]
n Hardening exponent.

(Real)

 
εpmax Failure plastic strain.

Default = 1030 (Real)

 
σmax0 Maximum stress.

Default = 1030 (Real)

[Pa]
c Strain rate coefficient.
= 0
No strain rate effect

Default = 0.00 (Real)

 
ε˙0 Reference strain rate.

If ε˙ε˙0 , no strain rate effect.

(Real)

[1s]
ICC Strain rate computation flag. 2
= 0 (Default)
Set to 1
.
= 1
Strain rate effect on σmax .
= 2
No strain rate effect on σmax .

(Integer)

 
εdam Damage model starts at εdam .

Default = 0.15 (Real)

 
Et Softening damage slope ( E<Et0 ).

Default = 0.00 (Real)

[Pa]

Example (Aluminum)

Comments

  1. Damage is isotropic, its effect are the same in tension and compression.
    (1)
    σ=(a+bεpn)(1+clnε˙ε˙0)
    Where,
    εp
    Plastic strain
    ε˙
    Strain rate
  2. ICC is a flag of the strain rate effect on material maximum stress σmax .


    σ=σy(1+cln(ε˙ε˙o)) σ=σy(1+cln(ε˙ε˙o))
    σmax=σmax0(1+cln(ε˙ε˙o)) σmax=σmax0
    Figure 1.
  3. The damage appears in the material when the strain is larger than a maximum value εdam :(2)
    0δ1

    If ε<εdamδ=0 , Law 22 is identical to law /MAT/LAW2.

    If εεdamEdam=(1δ)E and νdam=12δ+(1δ)ν

    clip0053
    Figure 2.
  4. For solid elements, the damage law can only be applied to the deviatoric stress tensor sij and Gdam=Edam2(1+νdam) .
  5. When εp reaches εpmax in one integration point, then based on the element type:
    • Shell elements: The corresponding shell element is deleted.
    • Solid elements: The deviatoric stress of the corresponding integral point is permanently set to 0, however, the solid element is not deleted.