/MAT/LAW3 (HYDPLA)

Block Format Keyword This law represents an isotropic elasto-plastic material using the Johnson-Cook material model.

This model expresses material stress as a function of strain and may account for the nonlinear dependence between pressure and volumetric strain when corresponding equation of state is specified. A built-in failure criterion based on the maximum plastic strain is available. This material law is compatible with solid elements only.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/MAT/LAW3/mat_ID/unit_ID or /MAT/HYDPLA/mat_ID/unit_ID
mat_title
ρi ρ0
E ν
a b n εmaxp σmax
Pmin

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]
ρ0 Reference density used in E.O.S (equation of state).

Default = ρ0=ρi (Real)

[kgm3]
E Young's modulus.

(Real)

[Pa]
ν Poisson's ratio.

(Real)

a Plastic yield stress.

(Real)

[Pa]
b Plastic hardening parameter.

(Real)

[Pa]
n Plastic hardening exponent.

(Real)

εmaxp Failure plastic strain.

Default = 1030 (Real)

σmax Maximum stress.

Default = 1030 (Real)

[Pa]
Pmin Cutoff minimum pressure ( < 0 ).

Default = -1030 (Real)

[Pa]

Example (Aluminum)

Comments

  1. In this model, the material behaves as a linear-elastic material when the equivalent stress is lower than the plastic yield stress. For higher stress values, the material behavior is plastic and the stress is calculated as:
    σ=(a+bεnp)

    Where, ˉεp is the plastic strain.

  2. The plastic yield stress should always be greater than zero. To model pure elastic behavior, the plastic yield stress will be set to 1030.
  3. By default, the hydrostatic pressure is linearly proportional to volumetric strain:
    P=Kμ

    Where, K=E3(12ν) is the bulk modulus and μ=ρρ01 is the volumetic strain.

    An additional Equation of State (Equation of State) card can refer to this material in order to incorporate a nonlinear dependency between hydrostatic pressure and volumetric strain. The yield stress should be strictly positive.

  4. When ˉεp attains (or exceeds) the value of εmaxp (for tension, compression or shear), in one integration point, the solid element are deleted.