Defining Elastoplastic Materials

In many cases, materials can be described as elastoplastic. Elastoplastic materials transition from a linear elastic behavior to a plastic behavior as the stresses increase. Plastic deformation is irreversible, that is, the material does not return to its original shape when the load is removed. The stress at which a material begins to deform plastically is known as the yield stress.

To model elastoplastic materials:
  1. Create a material law and assign it to the relevant solid materials, as explained in Defining the Solid Materials.
  2. Right-click the Material Laws > [Material Law 1] > Models node and choose Select models...
  3. In the Material Law 1 Model Selection dialog, activate the following models:
    Group box Model
    Material Stiffness Models To account for the linear elastic behavior, activate Linear Elasticity.
    Material Strain Measures
    • To model linear geometries, activate Linear Strain (Small Strain).
    • To model nonlinear geometries, activate Green-Lagrange (Small Strain).
    Linear Elastic Material Models Choose one of: Isotropic Linear Elastic, Orthotropic Linear Elastic, or Anisotropic Linear Elastic (for guidelines, see Defining Linear Elastic Materials)
    Optional Models To account for the plastic behavior, activate Plasticity
    Plasticity Activate J2 plasticity model
For each material in the simulation, Simcenter STAR-CCM+ adds the relevant material properties under the Material Properties node based on the selected models. Define the material properties as follows:
  1. Expand the Material Properties node.
  2. Define the material Density.
  3. Define the properties that define the linear elastic behavior, such as the Poisson's Ratio and Young's Modulus.
  4. To define the plastic behavior, select the Plastic Yield Stress node and set Method to one of the following:
    • Linear Isotropic Hardening—the yield stress is a linear function of the plastic strain defined by Eqn. (4523).
    • Saturation Hardening—the yield stress is a nonlinear function of the plastic strain defined by Eqn. (4524).
    • User-Defined—the stress-strain curve is defined directly by specifying the yield stress and its derivative with respect to the plastic strain (see Eqn. (4525)).
  5. Depending on the selected method, expand the Plastic Yield Stress > [hardening method] node and define the following quantities:
    Method Steps
    Linear Isotropic Hardening Specify sigmaY and H0 using either a constant value, a space-invariant expression, or a field function. These coefficients represent σY0 and H0 in Eqn. (4523). For H0=0 the material is perfectly plastic.
    Saturation Hardening Specify sigmaY_0, sigmaY_inf, H_bar, delta, and m using either a constant value, a space-invariant expression, or a field function. These coefficients represent σY0, σY∞, H¯, δ, and m in Eqn. (4524).
    User-Defined Specify sigma_Y and its derivative with respect to strain, d(sigma_Y), using either a constant value, a space-invariant expression, a field function, or tabular data.

    For more information, see Material Law Models Reference.