Skip to content

Change Material

Upcoming release

Model change will be available with the upcoming release

Use this option to reassign materials during analysis by changing the material definition for all elements in the specified element set to the new material.

Note that:

  • Both the element set and the new material name must be defined before any step definitions, even if they weren't previously used.
  • A change in material model requires a transfer of state variables. Only state variables present in both materials will be transferred. State variables present in the old material model but not in the new one will be lost and state variables present in the new model but not the old will be initialized as zero. Example:
    • During the first steps of the analysis the Mohr-Coulomb-2 model is assigned to the elements. This model has two state variables, namely void ratio void_ratio and factor of safety FoS.
    • At a given step of the analysis the material model is changed to the hypoplastic model with intergranular strain. This model has seven state variables: void ratio void_ratio and the six components of the intergranular strain tensor int_strain_11, int_strain_22, ...
    • During the transfer of state variables, the void ratio void_ratio (present in both models) will be transferred, the factor of safety FoS (present in the old model) will be lost and the six components of the intergranular strain tensor int_strain_11, etc. will be initialized to zero.
  • Changing the stress-strain relation model (*Mechanical model) requires careful consideration, particularly when failure criteria are involved, as admissible stress states may change. This can cause numerical difficulties if the current stress state is invalid under the new model, potentially resulting in sudden plastic strain jumps.
  • For challenging material transitions, consider a two-step approach:
    1. First *Step: Change the material model while constraining all displacements of nodes in the element set using *Boundary, increment and record reaction forces with *Save reaction forces.
    2. Second *Step: Gradually release these reaction forces using *Reaction force, amplitude = ... to establish a new equilibrium that finds an admissible stress state through controlled plastic deformations.