The Inelastic Strain Rate node allows to enter inelastic strain contributions to the Linear Elastic Material, Nonlinear Elastic Material, and Hyperelastic Material models on a variety of formats. As opposed to the External Strain feature, the inelastic contribution is given as a strain rate, and the inelastic contribution is added after integrating this rate in time.

The Inelastic Strain Rate node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/). The node is available for 3D, 2D, and 2D axisymmetry.

Select a Coordinate system. All inputs are interpreted in the given coordinate system. This also implies that external code should assume that strains are passed with its local orientations. Deformation gradients are rotated by the local system in both indices.

Select the type of Strain input — Strain tensor, Deformation gradient, Deformation gradient, inverse, or Stretches.

Enter an initial value for the inelastic quantity as specified by the Strain input setting.

Select a Method — Automatic, Backward Euler, or Domain ODEs.

The Automatic option corresponds to the backward Euler method except with predefined settings for the Newton loop used to solve the local equations.

For the Backward Euler method, enter the following settings:

If both a step size and residual convergence check is requested, it is sufficient that either of the conditions are fulfilled. Setting either the Absolute tolerance and Relative tolerance or the Residual tolerance to zero ignores the corresponding convergence check. An error is returned if all are set to zero.

No settings are needed for the Domain ODEs method. However, this method adds degrees-of-freedom that are solved as part of the general solver sequence. The scaling of these fields can affect the convergence of the overall solution

Physics tab with Linear Elastic Material, Nonlinear Elastic Material, Hyperelastic Material, Layered Linear Elastic Material or Layered Hyperelastic Material node selected in the model builder tree: