Geomechanics Module Updates

For users of the Geomechanics Module, COMSOL Multiphysics® version 6.0 brings nonlocal plasticity, large improvements in computational speed and memory usage for creep functionality, and one new tutorial model. Read more about these updates below.

Nonlocal Plasticity

Shear bands or plastic strain localization might occur when modeling plasticity in ductile materials. These zones evolve differently for different mesh sizes. The new Nonlocal Plasticity functionality has been added to the Plasticity, Soil Plasticity, and Elastoplastic Soil material models and allows you to obtain a mesh-independent solution when plastic strain localization occurs. You can see this update in the existing Slope Stability in an Embankment Dam tutorial model.

An embankment dam model showing the displacement magnitude on the surface and the pressure head as streamlines against the walls.
A slope stability analysis of an embankment dam showing the displacement magnitude and pressure head.

New Inelastic Strain Rate Node

The new Inelastic Strain Rate attribute has a similar effect to the existing External Strain feature, the difference being that you can now specify an inelastic strain rate that is then integrated in time into an inelastic strain contribution. The strain rate can be specified in terms of a strain tensor, a deformation gradient, an inverse deformation gradient, or three orthogonal stretches.

New Reduced Integration Framework

A new framework has been added for reduced integration, including hourglass stabilization. Reduced integration is particularly useful when the computational cost per integration point is high, which is true for many nonlinear material models such as Plasticity or Creep.

Reduced integration is controlled from the new Quadrature Settings section. It is available in the settings for top-level material models like Linear Elastic Material and Nonlinear Elastic Material. The selected reduced integration rule will then be inherited by any subnodes that may be added. You can see this new framework in the existing Slope Stability in an Embankment Dam tutorial model.

Creep Improvements

A new general framework for Creep gives large improvements in computational speed and memory usage. For larger models, a speedup by a factor of 10 or more is achieved. The inelastic strain variables are now solved with either a Backward Euler, Forward Euler, or Domain ODEs time-stepping method.

The type of equivalent stress used to determine the creep rate is now a user input. You can select von Mises, Hill Orthotropic, Pressure, or User defined to model nonisotropic creep. When more than one creep mechanism is acting, you can also add one or more Additional Creep nodes under a Creep node.

New Tutorial Models

COMSOL Multiphysics® version 6.0 brings one new tutorial model to the Geomechanics Module.

Transient Response of a Shallow Foundation on Unsaturated Soil

Two 2D plots showing the volumetric strain in a clay stratum with the after rainfall results on the left and after evaporation results on the right.
Volumetric strain in a clay stratum after five days of rainfall and subsequent evaporation.

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