MEMS Module Updates

For users of the MEMS Module, COMSOL Multiphysics® version 5.5 brings improved contact modeling, fluid-structure interaction for two-phase flows, random vibration analysis, and more. Browse all of the MEMS updates below.

Random Vibration Analysis

When loads are random in nature, such as turbulent wind gusts or road-induced vibrations on a vehicle, it is not possible to describe them in a deterministic way. Using the new functionality for random response analysis, you can study the response to loads that are represented by their power spectral density (PSD). The loads can be fully correlated, uncorrelated, or have a specific user-defined cross-correlation. Examples of computed results include PSDs of displacements or stresses, as well as the root mean square (RMS) value or higher moments of the spectral distributions.

This new functionality is demonstrated in the following models:

A 3D model of a motherboard in rainbow color table. RMS vertical acceleration in a motherboard subjected to vibration testing with a given acceleration spectral density.

Contact Modeling Improvements

The contact modeling functionality has been enhanced in several ways:

  • It is possible to model contact between boundaries in a Solid Mechanics interface and arbitrary meshed surfaces
  • The penalty formulation for contact is now the default, providing better stability
  • The friction forces are now formulated in local directions along the tangents to the contact boundary, reducing the number of degrees of freedom
  • New default plots of the contact forces have been added
A closeup view of a flange model with normal pressure and friction traction shown around the bolts in green and magenta, respectively. Normal pressure (green) and friction traction (magenta) around the bolts in a flange.

Decohesion Enhancements

There are now two fundamental families of decohesion models: Displacement based damage and the new Energy based damage. Additionally, you can set up models with a new traction separation law, Exponential separation. Decohesion models are inherently unstable, due to the loss of material stiffness, and to improve the numerical behavior, you can include a Delayed damage regularization method.

The COMSOL Multiphysics UI showing the Model Builder, Decohesion feature settings, a load-displacement curve, and a laminated composite model undergoing debonding. Debonding of a laminated composite using the Displacement based damage decohesion model.

Fluid-Structure Interaction for Two-Phase Flows

The suite of multiphysics interfaces for fluid-structure interaction has two new entries for two-phase flows: Fluid-Solid Interaction, Two-Phase Flow, Phase Field and Fluid-Solid Interaction, Two-Phase Flow, Phase Field, Fixed Geometry. When you select the Fluid-Solid Interaction, Two-Phase Flow, Phase Field option from the Model Wizard, the Laminar Flow, Solid Mechanics, and Phase Field interfaces are added, along with the Fluid-Structure Interaction and Two-Phase Flow multiphysics couplings and a Deforming Domain feature. The fixed geometry option includes the same, minus the Deforming Domain feature. You can see this new functionality in the Two-Phase Flow with Fluid-Structure Interaction model.

A model of water, shown in blue, and air, shown as streamlines, interacting with a thin shell. Simulation of two-phase flow (water and air) interacting with a thin shell. The blue surface is the free water boundary. The displacements in the shell and flow streamlines are also shown.

Multiphysics Interface for FSI with Heat Transfer

In some fluid-structure interaction (FSI) problems, heat transfer between the fluid and the solid is important. Usually, this is also accompanied by thermally induced deformations or stresses in the solid. A new multiphysics interface, Fluid-Solid Interaction, Conjugate Heat Transfer has been added to make it convenient to set up models combining these effects. It combines the three physics interfaces Heat Transfer in Solids and Fluids, Solid Mechanics, and Laminar Flow together with a moving mesh and appropriate multiphysics couplings. As with all other FSI interfaces, the flow can easily be changed from laminar to be turbulent. You can see this new feature in the Bimetallic Strip in Airflow model.

A model of a bending bimetallic strip with airflow around it. Flow around a bimetallic strip that bends when subjected to heating from the fluid.
The Select Physics window in COMSOL Multiphysics version 5.5 with the Fluid-Solid Interaction option selected under the Conjugate Heat Transfer option. When you select the Fluid-Solid Interaction option under Conjugate Heat Transfer, the software will create the appropriate physics interfaces with automatic multiphysics couplings set up.

Solid Mechanics on Rotating Domains

When modeling multiphysics problems in systems where there is a mixture of rotating and stationary domains, you can use the Solid Mechanics interface in a corotating configuration, such that only the deformations relative to the rotation are modeled. This is far more efficient than solving for the total displacements that include large global rotations. In many cases, it is even possible to use a linear formulation for the mechanical problem. To this end, the Rotating Frame feature provides a superposition of the rigid body rotation, and the relative displacements, for controlling the spatial frame on which the other physics interfaces are operating.

Two side-by-side models of an electric generator rotor where one shows the magnetic field with contours and a green-purple gradient and the other shows stresses in rainbow. Electric generator where the rotor is modeled using the Solid Mechanics interface. Results show the magnetic field (left) and stresses (right).

Magnetostrictive Material with Hysteresis

The nonlinear Magnetostrictive Material has been extended to include the Jiles–Atherton model of magnetic hysteresis. The model is suitable for investigating the hysteretic loss effects in applications such as power transformers and rotating electric machines. The model parameters are related to microscopic physical effects in magnetic materials and they can also be estimated based on experimental data.

The Settings window for the Magnetostrictive Material feature is shown with the Magnetization section expanded. Settings for the hysteretic magnetostrictive model, together with hysteresis loops generated from simulation.

Thin Elastic Layers with Mass

The Thin Elastic Layer feature, intended for abstract modeling of layers that are thin compared to the rest of the geometry, has been augmented by a possibility to add a mass distribution. This can be important for high-fidelity structural dynamics simulations.

Piezoelectric Material in Layered Shell Interface

The addition of piezoelectric material modeling capability to the Layered Shell interface makes it possible to model thin piezoelectric devices and sensors where a piezoelectric material is embedded in a composite laminate. A new multiphysics interface, Piezoelectricity, Layered Shell has been added for a convenient setup of models. It combines the two physics interfaces Layered Shell and Electric Currents in Layered Shells with a Layered Piezoelectric Effect multiphysics coupling. You can see this functionality in the new Piezoelectricity in a Layered Shell model. Note that to access this functionality, you need either the AC/DC Module or MEMS Module in addition to the Structural Mechanics Module and the Composite Materials Module.

A layered shell model where the middle layer is made of piezoelectric material. A layered shell with a piezoelectric layer embedded in the middle. The axial compression and out-of-plane displacement are shown in the piezoelectric layer (color wireframe plot) and in metal layers (color plot).

Electric Currents in Shells and Electric Currents in Layered Shells Interfaces

The new (layered) shell interfaces are an evolution of the previously available Electric Currents, Layered Shell and Electric Currents, Shell interfaces, with a focus on better usability and robustness. Modeling of both nonlayered shells, as well as layered shells, has become more streamlined with improved integration to other physics (multiphysics).

For layered shells, the physics interface models the shell’s boundary selection in 3D, as well as an extra dimension that points in the shell’s normal direction. This way, you can model both tangential and normal electric fields inside the shell, and as a result, you can use the interface to model conductors and dielectrics for Stationary, Time Dependent, and Frequency Domain studies. Combining either the MEMS Module or Structural Mechanics Module with the Composite Materials Module, this allows for modeling piezoelectric materials in layered shells.

You can see these new interfaces in the following models:

Two side-by-side models of the electric potential in a bracket that look very similar, but were created using two different techniques. Direct comparison between the solid (left) and shell description (right) of the same bracket. The results plot shows the electric potential.

New Elastic Waves, Time Explicit Physics Interface

The new Elastic Waves, Time Explicit physics interface is based on the discontinuous Galerkin time explicit method and enables efficient multicore computations of elastic wave propagation in solids. Features are included to provide realistic material data including anisotropy and damping. The interface is suited for modeling ultrasound propagation in solids, such as with transducers and sensors, and for nondestructive testing (NDT) applications, and is applicable to any acoustically large system that involves transient propagation over many wavelengths, which includes seismic wave propagation in soil and rock.

You can see the new interface used in the following models:

The COMSOL Multiphysics UI with the Settings window open for the Elastic Waves, Time Explicit interface and a plot showing seismic waves at 5 seconds. User interface for the new Elastic Waves, Time Explicit interface shown here in a model of seismic waves propagating in the soil.

New Tutorial Models

Version 5.5 brings new tutorial models.