Release Notes > MEMS Module

MEMS Module
New Functionality in Version 5.2a
Piezoresistivity Multiphysics Couplings
The three dedicated physics interfaces for the piezoresistive effect, namely, Piezoresistivity, Domain Currents; Piezoresistivity, Boundary Currents; and Piezoresistivity, Shell, have all been upgraded to corresponding multiphysics couplings. The old dedicated physics interfaces will be deprecated in a future version.
The new multiphysics couplings allow the flexibility to easily enable and disable each constituent physics interface and the couplings between the physics.
electric currents, shell
The Electric Currents, Shell interface is now included with the MEMS Module for the Piezoresistivity, Shell multiphysics coupling.
Magnetostriction Interface
A new Magnetostriction interface has been introduced. When added, a Solid Mechanics interface, a Magnetic Fields interface, and a Magnetostriction multiphysics coupling are created.
In the Solid Mechanics interface, a new material model, Magnetostrictive Material, has been added. This material has three different formulations: Linear, Nonlinear Isotropic, and Nonlinear cubic crystal.
In the Magnetic Fields interface, the new Ampere’s law, Magnetostrictive feature is used when modeling a magnetostrictive material.
The magnetostrictive coupling requires the AC/DC Module together with either the Structural Mechanics Module, Acoustics Module, or MEMS Module.
Serendipity Elements
In the Solid Mechanics interface, elements with so-called serendipity shape functions have been added. The serendipity elements have fewer degrees of freedom than the standard Lagrange elements. The default element type in these interfaces has been changed to Quadratic serendipity. The element type in existing models is not changed when the model is opened, so if you want to employ the serendipity elements, you must change the element type in the Discretization section of the physics interface settings.
The serendipity shape functions affect hexahedral, prism, pyramid, and quadrilateral elements. For a model with only hexahedral elements, the solution time is typically decreased by a factor of two when serendipity elements replace Lagrange elements in the same mesh.
Adhesion and Decohesion
The Contact node has a new Adhesion subnode. When using adhesion, the contacting boundaries will stick together when a certain criterion has been fulfilled. This criterion can be either a contact pressure, gap distance, or arbitrary user-defined expression. Using adhesion requires a penalty contact formulation.
Two boundaries that are joined by adhesion can separate again if a decohesion law is specified. There are three different decohesion laws: Linear, Polynomial, and Multilinear. The decohesion laws allow mixed mode decohesion with independent properties for the normal and tangential directions.
New and Modified Variables for Contact Analysis
Total forces are now computed for each Contact node as well as summed over all Contact nodes.
In general, the postprocessing variables for contact analysis have been restructured so that they are available for both the individual and aggregated Contact nodes.
The friction slip velocity is no longer defined as a dependent variable. When running a model using the COMSOL API, you will need to remove the reference to this variable in the solver settings. The friction slip velocity is usually defined as <comp>_<solid>_vslip_<pairname>, where <comp> is the tag of the component, <solid> is the tag of the Solid Mechanics physics interface where the Friction node is defined, and <pairname> is the name of the contact pair.
New Methods for Entering Thermal Expansion Data
There are now three different ways on which thermal expansion data can be entered:
By selecting the appropriate option, you can use different types of measured data without conversions. This new functionality is available in the Solid Mechanics interface.
Thermal Expansion of Constraints
Constraints like Fixed Constraint and Prescribed Displacement can now be augmented with a Thermal Expansion subnode. This makes it possible to relieve the stresses induced by constraints when the surrounding structure, idealized by the constraints, is not held at a fixed temperature.
Similarly, a Thermal Expansion subnode has been added to the Rigid Domain and the Rigid Connector. This allows for a thermal expansion of these otherwise rigid objects.
Harmonic Perturbation for Prescribed Velocity and Acceleration
The Prescribed Velocity and Prescribed Acceleration features have been augmented with a Harmonic Perturbation subnode. These boundary conditions can thus be used as a fixed constraint in a stationary study step, and then provide a harmonic vibration in a subsequent prestressed frequency domain study. This new functionality is available in the Solid Mechanics interface.
Smith Plots
Smith plots are now included in the MEMS Module.