Structural Mechanics Module

A new Magnetostriction interface has been introduced. When added, a Solid Mechanics interface, a Magnetic Fields interface, and a multiphysics coupling are created.

In the Solid Mechanics interface, a new material model, , has been added. This material has three different formulations: , , and .

In the Magnetic Fields interface, the new 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.

A new multiphysics coupling between Solid Mechanics and Darcy’s law has been introduced. When adding a Poroelasticity interface in version 5.2a, the two separate physics interfaces and the multiphysics coupling will be created. This will give access to all functionality available in the constituent interfaces. As an example, it is now possible to model poroplasticity.

The Poroelasticity interface existing in previous versions is now obsolete. Old models containing this interface can still be opened and used. In the future, it will be removed.

In the Solid Mechanics and Membrane interfaces, 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 . 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 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.

A boundary condition node has been added to the Shell interface. This feature, which is similar to the one in Solid Mechanics, allows for efficient modeling of periodic structures by coupling corresponding edges. There are five different selections for the type of periodicity: , , , , and .

The node has a new 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, a gap distance, or an 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: , , and . The decohesion laws allow mixed mode decohesion with independent properties for the normal and tangential directions.

The Application Libraries example Mixed-Mode Debonding of a Laminated Composite has been revised to make use this new built-in functionality.

Total forces are now computed for each node as well as summed over all nodes.

In general, the postprocessing variables for contact analysis have been restructured so that they are available both for the individual node, and aggregated.

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 node is defined, and <pairname> is the name of the contact pair.

There are now three different ways in which thermal expansion data can be entered:

By selecting the appropriate option, you can use different types of measured data without conversions. The new options are available in the Solid Mechanics, Membrane, and Truss interfaces.

Constraints like and can now be augmented with a 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 subnode has been added to the and nodes. This allows for a thermal expansion of these otherwise rigid objects.

The local coordinate system used in the Shell interface is now defined in a subnode under the . This means that it is easier to use different material orientations with the same material data.

A new node, , is also created under when a Shell interface is added. This system contains the local directions for all boundaries on which the Shell interface is active, and can be referenced, for example, when setting up multiphysics couplings.

The in the Truss interface has a new control . The default state is selected. This gives a significant performance improvement for the common case when these constraints are not needed.

The default mesh in the Truss interface uses one element per edge, and then the straight edge constraints are not needed. Thus, there will not be any difference in behavior unless the mesh settings have been changed, in which case you may have to deselect .

The and features have been augmented with a 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, Membrane, and Truss interfaces.