In some applications, it is necessary to approximate a general 3D stress state by a set of linearized stresses through a cross section of a thin structure. This is important for applications like the analysis of pressure vessels, fatigue analysis of welds, and determination of reinforcement requirements in concrete. In this blog post, we discuss why such an approach is useful as well as how to compute linearized stresses in the Structural Mechanics Module for COMSOL Multiphysics® version 5.3.

In the latest version of COMSOL Multiphysics® — version 5.2a — we bring you new features designed to enhance your structural mechanics contact modeling. You can, for instance, simulate objects that stick together once they come in contact (adhesion) as well as those that pull apart (decohesion), including full cohesive-zone modeling. Learn how to address each of these scenarios using the new functionality in COMSOL Multiphysics.

After recently encountering the equations of motion for rotating bodies for the first time, one of my sons came home with a number of interesting questions. His questions brought about a flashback, as I remembered sharing this sense of confusion when studying mechanics many years ago. In today’s blog post, I will present two COMSOL Multiphysics models — one of a gyroscope and one of a spinning top — that illustrate the remarkable properties of rotating bodies.

The most fundamental material model for structural mechanics analysis is the linear elastic model. Trivial as it may sound, there are some important details that may not be obvious at first glance. In this blog post, we will dive deeper into the theory and application of this material model and give an overview of isotropy and anisotropy, allowable values for material data, incompressibility, and interaction with geometric nonlinearity.

In Part 1 of this blog series, we discussed some of the considerations that you need to make when transforming your measured material data into a constitutive model. Hyperelastic materials were discussed in some detail. Today, we will have a look at how to use nonlinear elastic and elastoplastic materials, and show one way in which you can use your measured data directly in COMSOL Multiphysics.

In finite element modeling, you may encounter formulations where a force does not monotonically increase with displacement. You can see this property in many material models that include degradation of the material. Such behavior is represented by a negative stiffness. In this blog post, we discuss some examples of negative stiffness, including the physical backgrounds and numerical implications. These ideas are not confined to mechanical analysis, even though the term stiffness originates in that field.

Say you are working on a modeling case where loads are moving in such a way that they cross over different mesh elements and boundaries during the simulation. In these cases, among other instances, you may want to apply a boundary condition to only part of the geometrical boundary or only under certain conditions. In this blog post, we’ll discuss how you can utilize the flexibility of COMSOL Multiphysics to handle such situations.

When performing structural mechanics analyses, you will inevitably encounter the concept of geometric nonlinearity. In this blog post, we discuss what is meant by geometric nonlinearity and when you should take this effect into consideration.

Your finite element model will sometimes contain singularities — that is, points where some aspect of the solution tends toward an infinite value. In this blog post, we will explore the common causes of singularities, when and how to remove them, and how to interpret results when singularities are present in your model. While most of this discussion is in terms of structural mechanics, similar phenomena can also be found in many other physics fields.

We often get requests of the type “I would like to just enter my measured stress-strain curve directly into COMSOL Multiphysics”. In this new blog series, we will take a detailed look at how you can process and interpret material data from tests. We will also explain why it is not a good idea to just enter a simple stress-strain curve as input.