## What Is the Physics Behind a Counterweight Trebuchet?

##### Mats Danielsson October 11, 2017

The trebuchet is a large siege weapon that you might recognize from movies set in the Middle Ages or fantasy worlds. This weapon is built on the idea of converting potential energy into kinetic energy to hurl a projectile over a large distance. Simple as it seems, the trebuchet is a complicated dynamical system. In this blog post, we will build a simplified model of a counterweight trebuchet using the Multibody Dynamics Module and examine some of its design features.

### Analyzing a Unique Poroelastic Metamaterial with Simulation

##### Caty Fairclough August 7, 2017

Metamaterials are artificial materials with properties that rely on a particular structural design rather than chemistry. Their structure is often complicated, making these materials challenging to fabricate. Here, we present numerical research that investigates one such material — a poroelastic metamaterial (made from a single material with voids) with the ability to expand under hydrostatic pressure.

### How to Model Generalized Plane Strain with COMSOL Multiphysics®

##### Peter Yakubenko July 26, 2017

Many elongated structures can be modeled effectively using 2D representations of their cross sections. A typical assumption is the plane strain approximation, which implies that all out-of-plane strain components are zero. This assumption is valid when the out-of-plane deformation is restrained; for example, when the ends of the structure are fixed. However, in many cases, the structure is free to expand in the out-of-plane direction. Let’s discuss how to model this case, which is sometimes called generalized plane strain.

### How to Perform Various Rotor Analyses in the COMSOL® Software

##### Prashant Srivastava July 12, 2017

Vibration in rotating machinery is very sensitive to the geometric, structural, and inertial properties of the various rotating and stationary components interacting with each other. These properties include the location of the mounted components and their inertial properties, bearing characteristics, and shaft properties. To understand the effects of these parameters, start with a simple model and perform various analyses to correlate the rotor response within the same model. Let’s demonstrate this process with a simply supported beam rotor example.

### Simulating Powder Compaction with Porous Plasticity Models

##### Bridget Cunningham June 12, 2017

In the last seven years, the output of the manufacturing industry has increased by a total of around 10–20%. This growth is partly thanks to technologies and processes that save on time and costs, such as 3D printing and, as is described here, powder compaction. To model this process, we can use the new porous plasticity models in the latest version of the COMSOL Multiphysics® software.

#### Categories

##### Bridget Cunningham May 30, 2017

Every year, over 40 million fire sprinkler systems are fitted worldwide. These systems are effective due to their piping designs, which are resistant to high heat and mechanical damage. A popular choice for such designs is threaded steel pipe. But analyzing a complex pipe design is challenging because of the detailed geometry. What approach can we take to efficiently combine accurate geometrical designs with reliable stress analyses? Version 5.3 of the COMSOL® software offers functionality for this purpose.

### How to Model Gearbox Vibration and Noise in COMSOL Multiphysics®

##### Pawan Soami May 23, 2017

Gears are used in a variety of applications, such as clocks, industrial machinery, music boxes, bicycles, and automobiles. A gearbox is a major source of vibration and noise irrespective of how it is used. The most effective approach to reduce the noise radiation from a gearbox is to perform a vibroacoustic analysis to improve the design. Let’s see how the COMSOL Multiphysics® software can be used to help build quieter transmission systems.

### How to Analyze Eigenfrequencies That Change with Temperature

##### Henrik Sönnerlind May 22, 2017

In some applications, particularly within the MEMS field, it is important to study the sensitivity of a device’s eigenfrequencies with respect to a variation in temperature. In this blog post, we show how to do this using COMSOL Multiphysics® version 5.3. We also explore effects like stress softening, geometric changes, and the temperature dependence of material properties.

### Studying the Artificial Ground Freezing Method with Simulation

##### Bridget Cunningham May 18, 2017

When the German engineer F. H. Poetsch first developed the artificial ground freezing (AGF) method in 1883, he did so to avoid water within Belgian coal mines. The method, which first received praise in the late 1800s, remains similar to its original form and is still valuable today. To develop a more effective AGF method, we can turn to simulation analyses.

### Introduction to Modeling Stress Linearization in COMSOL Multiphysics®

##### Henrik Sönnerlind May 16, 2017

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.

### Modeling a Transient Contact Problem with Stick-Slip Friction Transition

##### Bridget Cunningham May 3, 2017

For many mechanical contact problems, stick-slip friction transition is an important point of analysis. When present, this phenomenon influences the stresses, strains, and deformations near the contact area between the two bodies. In version 5.3 of the COMSOL Multiphysics® software, we have the tools necessary to handle this type of mechanical contact problem and validate the results. With a better understanding of stick-slip friction transition and its subsequent effects, we can improve the safety and energy efficiency of relative systems.