## Can a Stiffness Be Negative?

##### Henrik Sönnerlind December 5, 2016

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.

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### Identify a Cricket Bat’s Sweet Spots with Structural Mechanics Analysis

##### Caty Fairclough November 11, 2016

In the highly competitive world of professional cricket, every swing is important. To deliver powerful shots, a batsman needs a well-designed bat and knowledge of how to best use it. One way to improve a player’s batting skills, and perhaps design better bats, is to locate their so-called “sweet spots”. A research team from the University of the West Indies achieved this by performing a structural analysis with the COMSOL Multiphysics® software.

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### How to Reuse a Deformed Shape as a Geometry Input

##### Temesgen Kindo September 1, 2016

Suppose you take a piece of metal — a thin sheet, for example — and apply some mechanical loads. The metal will deform and take on a new shape that differs from the original undeformed configuration. Say you now want to use this deformed object as part of a new geometry construction. You can then solve another physics problem on the new composite domain. Today, we’ll demonstrate how to use a deformed object as an input to a geometry sequence.

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### How to Model Adhesion and Decohesion in COMSOL Multiphysics

##### Henrik Sönnerlind July 28, 2016

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.

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### Evaluating an Insulin Micropump Design for Treating Diabetes

##### Bridget Cunningham July 21, 2016

In any form of treatment, it is always desirable to minimize the level of discomfort that the treatment process causes patients, while ensuring overall safety and effectiveness. For diabetes patients, insulin injections remain an important form of treatment, but the process itself can be painful. With the help of multiphysics simulation, a team of researchers from the University of Ontario Institute of Technology sought to develop a MEMS-based micropump that could administer insulin injections in a safe and painless way.

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### GTI Streamlines Gas Pipeline Maintenance Procedures with Simulation

##### Brianne Costa July 11, 2016

For gas pipeline maintenance standards, the adage “rules are meant to be broken” may not apply, but “rules are meant to be updated” certainly does. Specifically, the generous distance requirements between pipeline squeeze-off locations and pipe fittings cause potentially unnecessary digging. This prompted Operations Technology Development (OTD), a partnership of natural gas distribution companies, to initiate a project with Gas Technology Institute (GTI), where researchers used simulation to investigate the standard distance requirements for streamlined and safe pipeline maintenance.

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### Efficiently Analyze Civil Engineering Designs Using an App

##### Abbie Weingaertner July 6, 2016

Consider a class of civil engineering structures like the Pratt truss bridge. While the concept behind each design is similar, the actual configuration of the bridge and the loads that are applied to it varies by each case. With the Application Builder, you can design a simulation tool that enables users to easily modify parameters to account for these differences in geometry and loads. Learn more with our Truss Bridge Designer computational app.

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### Connecting the Dots Between Theory, Model, and App

##### Amlan Barua June 29, 2016

Simulation apps, as we’ve highlighted on the blog, are a powerful tool for hiding complex physics behind an easy-to-use, intuitive interface. While the app can be used by those with little simulation expertise, understanding the layers beneath its interface — the embedded model and underlying theory — does require a good understanding of COMSOL Multiphysics and the physics at hand. Let’s explore the connection between theory, model, and app using the example of analyzing buckling in a truss tower design.

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### App: Analyze the Design of a Viscoelastic Structural Damper

##### Abbie Weingaertner June 9, 2016

Ever been in a tall building on a windy day or had an aircraft pass over your house? Along with the noise that you hear, which can be disruptive and unpleasant in its own right, you’ll also notice some low-frequency vibrations that can ultimately affect the structure’s stability. One solution to this problem is to incorporate dampers, particularly viscoelastic structural dampers, into the structure’s design. With simulation apps, the path to optimizing these devices is more efficient than ever before.

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### Analyze Porous Structures with Numerical Modeling

##### Brianne Costa May 31, 2016

Reservoirs, dams, and other outdoor structures need to be strong, reliable, and sound. The porous materials found within these structures can be easily damaged by pressure changes that cause fluid flow and gradual caving and sinking. Using the multiphysics simulation capabilities of COMSOL Multiphysics and the Poroelasticity interface, we can accurately analyze porous materials to evaluate and avoid deformation in such structures.

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### ETREMA Analyzes Magnetostrictive Materials with Simulation

##### Caty Fairclough May 24, 2016

The magnetostrictive effect causes magnetic materials to change their shape when a magnetic field is applied. Materials that exhibit such behavior are used in a range of devices, from loudspeakers to actuators. In order to analyze one type of device, a magnetostrictive transducer, researchers from ETREMA Products, Inc. performed single-physics and multiphysics simulation studies in COMSOL Multiphysics. See how the flexible nature of the software enabled the team to study various aspects of the device and optimize its overall design.

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