Granular materials play an important role in many industrial and natural processes. Researchers are combining theoretical, computational and experimental techniques to both investigate the fundamental behaviour of these materials and design new acoustic devices, as Dr Georgios Theocharis explains
A clearer picture of granular materials The development of
new materials often leads on to further technical innovations, as scientists seek to harness their properties to develop new technologies and devices. Granular crystals can act as important building blocks in materials development, while they also hold intrinsic scientific interest, both of which are key motivating factors behind the work of the Comgransol project. “The main objectives of the project are on the one hand to achieve a better understanding of the physics of driven granular media. Then secondly, to design granular-based acoustic devices for the control of acoustic propagation,” says Dr Georgios Theocharis, the project’s Principal Investigator. These granular materials are effectively collections of macroscopic grains; analysis of these grains and their behaviour within wider structures can lead to new insights in physics and materials science, underlining the wider importance of Dr Theocharis’s research. “Understanding the physics of contact forces in these materials enables us to develop a deeper understanding of wave physics in granular solids, and also of the physics of granular materials in general,” he outlines.
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Granular solids This area forms a central part of the project’s overall agenda, with Dr Theocharis and his colleagues combining theoretical, computational and experimental techniques to gain new insights into the physics of granular materials. Experiments are being performed on metallic grains, such as stainless steel; there are two main reasons behind the decision to use this type of
structures. “We’ll investigate waveguides in different network configurations, such as branched waveguides, L-shaped waveguides, or two dimensional crystals in different geometries, like square or honeycomb crystal geometries,” says Dr Theocharis. The great advantage of using these granular solids, in comparison to other solid structures, is the strong nonlinear response. This nonlinearity is derived
The main objectives of the project are on the one hand to achieve a better understanding of the physics of driven granular media. Then secondly, to design granular-based acoustic devices for the control of acoustic propagation material. “We are using external magnetic fields to magnetize the grains and thus design particular granular structures, so it is necessary to use magnetisable grains. On the other hand, we’ve found metallic grains with a very smooth surface, which is very important for us. The interaction of grains happens due to contact forces. Thus, the high quality of smoothness of their surface means we don’t have to use more complicated processes,” explains Dr Theocharis. Researchers are also looking at the behaviour of different granular
from the geometry of these solids, from contact deformations of the particles. “Our goal is to take advantage of this strong nonlinear response and combine it with the proper geometry of the structure – using different network configurations – to achieve an advanced level of control over wave propagation,” explains Dr Theocharis. Although adding nonlinearity makes the wave physics much more complicated, it also opens up the possibility of enabling more precise control of waves. “There are a plethora of
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