Henrik Rasmus Thomsen

ETH Zurich | ETH Zürich · Department of Civil, Environmental and Geomatic Engineering

In this work, the Schwarz primitive unit cell is used as the building block of different types of metastructures for steering and focusing elastic vibrations. The emergence of a Bragg-type bandgap when constructing a two-dimensional plate from such unit cells is experimentally validated. It is demonstrated that increasing both mass and porosity of...

In this work, the Schwarz primitive unit cell is used as the building block of different types of metastructures for steering and focusing elastic vibrations. The emergence of a Bragg-type bandgap when constructing a two-dimensional plate from such unit cells is experimentally validated. It is demonstrated that increasing both mass and porosity of...

In this paper, we incorporate the effect of nonlinear damping with the concept of locally resonant metamaterials to enable vibration attenuation beyond the conventional bandgap range. The proposed design combines a linear host cantilever beam and periodically distributed inertia amplifiers as nonlinear local resonators. The geometric nonlinearity i...

Mitigating the energy requirements of artificial intelligence requires novel physical substrates for computation. Phononic metamaterials have vanishingly low power dissipation and hence are a prime candidate for green, always‐on computers. However, their use in machine learning applications has not been explored due to the complexity of their desig...

In this paper, we incorporate the effect of nonlinear damping with the concept of locally resonant metamaterials to enable vibration attenuation beyond the conventional bandgap range. The proposed design combines a linear host cantilever beam and periodically distributed inertia amplifiers as nonlinear local resonators. The geometric nonlinearity i...

We experimentally implement a one-directional virtual geometric periodicity in an elastic metamaterial. First, unwanted boundary reflections at the domain ends are cancelled through the iterative injection of the polarity-reversed reflected wave field. The resulting boundless experimental state allows for a much better analysis of the influence of...

We experimentally demonstrate the capability of architected plates, with a frame-like cellular structure, to inhibit the propagation of elastic flexural waves. By leveraging the octet topology as a unit cell to design the tested prototypes, a broad and easy-to-tune bandgap is experimentally generated. The experimental outcomes are supported by exte...

This work proposes a graded metamaterial-based energy harvester integrating the piezoelectric energy harvesting function targeting low-frequency ambient vibrations (<100 Hz). The harvester combines a graded metamaterial with beam-like resonators, piezoelectric patches, and a self-powered interface circuit for broadband and high-capability energy ha...

This work studies a broadband graded metamaterial, which integrates the piezoelectric energy harvesting function targeting low-frequency structural vibrations, lying below 100 Hz. The device combines a graded metamaterial with beam-like resonators, piezoelectric patches and a self-powered piezoelectric interface circuit for energy harvesting. Based...

Time reversal (TR) is a method of focusing wave energy at a point in space. The optimization of a TR demonstration is described, which knocks over one selected LEGO minifigure among other minifigures by focusing the vibrations within an aluminum plate at the target minifigure. The aim is to achieve a high repeatability of the demonstration along wi...

Many electronic devices spend most of their time waiting for a wake-up event: pacemakers waiting for an anomalous heartbeat, security systems on alert to detect an intruder, smartphones listening for the user to say a wake-up phrase. These devices continuously convert physical signals into electrical currents that are then analyzed on a digital com...

In this work, we investigate the dynamics and attenuation properties of a one-dimensional inertial amplified lattice with opposite chirality. The unit cell of the structure consists of a hollow-square plate connected to a ring through arch-like ligaments. The peculiar geometry and orientation of the links allow for coupling the axial and the torsio...

No PDF available ABSTRACT Time reversal (TR) of impulse responses can be used to focus wave energy, even in a reverberant environment. A demonstration of TR focusing was developed to knock over a targeted LEGO minifigure, standing among other minifigures (who remain standing), by focusing plate vibrations under the target minifigure\rquote s feet....

An important step in the processing of seismic data that are recorded at the free surface is the isolation of the primary incident wavefield from the total recorded wavefield (which is contaminated with the immediate reflections off the free surface). We present a 3-D wavefield reconstruction technique, based on numerical wavefield injection along...

The ability to extract information from scattered waves is usually limited to singly scattered energy even if multiple scattering might occur in the medium. As a result, the information in arrival times of higher-order scattered events is underexplored. This information is extracted using fingerprinting theory. This theory has never previously been...

In this paper, the physics of horizontally polarized shear waves traveling across a locally resonant metasurface in an unconsolidated granular medium is experimentally and numerically explored. The metasurface is comprised of an arrangement of subwavelength horizontal mechanical resonators embedded in a granular layer made of silica microbeads. The...

We present a proof of concept of elastic immersive wave experimentation. A physical experiment of finite volume is connected with a numerical domain via the novel theory of immersive boundary conditions. We show that by applying the incident traction measured at the free surface of a solid target, we can completely cancel unwanted boundary reflecti...

In this article the physics of horizontally polarized shear waves travelling across a locally resonant metasurface in an unconsolidated granular medium is experimentally and numerically explored. The metasurface is comprised of an arrangement of sub-wavelength horizontal mechanical resonators embedded in silica microbeads. The metasurface supports...

No PDF available ABSTRACT In immersive experimentation, a physical experimentation domain is immersed in a numerical simulation such that waves propagate seamlessly from the physical domain into the numerical simulation and vice-versa. The interaction, governed by a novel immersive boundary condition (IBC), takes place in real-time using hundreds o...

No PDF available ABSTRACT In immersive wave experimentation, a physical experimentation domain is immersed in a larger numerical simulation such that waves in the physical domain drive the numerical simulation and vice-versa. For elastic media, the interaction takes place through sources and sensors at the free surface, where the wavefield is measu...

Immersive experimentation is a new paradigm for wave-based laboratory experimentation aimed at overcoming the laboratory- and sample-size related limitations of conventional approaches and thereby significantly extending downwards the usable frequency range. Using so-called immersive boundary conditions, a physical experimentation domain or elastic...