Visualisation of ultrasound waves in air to support acoustic levitation

Acoustic levitation is an novel method that could lend itself very useful to fast and precise transportation of small objects. To verify the acoustic field and the modelling assumptions, the acoustic field must be visualised and quantified. Different methods to visualise a pressure gradient are investigated and rated against design requirements....

Air loading on ultrathin graphene membranes for microphone application

This thesis explores the challenges of using ultrathin graphene membranes in microelectronic mechanical sensors (MEMS) technology, specifically in the development of MEMS microphones. Graphene, being only an atom thin and one of the strongest known materials, offers promising potential for further miniaturization of MEMS microphones. However,...

Tuning graphene dynamics by mechanical strain

Two-dimensional (membrane) materials have been receiving much scientific attention due to their unique material properties that can be used to study the smallest physical phenomena. One such material is graphene, perceived as the holy grail in material physics, due to its unique material properties. Its aspect ratio diminishes the bending...

Studying the effect of strain on the mechanical properties of wrinkled graphene

Surface corrugations in graphene negatively effect the unique and useful properties of graphene. In order to exploit the special properties of graphene, it is therefore important to understand the phenomenon of wrinkling. In this study, strain engineering was applied to study the flattening of wrinkles in a suspended graphene membrane. Initially...

Investigation of the nonlinear dynamics of a diamagnetically levitating plate

Over the past decades the diamagnetic effect has been used for a variety of applications. This ranges from levitating a living frog to stabilizing a force sensor, designing an acceleration sensor and determin­ing the power of a laser. Diamagnetic levitation is the only method in which a passive stable levitation of an object can be achieved....

Influence of Mode-Coupling on Q-factor in Nanomechanical Resonators

Nanomechanical resonators with low dissipation rates are ideal tools in fundamental science applications. They have been used in the field of cavity optomechanics for example in ground-state cooling, and in sensing applications, such as atomic resolution mass sensors. Their great sensitivity is due to their high Q-factor, which is a metric that...

Examination of large amplitude vibrations of a nonlinear oscillator for energy harvesting

Vibration energy harvesting is a promising step towards a more sustainable society. The world is getting more and more connected through electronic devices, which all require electrical energy. A battery can deliver electrical energy; however, such a battery needs to be replaced or recharged; this is where energy harvesters become interesting....

Dynamics of a machine tool cross-slide

Within a great variety in high tech industry there is an increasing demand for complex shaped turning workpieces with diameters up to a meter and accuracy within microns. Examples are bearings in offshore wind energy and high precision applications. For the production of these parts CNC controlled turning machines are used. A motorized spindle...

Nonlinear dynamics of graphene membranes: Quality factor limits of membranes caused by mode interaction

Graphene is expected to open up a world of new possibilities in the field of micro and nano sensors, due to its outstanding properties. However, graphene membranes suffer from high damping which limit their performance. The physical mechanism behind this damping is still unknown. Therefore, in this work, it is investigated how coupling between...

Equivalence in Experimental Source Characterisation

Transfer Path Analysis methods allow to describe the propagation of vibrations from an active source to a passive receiving structure. These methods are based in the experimental modelling domain, where the dynamics of the problem are described based on empirical observations from an experiment, as opposed to a numerical model based on natural...

Stinger monitoring system: A sensor placement method for damage localisation and damage quantification applied to a stinger monitoring system

A stinger is a steel space frame structure, used on pipe-lay vessels, to support the weight of a suspended pipeline. A stinger is highly fatigue loaded due to environmental loads, vessel motions and variable pipe loads. In the design phase, predictions for the structural behaviour of the stinger were made. However, inspection history showed...

Diamagnetically Levitated Resonant Mass Sensor: Master of Science Thesis

In the past few decades, there has been a growing demand for low-cost disposable sensors to be utilized in hazardous and toxic environments such as high temperature and chemically aggressive environments, which can lead to irreversible damage to the sensor. Moreover, by cost reduction, they become more attractive for utilization in developing...

Ice-induced vibrations of wind turbines with a jacket support structure

The offshore wind industry is a relatively new but fast growing field in the global shift towards renergy to reduce carbon emissions. However, more difficulties arise in the design of an offshore wind turbine (OWT) compared to an onshore wind turbine, as the offshore structures are exposed to more environmental influences. One of those is sea...

Robust Experimental Dynamic Substructuring: Enhanced quality indicators & application of SEMM to an industrial case

A popular strategy in structural dynamic modeling is breaking the structure down into separable, manageable substructures. By doing so, one can choose the most efficient way of modeling the substructures, before synthesizing the full system model. This method is known as Dynamic Substructuring (DS). One method of DS, is Frequency Based...

Characterization and Dynamics of Diamagnetically Levitated Objects

From the earliest days, the phenomenon of levitation has always aroused the curiosity of humankind due to its mysterious and unique nature. Levitation systems are particularly interesting because of their non-contact characteristic which provides the possibility to isolate the levitated object from environmental effects like mechanical friction...

A cascade of autoresonances in an accelerating elevator cable system

In this project the transversal vibrations of an accelerating elevator cable system are studied, with the aim to find the resonance times, the resonance duration and the resonance amplitude. The elevator cable is modelled as an axially moving string, with length given by l(t) = l0 + 1/2 at2, with a the acceleration and t the...

Analysis of an actuated microbeam

Faculty EEMCS (Mathematical Physics) and Applied Sciences (Quantum Nanoscience). - In this project, we study the governing differential equation for a supported microbeam which is electrostatically actuated. The differential equation has been derived using a Hamiltonian principle and Kirchoff's approximation. Our questions on this differential...

Opto-electronic MEMS oscillator for resonant pressure sensing

This thesis details the design of a self-oscillating MEMS resonator as a pressure sensor. A bi-layer circular diaphragm with a single center perforation is used as a pressure sensitive membrane which measures the absolute pressure of the surrounding medium. A novel aspect of the proposed sensor is that the resonator is made to oscillate by an...