Jieun Yang
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4 records found
1
Multi-Directional Vibrational Energy Harvester with In-Plane Motion
Exploiting Degenerate Modes
A novel multi-directional piezoelectric vibrational energy harvester (PVEH) is proposed that can harvest from excitation angles in the XY-plane. The design is a parallel three-chain rotationally symmetric folded-flexure (3CR-FF) topology with a PZT-5H patch on each arm, that achieves multi-directionality utilising degenerate in-plane translational modes. Finite-element modelling guides the geometric design, system identification with a single-degree-of-freedom fit determines the near-optimal load, and the prototype is then evaluated experimentally at 15◦ angular increments in the XY- plane. The 3CR-FF prototype delivers an angle-averaged peak acceleration-normalised power of 1.35 ± 0.23 µW/mg^2 at 43.48 ± 0.12 Hz, with a localised performance dip between 330◦ and 15◦. Its performance is benchmarked against an array of three equally spaced cantilever beams (3TC) of equal total proof mass, which achieves roughly three times lower mean peak power and a wider frequency spread across angles (±0.45 Hz).
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A novel multi-directional piezoelectric vibrational energy harvester (PVEH) is proposed that can harvest from excitation angles in the XY-plane. The design is a parallel three-chain rotationally symmetric folded-flexure (3CR-FF) topology with a PZT-5H patch on each arm, that achieves multi-directionality utilising degenerate in-plane translational modes. Finite-element modelling guides the geometric design, system identification with a single-degree-of-freedom fit determines the near-optimal load, and the prototype is then evaluated experimentally at 15◦ angular increments in the XY- plane. The 3CR-FF prototype delivers an angle-averaged peak acceleration-normalised power of 1.35 ± 0.23 µW/mg^2 at 43.48 ± 0.12 Hz, with a localised performance dip between 330◦ and 15◦. Its performance is benchmarked against an array of three equally spaced cantilever beams (3TC) of equal total proof mass, which achieves roughly three times lower mean peak power and a wider frequency spread across angles (±0.45 Hz).
Auxetic metamaterials are engineered structures commonly characterised by their negative Poisson’s ratio, which indicates transverse expansion when the structure is stretched axially. However, Poisson’s ratio becomes increasingly difficult to apply and interpret for non-cubic unit cells with higher-order symmetry or complex geometries. This limitation contributes to the strong focus on cubic unit cells in current research, despite their limited robustness due to a restricted number of symmetry axes. This study proposes volumetric strain as an alternative and geometry-independent measure of auxeticity. The approach is demonstrated through a case study on non-cubic polygon-prism unit cells generated by in-plane copy rotation. The mechanical behaviour of 2-, 4-, 6-, and 8-fold configurations is analysed using an analytical rigid-body replacement model, finite element simulations, and experimental testing. A Hoberman ring is introduced as an intermediary mechanism to enable uniform multi-directional actuation using a one-dimensional tensile tester. The results show that volumetric strain provides a consistent and robust description of auxetic behaviour across all configurations and modelling approaches. In contrast, Poisson’s ratio exhibits strong sensitivity to small deviations near zero strain and leads to inconsistencies between analytical, numerical, and experimental results. The experimental force–displacement response confirms a linear scaling with the number of bases, while the volumetric strain remains independent of the initial polygonal shape of the unit cell. These findings demonstrate that volumetric strain is a reliable measure of auxeticity for non-cubic unit cells and offers clear advantages for the analysis and experimental validation of complex auxetic geometries. The proposed framework provides a foundation for extending auxetic metamaterial design towards more intricate structures, including spatially copy-rotated unit cells and honeycombs based on Archimedean solids.
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Auxetic metamaterials are engineered structures commonly characterised by their negative Poisson’s ratio, which indicates transverse expansion when the structure is stretched axially. However, Poisson’s ratio becomes increasingly difficult to apply and interpret for non-cubic unit cells with higher-order symmetry or complex geometries. This limitation contributes to the strong focus on cubic unit cells in current research, despite their limited robustness due to a restricted number of symmetry axes. This study proposes volumetric strain as an alternative and geometry-independent measure of auxeticity. The approach is demonstrated through a case study on non-cubic polygon-prism unit cells generated by in-plane copy rotation. The mechanical behaviour of 2-, 4-, 6-, and 8-fold configurations is analysed using an analytical rigid-body replacement model, finite element simulations, and experimental testing. A Hoberman ring is introduced as an intermediary mechanism to enable uniform multi-directional actuation using a one-dimensional tensile tester. The results show that volumetric strain provides a consistent and robust description of auxetic behaviour across all configurations and modelling approaches. In contrast, Poisson’s ratio exhibits strong sensitivity to small deviations near zero strain and leads to inconsistencies between analytical, numerical, and experimental results. The experimental force–displacement response confirms a linear scaling with the number of bases, while the volumetric strain remains independent of the initial polygonal shape of the unit cell. These findings demonstrate that volumetric strain is a reliable measure of auxeticity for non-cubic unit cells and offers clear advantages for the analysis and experimental validation of complex auxetic geometries. The proposed framework provides a foundation for extending auxetic metamaterial design towards more intricate structures, including spatially copy-rotated unit cells and honeycombs based on Archimedean solids.
Towards prestressing neutrally stable joints with pressure
Experimentation and parameter study on a spatial compliant enclosed volume joint
In the field of compliant mechanisms, neutrally stable mechanisms are gaining interest for among others increasing actuation efficiency, vibration isolation and their use in metamaterials. Prestressing these mechanisms is necessary to provide the potential energy they require to reach their state of neutral stability. Current prestressing methods are limited by their need for individual application or relatively long activation times and limited reversibility, limiting mechanisms which utilize a multitude of neutrally stable flexures. This research aims to design a neutrally stable, enclosed volume joint on which prestressing utilizing a negative internal pressure is tested. The joint is first characterized together with a parameter study, used to understand the influence of its geometry, and a finite element model, to assess its predictive accuracy. An experimental setup is constructed, which measures the torque-angle behavior of the joint under different prestress conditions. The results are compared to the expected behavior, which is closely resembled for some of the prototypes, while the simulations prove to be only indicative of the general trend.
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In the field of compliant mechanisms, neutrally stable mechanisms are gaining interest for among others increasing actuation efficiency, vibration isolation and their use in metamaterials. Prestressing these mechanisms is necessary to provide the potential energy they require to reach their state of neutral stability. Current prestressing methods are limited by their need for individual application or relatively long activation times and limited reversibility, limiting mechanisms which utilize a multitude of neutrally stable flexures. This research aims to design a neutrally stable, enclosed volume joint on which prestressing utilizing a negative internal pressure is tested. The joint is first characterized together with a parameter study, used to understand the influence of its geometry, and a finite element model, to assess its predictive accuracy. An experimental setup is constructed, which measures the torque-angle behavior of the joint under different prestress conditions. The results are compared to the expected behavior, which is closely resembled for some of the prototypes, while the simulations prove to be only indicative of the general trend.
Master thesis
(2025)
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L. Costa Arslanian, P.G. Steeneken, Bart van der Aa, Haydar Dirik, Jieun Yang
Acoustic-structural interactions present significant engineering challenges, particularly in the domains of noise reduction and vibration control. At ASML, measurement-based analyses have revealed that acoustic disturbance paths often dominate the dynamic behavior of atmospheric lithography machines. This project focuses on enhancing ASML’s current one-way coupled acoustic-structural modelling approach by developing a two-way coupled, known as vibro-acoustic, modelling framework. However, this advancement introduces substantial computational complexity, necessitating effective model reduction techniques. The primary objective of this work is to reduce vibro-acoustic models in a way that preserves their ability to be modularly coupled with other system components. To this end, three Component Mode Synthesis (CMS)-based reduction methods were evaluated, with only one proving suitable for both academic and industry-scale models. The resulting reduced-order models successfully retained the dynamic fidelity of the full system and enabled efficient coupling with other substructures. When applied to harmonic excitation analyses, the reduced models achieved a dramatic reduction in computational time, from several hours to approximately one minute, while accounting for the cost of model reduction.
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Acoustic-structural interactions present significant engineering challenges, particularly in the domains of noise reduction and vibration control. At ASML, measurement-based analyses have revealed that acoustic disturbance paths often dominate the dynamic behavior of atmospheric lithography machines. This project focuses on enhancing ASML’s current one-way coupled acoustic-structural modelling approach by developing a two-way coupled, known as vibro-acoustic, modelling framework. However, this advancement introduces substantial computational complexity, necessitating effective model reduction techniques. The primary objective of this work is to reduce vibro-acoustic models in a way that preserves their ability to be modularly coupled with other system components. To this end, three Component Mode Synthesis (CMS)-based reduction methods were evaluated, with only one proving suitable for both academic and industry-scale models. The resulting reduced-order models successfully retained the dynamic fidelity of the full system and enabled efficient coupling with other substructures. When applied to harmonic excitation analyses, the reduced models achieved a dramatic reduction in computational time, from several hours to approximately one minute, while accounting for the cost of model reduction.