1,721,058 research outputs found
Design and characterization of a fractal-inspired multi-frequency piezoelectric energy converter
Full text linkA promising harvesting technique, in terms of simplicity and efficiency, is the conversion of ambient kinetic energy through piezoelectric materials. This work aims to design and investigate a piezoelectric converter conform to a fractal-inspired, multi-frequency structure previously presented by the author. A physical prototype of the converter is built and experimentally examined, up to 120 Hz, in terms of modal response and power output. Three eigenfrequencies are registered and the power output is particularly good at the fundamental eigenfrequency. Also the effect of the resistive load applied to the converter is investigated
Experimental Modal Analysis of Fractal-Inspired Multi-Frequency Piezoelectric Energy Converters
No full textAn important issue in the field of energy harvesting through piezoelectric materials is the design of simple and efficient structures which are multi-frequency in the ambient vibration range. This paper deals with the experimental assessment of four fractal-inspired multi-frequency structures for piezoelectric energy harvesting. These structures, thin plates of square shape, were proposed and numerically analyzed, with regard to their modal response, in a previous work by the author. The aim of this work is twofold. First, to assess the modal response of these structures through an experimental investigation. Second, to evaluate, through computational simulation, the performance of a piezoelectric converter prototype relying on one of these fractal-inspired structures. The four fractal-inspired structures are examined experimentally in the range between 0 and 100 Hz, both with regard to eigenfrequencies and eigenmodes. In the same frequency range are investigated the modal response and power output of a converter prototype
A fractal-inspired multi-frequency piezoelectric energy converter: computational and experimental characterization
No full textIn order to develop self-powered wireless sensor nodes, many energy harvesting devices, able to convert freely available ambient energy into electrical energy, have been proposed in the literature. A promising technique, in terms of simplicity and high conversion efficiency, is the harvesting of ambient kinetic energy through piezoelectric materials.The aim of this work is to design and investigate the modal response and the power output of a fractal-inspired, multi-frequency, piezoelectric energy converter, previously presented by the author. Two are the steps of the work. First, a computational modal analysis of the converter is performed. Second, a physical prototype of the converter is built and its eigenfrequencies and power generation under different resistive loads are experimentally examined in the range between 0 and 120 Hz. The converter exhibits three eigenfrequencies and a good power output, in particular at the first eigenfrequency
A wideband fractal-inspired piezoelectric energy converter: design, simulation and experimental characterization
No full textIn order to develop self-powered wireless sensor nodes, many energy harvesting devices that are able to convert available ambient energy into electrical energy have been proposed in the literature. A promising technique, in terms of simplicity and high conversion efficiency, is the harvesting of ambient kinetic energy through piezoelectric materials. The aim of this work is to design and investigate the modal response and power output of a fractal-inspired, multi-frequency, piezoelectric energy converter. The converter is a square, thin sheet structure, characterized by a fractal geometry obtained through a pattern of cuts in the plate. There are two steps involved. First, a computational analysis of the converter is performed. Second, a physical prototype of the converter is built and its eigenfrequencies and power generation under different resistive loads are experimentally examined in the range from 0 to 120 Hz. The converter exhibits three eigenfrequencies and a good power output, particularly at the first eigenfrequency
Comparison between a wideband fractal-inspired and a traditional multicantilever piezoelectric energy converter
No full textHarvesting energy from ambient vibrations in order to power autonomous sensors is a challenging issue. The aim of this work is to compare the power output from an innovative wideband fractal-inspired piezoelectric converter to that from a traditional multicantilever
piezoelectric energy converter. In a given frequency range, the converters are tuned on the same eigenfrequencies. The effect of the input acceleration and of the resistive load applied to the converters is investigated experimentally for each of the three eigenfrequencies in the range between 0 and 120 Hz. The fractal-inspired converter exhibits a significantly higher specific output power at the first and third of the eigenfrequencies investigated
Wideband fractal-inspired piezoelectric energy harvesters
No full textHarvesting kinetic ambient energy from vibrations or impact loads to obtain electrical energy useful to supply electronic sensors is still a challenging issue, with a huge number of potential applications, from the industrial field to consumer goods. This work investigates four simple piezoelectric energy harvesters developed from fractal-inspired structures: these structures are square laminas with inner divisions that originate a fractal geometry, since it is obtained by the repetition of a base configuration. Starting from the description of the fractal-inspired structures, the work presents a computational modal analysis highlighting the peculiar wideband frequency response of these structures and thus their applicability as energy converters. Using commercial piezoelectric transducers, we built four energy harvesters and assessed their output voltage and output power performing dynamic tests on a vibrating table. The proposed structures exhibit a wideband frequency response and a good energy conversion, specifically at the fundamental eigenfrequency
A Belleville-spring-based electromagnetic energy harvester
No full textEnergy harvesting from kinetic ambient energy is particularly effective to power autonomous sensors. This work proposes an innovative energy converter based on two counteracting
Belleville springs and exploiting their peculiarity, for a height to thickness ratio equal to 1.414, of nearly zero stiffness over a wide deflection range. After analytical and numerical modelling a
prototype is developed and experimentally investigated. The sub-optimal geometry of the commercial springs used in the prototype, together with a non-ideal response, makes the
operating frequency for the prototype higher than in analytical and numerical predictions. Nevertheless, the harvester exhibits a significantly large bandwidth, together with a high output
power, compared to similar solutions in the literature, for all the examined configurations and input excitations
Caratterizzazione di provini tubolari incollati: regolarizzazione della tensione normale mediante gole schermo
No full textThis paper experimentally investigates bonded tubular specimens, which exhibit uniform stress distribution within the adhesive layer. The mechanical properties of a thin adhesive layer, subject to a singularity-free stress distribution, are immediately applicable to the description of real joint behavior. The proposed specimen consists of a tubular butt joint, with circumferentially machined stress-relief grooves adjacent to the adherend-adhesive interface. The groove geometry, simplified with respect to a previous numerical work from the author, allows significant reduction in edge effects - as confirmed by finite element analyses. The experimental campaign involves three variables: presence of the grooves, adherend material and adhesive thickness. The presence of stress-relief grooves gives higher failure loads for steel adherends, whilst aluminum adherends show strength reduction as adhesive thickness increases
Experimental comparison between a fractal-inspired multi-frequency piezoelectric energy converter and a traditional converter
No full textHarvesting energy from ambient vibrations in order to power autonomous sensors is a challenging issue. The aim of this work is to compare the power output from an innovative multi-frequency fractal-inspired piezoelectric converter to that from a traditional multi-cantilever piezoelectric converter. The converters are designed in order to give the same eigenfrequencies in a given range and a prototype of both is built using commercial materials. The experimental tests investigate both the effect of the acceleration and of the resistive load applied to the converters for each of the three eigenfrequencies in the range between 0 and 120 Hz. The fractal-inspired converter exhibits a significantly higher specific output power at the first and third of the eigenfrequencies investigated.Harvesting energy from ambient vibrations in order to power autonomous sensors is a challenging issue. The aim of this work is to compare the power output from an innovative multi-frequency fractal-inspired piezoelectric converter to that from a traditional multi-cantilever piezoelectric converter. The converters are designed in order to give the same eigenfrequencies in a given range and a prototype of both is built using commercial materials. The experimental tests investigate both the effect of the acceleration and of the resistive load applied to the converters for each of the three eigenfrequencies in the range between 0 and 120 Hz. The fractal-inspired converter exhibits a significantly higher specific output power at the first and third of the eigenfrequencies investigated. Copyright © 2013 by Alstom Technologie AG
Fractal-inspired multi-frequency structures for piezoelectric harvesting of ambient kinetic energy
No full textEnergy harvesting devices capable of converting freely-available ambient energy into electrical energy have received significant attention recently. Ambient kinetic energy is particularly attractive for conversion since it is almost ubiquitous and easily accessible. Piezoelectric energy harvesting devices are promising due to their simple configuration and high conversion efficiency. This paper studies multifrequency structures for piezoelectric energy harvesting of ambient kinetic energy, inspired by fractal geometry. Identifying such structures that are simple and efficient is challenging. We propose four fractal-inspired structures and we examine them at both micro and macroscales. We calculate their frequency response up to 100 Hz with computational modeling, and we also examine the effect of the fractal geometry iteration level. We use a cantilever plate example as a reference to validate computational results against analytical ones. A quantitative criterion to assess the harvesting efficiency of the proposed structures is introduced using the bending strain associated with each mode shape. Results show that a large number of eigenfrequencies is obtained, evenly distributed below 100 Hz, particularly in the macroscale. In addition, the iteration level of the fractal geometry affects the number and distribution of eigenfrequencies in the range of interest. Comparison with a conventional batch of cantilevers of the same size as the proposed structures shows noticeable improvement in electric charge generation
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