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11 pages, 5506 KiB

Open AccessArticle

Crack Detection Method for Wind Turbine Tower Bolts Using Ultrasonic Spiral Phased Array

by Hongyu Sun, Jingqi Dong, Xi Diao, Xincheng Huang, Ziyi Huang and Zhichao Cai

Sensors 2024, 24(16), 5204; https://doi.org/10.3390/s24165204 - 11 Aug 2024

Cited by 3 | Viewed by 2061

High-strength bolts are crucial load-bearing components of wind turbine towers. They are highly susceptible to fatigue cracks over long-term service and require timely detection. However, due to the structural complexity and hidden nature of the cracks in wind turbine tower bolts, the small size of the cracks, and their variable propagation directions, detection signals carrying crack information are often drowned out by dense thread signals. Existing non-destructive testing methods are unable to quickly and accurately characterize small cracks at the thread roots. Therefore, we propose an ultrasonic phased array element arrangement method based on the Fermat spiral array. This method can greatly increase the fill rate of the phased array with small element spacing while reducing the effects of grating and sidelobes, thereby achieving high-energy excitation and accurate imaging with the ultrasonic phased array. This has significant theoretical and engineering application value for ensuring the safe and reliable service of key wind turbine components and for promoting the technological development of the wind power industry. Full article

(This article belongs to the Special Issue Intelligent Sensors and Signal Processing in Industry)

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15 pages, 5207 KiB

Open AccessArticle

Novel Design Techniques for the Fermat Spiral in Antenna Arrays, for Maximum SLL Reduction

by Kleiverg Encino, Marco A. Panduro, Alberto Reyna and David H. Covarrubias

Micromachines 2022, 13(11), 2000; https://doi.org/10.3390/mi13112000 - 17 Nov 2022

Cited by 1 | Viewed by 2305

Abstract

This paper presents novel design techniques for the Fermat spiral, considering a maximum side lobe level (SLL) reduction. The array system based on a Fermat spiral configuration considers techniques based on uniform and non-uniform amplitude excitation. The cases of uniform amplitude excitation are the golden angle and the optimization of the angular separations. The cases of non-uniform amplitude excitations consider a raised cosine distribution and the optimization of the amplitude excitations through the Fermat spiral array. In this study, the method of genetic algorithms (GA) was used in the cases to find the values of the angular separations and the amplitude excitations of the Fermat spiral array. A performance evaluation was conducted for all these design cases, considering the Fermat spiral geometry. These design cases were validated using electromagnetic simulation to take mutual coupling into account and consider the effect of the antenna element pattern in each proposed design case. Full article

(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)

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12 pages, 4704 KiB

Open AccessArticle

Modified Transceiver Antenna for NQR Detection of Explosive Objects in Demining Conditions

by Andrii Samila, Oleksandra Hotra, Oleksandr Moisiuk, Mykola Khobzei and Taras Kazemirskiy

Energies 2022, 15(19), 7348; https://doi.org/10.3390/en15197348 - 6 Oct 2022

Cited by 3 | Viewed by 2187

Abstract

This paper presents the conceptual stages of the simulation and development of a modified transceiver antenna for a high-power pulsed nuclear quadrupole resonance (NQR) detector of explosives containing the ¹⁴N isotope. At a frequency of 4.645 MHz, better characteristics are obtained using a nine-turn coil shaped as half of a Fermat spiral with an outer radius of 75 mm. Using a COMSOL Multiphysics numerical parametric simulation and a materials browser, it was possible to calculate a physical system with parameters as close to reality as possible. According to the results of the experimental studies of the radio frequency (RF) energy, the proposed antenna features an increase in the working area compared to a similar antenna, the topology of the conductive coil of which has the form of an Archimedean spiral. The resulting diagrams of the distribution of the magnetic induction also indicate that the topology of the electromagnetic (EM) field does not depend on the orientation of the sample under study relative to the axis of the radial symmetry observed in square–rectangular planar antennas. Full article

(This article belongs to the Section F: Electrical Engineering)

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20 pages, 12046 KiB

Open AccessArticle

Design of Ultrasonic Synthetic Aperture Imaging Systems Based on a Non-Grid 2D Sparse Array

by Júlio Cesar Eduardo de Souza, Montserrat Parrilla Romero, Ricardo Tokio Higuti and Óscar Martínez-Graullera

Sensors 2021, 21(23), 8001; https://doi.org/10.3390/s21238001 - 30 Nov 2021

Cited by 5 | Viewed by 3303

Abstract

This work provides a guide to design ultrasonic synthetic aperture systems for non-grid two-dimensional sparse arrays such as spirals or annular segmented arrays. It presents an algorithm that identifies which elements have a more significant impact on the beampattern characteristics and uses this information to reduce the number of signals, the number of emitters and the number of parallel receiver channels involved in the beamforming process. Consequently, we can optimise the 3D synthetic aperture ultrasonic imaging system for a specific sparse array, reducing the computational cost, the hardware requirements and the system complexity. Simulations using a Fermat spiral array and experimental data based on an annular segmented array with 64 elements are used to assess this algorithm. Full article

(This article belongs to the Special Issue Ultrasonic Imaging and Sensors)

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15 pages, 7005 KiB

Open AccessArticle

3D Printing of Objects with Continuous Spatial Paths by a Multi-Axis Robotic FFF Platform

by Yuan Yao, Yichi Zhang, Mohamed Aburaia and Maximilian Lackner

Appl. Sci. 2021, 11(11), 4825; https://doi.org/10.3390/app11114825 - 24 May 2021

Cited by 25 | Viewed by 6729

Abstract

Conventional Fused Filament Fabrication (FFF) equipment can only deposit materials in a single direction, limiting the strength of printed products. Robotic 3D printing provides more degrees of freedom (DOF) to control the material deposition and has become a trend in additive manufacturing. However, there is little discussion on the strength effect of multi-DOF printing. This paper presents an efficient process framework for multi-axis 3D printing based on the robot to improve the strength. A multi-DOF continuous toolpath planning method is designed to promote the printed part’s strength and surface quality. We generate curve layers along the model surfaces and fill Fermat spiral in the layers. The method makes it possible to take full advantage of the multi-axis robot arm to achieve smooth printing on surfaces with high curvature and avoid the staircase effect and collision in the process. To further improve print quality, a control strategy is provided to synchronize the material extrusion and robot arm movement. Experiments show that the tensile strength increases by 22–167% compared with the conventional flat slicing method for curved-surface parts. The surface quality is improved by eliminating the staircase effect. The continuous toolpath planning also supports continuous fiber-reinforced printing without a cutting device. Finally, we compared with other multi-DOF printing, the application scenarios, and limitations are given. Full article

(This article belongs to the Section Additive Manufacturing Technologies)

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11 pages, 3952 KiB

Open AccessArticle

Characterization of the Vortex Beam by Fermat’s Spiral

by Ewa Frączek, Agnieszka Popiołek-Masajada and Sławomir Szczepaniak

Photonics 2020, 7(4), 102; https://doi.org/10.3390/photonics7040102 - 5 Nov 2020

Cited by 11 | Viewed by 3543

Abstract

In this paper, we characterize the helical beam structure through an analysis of the spiral character of the phase distribution inside a light beam. In particular, we show that a line connected with the 2π phase jump in the Laguerre–Gauss beam can be described by a Fermat’s spiral. We propose a numerical fitting method to determine the parameters of a spiral equation for the phase distribution of the helical beam. Next, we extend the procedure to a vortex beam created by the spiral phase plate and apply it to experimental phase maps, which allows us to recover the phase shift introduced into the object beam in the optical vortex scanning microscope. Full article

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3 pages, 780 KiB

Open AccessProceeding Paper

Low-Frequency Piezoelectric Accelerometer Array for Fully Implantable Cochlear Implants

by János Radó, Péter Udvardi, Saeedeh Soleimani, Lucky Kenda Peter, István Bársony, Péter Révész and János Volk

Proceedings 2018, 2(13), 1059; https://doi.org/10.3390/proceedings2131059 - 26 Nov 2018

Cited by 1 | Viewed by 1953

Abstract

We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO₂) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies. Full article

(This article belongs to the Proceedings of EUROSENSORS 2018)

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