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Keywords = bending-twisting coupling effect

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38 pages, 18471 KB  
Article
Bend–Twist Coupling for Small Wind Turbines: A Blade Design Methodology to Enhance Power Generation
by Juan Pablo Vanegas-Alzate, María Antonia Restrepo-Madrigal, José Luis Torres-Madroñero, César Nieto-Londoño, Germán Alberto Barragán de los Rios, Jorge Mario Tamayo-Avendaño, Julián Sierra-Pérez, Joham Alvarez-Montoya and Daniel Restrepo-Montoya
Energies 2025, 18(20), 5353; https://doi.org/10.3390/en18205353 - 11 Oct 2025
Viewed by 171
Abstract
Small-scale wind turbines (SWTs) represent a promising solution for the energy transition and the decentralization of electricity generation in non-interconnected areas. Conventional strategies to improve SWT performance often rely on active pitch control, which, while effective at rated conditions, is too costly and [...] Read more.
Small-scale wind turbines (SWTs) represent a promising solution for the energy transition and the decentralization of electricity generation in non-interconnected areas. Conventional strategies to improve SWT performance often rely on active pitch control, which, while effective at rated conditions, is too costly and complex for small systems. An alternative is passive pitch control through bend–twist coupling in the blade structure, which enables self-regulation and improved power generation. This work proposes a novel blade design methodology for a 5 kW SWT that integrates passive bend–twist coupling with conventional pitch adjustment, thereby creating a hybrid passive–active control strategy. The methodology encompasses the definition of aerodynamic blade geometry, laminate optimization via genetic algorithms combined with finite element analysis, and experimental characterization of composite materials. Aerodynamic–structural interactions are studied using one-way fluid–structure simulations, with responses analyzed through the blade element momentum method to assess turbine performance. The results indicate that the proposed design enhances power generation by about 4%. The study’s originality lies in integrating optimization, structural tailoring, and material testing, offering one of the first demonstrations of combined passive–active pitch control in SWTs, and providing a cost-effective route to improve efficiency and reliability in decentralized renewable energy systems. Full article
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32 pages, 26848 KB  
Article
The Development of a Robust Rigid–Flexible Interface and Continuum Model for an Elephant’s Trunk Using Hybrid Coordinate Formulations
by Ahmed Ghoneimy, Mohamed O. Helmy, Ayman Nada and Ahmed El-Assal
Appl. Syst. Innov. 2025, 8(2), 42; https://doi.org/10.3390/asi8020042 - 24 Mar 2025
Cited by 1 | Viewed by 1195
Abstract
The goal of this study was to construct a mathematical and computational model that accurately represents the complex, flexible movements and mechanics of an elephant’s trunk. Rather than serving as a biological study, the elephant trunk model was used as an application to [...] Read more.
The goal of this study was to construct a mathematical and computational model that accurately represents the complex, flexible movements and mechanics of an elephant’s trunk. Rather than serving as a biological study, the elephant trunk model was used as an application to demonstrate the effectiveness of a proposed rigid–flexible coupling framework. This model has broader applications beyond understanding the mechanics of an elephant trunk, including its potential use in designing flexible robotic systems and prosthetics, as well as contributions to the fields of biomechanics and animal locomotion. An elephant’s trunk, a highly flexible and muscular organ without bones, is best modeled using continuum mechanics to capture the dynamic behavior of its motion. Given the rigid body nature of an elephant’s head movement and the highly flexible nature of the trunk, a robust geometric framework for the rigid–flexible interface is crucial to accurately capture the complex interactions, force transmission, and dynamic behavior arising from their distinct motion characteristics and differing coordinate representations. Under the umbrella of flexible multibody dynamics, this study introduced a hybrid coordinate system, integrating the Natural Coordinates Formulation (NCF) and the Absolute Nodal Coordinates Formulation (ANCF), to establish the geometric constraints governing the interaction between the rigid body (the head) and the highly flexible body (the trunk). Moreover, the model illustrates how forces and moments are transmitted between these components in both direct and inverse scenarios. Various finite elements were evaluated to identify suitable elements for modeling the elephant’s trunk. The model’s accuracy was validated through simulations of bending, twisting, compression, and other characteristic trunk movements. The solution method is presented alongside the simulation analysis for various motion scenarios, providing a comprehensive framework for understanding and replicating the trunk’s complex dynamics. Full article
(This article belongs to the Section Control and Systems Engineering)
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14 pages, 3995 KB  
Article
An Intensity-Variation RI Sensor for Multi-Variant Alcohol Detection with Twisted Structure Using Polymer Optical Fiber
by Abdul Ghaffar, Rehan Mehdi, Irfan Mehdi, Bhagwan Das, Vicky Kumar, Sadam Hussain, Gul Sher, Kamran Ali Memon, Sikandar Ali, Mujahid Mehdi and Khurram Karim Qureshi
Chemosensors 2024, 12(12), 252; https://doi.org/10.3390/chemosensors12120252 - 3 Dec 2024
Cited by 2 | Viewed by 1331
Abstract
This research introduces an RI sensor for detecting various alcohol species with a designed twisted polymer optical fiber (POF) sensor. The sensor is developed via a straightforward twisting technique to form an effective coupling mechanism. The sensor works on intensity variation where coupled [...] Read more.
This research introduces an RI sensor for detecting various alcohol species with a designed twisted polymer optical fiber (POF) sensor. The sensor is developed via a straightforward twisting technique to form an effective coupling mechanism. The sensor works on intensity variation where coupled intensity varies when different types of alcohol are added. The structure relies on the twisting of two fibers, where one fiber is used as the illuminating fiber and the other fiber is used as the receiving fiber. Five different types of alcohol are tested (methanol, ethanol, propanol, butanol, and pentanol) as a substant. The experimental results reveal that the sensor is able to detect all five distinct substants effectively by optical power intensity variation. Moreover, the sensor’s sensitivity is analyzed with different factors such as the influence of the bending radius and the coupling length, which reveals that the sensing parameters could be customized depending on specific requirements. The sensor demonstrated consistent responses in repeatability tests, with minimal variation across multiple measurements, highlighting its stability. Additionally, the study explores temperature’s influence, revealing a sensitivity shift for every degree Celsius of change. This POF-based alcohol sensor represents a significant leap forward in optical sensing technology. Full article
(This article belongs to the Special Issue Advanced Chemical Sensors for Gas Detection)
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11 pages, 4690 KB  
Communication
Inter-Mode Crosstalk Estimation between Cores for LPmn Modes in Weakly Coupled Few-Mode Multicore Fiber with Perturbations
by Shuangmeng Liu and Lian Xiang
Sensors 2024, 24(18), 5969; https://doi.org/10.3390/s24185969 - 14 Sep 2024
Viewed by 1233
Abstract
A novel inter-mode crosstalk (IMXT) model of LPmn mode for weakly coupled few-mode multicore fiber is proposed based on the coupled mode theory (CMT) with bending and twisting perturbations. A universal expression of the mode coupling coefficient (MCC) between [...] Read more.
A novel inter-mode crosstalk (IMXT) model of LPmn mode for weakly coupled few-mode multicore fiber is proposed based on the coupled mode theory (CMT) with bending and twisting perturbations. A universal expression of the mode coupling coefficient (MCC) between LPmn modes is derived. By employing this MCC, the universal semi-analytical model (USAM) of inter-core crosstalk (ICXT) can be applied to calculate the IMXT. Simulation results show that our model is generally consistent with previous theories when stochastic perturbations are absent. Moreover, our model can work effectively when stochastic perturbations are present, where former theories are not able to work properly. It has been theoretically found that the MCC has an intimate relationship with core pitch. Our model, based on the CMT, can provide physical characteristics in detail, which has not been reported clearly by former theories. In addition, our model is applicable to phase-matching and non-phase-matching regions of both real homogeneous and heterogeneous few-mode multicore fibers (FM-MCFs) with a wider range of applications. Full article
(This article belongs to the Special Issue Novel Technology in Optical Communications)
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26 pages, 5224 KB  
Article
Fluid–Structure Interaction Analysis of a Wind Turbine Blade with Passive Control by Bend–Twist Coupling
by Jorge Mario Tamayo-Avendaño, Ivan David Patiño-Arcila, César Nieto-Londoño and Julián Sierra-Pérez
Energies 2023, 16(18), 6619; https://doi.org/10.3390/en16186619 - 14 Sep 2023
Cited by 3 | Viewed by 2571
Abstract
The idea of improving the energy output for small wind turbines without compromising the remaining aspects of the technology, such as costs and structural integrity, is very appealing in the context of the growing concern for global warming and the goal of providing [...] Read more.
The idea of improving the energy output for small wind turbines without compromising the remaining aspects of the technology, such as costs and structural integrity, is very appealing in the context of the growing concern for global warming and the goal of providing electricity to remote and isolated regions. This work aims to contribute to the development of distributed wind generation by exploring the effects of bend–twist coupling on the performance of a wind turbine with a focus on a small rotor based on the NREL Phase VI blade geometry. After defining a structure in composite materials exhibiting the coupling behavior along with a reference counterpart, a comparative numerical analysis is performed using a Fluid–Structure Interaction (FSI) analysis. The main numerical framework is based on commercial software and consists of a finite-volume solver for fluid physics, a finite-element solver for solid physics, and a coupling interface for the interaction problem. The results, complemented with the predictions from a one-way analysis based on the blade-element momentum theory are used to define the increments in rotor torque. The analysis of the annual energy yield shows a 3% increase due to the bend–twist coupling used as a passive pitch mechanism, considering a Rayleigh distribution with an 11 m/s average wind speed. Simultaneously, the coupling causes increments of 0.2% and 0.3% for the blade root flapwise moment and the rotor thrust force, respectively, when considering parked conditions and a simplified extreme wind model. Full article
(This article belongs to the Special Issue Advanced Structural Response and Performance of Wind Turbines)
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20 pages, 3371 KB  
Article
The Impact of Bend–Twist Coupling on Structural Characteristics and Flutter Limit of Ultra-Long Flexible Wind Turbine Composite Blades
by Bei Li, De Tian, Xiaoxuan Wu, Huiwen Meng and Yi Su
Energies 2023, 16(15), 5829; https://doi.org/10.3390/en16155829 - 6 Aug 2023
Cited by 10 | Viewed by 3014
Abstract
Flutter is an instability phenomenon that can occur in wind turbine blades due to fluid–structure interaction, particularly for longer and more flexible blades. Aeroelastic tailoring through bend–twist coupling is an effective method to enhance the aeroelastic performance of blades. In this study, we [...] Read more.
Flutter is an instability phenomenon that can occur in wind turbine blades due to fluid–structure interaction, particularly for longer and more flexible blades. Aeroelastic tailoring through bend–twist coupling is an effective method to enhance the aeroelastic performance of blades. In this study, we investigate the impact of bend–twist coupling on the structural performance and flutter limit of the IEA 15 MW blade, which is currently the longest reference wind turbine blade, and determine the optimal layup configuration that maximizes the flutter speed. The blade is modeled by NuMAD and iVABS, and the cross-section properties are obtained by PreComb and VABS. The accuracy of the blade model is verified in terms of stiffness and frequency. The bend–twist coupling is implemented by changing the fiber angle of the skin and spar cap considering symmetric and asymmetric layups. The flutter limits of both the baseline and the bend–twist coupled blade are evaluated based on HAWC2. The results show that the angle of spar cap carbon fiber has a greater effect on the blade’s structural properties and flutter speed than the skin fiber. Varying the spar cap carbon fiber angle increases the flutter speed, with the effect being more significant for the symmetric layup, up to 9.66% at a fiber angle of 25 degrees. In contrast, the variation in skin fiber angle has a relatively small impact on flutter speed—within ±3%. Full article
(This article belongs to the Special Issue Wind Turbine 2023)
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22 pages, 2907 KB  
Article
Experimental and Numerical Analysis of Triply Coupled Vibration of Thin-Walled Beam with Arbitrary Closed Cross-Section
by Jianglin Yang, Ting Xu, Haolong Zhong, Meng Sun and Fei Gao
Machines 2023, 11(2), 251; https://doi.org/10.3390/machines11020251 - 8 Feb 2023
Cited by 3 | Viewed by 1839
Abstract
In this paper, a numerical experimental study about coupled vibration and natural frequency of thin-walled beams with an arbitrary closed cross-section is presented. A new thin-walled beam dynamic transfer matrix method, named TDTMM, is presented in the frequency domain for the thin-walled beam, [...] Read more.
In this paper, a numerical experimental study about coupled vibration and natural frequency of thin-walled beams with an arbitrary closed cross-section is presented. A new thin-walled beam dynamic transfer matrix method, named TDTMM, is presented in the frequency domain for the thin-walled beam, which expands the advantages of the general dynamic transfer matrix method (GDTMM). The theory takes into account the influence of warping effect, that is, both the bimoment B and the rate of twist ϕ(x) of the beam are considered, and the TDTMM is derived by solving the governing differential equations of motion for coupled bending and torsional vibration of the thin-walled beam. Finally, two numerical examples and one experimental example are given and compared with the GDTMM and the finite element method (FEM) results to validate the developed theory. Full article
(This article belongs to the Section Machine Design and Theory)
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14 pages, 3579 KB  
Article
Dynamic Rotational Sensor Using Polymer Optical Fiber for Robot Movement Assessment Based on Intensity Variation
by Jianwei Shi, Abdul Ghaffar, Yongwei Li, Irfan Mehdi, Rehan Mehdi, Fayaz A. Soomro, Sadam Hussain, Mujahid Mehdi, Qiang Li and Zhiqiang Li
Polymers 2022, 14(23), 5167; https://doi.org/10.3390/polym14235167 - 28 Nov 2022
Cited by 10 | Viewed by 2471
Abstract
A complex signal processing technique is usually required to process the data in most sensor design structures, and integration into real applications is also challenging. This work presents a dynamic rotational sensor using polymethyl methacrylate (PMMA) fiber for robot movement assessment. The sensor [...] Read more.
A complex signal processing technique is usually required to process the data in most sensor design structures, and integration into real applications is also challenging. This work presents a dynamic rotational sensor using polymethyl methacrylate (PMMA) fiber for robot movement assessment. The sensor design structure is based on the coupling of light intensity, in which two PMMA fibers are twisted together. Both fibers are bent after twisting and attached on the linear translation stage, which is further attached to the robot. The variation in bending radius causes the bending loss, and that loss is coupled in the second fiber. The change in the macro-bend radius corresponds to the rotation of the robot. Experimental results indicate that the sensor can operate in full rotational cycle (i.e., 0°–360°) as well as for clock and anti-clockwise rotation. Moreover, different rotational speeds (2°/s, 3°/s, 5°/s, and 10°/s) were carried out. The hysteresis loss of the sensor was about 0.77% and the sensitivity was 8.69 nW/°. The presented dynamic rotational sensor is cost-effective and easily integrated into the robot structure to analyze the robot’s circular motion. Full article
(This article belongs to the Special Issue Polymer Optical Fibers: Recent Developments and Applications)
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14 pages, 6738 KB  
Article
Effects of Elastic Couplings in a Compressed Plate Element with Cut-Out
by Katarzyna Falkowicz, Sylwester Samborski and Paolo Sebastiano Valvo
Materials 2022, 15(21), 7752; https://doi.org/10.3390/ma15217752 - 3 Nov 2022
Cited by 9 | Viewed by 2019
Abstract
Analytical calculations were performed on carbon fiber-reinforced polymer (CFRP) laminates in an asymmetrical configuration. The asymmetric configuration of composites was investigated, where extension–twisting and extension–bending couplings were used to obtain the elastic element. Analysis of the presence of elastic couplings was conducted according [...] Read more.
Analytical calculations were performed on carbon fiber-reinforced polymer (CFRP) laminates in an asymmetrical configuration. The asymmetric configuration of composites was investigated, where extension–twisting and extension–bending couplings were used to obtain the elastic element. Analysis of the presence of elastic couplings was conducted according to Classical Laminate Theory (CLT). Components of matrices A, B, and D, as well as the parameters Dc and Bt, were obtained using the MATLAB software environment. The results show that couplings between the extension and bending, as well as between the extension and twisting, were strongly dependent on specimen plies’ orientation. Moreover, additional analysis was performed on the influence of layer angle on the terms which are components of the Bt and Dc coefficients. The results indicate that the angle of laying fibers around 45–50° significantly amplifies the effects of elastic couplings. Full article
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17 pages, 7247 KB  
Article
Numerical Simulation and Process Optimization on Hot Twist-Stretch Straightening of Ti-6Al-4V Alloy Profile
by Xuwen Deng, Songxiao Hui, Wenjun Ye, Rui Liu and Liang Huang
Materials 2022, 15(13), 4522; https://doi.org/10.3390/ma15134522 - 27 Jun 2022
Cited by 3 | Viewed by 1951
Abstract
Ti-6Al-4V profiles prepared by hot extrusion are usually accompanied by bending and twisting. The hot twist-stretch straightening is an effective strategy such that the bending deflection and twisting angle can be simultaneously decreased by a single straightening process. In addition, utilizing stress relaxation [...] Read more.
Ti-6Al-4V profiles prepared by hot extrusion are usually accompanied by bending and twisting. The hot twist-stretch straightening is an effective strategy such that the bending deflection and twisting angle can be simultaneously decreased by a single straightening process. In addition, utilizing stress relaxation effect, the residual stress and springback can be greatly reduced by holding the straightening temperature and strain constant for a period after twist-stretch straightening. In this study, the hot deformation behaviors of the Ti-6Al-4V profile were revealed by experiments. The tensile model was obtained by uniaxial tensile tests within ranges of temperatures (500–700 °C) and strain rates (5 × 10−5–1 × 10−3 s−1). The creep constitutive model was acquired with stress relaxation experiments in ranges of temperatures (500–700 °C) and pre-strain of 1.5%. Then, the coupled thermo-mechanical model of hot twist-stretch straightening was established. Based on orthogonal experiment strategy, the effects of straightening temperature, stretch strain, and holding time on the bending deflection and torsion angle of profile were investigated systematically and the process was optimized. The straightening accuracy is significantly affected by straightening temperature and holding time. By using optimized process parameters in practical straightening experiments, the deflection/length and angle/length after straightening does not exceed 2‰ and 2.5‰°/mm, respectively, which is basically consistent with the numerical simulation result. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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15 pages, 5240 KB  
Article
Multi-Mode Shape Control of Active Compliant Aerospace Structures Using Anisotropic Piezocomposite Materials in Antisymmetric Bimorph Configuration
by Xiaoming Wang, Xinhan Hu, Chengbin Huang and Wenya Zhou
Aerospace 2022, 9(4), 195; https://doi.org/10.3390/aerospace9040195 - 6 Apr 2022
Cited by 5 | Viewed by 2888
Abstract
The mission performance of future advanced aerospace structures can be synthetically improved via active shape control utilizing piezoelectric materials. Multiple work modes are required. Bending/twisting mode control receives special attention for many classic aerospace structures, such as active reflector systems, active blades, and [...] Read more.
The mission performance of future advanced aerospace structures can be synthetically improved via active shape control utilizing piezoelectric materials. Multiple work modes are required. Bending/twisting mode control receives special attention for many classic aerospace structures, such as active reflector systems, active blades, and compliant morphing wings. Piezoelectric fiber composite (Piezocomposite) material features in-plane anisotropic actuation, which is very suitable for multiple work modes. In this study, two identical macro-fiber composite (MFC) actuators of the F1 type were bonded to the base plate structure in an “antisymmetric angle-ply bimorph configuration” in order to achieve independent bending/twisting shape control. In terms of the finite element model and homogenization strategy, the locations of bimorph MFCs were determined by considering the effect of trade-off control capabilities on the bending and twisting shapes. The modal characteristics were investigated via both experimental and theoretical approaches. The experimental tests implied that the shape control accuracy was heavily reduced due to various uncertainties and nonlinearities, including hysteresis and the creep effect of the actuators, model errors, and external disturbances. A multi-mode feedback control law was designed and the experimental tests indicated that synthetic (independent and coupled) bending/twisting deformations were achieved with improved shape accuracy. This study provides a feasible multi-mode shape control approach with high surface accuracy, especially by employing piezocomposite materials. Full article
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16 pages, 6373 KB  
Article
Using a Fiber Bragg Grating Sensor to Measure Residual Strain in the Vacuum-Assisted Resin Transfer Molding Process
by Guang-Min Luo, Guang-Yen Liou and Hong-Zhe Xiao
Polymers 2022, 14(7), 1446; https://doi.org/10.3390/polym14071446 - 1 Apr 2022
Cited by 7 | Viewed by 2711
Abstract
Vinyl ester (VE) resin has strong environmental tolerance and is the matrix commonly used in the composite materials of fiber-reinforced plastics (FRP). VE resin is often combined with glass fiber in different maritime structures, such as wind turbine blades, spinner cases, and nacelle [...] Read more.
Vinyl ester (VE) resin has strong environmental tolerance and is the matrix commonly used in the composite materials of fiber-reinforced plastics (FRP). VE resin is often combined with glass fiber in different maritime structures, such as wind turbine blades, spinner cases, and nacelle cases. However, VE resin exhibits exothermic reactions and shrinkage during curing, which often generates residual strain in large structures and those with a high stacking number. This study explored the exothermic reaction and shrinkage of VE resin and glass fiber during the vacuum-assisted resin transfer molding process, as measured using a fiber Bragg grating sensor. The experiment results verified the relationship between the stacking number and residual strain shrinkage. In addition, the symmetric laminate method was used to prevent the bending–twisting coupling effect and subsequent warping deformation of the FRP laminated plate during curing. The experiment results also verified that the bottom layers of the FRP laminated plates produced using VE resin were closer to the mold, and exhibited more shrinkage as the stacking number increased. In addition, this study discovered that during the experiment, the symmetry layer of the FRP laminated plate had a higher exothermic temperature than the bottom layer as a result of the symmetry layer’s ineffective heat dissipation. Therefore, the curing shrinkage of the symmetry layer resin was measured. The experiment results indicated that if the stacking number was between 10 and 30, the residual strain shrinkage of the symmetry layer was greater than that of the surface layer. However, because of the symmetric laminate, the residual strain of the symmetry layer did not increase when the temperature increased. Therefore, the greatest residual strain occurred at the surface of the bottom layer of the laminated plate with a stacking number of 40. Full article
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15 pages, 3735 KB  
Article
A Stretchable and Self-Healing Hybrid Nano-Generator for Human Motion Monitoring
by Yongsheng Zhu, Fengxin Sun, Changjun Jia, Tianming Zhao and Yupeng Mao
Nanomaterials 2022, 12(1), 104; https://doi.org/10.3390/nano12010104 - 29 Dec 2021
Cited by 59 | Viewed by 4540
Abstract
Transparent stretchable wearable hybrid nano-generators present great opportunities in motion sensing, motion monitoring, and human-computer interaction. Herein, we report a piezoelectric-triboelectric sport sensor (PTSS) which is composed of TENG, PENG, and a flexible transparent stretchable self-healing hydrogel electrode. The piezoelectric effect and the [...] Read more.
Transparent stretchable wearable hybrid nano-generators present great opportunities in motion sensing, motion monitoring, and human-computer interaction. Herein, we report a piezoelectric-triboelectric sport sensor (PTSS) which is composed of TENG, PENG, and a flexible transparent stretchable self-healing hydrogel electrode. The piezoelectric effect and the triboelectric effect are coupled by a contact separation mode. According to this effect, the PTSS shows a wide monitoring range. It can be used to monitor human multi-dimensional motions such as bend, twist, and rotate motions, including the screw pull motion of table tennis and the 301C skill of diving. In addition, the flexible transparent stretchable self-healing hydrogel is used as the electrode, which can meet most of the motion and sensing requirements and presents the characteristics of high flexibility, high transparency, high stretchability, and self-healing behavior. The whole sensing system can transmit signals through Bluetooth devices. The flexible, transparent, and stretchable wearable hybrid nanogenerator can be used as a wearable motion monitoring sensor, which provides a new strategy for the sports field, motion monitoring, and human-computer interaction. Full article
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15 pages, 15448 KB  
Article
Experimental Investigation of Bubble Migration near Anisotropic Beams
by Zhicheng Xu, Xiaojian Ma, Qidong Yu, Jing Zhao, Dapeng Wang, Xiaosheng Bi and Fen Qin
Micromachines 2021, 12(12), 1518; https://doi.org/10.3390/mi12121518 - 6 Dec 2021
Cited by 1 | Viewed by 2254
Abstract
In order to resist bubble loading, anisotropic composite materials are the development direction of the future. The objective of this paper was to experimentally investigate the hydrodynamic performance of anisotropic laminate composite plates, with a focus on the effect of its anisotropic characteristics [...] Read more.
In order to resist bubble loading, anisotropic composite materials are the development direction of the future. The objective of this paper was to experimentally investigate the hydrodynamic performance of anisotropic laminate composite plates, with a focus on the effect of its anisotropic characteristics on single bubble migration. In these experiments, the bubble was generated in a transparent water tank filled with sufficiently degassed water by Joule heating at the connecting point of the electrodes through the discharge of a 6600 μF charge to 800 V, and a high-speed camera system with a recording speed of 40,000 frames per second was used to record the temporal evolution of bubble patterns and the dynamic responses of the laminated composite plates. The results are presented for two anisotropic cantilever composite beams with different ply angles, namely, 0° and 30°. Several variables, such as the shapes of the bubble, the curved trail of motion of the bubble center, bubble collapse time, and bubble initial standoff distances were extracted from the photographic images. The results showed that bubble migration near the 30° plate presents a curved bubble trail with an evident tilted angle during the collapse and rebound stages, which is very different from bubbles that all move vertically above the 0° plate. Furthermore, a characterization method for bubble migration was proposed to quantitatively describe the curved bubble trails and the deformation of the composite beams in temporal and spatial scales. This method shows that the curved bubble trails near the 30° plate are closely related to the dynamic response of composite beams, with a focus on the bending-twisting coupling effect. Full article
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24 pages, 8098 KB  
Article
Suction Bucket Pile–Soil–Structure Interactions of Offshore Wind Turbine Jacket Foundations Using Coupled Dynamic Analysis
by Pasin Plodpradit, Osoon Kwon, Van Nguyen Dinh, Jimmy Murphy and Ki-Du Kim
J. Mar. Sci. Eng. 2020, 8(6), 416; https://doi.org/10.3390/jmse8060416 - 8 Jun 2020
Cited by 23 | Viewed by 8361
Abstract
This paper presents a procedure for the coupled dynamic analysis of offshore wind turbine–jacket foundation-suction bucket piles and compares the American Petroleum Institute (API) standard method and Jeanjean’s methods used to model the piles. Nonlinear springs were used to represent soil lateral, axial, [...] Read more.
This paper presents a procedure for the coupled dynamic analysis of offshore wind turbine–jacket foundation-suction bucket piles and compares the American Petroleum Institute (API) standard method and Jeanjean’s methods used to model the piles. Nonlinear springs were used to represent soil lateral, axial, and tip resistances through the P–Y, T–Z, and Q–Z curves obtained by either API’s or Jeanjean’s methods. Rotational springs with a stiffness equated to the tangent or secant modulus characterized soil resistance to acentric loads. The procedure was implemented in X-SEA program. Analyses of a laterally loaded single pile in a soft clay soil performed in both the X-SEA and Structural Analysis Computer System (SACS) programs showed good agreements. The behaviors of a five MW offshore wind turbine system in South Korea were examined by considering waves, current, wind effects, and marine growth. In a free vibration analysis done with soil stiffness through the API method, the piles were found to bend in their first mode and to twist in the second and third modes, whereas the first three modes using Jeanjean’s method were all found to twist. The natural frequencies resulting from Jeanjean’s method were higher than those from the API method. In a forced vibration analysis, the system responses were significantly influenced by soil spring stiffness type. The procedure was found to be computationally expensive due to spring nonlinearities introduced. Full article
(This article belongs to the Special Issue Analysis and Design of Offshore Wind Turbine Support Structures)
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