Pub Date : 2024-10-22DOI: 10.1016/j.jsv.2024.118787
Mikel Brun, Fernando Cortés, María Jesús Elejabarrieta
Vibration attenuation is a key aspect of mechanical engineering. One method to achieve this is through eddy currents, which can be generated in a vibrating system when a magnetic field is present, creating forces that oppose motion. This study examines a mechanical system consisting of a thin cantilever beam vibrating in a uniform and time-invariant magnetic field under steady-state conditions to understand the nature of energy dissipation and the relationship between motion, eddy currents, and damping forces. The calculation of eddy currents generally requires the use of complex numerical procedures. However, for systems with simple geometry, such as a cantilever beam, a recent numerical procedure based on the finite difference method, known for its simplicity in implementation, has been adapted and expanded to determine eddy currents under motional induction. A numerical application has been developed in which the vibration of a specific beam is characterised by its bending or torsional mode shapes, and the nature of the corresponding dissipative forces is analysed. Results indicate that the eddy currents are an effective means of dissipating energy at lower-order modes. Additionally, the direction of the applied magnetic field can induce coupling between bending and torsional vibrations.
{"title":"Numerical analysis of energy dissipation due to eddy currents in a vibrating beam","authors":"Mikel Brun, Fernando Cortés, María Jesús Elejabarrieta","doi":"10.1016/j.jsv.2024.118787","DOIUrl":"10.1016/j.jsv.2024.118787","url":null,"abstract":"<div><div>Vibration attenuation is a key aspect of mechanical engineering. One method to achieve this is through eddy currents, which can be generated in a vibrating system when a magnetic field is present, creating forces that oppose motion. This study examines a mechanical system consisting of a thin cantilever beam vibrating in a uniform and time-invariant magnetic field under steady-state conditions to understand the nature of energy dissipation and the relationship between motion, eddy currents, and damping forces. The calculation of eddy currents generally requires the use of complex numerical procedures. However, for systems with simple geometry, such as a cantilever beam, a recent numerical procedure based on the finite difference method, known for its simplicity in implementation, has been adapted and expanded to determine eddy currents under motional induction. A numerical application has been developed in which the vibration of a specific beam is characterised by its bending or torsional mode shapes, and the nature of the corresponding dissipative forces is analysed. Results indicate that the eddy currents are an effective means of dissipating energy at lower-order modes. Additionally, the direction of the applied magnetic field can induce coupling between bending and torsional vibrations.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"595 ","pages":"Article 118787"},"PeriodicalIF":4.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142551887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.jsv.2024.118776
Shail A. Shah, Hans Bodén, Susann Boij
The usage of perforated plates in passive noise-control systems in e.g. aircraft liners and mufflers involves the standard operating conditions of grazing flow and high-amplitude acoustic incidence. This study focuses on the usage of the three-port experiment technique for the experimental passive acoustic characterisation of a perforated plate. Expanding on the previous paper about the resistance of the perforate, the influence of operating conditions on the imaginary part of the transfer impedance, i.e., the reactance is discussed here. The relationship between the end correction in the linear range, without the presence of grazing flow, and the frequency of acoustic excitation is demonstrated. The reduction in the value of the mass end correction under the individual effects of grazing flow, and high-amplitude excitation is presented. Additionally, depending on the excitation wavelength, the partial recovery of the reduced value of the end correction under simultaneous exposure is also shown. Using the experimental results, models for the end correction, and by extension the reactance are proposed. These models take into account the geometrical parameters of the perforate, and the dimensionless Mach, Shear and Strouhal numbers.
{"title":"An experimental study on three-port measurements for acoustic characterisation of the perforate reactance","authors":"Shail A. Shah, Hans Bodén, Susann Boij","doi":"10.1016/j.jsv.2024.118776","DOIUrl":"10.1016/j.jsv.2024.118776","url":null,"abstract":"<div><div>The usage of perforated plates in passive noise-control systems in e.g. aircraft liners and mufflers involves the standard operating conditions of grazing flow and high-amplitude acoustic incidence. This study focuses on the usage of the three-port experiment technique for the experimental passive acoustic characterisation of a perforated plate. Expanding on the previous paper about the resistance of the perforate, the influence of operating conditions on the imaginary part of the transfer impedance, i.e., the reactance is discussed here. The relationship between the end correction in the linear range, without the presence of grazing flow, and the frequency of acoustic excitation is demonstrated. The reduction in the value of the mass end correction under the individual effects of grazing flow, and high-amplitude excitation is presented. Additionally, depending on the excitation wavelength, the partial recovery of the reduced value of the end correction under simultaneous exposure is also shown. Using the experimental results, models for the end correction, and by extension the reactance are proposed. These models take into account the geometrical parameters of the perforate, and the dimensionless Mach, Shear and Strouhal numbers.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"596 ","pages":"Article 118776"},"PeriodicalIF":4.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.jsv.2024.118788
Nathaniel DeVol , Christopher Saldaña , Katherine Fu
Data preprocessing is a key step in extracting useful information from sound and vibration data and often involves selecting a time-frequency representation. No single time-frequency representation is always optimal, and no standard method exists for selecting the appropriate time-frequency representation, so selecting the time-frequency representation requires expert knowledge and is susceptible to human bias. To address this, this work introduces a methodology to automate the selection of a time-frequency representation for a dataset using only a subset of the healthy, or normal, class of data. To select the parameters for each type of time-frequency representation, Bayesian optimization is used. With a candidate from each type of time-frequency representation, the average similarity is used to select the final candidate. Additionally, the use of multiple time-frequency representations within a single model is explored. Because there is currently no objective method to compare the selected time frequency representations against, the proposed methodology is evaluated in two case studies. In the case studies, the time frequency representations are used as inputs to a simple convolutional neural network that achieved 100% accuracy in classifying bearing faults and 94% accuracy in classifying the contact tip to workpiece distance in wire arc additive manufacturing. Additionally, the proposed methodology presents a 75% and 94% reduction in the data size for the two case studies. This offers further benefits for reducing costs of data transmission and storage in modern digital manufacturing architectures.
{"title":"Methodology for the automated selection of time-frequency representations","authors":"Nathaniel DeVol , Christopher Saldaña , Katherine Fu","doi":"10.1016/j.jsv.2024.118788","DOIUrl":"10.1016/j.jsv.2024.118788","url":null,"abstract":"<div><div>Data preprocessing is a key step in extracting useful information from sound and vibration data and often involves selecting a time-frequency representation. No single time-frequency representation is always optimal, and no standard method exists for selecting the appropriate time-frequency representation, so selecting the time-frequency representation requires expert knowledge and is susceptible to human bias. To address this, this work introduces a methodology to automate the selection of a time-frequency representation for a dataset using only a subset of the healthy, or normal, class of data. To select the parameters for each type of time-frequency representation, Bayesian optimization is used. With a candidate from each type of time-frequency representation, the average similarity is used to select the final candidate. Additionally, the use of multiple time-frequency representations within a single model is explored. Because there is currently no objective method to compare the selected time frequency representations against, the proposed methodology is evaluated in two case studies. In the case studies, the time frequency representations are used as inputs to a simple convolutional neural network that achieved 100% accuracy in classifying bearing faults and 94% accuracy in classifying the contact tip to workpiece distance in wire arc additive manufacturing. Additionally, the proposed methodology presents a 75% and 94% reduction in the data size for the two case studies. This offers further benefits for reducing costs of data transmission and storage in modern digital manufacturing architectures.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"596 ","pages":"Article 118788"},"PeriodicalIF":4.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-19DOI: 10.1016/j.jsv.2024.118783
Wei Shen , Yuguang Fu , Qingzhao Kong , Jin-Yang Li
Compared to parametric counterparts, non-parametric (aka, model-free) damage detection methods have no requirements of accurate models, with the potential of autonomous monitoring of various complex structures. However, noises, or low signal-to-noise ratio (SNR), are one of the main challenges. This study is aimed at improving blind source separation (BSS)-based damage detection method, one of the most advanced non-parametric methods, in both aspects of noise robustness and autonomous operation. In particular, the measured acceleration responses are processed by variational mode decomposition (VMD) and wavelet transform (WT) in sequential, acting as the input for a BSS model. The BSS is then solved by independent component analysis (ICA), which approves to be more noise-robust compared to the state-of-the-art counterparts. Furthermore, shapelet transform is applied to extract the universal shape-based spike-like feature from the BSS model for training a support vector machine (SVM) model, applicable to different structures; it finally automates the sudden damage detection process and enables online monitoring. The effectiveness of the proposed method is illustrated by a numerical example and an experimental test, and demonstrated by a real-world seismic-excited structure. The results show that both single and multiple sudden damages can be automatically detected with high accuracy. Compared with the existing BSS methods, the proposed BSS method is more capable to detect small damages at relatively low SNR. In addition, the classification accuracy of SVM is also improved when shapelet-based feature is used for training, which reduces the malfunction of automated damage detection as shown by the numerical example. Therefore, the proposed strategy has the potential for rapid condition assessment of structures during rare/extreme events, before engineers are sent for further post-event inspection.
{"title":"Noise-robust automated sudden damage detection using blind source separation enhanced by variational mode decomposition and support vector machine based on shapelet transform","authors":"Wei Shen , Yuguang Fu , Qingzhao Kong , Jin-Yang Li","doi":"10.1016/j.jsv.2024.118783","DOIUrl":"10.1016/j.jsv.2024.118783","url":null,"abstract":"<div><div>Compared to parametric counterparts, non-parametric (aka, model-free) damage detection methods have no requirements of accurate models, with the potential of autonomous monitoring of various complex structures. However, noises, or low signal-to-noise ratio (SNR), are one of the main challenges. This study is aimed at improving blind source separation (BSS)-based damage detection method, one of the most advanced non-parametric methods, in both aspects of noise robustness and autonomous operation. In particular, the measured acceleration responses are processed by variational mode decomposition (VMD) and wavelet transform (WT) in sequential, acting as the input for a BSS model. The BSS is then solved by independent component analysis (ICA), which approves to be more noise-robust compared to the state-of-the-art counterparts. Furthermore, shapelet transform is applied to extract the universal shape-based spike-like feature from the BSS model for training a support vector machine (SVM) model, applicable to different structures; it finally automates the sudden damage detection process and enables online monitoring. The effectiveness of the proposed method is illustrated by a numerical example and an experimental test, and demonstrated by a real-world seismic-excited structure. The results show that both single and multiple sudden damages can be automatically detected with high accuracy. Compared with the existing BSS methods, the proposed BSS method is more capable to detect small damages at relatively low SNR. In addition, the classification accuracy of SVM is also improved when shapelet-based feature is used for training, which reduces the malfunction of automated damage detection as shown by the numerical example. Therefore, the proposed strategy has the potential for rapid condition assessment of structures during rare/extreme events, before engineers are sent for further post-event inspection.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"595 ","pages":"Article 118783"},"PeriodicalIF":4.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-19DOI: 10.1016/j.jsv.2024.118773
Sean T. Kelly, Bogdan I. Epureanu
Integrally bladed rotors are commonly used in aircraft and rocket turbomachinery and known to exhibit complex dynamics when subject to operational loading conditions. Though nominally cyclic-symmetric structures, in practice, cyclic symmetry is destroyed due to mistuning caused by random sector-to-sector imperfections in material properties and geometry. Simulating mistuned blisk dynamics using high-fidelity models can be computationally expensive, thus, a variety of physics-based reduced-order models have been previously developed. However, these models cannot easily incorporate experimental data nor leverage potential benefits of data-driven and machine-learning-based approaches. Here, we present a novel first-of-its-kind physics-informed machine learning modeling approach that incorporates physical laws directly into a novel network architecture while maintaining a sector-level viewpoint. The approach is combined with an assembly procedure resulting in a significantly smaller linear system based on blade-alone response data, and can directly incorporate physical response data like that measured with blade tip timing and/or traveling-wave excitation. Validation is shown using a large-scale finite-element model, with multiple traveling-wave forced-response predictions and response selection cases considered. Using only as little as a single degree of freedom per sector from the blade tip, this approach shows high accuracy relative to high-fidelity simulations.
{"title":"Physics-informed machine learning approach for reduced-order modeling of integrally bladed rotors: Theory and application","authors":"Sean T. Kelly, Bogdan I. Epureanu","doi":"10.1016/j.jsv.2024.118773","DOIUrl":"10.1016/j.jsv.2024.118773","url":null,"abstract":"<div><div>Integrally bladed rotors are commonly used in aircraft and rocket turbomachinery and known to exhibit complex dynamics when subject to operational loading conditions. Though nominally cyclic-symmetric structures, in practice, cyclic symmetry is destroyed due to mistuning caused by random sector-to-sector imperfections in material properties and geometry. Simulating mistuned blisk dynamics using high-fidelity models can be computationally expensive, thus, a variety of physics-based reduced-order models have been previously developed. However, these models cannot easily incorporate experimental data nor leverage potential benefits of data-driven and machine-learning-based approaches. Here, we present a novel first-of-its-kind physics-informed machine learning modeling approach that incorporates physical laws directly into a novel network architecture while maintaining a sector-level viewpoint. The approach is combined with an assembly procedure resulting in a significantly smaller linear system based on blade-alone response data, and can directly incorporate physical response data like that measured with blade tip timing and/or traveling-wave excitation. Validation is shown using a large-scale finite-element model, with multiple traveling-wave forced-response predictions and response selection cases considered. Using only as little as a single degree of freedom per sector from the blade tip, this approach shows high accuracy relative to high-fidelity simulations.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"596 ","pages":"Article 118773"},"PeriodicalIF":4.3,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142650925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jsv.2024.118778
Chao Zheng, Jun Wu, Jianchao Liu, Xin Xue
This work aims to identify ways to model a high-accuracy hysteresis dynamic model for an innovative 4-SPS parallel all-metallic isolator. Firstly, a three-dimensional contact model of spherical joints under different conditions (stretching and compression) is proposed, referred to as the integrated model of nonlinear micro-collision and interfacial friction (INCF model). Simultaneously, in conjunction with the nonlinear elastic recovery force, nonlinear damping force, and nonlinear hysteresis damping force, the high-accuracy hysteresis dynamic model of the isolator is constructed. To validate the accuracy, dynamic experiments are conducted on the isolator at distinct frequencies (6–9 Hz) and amplitudes (0.6–0.9 mm). The results indicate that the hysteresis dynamic model constructed based on the INCF model exhibits a remarkably high level of precision compared to the classic model (R2=0.998). This increased accuracy is attributed to the consideration of influencing factors of the INCF model, such as micro-collisions between spherical joints and interfacial friction during the operation of the isolator. These variables are determined by the material properties and geometric dimensions of the spherical joint and can be adjusted in real time based on the isolator deformations to enhance the model's accuracy. The method of parameter identification applied to overall structure resolves challenge of measuring the internal deformation of spherical joints. Importantly, the INCF model is not limited to the isolators proposed in this work but can also be applied to similar isolators with Stewart structure-type connections that employ spherical joints. These research findings provide a robust theoretical support for the design and performance optimization of the isolator, with the potential to positively impact related engineering applications.
{"title":"Hysteresis dynamic modeling of 4-SPS parallel all-metallic isolator with spherical joints considering nonlinear micro-collision and interfacial friction","authors":"Chao Zheng, Jun Wu, Jianchao Liu, Xin Xue","doi":"10.1016/j.jsv.2024.118778","DOIUrl":"10.1016/j.jsv.2024.118778","url":null,"abstract":"<div><div>This work aims to identify ways to model a high-accuracy hysteresis dynamic model for an innovative 4-SPS parallel all-metallic isolator. Firstly, a three-dimensional contact model of spherical joints under different conditions (stretching and compression) is proposed, referred to as the integrated model of nonlinear micro-collision and interfacial friction (INCF model). Simultaneously, in conjunction with the nonlinear elastic recovery force, nonlinear damping force, and nonlinear hysteresis damping force, the high-accuracy hysteresis dynamic model of the isolator is constructed. To validate the accuracy, dynamic experiments are conducted on the isolator at distinct frequencies (6–9 Hz) and amplitudes (0.6–0.9 mm). The results indicate that the hysteresis dynamic model constructed based on the INCF model exhibits a remarkably high level of precision compared to the classic model (<em>R</em><sup>2</sup>=0.998). This increased accuracy is attributed to the consideration of influencing factors of the INCF model, such as micro-collisions between spherical joints and interfacial friction during the operation of the isolator. These variables are determined by the material properties and geometric dimensions of the spherical joint and can be adjusted in real time based on the isolator deformations to enhance the model's accuracy. The method of parameter identification applied to overall structure resolves challenge of measuring the internal deformation of spherical joints. Importantly, the INCF model is not limited to the isolators proposed in this work but can also be applied to similar isolators with Stewart structure-type connections that employ spherical joints. These research findings provide a robust theoretical support for the design and performance optimization of the isolator, with the potential to positively impact related engineering applications.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"596 ","pages":"Article 118778"},"PeriodicalIF":4.3,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jsv.2024.118772
Chenghao Yang , Yu Liu , Guanjiang Chen , Xiaozheng Zhang , Chuan-Xing Bi
This numerical study proposes an active control method aiming to suppress aerodynamic noise from bluff bodies by employing a forced rotating cylinder and investigates its noise reduction effects and mechanisms. A three-dimensional large eddy simulation combined with the Ffowcs William–Hawkings equation was adopted to study the influence of different rotation ratios on the aerodynamic and aeroacoustic characteristics of a cylinder at a Reynolds number of , and to elucidate the primary mechanisms by which cylinder rotation reduces aerodynamic noise. The numerical method is validated through a comparison with previous numerical and experimental results of both flow field and far-field noise. The present numerical results indicate that cylinder rotation can not only effectively reduce aerodynamic drag but also significantly suppress aerodynamic noise across the entire frequency range, including vortex-shedding tonal noise and broadband noise. Two primary mechanisms of flow and noise control by the rotating cylinder are revealed within different ranges of rotation ratio. One mechanism stabilizes the shear layer, thereby suppressing vortex shedding. The other mechanism attenuates the Kelvin–Helmholtz instability on the upper side of the cylinder, leading to a transition into laminar flow which inhibits the formation of large-scale coherent turbulent structures.
{"title":"Numerical study on the flow and noise control mechanisms of a forced rotating cylinder","authors":"Chenghao Yang , Yu Liu , Guanjiang Chen , Xiaozheng Zhang , Chuan-Xing Bi","doi":"10.1016/j.jsv.2024.118772","DOIUrl":"10.1016/j.jsv.2024.118772","url":null,"abstract":"<div><div>This numerical study proposes an active control method aiming to suppress aerodynamic noise from bluff bodies by employing a forced rotating cylinder and investigates its noise reduction effects and mechanisms. A three-dimensional large eddy simulation combined with the Ffowcs William–Hawkings equation was adopted to study the influence of different rotation ratios on the aerodynamic and aeroacoustic characteristics of a cylinder at a Reynolds number of <span><math><mrow><mn>4</mn><mo>.</mo><mn>7</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span>, and to elucidate the primary mechanisms by which cylinder rotation reduces aerodynamic noise. The numerical method is validated through a comparison with previous numerical and experimental results of both flow field and far-field noise. The present numerical results indicate that cylinder rotation can not only effectively reduce aerodynamic drag but also significantly suppress aerodynamic noise across the entire frequency range, including vortex-shedding tonal noise and broadband noise. Two primary mechanisms of flow and noise control by the rotating cylinder are revealed within different ranges of rotation ratio. One mechanism stabilizes the shear layer, thereby suppressing vortex shedding. The other mechanism attenuates the Kelvin–Helmholtz instability on the upper side of the cylinder, leading to a transition into laminar flow which inhibits the formation of large-scale coherent turbulent structures.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"596 ","pages":"Article 118772"},"PeriodicalIF":4.3,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1016/j.jsv.2024.118770
Cheng Ning Loong, Elias G. Dimitrakopoulos
This study examines the modal properties of fractal-idealized monopodial trees, which comprise a main trunk with branches grown laterally and axially from it. Analysis via a renormalization technique shows that monopodial trees possess emerging modes, self-similar modes with lateral branching, and self-similar modes with axial branching. The study introduces a recursive analytical approach, which involves the construction of auxiliary -functions to characterize the modal properties. Results reveal that monopodial trees’ modal frequencies are closely spaced because their emerging modes increase exponentially in number. Under the self-similar modes with lateral branching, the trees inherit all modes from their fractal ancestors, while under the self-similar modes with axial branching, they inherit only the self-similar modes from their ancestors. Hence, the main trunk stands still at self-similar modes, and the trees localize vibration at higher-order lateral branches. Therefore, the monopodial branching architecture is advantageous for reducing the vibration of the main trunk. This study also derives analytical formulas for the modal frequencies of trees with infinite order via a group tree modeling approach. Monopodial trees acquire the highest natural frequency when they have a one-to-one lateral-to-axial-branching ratio. The proposed formulas are verified with independent literature results and are shown to be accurate.
本研究探讨了分形理想化单叉树的模态特性，单叉树由主干和从主干向横向和轴向生长的分支组成。通过重正化技术进行的分析表明，单叉树具有新出现的模态、横向分支的自相似模态和轴向分支的自相似模态。研究引入了一种递归分析方法，包括构建辅助 P 函数来描述模态特性。结果表明，单峰树的模态频率间隔很近，因为其新出现的模态数量呈指数增长。在横向分支的自相似模态下，单模树继承了分形祖先的所有模态，而在轴向分支的自相似模态下，单模树只继承了祖先的自相似模态。因此，主干在自相似模态下静止不动，而树木在高阶侧枝上局部振动。因此，单轴分支结构有利于减少主干的振动。本研究还通过树群建模方法推导出无限阶树木模态频率的分析公式。当单轴树的横向与轴向分支比为一比一时，其固有频率最高。提出的公式与独立的文献结果进行了验证，结果表明是准确的。
{"title":"Recursive modal properties of fractal monopodial trees, from finite to infinite order","authors":"Cheng Ning Loong, Elias G. Dimitrakopoulos","doi":"10.1016/j.jsv.2024.118770","DOIUrl":"10.1016/j.jsv.2024.118770","url":null,"abstract":"<div><div>This study examines the modal properties of fractal-idealized monopodial trees, which comprise a main trunk with branches grown laterally and axially from it. Analysis via a renormalization technique shows that monopodial trees possess <em>emerging modes</em>, <em>self-similar modes with lateral branching</em>, and <em>self-similar modes with axial branching</em>. The study introduces a recursive analytical approach, which involves the construction of auxiliary <span><math><mi>P</mi></math></span>-functions to characterize the modal properties. Results reveal that monopodial trees’ modal frequencies are closely spaced because their emerging modes increase exponentially in number. Under the self-similar modes with lateral branching, the trees inherit all modes from their fractal ancestors, while under the self-similar modes with axial branching, they inherit only the self-similar modes from their ancestors. Hence, the main trunk stands still at self-similar modes, and the trees localize vibration at higher-order lateral branches. Therefore, the monopodial branching architecture is advantageous for reducing the vibration of the main trunk. This study also derives analytical formulas for the modal frequencies of trees with infinite order via a group tree modeling approach. Monopodial trees acquire the highest natural frequency when they have a one-to-one lateral-to-axial-branching ratio. The proposed formulas are verified with independent literature results and are shown to be accurate.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"595 ","pages":"Article 118770"},"PeriodicalIF":4.3,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.jsv.2024.118768
Yunxi Zhu , Yankai Zhang , Fengyi Fan , Wenyao Ma , Liwen Qin , Zheng Kuang , Ming Wu , Jun Yang
A multi-channel parametric array loudspeaker (PAL) array can steer an audio beam using a digital signal processing technique. However, it faces the challenge posed by grating lobes in the ultrasonic radiation pattern, which leads to unwanted sidelobes in the steering audio beam when the Nyquist criterion is not satisfied due to short ultrasonic wavelengths. As a result, the audio beam not only fails to steer in the desired direction but also loses its inherent advantage of high directivity when using a beamsteer with a delay-and-sum (DAS) structure. This work proposes an enhanced beamsteering algorithm to suppress the sidelobes by optimizing the channel weight coefficients. The nonlinear optimization problem is transformed into a linear expression, making the minimum-variance-distortionless-response (MVDR) algorithm applicable. Both simulations and experiments validate the effective suppression of sidelobes and the mitigation of sound fuzziness within the range from the sidelobe to the mainlobe. The audio beam successfully steers in the desired direction and maintains a high directivity. However, the performance of the algorithm deteriorates at high audio frequencies due to the inherent physical limitations of wave interference in sound field control strategies.
{"title":"An enhanced beamsteering algorithm based on MVDR for a multi-channel parametric array loudspeaker array","authors":"Yunxi Zhu , Yankai Zhang , Fengyi Fan , Wenyao Ma , Liwen Qin , Zheng Kuang , Ming Wu , Jun Yang","doi":"10.1016/j.jsv.2024.118768","DOIUrl":"10.1016/j.jsv.2024.118768","url":null,"abstract":"<div><div>A multi-channel parametric array loudspeaker (PAL) array can steer an audio beam using a digital signal processing technique. However, it faces the challenge posed by grating lobes in the ultrasonic radiation pattern, which leads to unwanted sidelobes in the steering audio beam when the Nyquist criterion is not satisfied due to short ultrasonic wavelengths. As a result, the audio beam not only fails to steer in the desired direction but also loses its inherent advantage of high directivity when using a beamsteer with a delay-and-sum (DAS) structure. This work proposes an enhanced beamsteering algorithm to suppress the sidelobes by optimizing the channel weight coefficients. The nonlinear optimization problem is transformed into a linear expression, making the minimum-variance-distortionless-response (MVDR) algorithm applicable. Both simulations and experiments validate the effective suppression of sidelobes and the mitigation of sound fuzziness within the range from the sidelobe to the mainlobe. The audio beam successfully steers in the desired direction and maintains a high directivity. However, the performance of the algorithm deteriorates at high audio frequencies due to the inherent physical limitations of wave interference in sound field control strategies.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"595 ","pages":"Article 118768"},"PeriodicalIF":4.3,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.jsv.2024.118755
C. da Silveira Zanin , S. Missoum , A. Ture Savadkoohi , S. Baguet , E. Gourdon , R. Dufour
This article investigates the optimization under uncertainty of a mass-in-mass meta-cell for its potential use within a metamaterial. The specificity of the proposed mass-in-mass system stems from the hybrid nonlinear–linear stiffness at the inner level. It is well known that these systems are highly sensitivity to small perturbations in loading conditions or design parameters. In fact, the sensitivity is such that the system can exhibit discontinuous behaviors. Therefore the proposed optimization approach not only accounts for sources of uncertainties but also can handle discontinuous responses. The objective of the stochastic optimization is to find the stiffness properties of the mass-in-mass system which minimize the expected value of a specific efficiency metric. In order to better understand the system’s dynamic behavior and the origins of the discontinuities, slow invariant manifolds and frequency response curves are provided. The efficiency of the optimized system with hybrid stiffness is compared with that of a similar optimized system featuring pure cubic nonlinearity.
{"title":"Stochastic optimization of a mass-in-mass cell with piecewise hybrid nonlinear–linear restoring force","authors":"C. da Silveira Zanin , S. Missoum , A. Ture Savadkoohi , S. Baguet , E. Gourdon , R. Dufour","doi":"10.1016/j.jsv.2024.118755","DOIUrl":"10.1016/j.jsv.2024.118755","url":null,"abstract":"<div><div>This article investigates the optimization under uncertainty of a mass-in-mass meta-cell for its potential use within a metamaterial. The specificity of the proposed mass-in-mass system stems from the hybrid nonlinear–linear stiffness at the inner level. It is well known that these systems are highly sensitivity to small perturbations in loading conditions or design parameters. In fact, the sensitivity is such that the system can exhibit discontinuous behaviors. Therefore the proposed optimization approach not only accounts for sources of uncertainties but also can handle discontinuous responses. The objective of the stochastic optimization is to find the stiffness properties of the mass-in-mass system which minimize the expected value of a specific efficiency metric. In order to better understand the system’s dynamic behavior and the origins of the discontinuities, slow invariant manifolds and frequency response curves are provided. The efficiency of the optimized system with hybrid stiffness is compared with that of a similar optimized system featuring pure cubic nonlinearity.</div></div>","PeriodicalId":17233,"journal":{"name":"Journal of Sound and Vibration","volume":"595 ","pages":"Article 118755"},"PeriodicalIF":4.3,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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