Abstract In conventional and skin-drive bone conduction, the performance of the exciter is strongly influenced by the mechanical impedance of the skin. This impedance is characterized by the resonance of the cutis on the underlying adipose layer. Although the existing Kelvin-Voigt based lumped parameter skin model allows satisfactory approximation of the magnitude of the measured skin impedance, substantial deviations appear in the associated phase. The use of the existing skin model in coupled exciter-skin response calculations may thus lead to prediction errors at resonance peaks. The present work proposes an alternative model which considers the bending wave propagation in the cutis using a continuum model combined with a Zener material model for the underlying adipose tissue. It shows good agreement with the measurement results and leads to insights in the role of the different skin layers in the observed dynamic response.
{"title":"Bone conduction: A linear viscoelastic mixed lumped-continuum model for the human skin in the acoustic frequency range","authors":"Linda Lüchtrath, Eugène Nijman","doi":"10.1115/1.4063936","DOIUrl":"https://doi.org/10.1115/1.4063936","url":null,"abstract":"Abstract In conventional and skin-drive bone conduction, the performance of the exciter is strongly influenced by the mechanical impedance of the skin. This impedance is characterized by the resonance of the cutis on the underlying adipose layer. Although the existing Kelvin-Voigt based lumped parameter skin model allows satisfactory approximation of the magnitude of the measured skin impedance, substantial deviations appear in the associated phase. The use of the existing skin model in coupled exciter-skin response calculations may thus lead to prediction errors at resonance peaks. The present work proposes an alternative model which considers the bending wave propagation in the cutis using a continuum model combined with a Zener material model for the underlying adipose tissue. It shows good agreement with the measurement results and leads to insights in the role of the different skin layers in the observed dynamic response.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136262348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Presently, passive methods of controlling combustion instability fall short when one considers stabilizing multiple acoustic modes. In this paper, we present a passive control approach based on the locations of the burners to stabilize multiple acoustic modes. The approach is demonstrated using linear stability analysis performed on a canonical open–open rectangular tube enclosing a flame. A linear flame model based on the kinematic description of the flame surface is used. A simultaneous solution method, as opposed to a segregated method, is developed to calculate the mean flow and to evaluate mode shapes and eigenvalues. The stability analysis is performed both on single and on multiple-burner combustors. In the latter case, the axial and transversal arrangement of burners considered preserves the net volumetric heat release rate and exit temperature. The problem of stabilizing the first three acoustic modes is cast as a multi-objective optimization problem for both types of combustors using the location(s) of the burner(s) as decision variable(s). We show that the use of multiple burners markedly increases the stability of the first three modes while not disturbing the combustor design parameters.
{"title":"A Multiple-Burner Approach to Passive Control of Multiple Longitudinal Acoustic Instabilities in Combustors","authors":"Supreeth S, S. R. Chakravarthy","doi":"10.1115/1.4063550","DOIUrl":"https://doi.org/10.1115/1.4063550","url":null,"abstract":"Abstract Presently, passive methods of controlling combustion instability fall short when one considers stabilizing multiple acoustic modes. In this paper, we present a passive control approach based on the locations of the burners to stabilize multiple acoustic modes. The approach is demonstrated using linear stability analysis performed on a canonical open–open rectangular tube enclosing a flame. A linear flame model based on the kinematic description of the flame surface is used. A simultaneous solution method, as opposed to a segregated method, is developed to calculate the mean flow and to evaluate mode shapes and eigenvalues. The stability analysis is performed both on single and on multiple-burner combustors. In the latter case, the axial and transversal arrangement of burners considered preserves the net volumetric heat release rate and exit temperature. The problem of stabilizing the first three acoustic modes is cast as a multi-objective optimization problem for both types of combustors using the location(s) of the burner(s) as decision variable(s). We show that the use of multiple burners markedly increases the stability of the first three modes while not disturbing the combustor design parameters.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135805984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhenkun Guo, Jiaqi Wen, Dewen Yu, Guobiao Hu, Yaowen Yang
Abstract This paper proposes a novel phononic crystal sandwich beam (PCSB) for low-frequency and broadband vibration suppression. The representative volume element (RVE) consists of two hourglass truss unit cells with the same span but different rod radii. After validating the modeling method, a model of the PCSB is established to calculate band structure and transmittance response, and the results show good agreement. It is found that the PCSB can open wider and lower band gaps compared to a traditional sandwich beam (TSB). The band-folding mechanism is applied. The PCSB breaks the spatial symmetry, becomes diatomic, and opens the folding points, finally leading to two band-folding-induced gaps. The experiment is conducted on the PCSB, and the vibration band gap property is confirmed. Subsequently, the impacts of geometric parameters on the PCSB’s band gaps are investigated in detail. Design guidelines for tuning the geometric parameters toward lower frequency and broadband band gap are provided based on the parametric study results. In addition, the higher-order band-folding strategy is proposed. It is shown that a multi-folding PCSB can produce more band gaps. However, through two examples, i.e., second-folding and third-folding PCSBs, it is known that simply increasing the folding order may not be effective and even could deteriorate the vibration attenuation ability. In summary, this work explores a general strategy for designing sandwich beams with low-frequency and broadband vibration suppression ability.
{"title":"Widening the Band Gaps of Hourglass Lattice Truss Core Sandwich Structures for Broadband Vibration Suppression","authors":"Zhenkun Guo, Jiaqi Wen, Dewen Yu, Guobiao Hu, Yaowen Yang","doi":"10.1115/1.4063443","DOIUrl":"https://doi.org/10.1115/1.4063443","url":null,"abstract":"Abstract This paper proposes a novel phononic crystal sandwich beam (PCSB) for low-frequency and broadband vibration suppression. The representative volume element (RVE) consists of two hourglass truss unit cells with the same span but different rod radii. After validating the modeling method, a model of the PCSB is established to calculate band structure and transmittance response, and the results show good agreement. It is found that the PCSB can open wider and lower band gaps compared to a traditional sandwich beam (TSB). The band-folding mechanism is applied. The PCSB breaks the spatial symmetry, becomes diatomic, and opens the folding points, finally leading to two band-folding-induced gaps. The experiment is conducted on the PCSB, and the vibration band gap property is confirmed. Subsequently, the impacts of geometric parameters on the PCSB’s band gaps are investigated in detail. Design guidelines for tuning the geometric parameters toward lower frequency and broadband band gap are provided based on the parametric study results. In addition, the higher-order band-folding strategy is proposed. It is shown that a multi-folding PCSB can produce more band gaps. However, through two examples, i.e., second-folding and third-folding PCSBs, it is known that simply increasing the folding order may not be effective and even could deteriorate the vibration attenuation ability. In summary, this work explores a general strategy for designing sandwich beams with low-frequency and broadband vibration suppression ability.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135302902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Additive manufacturing, such as 3D printing, offers unparalleled opportunities for rapid prototyping of objects, but typically requires simultaneous building of solid supports to minimize deformation and ensure contact with the printing surface. Here, we theoretically and experimentally investigate the concept of material extrusion on an “air bed” – an engineered ultrasonic acoustic field that stabilizes and supports the soft material by contactless radiation pressure force. We study the dynamics of polylactic acid (PLA) filament—a commonly used material in 3D printing—as it interacts with the acoustic potential during extrusion. We develop a numerical radiation pressure model to determine optimal configurations of ultrasonic transducers to generate acoustic fields and conditions for linear printing. We build a concept prototype that integrates an acoustic levitation array with a 3D printer and use this device to demonstrate linear extrusion on an acoustic air bed. Our results indicate that controlled interactions between acoustic fields and soft materials could offer alternative support mechanisms in additive manufacturing with potential benefits such as less material waste, fewer surface defects, and reduced material processing time.
{"title":"Material Extrusion on an Ultrasonic Air Bed for 3D Printing","authors":"Sam Keller, M. Stein, O. Ilic","doi":"10.1115/1.4063214","DOIUrl":"https://doi.org/10.1115/1.4063214","url":null,"abstract":"\u0000 Additive manufacturing, such as 3D printing, offers unparalleled opportunities for rapid prototyping of objects, but typically requires simultaneous building of solid supports to minimize deformation and ensure contact with the printing surface. Here, we theoretically and experimentally investigate the concept of material extrusion on an “air bed” – an engineered ultrasonic acoustic field that stabilizes and supports the soft material by contactless radiation pressure force. We study the dynamics of polylactic acid (PLA) filament—a commonly used material in 3D printing—as it interacts with the acoustic potential during extrusion. We develop a numerical radiation pressure model to determine optimal configurations of ultrasonic transducers to generate acoustic fields and conditions for linear printing. We build a concept prototype that integrates an acoustic levitation array with a 3D printer and use this device to demonstrate linear extrusion on an acoustic air bed. Our results indicate that controlled interactions between acoustic fields and soft materials could offer alternative support mechanisms in additive manufacturing with potential benefits such as less material waste, fewer surface defects, and reduced material processing time.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79282111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The inerter pendulum vibration absorber (IPVA) is integrated between a spar and an annulus floater using a ball-screw mechanism to study its wave energy conversion potential. Hydrodynamic stiffness, added mass and radiation damping effects on the spar-floater system are characterized using the boundary element method. It is found that a 1:2 internal resonance via a period doubling bifurcation in the system is responsible for nonlinear energy transfer between the spar-floater system and the pendulum vibration absorber. This nonlinear energy transfer occurs when the primary harmonic solution of the system becomes unstable due to the 1:2 internal resonance phenomenon. The focus of this paper is to analyze this 1:2 internal resonance phenomenon near the first natural frequency of the system. The IPVA system when integrated with the spar-floater system is shown to outperform a linear coupling between the spar and the floater both in terms of the response amplitude operator (RAO) of the spar and one measure of the energy conversion potential of the system. Finally, experiments are performed on the IPVA system integrated with single-degree-of-freedom system (without any hydrodynamic effects) to observe the 1:2 internal resonance phenomenon and the nonlinear energy transfer between the primary mass and the pendulum vibration absorber. It is shown experimentally that the IPVA system outperforms a linear benchmark in terms of vibration suppression due to the energy transfer phenomenon.
{"title":"Nonlinear Energy Transfer of a Spar-Floater System using the Inerter Pendulum Vibration Absorber","authors":"Aakash Gupta, V. Duong, Wei-Che Tai","doi":"10.1115/1.4063199","DOIUrl":"https://doi.org/10.1115/1.4063199","url":null,"abstract":"\u0000 The inerter pendulum vibration absorber (IPVA) is integrated between a spar and an annulus floater using a ball-screw mechanism to study its wave energy conversion potential. Hydrodynamic stiffness, added mass and radiation damping effects on the spar-floater system are characterized using the boundary element method. It is found that a 1:2 internal resonance via a period doubling bifurcation in the system is responsible for nonlinear energy transfer between the spar-floater system and the pendulum vibration absorber. This nonlinear energy transfer occurs when the primary harmonic solution of the system becomes unstable due to the 1:2 internal resonance phenomenon. The focus of this paper is to analyze this 1:2 internal resonance phenomenon near the first natural frequency of the system. The IPVA system when integrated with the spar-floater system is shown to outperform a linear coupling between the spar and the floater both in terms of the response amplitude operator (RAO) of the spar and one measure of the energy conversion potential of the system. Finally, experiments are performed on the IPVA system integrated with single-degree-of-freedom system (without any hydrodynamic effects) to observe the 1:2 internal resonance phenomenon and the nonlinear energy transfer between the primary mass and the pendulum vibration absorber. It is shown experimentally that the IPVA system outperforms a linear benchmark in terms of vibration suppression due to the energy transfer phenomenon.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80410441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Chanto, T. Pulngern, Chanachai Tangbanjongkij, Weeraphan Jiammeepreecha, S. Chucheepsakul
This paper focuses on free vibration of hemi-ellipsoidal shells with the consideration of the bending rigidity and nonlinear terms in strain energy. The appropriate form of the energy functional is formulated based on the principle of virtual work and the fundamental form of surfaces. Natural frequencies and their corresponding mode shapes are determined using the modified direct iteration method. The obtained results, which show a close agreement with previous research, are compared with those obtained based on the membrane theory. The effect of the support condition, thickness, size ratio, and volume constraint condition on frequency parameters and mode shapes is demonstrated. With the bending rigidity, shell thickness has a significant impact on the frequency, especially in higher vibration modes and in shells with a considerable thickness but the frequency parameter converges to that determined by using the membrane theory while the reference radius-to-thickness ratio is increasing. In addition, accounting for the bending rigidity solves the issue of determining natural frequencies and mode shapes of the shells using the membrane theory without the volume constraint condition. The obtained results also indicate that the free vibration analysis with bending is essential for the hemi-ellipsoidal shell with a base radius-to-thickness ratio of less than 100, which gives over 2.84% difference compared with that of the shell derived by membrane theory, and this allows engineers to perform the analysis in more applications.
{"title":"Effect of Bending Rigidity and Nonlinear Strains on Free Vibration of Hemi-ellipsoidal Shells","authors":"K. Chanto, T. Pulngern, Chanachai Tangbanjongkij, Weeraphan Jiammeepreecha, S. Chucheepsakul","doi":"10.1115/1.4063114","DOIUrl":"https://doi.org/10.1115/1.4063114","url":null,"abstract":"\u0000 This paper focuses on free vibration of hemi-ellipsoidal shells with the consideration of the bending rigidity and nonlinear terms in strain energy. The appropriate form of the energy functional is formulated based on the principle of virtual work and the fundamental form of surfaces. Natural frequencies and their corresponding mode shapes are determined using the modified direct iteration method. The obtained results, which show a close agreement with previous research, are compared with those obtained based on the membrane theory. The effect of the support condition, thickness, size ratio, and volume constraint condition on frequency parameters and mode shapes is demonstrated. With the bending rigidity, shell thickness has a significant impact on the frequency, especially in higher vibration modes and in shells with a considerable thickness but the frequency parameter converges to that determined by using the membrane theory while the reference radius-to-thickness ratio is increasing. In addition, accounting for the bending rigidity solves the issue of determining natural frequencies and mode shapes of the shells using the membrane theory without the volume constraint condition. The obtained results also indicate that the free vibration analysis with bending is essential for the hemi-ellipsoidal shell with a base radius-to-thickness ratio of less than 100, which gives over 2.84% difference compared with that of the shell derived by membrane theory, and this allows engineers to perform the analysis in more applications.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91174869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper addresses the experimental analysis of different stator configurations of an electric motor typically used within the automotive sector. The ongoing electrification of the automotive sector, combined with a desire to increase virtual prototyping, means that engineers are increasingly facing new challenges. Against this background, the numerical models of electric motors, particularly stators, are simplified and homogenized. However, this procedure must be supplemented by experimental data to ensure the high quality and reliability of the simulations. Unfortunately, broad experimental investigations are time-consuming and expensive, underlined by the lack of corresponding literature. For this reason, four different stator configurations were investigated as part of experimental modal analysis to highlight the influence of the stator lamination as well as the winding. The results provide the scientific community with a broad outline of how specific influences change modal parameters of each stator configuration. In particular, the results show that lamination significantly reduces axial stiffness. Highlights of the findings relate to the mode-dependent stiffness, mass, and damping influences due to the winding, with the influence of the stiffness deviating significantly from expectation. It was also found that the selected winding technology dominates the structural dynamic system characteristics. Therefore, it is advisable to include the manufacturing technology intended to be used for the lamination and the winding in the early simulative design phase to improve the model prediction quality.
{"title":"Experimental Modal Analysis of Stators Analyzing the Effects of Lamination and Winding","authors":"Manuel Islam, M. Maeder, R. Lehmann, S. Marburg","doi":"10.1115/1.4062839","DOIUrl":"https://doi.org/10.1115/1.4062839","url":null,"abstract":"\u0000 This paper addresses the experimental analysis of different stator configurations of an electric motor typically used within the automotive sector. The ongoing electrification of the automotive sector, combined with a desire to increase virtual prototyping, means that engineers are increasingly facing new challenges. Against this background, the numerical models of electric motors, particularly stators, are simplified and homogenized. However, this procedure must be supplemented by experimental data to ensure the high quality and reliability of the simulations. Unfortunately, broad experimental investigations are time-consuming and expensive, underlined by the lack of corresponding literature. For this reason, four different stator configurations were investigated as part of experimental modal analysis to highlight the influence of the stator lamination as well as the winding. The results provide the scientific community with a broad outline of how specific influences change modal parameters of each stator configuration. In particular, the results show that lamination significantly reduces axial stiffness. Highlights of the findings relate to the mode-dependent stiffness, mass, and damping influences due to the winding, with the influence of the stiffness deviating significantly from expectation. It was also found that the selected winding technology dominates the structural dynamic system characteristics. Therefore, it is advisable to include the manufacturing technology intended to be used for the lamination and the winding in the early simulative design phase to improve the model prediction quality.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85084685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaojie Zhang, Yanrong Wang, Dianyin Hu, Rongqiao Wang
Blade Tip Timing (BTT) technology is concerned with the estimation of turbomachinery blade stress. The stress is determined from BTT data by relating the measured tip displacement to the stress via Finite Element (FE) models based on the sensing position. However, the correlation of BTT data with FE predictions involves a number of uncertainties. One of the main ones is the effective positions detected by sensors may deviate from their nominal position due to the blade deformation, which will yield deceptive calibration factors. To deal with this problem, a novel method based on the amplitude ratio and virtual displacement optimization under the distance constraints of sensors installed in different axial positions is proposed to determine the accuracy calibration factors and sensing positions. It realizes the identification of sensing positions without the information of static deformation, and overcomes the inapplicability of the corrected displacement to bending modes. Both synchronous and asynchronous vibrations of five typical vibration modes are discussed to illustrate the applicability of this method. The results show that this method has better performance than traditional method. The prediction errors of bending modes are reduced from 20~30% to 7%, and the maximum error of other modes is reduced from 72% to 23%. In addition, sensitivity analysis is performed to investigate the influence of vibration levels and mode shape inaccuracies. Results demonstrate the great potential of this method in vibration stress determination.
{"title":"A novel method for the determination of blade vibration stress considering the change in blade tip timing sensing position","authors":"Xiaojie Zhang, Yanrong Wang, Dianyin Hu, Rongqiao Wang","doi":"10.1115/1.4062722","DOIUrl":"https://doi.org/10.1115/1.4062722","url":null,"abstract":"\u0000 Blade Tip Timing (BTT) technology is concerned with the estimation of turbomachinery blade stress. The stress is determined from BTT data by relating the measured tip displacement to the stress via Finite Element (FE) models based on the sensing position. However, the correlation of BTT data with FE predictions involves a number of uncertainties. One of the main ones is the effective positions detected by sensors may deviate from their nominal position due to the blade deformation, which will yield deceptive calibration factors. To deal with this problem, a novel method based on the amplitude ratio and virtual displacement optimization under the distance constraints of sensors installed in different axial positions is proposed to determine the accuracy calibration factors and sensing positions. It realizes the identification of sensing positions without the information of static deformation, and overcomes the inapplicability of the corrected displacement to bending modes. Both synchronous and asynchronous vibrations of five typical vibration modes are discussed to illustrate the applicability of this method. The results show that this method has better performance than traditional method. The prediction errors of bending modes are reduced from 20~30% to 7%, and the maximum error of other modes is reduced from 72% to 23%. In addition, sensitivity analysis is performed to investigate the influence of vibration levels and mode shape inaccuracies. Results demonstrate the great potential of this method in vibration stress determination.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91072452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sanders Aspelund, Mahmoud Abdullatif, R. Mukherjee, A. Hellum
Aquatic animals commonly oscillate their fins, tails, or other structures to propel and control themselves in water. These elements are not perfectly rigid, so the interplay between their stiffness and the fluid loading dictates their dynamics. We examine the propulsive qualities of a tail-like flexible beam actuated by a dynamic moment over a range of frequencies and flow speeds. This is accomplished using the equations of fluid-immersed beams in combination with a set of tractable expressions for thrust and efficiency. We solve these expressions over the velocity-frequency plane and show that the flexible propulsor has regions of both positive and negative thrust. We also show the behavior of a sample underwater vehicle with fixed drag characteristics as an illustration of a realizable system.
{"title":"Underwater Propulsion Using Forced Excitation of a Flexible Beam","authors":"Sanders Aspelund, Mahmoud Abdullatif, R. Mukherjee, A. Hellum","doi":"10.1115/1.4062450","DOIUrl":"https://doi.org/10.1115/1.4062450","url":null,"abstract":"\u0000 Aquatic animals commonly oscillate their fins, tails, or other structures to propel and control themselves in water. These elements are not perfectly rigid, so the interplay between their stiffness and the fluid loading dictates their dynamics. We examine the propulsive qualities of a tail-like flexible beam actuated by a dynamic moment over a range of frequencies and flow speeds. This is accomplished using the equations of fluid-immersed beams in combination with a set of tractable expressions for thrust and efficiency. We solve these expressions over the velocity-frequency plane and show that the flexible propulsor has regions of both positive and negative thrust. We also show the behavior of a sample underwater vehicle with fixed drag characteristics as an illustration of a realizable system.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90068404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dynamically substructured systems (DSS) are a typical technique to achieve real-time numerical simulations combined with physically tested components. However, the rigorous feasibility analysis before the implementation is missing. This paper is aimed to fill this gap by establishing rigorous conditions for when DSS is suitable for dynamic testing. The proposed method is based on novel symbolic recursive formulations for the transfer functions describing a generic lumped parameter vibrating structure, enabling the analysis of structural and other properties without requiring the computation of explicit symbolic expressions for the transfer functions involved, representing a significant breakthrough as it allows to perform feasibility analysis in analytical form, rather than solely relying on numerical approaches. The series of analytical conclusions presented in this paper, and future ones unlocked by the proposed approach, will significantly enrich the research in the community of DSS and structural vibrations. In particular, the proposed approach allows performing analysis of causality, controllability and observability using much reduced knowledge of the structure, thus significantly simplifying such analysis. Analytical conclusions on stability can also be made with the help of novel recursive form, removing the need of repeatedly calculating the roots of characteristic equations, a task that can be performed only via numerical approaches and for which analytical results are not available. The proposed methodology can be applied to a whole class of vibration problems and is not linked to any specific structure, going beyond the specific examples available in the literature.
{"title":"On the feasibility of dynamic substructuring for hybrid testing of vibrating structures","authors":"An Hu, P. Paoletti","doi":"10.1115/1.4062256","DOIUrl":"https://doi.org/10.1115/1.4062256","url":null,"abstract":"\u0000 Dynamically substructured systems (DSS) are a typical technique to achieve real-time numerical simulations combined with physically tested components. However, the rigorous feasibility analysis before the implementation is missing. This paper is aimed to fill this gap by establishing rigorous conditions for when DSS is suitable for dynamic testing. The proposed method is based on novel symbolic recursive formulations for the transfer functions describing a generic lumped parameter vibrating structure, enabling the analysis of structural and other properties without requiring the computation of explicit symbolic expressions for the transfer functions involved, representing a significant breakthrough as it allows to perform feasibility analysis in analytical form, rather than solely relying on numerical approaches. The series of analytical conclusions presented in this paper, and future ones unlocked by the proposed approach, will significantly enrich the research in the community of DSS and structural vibrations. In particular, the proposed approach allows performing analysis of causality, controllability and observability using much reduced knowledge of the structure, thus significantly simplifying such analysis. Analytical conclusions on stability can also be made with the help of novel recursive form, removing the need of repeatedly calculating the roots of characteristic equations, a task that can be performed only via numerical approaches and for which analytical results are not available. The proposed methodology can be applied to a whole class of vibration problems and is not linked to any specific structure, going beyond the specific examples available in the literature.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80408449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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