Traditional vibration isolation of satellite instruments has an inherent limitation—that low-frequency vibration suppression leads to structural instability. This paper explores a parallel-coupled quasi-zero stiffness (QZS) vibration isolator for an axially loaded beam, with the goal of enhancing the effectiveness of low-frequency isolation. A QZS contains two magnetic rings, which contribute negative stiffness, and one spiral spring, with positive stiffness, a combination that has high static stiffness to resolve the structural instability. The frequency response functions (FRFs) of power flow are used to measure the effectiveness of vibration isolation. The magnetic stiffness of the magnetic rings is calculated using the principle of equivalent magnetic charge. The heights, radii, and gap of the magnetic rings affect its stiffness. The parallel-coupled QZS vibration isolator of an axially loaded beam is modeled using an energy method. Based on the Galerkin truncation, harmonic balance analysis, and arc-length continuation, an approach is proposed to analyze the FRFs of power flow for the parallel-coupled QZS vibration isolation of an axially loaded beam. Numerical results support the analytical results. Both analytical and numerical results show that the power reduction of axially loaded beams with a parallel-coupled quasi-zero vibration isolation system is more significantly suppressed at low frequencies.
{"title":"Energy Transfer of an Axially Loaded Beam with a Parallel-Coupled Nonlinear Vibration Isolator","authors":"Ze-Qi Lu, Wen-Hang Liu, H. Ding, Liqun Chen","doi":"10.1115/1.4054324","DOIUrl":"https://doi.org/10.1115/1.4054324","url":null,"abstract":"\u0000 Traditional vibration isolation of satellite instruments has an inherent limitation—that low-frequency vibration suppression leads to structural instability. This paper explores a parallel-coupled quasi-zero stiffness (QZS) vibration isolator for an axially loaded beam, with the goal of enhancing the effectiveness of low-frequency isolation. A QZS contains two magnetic rings, which contribute negative stiffness, and one spiral spring, with positive stiffness, a combination that has high static stiffness to resolve the structural instability. The frequency response functions (FRFs) of power flow are used to measure the effectiveness of vibration isolation. The magnetic stiffness of the magnetic rings is calculated using the principle of equivalent magnetic charge. The heights, radii, and gap of the magnetic rings affect its stiffness. The parallel-coupled QZS vibration isolator of an axially loaded beam is modeled using an energy method. Based on the Galerkin truncation, harmonic balance analysis, and arc-length continuation, an approach is proposed to analyze the FRFs of power flow for the parallel-coupled QZS vibration isolation of an axially loaded beam. Numerical results support the analytical results. Both analytical and numerical results show that the power reduction of axially loaded beams with a parallel-coupled quasi-zero vibration isolation system is more significantly suppressed at low frequencies.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"18 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84648265","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}
Two types of liquid hole-pattern seals with axially-oblique (A-HPS) or circumferentially-oblique (C-HPS) hole cavities are designed. To evaluate the leakage and rotordynamic characteristics of the liquid hole-pattern seals, a 3D transient perturbation method is employed, which based on the multi-frequency one-dimensional rotor whirling model and the mesh deformation technique. The accuracy and reliability of the proposed numerical approach is demonstrated based on the published experimental data of the leakage and rotordynamic force coefficients for a hole-pattern seal (HPS). Seal leakage and force coefficients are presented and compared for the A-HPS (axially-oblique angle α = −30° −30°), C-HPS (circumferentially-oblique angle β = −30° − 30°), and HPS (α = 0, β = 0) at various rotational speeds (n=0.05, 2.0, 4.0, and 6.0 krpm). Results reveal that the tilted hole cavity with positive α or β can reduce the seal effective clearance and strengthen the kinetic dissipation in hole cavities, yielding less leakage by 5%-10%, especially at higher rotational speeds. The tilted hole cavity with a positive oblique angle (α = 30°, β = 30°) results in a moderate growth (by ~6% for the A-HPS, by ~15% for C-HPS) in the effective stiffness. Further, the tilted hole cavity shows a very weak influence (< 4.0%) on the effective damping, particularly for higher rotational speeds and vibration frequencies. Considering the decreasing leakage and non-worse rotordynamic characteristics, a tilted hole cavity with suitable positive oblique angles (10°~30°) is beneficial for the liquid hole-pattern seal.
{"title":"NUMERICAL INVESTIGATIONS ON STATIC AND ROTORDYNAMIC CHARACTERISTICS FOR TWO TYPES OF LIQUID HOLE-PATTERN SEALS WITH TILTED CAVITIES","authors":"Z. Fang, Zhigang Li, Jun Li","doi":"10.1115/1.4054323","DOIUrl":"https://doi.org/10.1115/1.4054323","url":null,"abstract":"\u0000 Two types of liquid hole-pattern seals with axially-oblique (A-HPS) or circumferentially-oblique (C-HPS) hole cavities are designed. To evaluate the leakage and rotordynamic characteristics of the liquid hole-pattern seals, a 3D transient perturbation method is employed, which based on the multi-frequency one-dimensional rotor whirling model and the mesh deformation technique. The accuracy and reliability of the proposed numerical approach is demonstrated based on the published experimental data of the leakage and rotordynamic force coefficients for a hole-pattern seal (HPS). Seal leakage and force coefficients are presented and compared for the A-HPS (axially-oblique angle α = −30° −30°), C-HPS (circumferentially-oblique angle β = −30° − 30°), and HPS (α = 0, β = 0) at various rotational speeds (n=0.05, 2.0, 4.0, and 6.0 krpm). Results reveal that the tilted hole cavity with positive α or β can reduce the seal effective clearance and strengthen the kinetic dissipation in hole cavities, yielding less leakage by 5%-10%, especially at higher rotational speeds. The tilted hole cavity with a positive oblique angle (α = 30°, β = 30°) results in a moderate growth (by ~6% for the A-HPS, by ~15% for C-HPS) in the effective stiffness. Further, the tilted hole cavity shows a very weak influence (< 4.0%) on the effective damping, particularly for higher rotational speeds and vibration frequencies. Considering the decreasing leakage and non-worse rotordynamic characteristics, a tilted hole cavity with suitable positive oblique angles (10°~30°) is beneficial for the liquid hole-pattern seal.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"10 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81533648","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}
Reduced order models (ROMs) provide an efficient, kinematically condensed representation of computationally expensive high dimensional dynamical systems; however, their accuracy depends crucially on the accurate estimation of their dimension. We here demonstrate how the energy closure criterion, developed in our prior work, can be experimentally implemented to accurately estimate the dimension of ROMs obtained using the proper orthogonal decomposition (POD). We examine the effect of using discrete data with and without measurement noise, as will typically be gathered in an experiment or numerical simulation, on estimating the degree of energy closure on a candidate reduced subspace. To this end, we used a periodically kicked Euler-Bernoulli beam with Rayleigh damping as the model system, and studied ROMs obtained by applying POD to discrete displacement field data obtained from simulated numerical experiments. An improved method for quantifying the degree of energy closure is presented: the convergence of energy input to or dissipated from the system is obtained as a function of the subspace dimension, and the dimension capturing a predefined percentage of either energy is selected as the ROM-dimension. This method was found to be more robust to data discretization error and measurement noise. The data processing necessary for the experimental application of energy closure analysis is discussed in detail. We show ROMs formulated from the simulated data using our approach accurately capture the dynamics of the beam for different sets of parameter values.
{"title":"Experimental Implementation of Energy Closure Analysis for Reduced Order Modeling","authors":"Suparno Bhattacharyya, J. Cusumano","doi":"10.1115/1.4054295","DOIUrl":"https://doi.org/10.1115/1.4054295","url":null,"abstract":"\u0000 Reduced order models (ROMs) provide an efficient, kinematically condensed representation of computationally expensive high dimensional dynamical systems; however, their accuracy depends crucially on the accurate estimation of their dimension. We here demonstrate how the energy closure criterion, developed in our prior work, can be experimentally implemented to accurately estimate the dimension of ROMs obtained using the proper orthogonal decomposition (POD). We examine the effect of using discrete data with and without measurement noise, as will typically be gathered in an experiment or numerical simulation, on estimating the degree of energy closure on a candidate reduced subspace. To this end, we used a periodically kicked Euler-Bernoulli beam with Rayleigh damping as the model system, and studied ROMs obtained by applying POD to discrete displacement field data obtained from simulated numerical experiments. An improved method for quantifying the degree of energy closure is presented: the convergence of energy input to or dissipated from the system is obtained as a function of the subspace dimension, and the dimension capturing a predefined percentage of either energy is selected as the ROM-dimension. This method was found to be more robust to data discretization error and measurement noise. The data processing necessary for the experimental application of energy closure analysis is discussed in detail. We show ROMs formulated from the simulated data using our approach accurately capture the dynamics of the beam for different sets of parameter values.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"8 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82411015","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 Inductrack system, which provides a novel way to achieve magnetic levitation by using Halbach arrays of permanent magnets (PMs), has been extensively studied in the past two decades. The transient responses of the Inductrack system in operation are physically unavoidable and unignorable. Due to the complexities of the electro-magneto-mechanical coupling in the system, most analyses of the Inductrack system rely on steady-state results, and consequently cannot fully capture the dynamic behaviors of the system in transient scenarios. In this article, a new 3-DOF transient model of the Inductrack system is proposed. This model describes the rigid-body motion of the Inductrack vehicle with axial (longitudinal) and vertical (transverse) displacements and pitch rotation, and it is derived without any assumption of steady-state quantities. Compared to a recently available 2-DOF lumped-mass model developed by the authors, the inclusion of the pitch rotation in the new model results in a much more complicated mechanism of electro-magneto-mechanical coupling. Numerical results show that the pitch rotation can have significant effect on the dynamic response and stability of the Inductrack system, which necessities vibration control for the safe operation of the Inductrack system.
{"title":"Dynamic Modeling and Transient Response of a Rigid-Body Inductrack Maglev System","authors":"Ruiyang Wang, Bing Yang","doi":"10.1115/1.4054296","DOIUrl":"https://doi.org/10.1115/1.4054296","url":null,"abstract":"\u0000 The Inductrack system, which provides a novel way to achieve magnetic levitation by using Halbach arrays of permanent magnets (PMs), has been extensively studied in the past two decades. The transient responses of the Inductrack system in operation are physically unavoidable and unignorable. Due to the complexities of the electro-magneto-mechanical coupling in the system, most analyses of the Inductrack system rely on steady-state results, and consequently cannot fully capture the dynamic behaviors of the system in transient scenarios. In this article, a new 3-DOF transient model of the Inductrack system is proposed. This model describes the rigid-body motion of the Inductrack vehicle with axial (longitudinal) and vertical (transverse) displacements and pitch rotation, and it is derived without any assumption of steady-state quantities. Compared to a recently available 2-DOF lumped-mass model developed by the authors, the inclusion of the pitch rotation in the new model results in a much more complicated mechanism of electro-magneto-mechanical coupling. Numerical results show that the pitch rotation can have significant effect on the dynamic response and stability of the Inductrack system, which necessities vibration control for the safe operation of the Inductrack system.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"6 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84804939","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 current study investigates the noise generation of an orifice jet upon impingement over different corrugated geometries for different nozzle pressure ratios. Semi-circular corrugations of different pitch lengths are considered for this study. A comparison of corrugated geometries is made with the flat plate. A standoff distance of 3.5 times jet diameter is considered. Several tones and their harmonics of the feedback loops established between the orifice exit and the plates are analyzed. The far-field acoustic spectra show that the corrugated geometries emit less noise at subsonic speed compared to supersonic speed. A reduction of overall sound pressure level (OASPL) up to a range of 3 dB to 8 dB is observed for the corrugated plate compared to the base plate at the subsonic range. The tonal noise is reduced for the corrugated geometries at all NPRs. The wavelength of the primary tones is compared with the pitch length of semi-circular corrugations. This indicates that semi- circular corrugations reduce the wavelength of fundamental tones and increase the time required to complete the feedback loop. Schlieren images show the presence of the acoustic feedback loop and standing waves near the impingement region for the flat plate. The flow field in between the semi-circular corrugations is analyzed by solving the large eddy simulation. The directivity study shows a reduction in OASPL value at the upstream direction at NPR 4 and 4.8 for the corrugated geometries.
{"title":"Tonal noise suppression of an underexpanded orifice jet upon impingement over corrugated geometries","authors":"D. Sarangi, Krishnamurthy Srinivasan","doi":"10.1115/1.4054254","DOIUrl":"https://doi.org/10.1115/1.4054254","url":null,"abstract":"\u0000 The current study investigates the noise generation of an orifice jet upon impingement over different corrugated geometries for different nozzle pressure ratios. Semi-circular corrugations of different pitch lengths are considered for this study. A comparison of corrugated geometries is made with the flat plate. A standoff distance of 3.5 times jet diameter is considered. Several tones and their harmonics of the feedback loops established between the orifice exit and the plates are analyzed. The far-field acoustic spectra show that the corrugated geometries emit less noise at subsonic speed compared to supersonic speed. A reduction of overall sound pressure level (OASPL) up to a range of 3 dB to 8 dB is observed for the corrugated plate compared to the base plate at the subsonic range. The tonal noise is reduced for the corrugated geometries at all NPRs. The wavelength of the primary tones is compared with the pitch length of semi-circular corrugations. This indicates that semi- circular corrugations reduce the wavelength of fundamental tones and increase the time required to complete the feedback loop. Schlieren images show the presence of the acoustic feedback loop and standing waves near the impingement region for the flat plate. The flow field in between the semi-circular corrugations is analyzed by solving the large eddy simulation. The directivity study shows a reduction in OASPL value at the upstream direction at NPR 4 and 4.8 for the corrugated geometries.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"61 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80281187","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}
Saint-Venant's method to solve the Poisson equation is applied to the Helmholtz equation which governs membrane vibration. A family of non-circular membrane shapes with N-fold rotational symmetry is presented. Membrane shapes, properties and fundamental frequencies are tabulated. The solutions are exact and can serve as accuracy standards for approximate methods.
{"title":"Exact Solution of a Class of Non-Circular Vibrating Membranes","authors":"C.Y. Wang","doi":"10.1115/1.4054256","DOIUrl":"https://doi.org/10.1115/1.4054256","url":null,"abstract":"\u0000 Saint-Venant's method to solve the Poisson equation is applied to the Helmholtz equation which governs membrane vibration. A family of non-circular membrane shapes with N-fold rotational symmetry is presented. Membrane shapes, properties and fundamental frequencies are tabulated. The solutions are exact and can serve as accuracy standards for approximate methods.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"22 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78943740","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}
Recent studies have shown that reconfigurable acoustic arrays inspired from rigid origami structures can be used to radiate and focus acoustic waves. Yet, there is a need for exploration of single-degree-of-freedom deployment to be integrated with such arrays for sake of tailoring wave focusing. This research explores a reconfigurable acoustic array inspired from a regular Miura-ori unit cell and threefold-symmetric Bricard linkage. The system focuses acoustic waves and has single-degree-of-freedom motion when incorporated with a modified threefold-symmetric Bricard linkage. Three configurations of the array are analyzed where array facets that converge towards the center axis are considered to vibrate like baffled pistons and generate acoustic waves into the surrounding fluid. An analytical model is constructed to explore the near-field acoustic focusing behavior of the proposed acoustic array. The wave focusing capabilities of the array are verified through proof-of-principle experiments. The results show that the wave focusing of the array is influenced by the geometric parameters of the facets and relative distance of facets to the center axis, in agreement with simplified ray acoustics estimates. These findings underscore the fundamental relationship between focusing sound radiators and geometric acoustics principles. The results encourage broader exploration of acoustic array designs inspired from integrated single-degree-of-freedom linkages and origami structures for sake of straightforward array deployment and reconfiguration.
{"title":"Acoustic wave focusing from reconfigurable acoustic arrays based on a Bricard-Miura synthesis","authors":"Christopher S. Bentley, R. Harne","doi":"10.1115/1.4054252","DOIUrl":"https://doi.org/10.1115/1.4054252","url":null,"abstract":"\u0000 Recent studies have shown that reconfigurable acoustic arrays inspired from rigid origami structures can be used to radiate and focus acoustic waves. Yet, there is a need for exploration of single-degree-of-freedom deployment to be integrated with such arrays for sake of tailoring wave focusing. This research explores a reconfigurable acoustic array inspired from a regular Miura-ori unit cell and threefold-symmetric Bricard linkage. The system focuses acoustic waves and has single-degree-of-freedom motion when incorporated with a modified threefold-symmetric Bricard linkage. Three configurations of the array are analyzed where array facets that converge towards the center axis are considered to vibrate like baffled pistons and generate acoustic waves into the surrounding fluid. An analytical model is constructed to explore the near-field acoustic focusing behavior of the proposed acoustic array. The wave focusing capabilities of the array are verified through proof-of-principle experiments. The results show that the wave focusing of the array is influenced by the geometric parameters of the facets and relative distance of facets to the center axis, in agreement with simplified ray acoustics estimates. These findings underscore the fundamental relationship between focusing sound radiators and geometric acoustics principles. The results encourage broader exploration of acoustic array designs inspired from integrated single-degree-of-freedom linkages and origami structures for sake of straightforward array deployment and reconfiguration.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"2009 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82523051","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 bistable Nonlinear Energy Sink (NES) shows high efficiency in mitigating vibration through Targeted Energy Transfer (TET). It performs well in low and high energy input cases, whereas, for a cubic NES, TET occurs only above a certain energy threshold. In this work, the measure of energy pumping time is extended to a harmonic excitation case by the application of a particular integration assumption. An equivalent point in the SIM structure can represent the average variation of the amplitudes of LO and NES. The marked robustness of this semi-analytical prediction method under parameter perturbation is investigated numerically here. The influence of parameters on the rate at which the amplitude declines is also investigated for both impulsive and harmonic excitation. The pumping time estimation is validated in a low energy input experimental test.
{"title":"Estimation of energy pumping time in bistable NES and experimental validation","authors":"Zhenhang Wu, S. Seguy, M. Paredes","doi":"10.1115/1.4054253","DOIUrl":"https://doi.org/10.1115/1.4054253","url":null,"abstract":"\u0000 The bistable Nonlinear Energy Sink (NES) shows high efficiency in mitigating vibration through Targeted Energy Transfer (TET). It performs well in low and high energy input cases, whereas, for a cubic NES, TET occurs only above a certain energy threshold. In this work, the measure of energy pumping time is extended to a harmonic excitation case by the application of a particular integration assumption. An equivalent point in the SIM structure can represent the average variation of the amplitudes of LO and NES. The marked robustness of this semi-analytical prediction method under parameter perturbation is investigated numerically here. The influence of parameters on the rate at which the amplitude declines is also investigated for both impulsive and harmonic excitation. The pumping time estimation is validated in a low energy input experimental test.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"6 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78693722","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}
Low-frequency vibration suppression is challenging in practical engineering problems due to the harsh requirement for vibration reduction devices, which requires constant low stiffness over a wide amplitude range. A passive tuned mass damper (TMD) composed of a positive stiffness module (PSM) in parallel with a negative stiffness module (NSM) is proposed, which are implemented by serial double-parallelograms (DP) and parallel-DP, respectively. The PSM has a large deflection range of constant stiffness for a given beam length, while the NSM offers negative stiffness within certain deflection range when applied with axial load above the critical threshold. Based on the closed-form modeling of the stiffness modules using the beam constraint model (BCM), the design and analysis of the PSM and NSM are carried out considering the nonlinearity under large deflections. Afterward, with the structure of TMD implemented, its stiffness characteristics and low-frequency tunability are experimentally validated. Finally, the application on a suspension bridge model shows that a maximum of 29.8 dB vibration reduction of low-frequency mode is attained within the frequency range of interest. The proposed TMD well attenuates the vibrations excited by sweep sinusoidal and harmonic excitations under prespecified threshold levels of acceleration.
{"title":"Design and application of double-parallelograms-based tuned mass damper for low-frequency vibration absorption","authors":"Wenshuo Ma, Jingjun Yu, Yiqing Yang","doi":"10.1115/1.4054255","DOIUrl":"https://doi.org/10.1115/1.4054255","url":null,"abstract":"\u0000 Low-frequency vibration suppression is challenging in practical engineering problems due to the harsh requirement for vibration reduction devices, which requires constant low stiffness over a wide amplitude range. A passive tuned mass damper (TMD) composed of a positive stiffness module (PSM) in parallel with a negative stiffness module (NSM) is proposed, which are implemented by serial double-parallelograms (DP) and parallel-DP, respectively. The PSM has a large deflection range of constant stiffness for a given beam length, while the NSM offers negative stiffness within certain deflection range when applied with axial load above the critical threshold. Based on the closed-form modeling of the stiffness modules using the beam constraint model (BCM), the design and analysis of the PSM and NSM are carried out considering the nonlinearity under large deflections. Afterward, with the structure of TMD implemented, its stiffness characteristics and low-frequency tunability are experimentally validated. Finally, the application on a suspension bridge model shows that a maximum of 29.8 dB vibration reduction of low-frequency mode is attained within the frequency range of interest. The proposed TMD well attenuates the vibrations excited by sweep sinusoidal and harmonic excitations under prespecified threshold levels of acceleration.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"54 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78823662","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}
Ning Jia, Zhilong Peng, Yin Yao, P. Wei, Shaohua Chen
Scattering of an elastic wave by cavities yields dynamic stress concentration around the cavities. When the characteristic size of the cavities shrinks to the nanometer scale, the surface effect becomes prominent. Based on a recently proposed theory of surface elastodynamics, the dynamic stress concentration factor (DSCF) in the scattering of a plane P wave by a spherical nanocavity has been investigated. Not only the surface energy effect but also the surface inertial effect is considered. The former depends on two easily-determined surface material parameters, namely, the bulk surface energy density and the surface relaxation parameter, whereas the latter is related to the surface mass density. Interestingly, due to the surface relaxation of nanocavity, a constant elastic field exists in the elastic medium even without any dynamic loadings. Furthermore, it is found that when the radius of cavity is at the nanoscale, the surface energy effect as well as the surface inertial effect has a significant influence on DSCF. The former attenuates the maximum DSCF, whereas the latter enhances it. With the increasing incident P wave frequency, the dominant role transits from the surface energy effect to the surface inertial effect. This indicates that the DSCF around the nanocavity can be properly tuned by adjusting the incident wave frequency, the cavity radius and the surface material parameters. The results can not only enable a deeper understanding of the surface effects on DSCF around the nanocavities, but also provide a guide for designing nanoporous materials exhibiting efficient dynamic performance.
{"title":"Dynamic stress concentration factor around a spherical nanocavity under a plane P wave","authors":"Ning Jia, Zhilong Peng, Yin Yao, P. Wei, Shaohua Chen","doi":"10.1115/1.4054053","DOIUrl":"https://doi.org/10.1115/1.4054053","url":null,"abstract":"\u0000 Scattering of an elastic wave by cavities yields dynamic stress concentration around the cavities. When the characteristic size of the cavities shrinks to the nanometer scale, the surface effect becomes prominent. Based on a recently proposed theory of surface elastodynamics, the dynamic stress concentration factor (DSCF) in the scattering of a plane P wave by a spherical nanocavity has been investigated. Not only the surface energy effect but also the surface inertial effect is considered. The former depends on two easily-determined surface material parameters, namely, the bulk surface energy density and the surface relaxation parameter, whereas the latter is related to the surface mass density. Interestingly, due to the surface relaxation of nanocavity, a constant elastic field exists in the elastic medium even without any dynamic loadings. Furthermore, it is found that when the radius of cavity is at the nanoscale, the surface energy effect as well as the surface inertial effect has a significant influence on DSCF. The former attenuates the maximum DSCF, whereas the latter enhances it. With the increasing incident P wave frequency, the dominant role transits from the surface energy effect to the surface inertial effect. This indicates that the DSCF around the nanocavity can be properly tuned by adjusting the incident wave frequency, the cavity radius and the surface material parameters. The results can not only enable a deeper understanding of the surface effects on DSCF around the nanocavities, but also provide a guide for designing nanoporous materials exhibiting efficient dynamic performance.","PeriodicalId":49957,"journal":{"name":"Journal of Vibration and Acoustics-Transactions of the Asme","volume":"25 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74361404","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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