Accepted Manuscripts

Yuting Wang and Marc P. Mignolet
J. Vib. Acoust   doi: 10.1115/1.4036277
Component-centric reduced order models (ROMs) are introduced here as small-size ROMs providing an accurate prediction of the linear response of part of a structure (the ? component) without focusing on the rest of it (the ? component). Craig-Bampton (CB) substructuring methods are first considered. In one method, the ? component response is modeled with its fixed interface modes while the other adopts singular value eigenvectors of the ? component deflections of the linear modes of the entire structure. The deflections in the ? component induced by harmonic motions of these ? component modes are processed by a proper orthogonal decomposition to model the ? component response. A third approach starts from the linear modes of the entire structure which are dominant in the ? component response. Then, the contributions of other modes in this part of the structure are approximated in terms of those of the dominant modes with close natural frequencies and similar mode shapes in the ? component, i.e., these non-dominant modal contributions are “lumped” onto dominant ones. This lumping permits to increase the accuracy in the ? component at a fixed number of modes. The three approaches are assessed on a structural finite element model of a 9-bay panel with the modal lumping-based method yielding the most “compact” ROMs. Finally, good robustness of the ROM to changes in the ? component properties (e.g., for design optimization) is demonstrated and a similar sensitivity analysis is carried out with respect to the loading under which the ROM is constructed.
TOPICS: Design, Modeling, Optimization, Deflection, Dynamic response, Eigenvalues, Finite element model, Principal component analysis, Robustness, Sensitivity analysis, Mode shapes
Magnus Knutsson and Mats Abom
J. Vib. Acoust   doi: 10.1115/1.4036276
The necessity of reducing CO2 emissions has lead to an increased number of passenger cars that utilizes turbo charging to maintain performance when the IC-engines are downsized. Charge air coolers are used on turbocharged engines to enhance the overall gas exchange efficiency. Cooling of charged air increases the air density and thus the volumetric efficiency and also increases the knock margin (for petrol engines). The acoustic properties of charge coolers have so far not been extensively treated in the literature. Since it is a large component with narrow flow passages it includes major resistive as well as reactive properties. Therefore it has the potential to largely affect the sound transmission in air intake systems and should be accurately considered in the gas exchange optimization process. In this paper a frequency domain acoustic model of a charge air cooler for a passenger car is presented. The cooler consists of two conical volumes connected by a matrix of narrow ducts where the cooling of the air takes place. A recently developed model for sound propagation in narrow ducts that takes into account the attenuation due to thermoviscous boundary layers and interaction with turbulence is combined with a multiport representation of the tanks to obtain an acoustic two-port representation where flow is considered. The predictions are compared with experimental data taken at room temperature and show good agreement. Sound transmission loss increasing from 5 to over 10 dB in the range 50-1600 Hz is demonstrated implying good noise control potential.
TOPICS: Acoustics, Modeling, Coolers, Automobiles, Ducts, Sound, Flow (Dynamics), Cooling, Noise control, Turbulence, Temperature, Turbochargers, Acoustical properties, Boundary layers, Internal combustion engines, Gasoline engines, Turbocharged engines, Emissions, Carbon dioxide, Optimization, Density
T.Y. Li, P. Wang, X. Zhu, J. Yang and W.B. Ye
J. Vib. Acoust   doi: 10.1115/1.4036209
A sound-structure interaction model is established to study the vibro-acoustic characteristics of a semi-submerged cylindrical shell using the wave propagation approach (WPA). The fluid free surface effect is taken into account by satisfying the sound pressure release condition. Then, the far-field sound pressure is predicted with shell's vibration response using the stationary phase method. Modal coupling effect arises due to the existence of fluid free surface. New approaches, diagonal coupling acoustic radiation model (DCARM) and column coupling acoustic radiation model (CCARM) are proposed to handle this problem. New approaches are approved to be able to deal with the modal coupling problem efficiently with a good accuracy at significantly reduced computational cost. Numerical results also indicate that the sound radiation characteristics of a semi-submerged cylindrical shell are quite different from those from the shell fully immersed in fluid. But the far-field sound pressure of a semi-submerged shell fluctuates around that from the shell ideally immersed in fluid. These new approaches can also be used to study the vibro-acoustic problems of cylindrical shells partially coupled with fluid.
TOPICS: Sound pressure, Pipes, Excitation, Fluids, Acoustics, Shells, Radiation (Physics), Sound, Wave propagation, Vibration
Lun Liu, Dengqing Cao, Jin Wei, Xiaojun Tan and Tianhu Yu
J. Vib. Acoust   doi: 10.1115/1.4036213
An approach is proposed to obtain the global analytical modes (GAMs) and establish discrete dynamic model with low degree of freedom for a three-axis attitude stabilized spacecraft installed with a pair of solar arrays. The flexible spacecraft is simplified as a hub-plate system which is a typical rigid-flexible coupling system. The governing equations of motion and corresponding boundary conditions are derived by using the Hamiltonian Principle. Describing the rigid motion and elastic vibration of all system components with a uniform set of generalized coordinates, the system GAMs are solved from those dynamic equations and boundary conditions, which are used to discretize the equations of motion. For comparison, another discrete model is also derived using assumed mode method (AMM). Using ANSYS software, a finite element model is established to verify the GAM and AMM models. Subsequently, the system global modes are investigated using the GAM approach. Further, the performance of GAM model in dynamic analysis and cooperative control for attitude motion and solar panel vibration is assessed by comparing with AMM model. The discrete dynamic model based on GAMs has the capability to carry out spacecraft dynamic analysis in the same accuracy as a high-dimensional AMM model. The controller based on GAM model can suppress the oscillation of solar panels and make the control torque stable in much shorter time.
TOPICS: Vibration control, Space vehicles, Dynamic modeling, Equations of motion, Dynamic analysis, Solar energy, Vibration, Boundary-value problems, Dynamic models, Degrees of freedom, Computer software, Finite element model, Solar cell arrays, Hamilton's principle, Oscillations, Torque, Control equipment
Takashi Ikeda and Yuji Harata
J. Vib. Acoust   doi: 10.1115/1.4036211
Passive control of vibrations in an elastic structure subjected to horizontal, harmonic excitation by utilizing a nearly square liquid tank is investigated. When the natural frequency ratio 1:1:1 is satisfied among the natural frequencies of the structure and the two predominant sloshing modes (1,0) and (0,1), the performance of a nearly square tank as a tuned liquid damper (TLD) is expected to be superior to rectangular TLDs due to internal resonance. In the theoretical analysis, Galerkin's method is used to determine the modal equations of motion for liquid sloshing considering the nonlinearity of sloshing. Then, van der Pol's method is used to obtain the expressions for the frequency response curves for the structure and sloshing modes. Frequency response curves and bifurcation set diagrams are shown to investigate the influences of the aspect ratio of the tank cross section and the tank installation angle on the system response. From the theoretical results, the optimal values of the system parameters can be determined in order to achieve maximum efficiency of vibration suppression for the structure. Hopf bifurcations occur and amplitude modulated motions may appear depending on the values of the system parameters. Experiments were also conducted, and the theoretical results agreed well with the experimental data.
TOPICS: Vibration control, Resonance, Sloshing, Bifurcation, Frequency response, Equations of motion, Dampers, Vibration, Vibration suppression, Theoretical analysis, Passive control, Excitation
W. Fan and W. D. Zhu
J. Vib. Acoust   doi: 10.1115/1.4036210
A new locking-free formulation of a three-dimensional shear-deformable beam with large deformations and large rotations is developed. The position of the centroid line of the beam is integrated from its slope that is related to the rotation of a corresponding cross-section and stretch and shear strains. The rotation is parametrized by a rotation vector, which has a clear and intuitive physical meaning. Taylor polynomials are used for certain terms that have zero denominators to avoid singularity in numerical implementation. Since the rotation vector can have singular points when its norm equals 2mπ, where m is a nonzero integer, a rescaling strategy is adopted to resolve the singularity problem when there is only one singular point at a time instant, which is the case for most engineering applications. Governing equations of the beam are obtained using Lagrange's equations for systems with constraints, and several benchmark problems are simulated to show the performance of the current formulation. Results show that the current formulation do not suffer from shear and Poisson locking problems that the absolute nodal coordinate formulation can have. Results from the current formulation for a planar static case are compared with its exact solutions, and they are in excellent agreement with each other, which verifies accuracy of the current formulation. Results from the current formulation are compared with those from commercial software ABAQUS and RecurDyn, and they are in good agreement with each other; the current formulation uses much fewer numbers of elements to yield converged results.
TOPICS: Shear (Mechanics), Rotation, Deformation, Engineering systems and industry applications, Computer software, Polynomials
Dean R. Culver and Earl. H Dowell
J. Vib. Acoust   doi: 10.1115/1.4036212
The RMS response of various points in a system comprised of two parallel plates coupled at a point undergoing high frequency, broadband transverse point excitation of one component is considered. Through this prototypical example, Asymptotic Modal Analysis (AMA) is extended to two coupled continuous dynamical systems. It is shown that different points on the plates respond with different RMS magnitudes depending on their spatial relationship to the excitation or coupling points in the system. The ability of AMA to accurately compute the RMS response of these points (namely the excitation point, the coupling points, and the hot lines through the excitation or coupling points) in the system is shown. The behavior of three representative prototypical configurations of the parallel plate system: two similar plates (in both geometry and modal density), two plates with similar modal density but different geometry, and two plates with similar geometry but different modal density. After examining the error between reduced modal methods (such as AMA) to Classical Modal Analysis (CMA), it is determined that these several methods are valid for each of these scenarios. The data from the various methods will also be useful in evaluating the accuracy of other methods including SEA.
TOPICS: Density, Dynamic systems, Plates (structures), Errors, Geometry, Seas, Modal analysis, Excitation
Jie Yuan, Fabrizio Scarpa, Branislav Titurus, Giuliano Allegri, Sophoclis Patsias and Ramesh Rajasekaran
J. Vib. Acoust   doi: 10.1115/1.4036110
The work investigates the application of a novel frame model to reduce the computational cost of the mistuning analysis of bladed disc systems. A full-scale finite element (FE) model of the bladed disc is considered as benchmark. The single blade frame configuration is identified via an optimization process. The individual blades are then assembled by 3D springs, whose parameters are determined via calibration process. The dynamics of the novel beam frame assembly is also compared to those obtained from three state-of-the-art FE-based reduced order models (ROMs): a lumped parameter approach; a Timoshenko beam assembly, and component mode synthesis (CMS) based techniques with free and fixed interfaces. The development of these classical ROMs to represent the bladed disc is also addressed in detail. A methodology to perform the mistuning analysis is then proposed and implemented. A comparison of the modal properties and forced response dynamics between the aforementioned ROMs and the full-scale FE model is presented. The case study demonstrates that the beam frame assembly can predict the variations of the blade amplitude factors with results being in agreement with the full-scale FE model. The CMS based ROMs underestimate the maximum amplitude factor, while the results obtained from beam frame assembly are generally conservative. The beam frame assembly is 4 times more computationally efficient than the CMS fixed-interface approach. This study proves that the beam frame assembly can efficiently predict the mistuning behavior of bladed discs when low order modes are of interest.
TOPICS: Disks, Manufacturing, Blades, Finite element model, Dynamics (Mechanics), Springs, Calibration, Finite element analysis, Optimization
Stefano Campagnari, Francesca di Matteo, Stefano Manzoni, Matteo Scaccabarozzi and Marcello Vanali
J. Vib. Acoust   doi: 10.1115/1.4036108
This paper deals with a new method to estimate axial load in tie-rods by means of indirect measurements. The knowledge of this information is of great importance to assess the health of the tie-rod itself and of the whole structure, which the beam is inserted in. The method is based on dynamic measurements and require the experimental estimation of the tie-rod eigenfrequencies and mode shapes in a limited number of points. Furthermore, the approach requires to develop a simple finite element model, which is then cross-correlated with the experimental data by means of a model updating procedure. Extensive numerical simulations and experimental tests demonstrated the capability of the new approach to give accurate estimates of the tie-rod axial load as well as to overcome some limitations of the methods currently available in literature.
TOPICS: Stress, Tie rods, Modal analysis, Computer simulation, Mode shapes, Finite element model
Hornsen TZOU, Bolei Deng and Huiyu LI
J. Vib. Acoust   doi: 10.1115/1.4036097
The converse flexoelectric effect, i.e., the polarization (or electric field) gradient induced internal stress (or strain), can be utilized to actuate and control flexible structures. This study focuses on the microscopic actuation behavior and effectiveness of a flexoelectric actuator patch laminated on an elastic ring shell. An atomic force microscope (AFM) probe is placed on the upper surface of the flexoelectric patch to induce an inhomogeneous electric field resulting in internal stresses of the actuator patch. The flexoelectric stress-induced membrane control force and bending control moment regulate the ring vibration and their actuation mechanics, i.e., transverse and circumferential control actions, are respectively studied. For the transverse direction, the electric field gradient quickly decays along the ring thickness, resulting in a nonuniform transverse distribution of the induced stress and this distribution profile is not influenced by the actuator thickness. The flexoelectric induced circumferential membrane control force and bending control moment resemble the Dirac delta functions at the AFM contact point. The flexoelectric actuation can be regarded as a localized drastic bending to the ring. To evaluate the actuation effect, dynamic responses and controllable displacements of the elastic ring with flexoelectric actuations are analyzed with respect to design parameters, such as the flexoelectric patch thickness, AFM probe radius, ring thickness and ring radius.
TOPICS: Vibration control, Shells, Atomic force microscopy, Electric fields, Actuators, Stress, Membranes, Probes, Polarization (Light), Design, Structural mechanics, Vibration, Dynamic response, Flexible structures, Polarization (Waves), Polarization (Electricity)
Sachiko Ishida, Hiroshi Uchida, Haruo Shimosaka and Ichiro Hagiwara
J. Vib. Acoust   doi: 10.1115/1.4036096
In this paper, a novel vibration isolator based on a foldable cylinder with Kresling’s pattern is proposed, and the performance of the proposed isolator in terms of preventing structural vibration is numerically evaluated. It is known that foldable cylinders with Kresling’s pattern provide bi-stable folding motions under specific conditions. For simplification, a foldable cylinder with Kresling’s pattern is modeled using horizontal, longitudinal, and diagonal truss elements connected by rotational joints and enforced by Ramen frames, while maintaining the bi-stability of the structure. Additional linear springs are incorporated into the structure in order to obtain a nonlinear spring with quasi-zero-stiffness characteristics. It is numerically established that the combined structure (i) does not have resonant frequencies and (ii) decreases the vibration response even at high frequencies when it is used around the equilibrium position at which the spring stiffness is quasi-zero.
TOPICS: Design, Numerical analysis, Vibration isolators, Stiffness, Cylinders, Springs, Vibration, Resonance, Stability, Trusses (Building), Equilibrium (Physics)
Tatsuya MIURA, Tsuyoshi INOUE and Hiroshi KANO
J. Vib. Acoust   doi: 10.1115/1.4036098
This paper demonstrates nonlinear theoretical analysis of a flexible rotor system supported by a full-circular journal bearing focusing on the bifurcation phenomenon in the vicinity of the bifurcation point. A third order polynomial approximation model is used for the representation of the oil film force of the journal bearing. The reduced order model, with modes concerning bifurcation, is deduced using the center manifold theory. The dynamical equation in the normal form relating the bifurcation which leads to the oil whirl is obtained using the normal form theory. The influences of various parameters are investigated based on the analysis of a deduced dynamical equation in the normal form. Furthermore, the validity of the derived analytical observation is confirmed by comparing it with the numerically obtained frequency response result.
TOPICS: Rotors, Bifurcation, Journal bearings, Frequency response, Manifolds, Polynomial approximation, Theoretical analysis, Whirls
Seunghun Baek and Bogdan Epureanu
J. Vib. Acoust   doi: 10.1115/1.4036105
A technique for generating reduced order models (ROMs) of bladed disks with small geometric mistuning is proposed. Discrepancies in structural properties (mistuning) from blade to blade can cause a significant increase in the maximum vibratory stress. The effects of mistuning have been studied over the past few decades. Many researchers have studied the dynamic behavior of mistuned bladed disks by using ROMs. Many of these techniques rely on the fact that the modes of a mistuned system can be approximated by a linear combination of modes of the corresponding tuned system. In addition, the tuned system modes have been modeled in component mode mistuning by using modal participation factors of cantilevered blade modes. Such techniques assume that mistuning can be well modeled as variations in blade alone frequencies. However, since geometric deformations contain stiffness and mass variations, mistuning can no longer be captured by cantilevered blade modes alone. To address this, several studies have focused on large and small geometric mistuning. These studies exploited the difference between tuned (with perturbed geometry) and nominal tuned mode shapes. In this work, we extend on that approach and devote particular attention to the development of ROMs of bladed disks with small geometric mistuning. The methodology requires only sector-level calculations and therefore can be applied to highly refined, realistic models of industrial size.
TOPICS: Deformation, Stress, Mechanical properties, Disks, Blades, Geometry, Stiffness, Mode shapes
Guanhua Mei, Jiazhong Zhang and Can Kang
J. Vib. Acoust   doi: 10.1115/1.4036103
In order to accurately study the effect of curvature on panel aeroelastic behaviors, a fluid-structure coupling algorithm is adopted to analyze the curved panel flutter in transonic and supersonic airflows. First, the governing equation for the motion of the curved panel and the structure solver are presented. Then the fluid governing equations, the fluid solver and the fluid-structure coupling algorithm are introduced briefly. Finally, rich aeroelastic responses of the curved panel are captured using this algorithm. And the mechanisms of them are explored by various analysis tools. It is found that the curvature produces initial aerodynamic load above the panel. Thus the static aeroelastic deformation exists for the curved panel in stable state. At Mach 2, with its stability lost on this static aeroelastic deformation, the curved panel shows asymmetric flutter. At Mach 0.8 and 0.9, the curved panel exhibits only positive static aeroelastic deformation due to this initial aerodynamic load. At Mach 1.0, as the dynamic pressure increases, the curved panel loses its static and dynamic stability in succession, and behaves static aeroelastic deformation, divergence and flutter consequentially. At Mach 1.2, with its stability lost, the curved panel flutters more violently towards the negative direction. The results obtained could guide the panel design and panel flutter suppression for flight vehicles with high performances.
TOPICS: Fluids, Air flow, Flutter (Aerodynamics), Algorithms, Deformation, Stress, Stability, Pressure, Design, Vehicles, Dynamic stability, Flight
April Bryan
J. Vib. Acoust   doi: 10.1115/1.4035958
This research presents a study of the free vibration of the thin, shallow elliptical shell. The equations of motion for the elliptical shell, which are developed from Love's equations, are coupled and non-linear. In this research, a new approach is introduced to uncouple the transverse motion of the shallow elliptical shell from the in-surface coordinates. Through the substitution of the strain-compatibility equation into the differential equations of motion in terms of strain, an explicit relationship between the curvilinear surface strains and transverse strains is determined. This latter relationship is then utilized to uncouple the spatial differential equation for transverse motion from that of the surface coordinates. The approach introduced provides a more explicit relationship between the surface and transverse coordinates than could be obtained through use of the Airy Stress Function. Angular and Radial Mathieu equations are used to obtain solutions to the spatial differential equation of motion. Since the recursive relationships that are derived from the Mathieu equations lead to an infinite number of roots, not all of which are physically meaningful, the solution to the eigenvalue problem is used to determine the mode shapes and eigenfrequencies of the shallow elliptical shell. The results of examples demonstrate that the eigenfrequencies of the thin shallow elliptical shell are directly proportional to the curvature of the shell and inversely proportional to the shell's eccentricity.
TOPICS: Free vibrations, Shells, Differential equations, Eigenvalues, Stress, Equations of motion, Mode shapes
Jinhong Qu, Clark B. Teeple and Kenn Oldham
J. Vib. Acoust   doi: 10.1115/1.4035959
A dynamic model is developed for small-scale robots with multiple high-frequency-actuated compliant elastic legs and a rigid body. The motion of the small-scale robots results from dual-direction motion of piezoelectric actuators attached to the legs, with impact dynamics increasing robot locomotion complexity. A dynamic model is developed to describe the small-scale robot motion in the presence of variable properties of the underlying terrain. The dynamic model is derived from beam theory with appropriate boundary and loading conditions and considers each robot leg as a continuous structure moving in two directions. Robot body motion is modeled in up to five degrees of freedom using a rigid body approximation for the central robot chassis. Individual modes of the resulting multi-mode robot are treated as second order linear systems. The dynamic model is tested with two different centimeter-scale robot prototypes having an analogous actuation scheme to millimeter-scale micro-robots. In accounting for the interaction between the robot and ground, a dynamic model using the first two modes of each leg shows good agreement with experimental results for the centimeter-scale prototypes, in terms of both magnitude and the trends in robot locomotion with respect to actuation conditions.
TOPICS: Robots, Modeling, Vibration, Contact dynamics, Dynamic models, Engineering prototypes, Robot motion, Degrees of freedom, Approximation, Linear systems, Piezoelectric actuators, Dynamics (Mechanics), Euler-Bernoulli beam theory, Accounting
DaeYi Jung and Hans A. DeSmidt
J. Vib. Acoust   doi: 10.1115/1.4035814
Due to inherent nonlinearity of the autobalancer, the potential for other, undesirable, non-synchronous limit-cycle vibration exists. In such undesirable situations, the balancer masses do not reach their desired synchronous balanced steady-state positions resulting in increased rotor vibration. Such behavior has been widely studied and is well understood for rotor systems on idealized bearings with symmetric supports. However, a comprehensive study into this non-linear behavior of an imbalanced planar rigid rotor/ABD system mounted on a general bearing holding asymmetric damping and stiffness forces including non-conservative effects cross-coupling ones has not been fully conducted. Therefore, this research primarily focuses on the unstable non-synchronous limit-cycle behavior of and the synchronous balancing condition of system under the influence of the general bearing support. Here, solutions for rotor limit-cycle amplitudes and corresponding whirl speeds are obtained via a harmonic balance approach. Furthermore, the limit-cycle stability is assessed via perturbation and Floquet analysis and all possible responses including undesirable coexistence for the bearing parameters and operating speeds have been thoroughly studied. It is found that, due to asymmetric behavior of bearing support, the multiple limit cycles are encountered in the range of supercritical speeds and more complicate coexistences are invited into the ABD-rotor system compared to the case with idealized symmetric bearing supports. The findings in this paper yield important insights for researchers wishing to utilize automatic balancing devices in more practical rotor systems mounted on a asymmetric general bearing support.
TOPICS: Rotors, Vibration, Bearings, Limit cycles, Stability, Damping, Rotor vibration, Steady state, Stiffness, Whirls
Technical Brief  
Mahdi Farahikia and Quang Su
J. Vib. Acoust   doi: 10.1115/1.4035813
Obtaining Head-Related Transfer Functions (HRTFs) is a challenging task, in spite of its importance in localizing sound in a 3D environment or improving the performance of hearing aids, among their various applications. In this paper, an optimized finite element method through adaptive dimension size based on wavelength (frequency) for acoustic scattering analyses using ANSYS is presented. Initial investigation of the validity of our method is conducted by simulating scattered sound field for a solid sphere exposed to a far-field plane sound wave at 100 (equally spaced in logarithmic scale) frequencies between 20 and 20k Hz. Comparison of the equivalent HRTF results between the two methods shows a maximum deviation of less than 0.6 dB between our method and the analytical solution depending on the angle of rotation of the sphere with respect to sound source.
TOPICS: Scattering (Physics), Acoustics, Transfer functions, Radiation scattering, Finite element methods, Electromagnetic scattering, Dimensions, Sound waves, Wavelength, Rotation
Xi Wang, Bintang Yang and Hu Yu
J. Vib. Acoust   doi: 10.1115/1.4035781
The inevitable manufacturing errors of rotational machineries cause vibration of multi-frequency. This paper presents a multi-dynamic vibration absorber (MDVA) to suppress the vibration of multi-frequency. The MDVA consists of two parts, and each part includes three dynamic vibration absorbers (DVA) with equal mass but different stiffness values. In order to improve the robustness of the system, an optimization method to obtain the optimal damping values of each DVA is proposed based on dynamic response. The objective function of optimization aims to flatten the frequency response of the primary system with the changeable excitation and reduce the vibration level in a limited frequency bandwidth. The multi-frequency vibration suppression is experimentally verified. To achieve the optimal damping values, the magnetic dampers are applied in the tests. The experimental results indicate that the sensitivity of the system is reduced and the robustness of the system is enhanced, which are coincident with the simulations.
TOPICS: Design, Vibration absorbers, Excitation, Vibration, Damping, Optimization, Robustness, Stiffness, Vibration suppression, Dynamic response, Errors, Frequency response, Engineering simulation, Manufacturing, Simulation, Dampers
Technical Brief  
Jiaxi Zhou, Kai Wang, Daolin Xu, Huajiang Ouyang and Yingli Li
J. Vib. Acoust   doi: 10.1115/1.4035715
A platform supported by a hexapod of quasi-zero-stiffness (QZS) struts is proposed to provide a solution for low-frequency vibration isolation in six degrees of freedom (DOFs). The QZS strut is developed by combining a pair of mutually repelling permanent magnets in parallel connection with a coil spring. Dynamic analysis of the 6-DOF QZS platform is carried out to obtain dynamic responses by using the Harmonic Balance method, and the vibration isolation performance in each DOF is evaluated in terms of force/moment transmissibility, which indicates that the QZS platform perform a good function of low-frequency vibration isolation within broad bandwidth, and has notable advantages over its linear counterpart in all six DOFs.
TOPICS: Vibration isolation, Stiffness, Dynamic response, Springs, Permanent magnets, Struts (Engineering), Degrees of freedom, Dynamic analysis

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