Design Of Damper Research Articles

Pounding Mitigation Design and Real-Time Hybrid Simulation for a Novel Viscous Damper Applied in Bridges

When the actual displacement of viscous damper exceeds the stroke limit, excessive pounding force may be generated, resulting in damage to the damper. To address this issue, a novel viscous damper with variable stiffness, simple processing, and good economy is proposed. First, the load-displacement relation of the novel viscous damper is established through theoretical analysis and experimental studies. Second, numerical simulations and a series of parametric analyses are conducted to analyze the pounding mitigation effect of the proposed damper. Third, real-time hybrid simulation (RTHS) for considering the pounding effect of the novel viscous damper is presented. Finally, design recommendations for the pounding mitigation design of the novel viscous damper are given. The results show that the novel viscous damper effectively reduces the amplitudes of the pounding force and acceleration by 25% and 24%, respectively. The Fourier power of acceleration decreases in the region from 0.6 Hz to 3.3 Hz. The results of RTHS demonstrate that the real-time hybrid testing system can effectively simulate the pounding effect of the proposed damper. However, the normalized error peak value of velocity between RTHS and the reference result exceeds 10%, indicating that the proposed damper considering the pounding effect imposes new requirements to the real-time hybrid testing method.

Multi-stage hysteresis modelling of magnetorheological dampers and experimental verification

An accurate theoretical model is the basis for the structural design and parameter optimisation of magnetorheological dampers (MRDs). Owing to the inability of existing models to accurately describe the motion characteristics of MRDs in the entire region, a multi-stage hysteresis (MSH) model for low-frequency conditions was proposed. The MSH model comprised a magnetic chain model and Bi-Viscous model to describe the characteristics of the pre-yield and yield flow stages, respectively. The local loss and inertia effect were considered in the MSH model. Steady-state and transient finite element methods were combined to analyse the magnetic field distribution during MRD motion, and an equivalent weighted mean magnetic field hypothesis was proposed to reduce the quantisation error and time consumption. The experimental results demonstrate the prediction effectiveness of the MSH model. Moreover, the quantitative evaluation parameters of the flow and hysteresis regions were obtained and the variation trend of the MRD main design indices with the magnetic circuit parameters was analysed. The obtained velocity distribution parameters indicate a smooth transition of the stages in the MSH model from a qualitative perspective. The mixed mode incorporates the physical properties of the shear and flow modes, but cannot simply be regarded as a linear superposition of these two modes.

Tuned Mass Damper Design for Vortex-Induced Vibration Control of a Bridge: Influence of Vortex-Induced Force Model

Existing studies optimized the tuned mass damper (TMD) for vortex-induced vibration (VIV) control of bridges based on an empirical linear model or Scanlan’s nonlinear model, which cannot accurately simulate the effect of the vortex-induced force and hence results in a TMD design that lacks effectiveness or robustness. Four vortex-induced force models are considered to systematically analyze the influence of force models on TMD design for VIV control. The design results based on various vortex-induced force models, as well as three design formulas, are compared in terms of effectiveness and robustness. Numerical results suggest that the empirical linear model and Scanlan’s nonlinear model significantly underestimate the TMD mass ratio required to suppress the VIV amplitude to be lower than a threshold. The empirical linear model may overestimate the robustness of the TMD to changing the frequency ratio, while Scanlan’s nonlinear model may overestimate or underestimate the robustness depending on the threshold VIV amplitude. The TMD design based on the polynomial model is considered more accurate since it can accurately predict VIV responses at various effective damping levels. The aerodynamic envelope model can be used as a convenient model for TMD optimization. The results generated using the free vibration formula are the closest to that of the polynomial model. An appropriate safety factor should be considered to convert the TMD design based on sectional model experiments to real bridges.

Development of a High-Performance Low-Weight Hydraulic Damper for Active Vibration Control of the Main Rotor on Helicopters—Part 1: Design and Mathematical Model

The helicopter vibrations generated by the main rotor/gearbox assembly are the principal cause of damage to cockpit instruments and discomfort of the crew in terms of cabin noise. The principal path of vibration transmission to the fuselage is through the gearbox rigid support struts. With the aim of reducing these vibrations, this paper presents the design of a low-weight high-performance active damper for vibration control developed by Elettronica Aster S.p.A. The system is intended to replace the conventional struts and is composed of an electro-hydraulic actuator hosted within a compliant structure. This parallel nested structure allows the system to reach a high-power density. A physics-based mathematical model was used as a design digital twin to optimize the performance to meet the strict requirements. The active damper was designed for a reference application of a 15-seat medium-sized twin-engine helicopter. The model was used to perform the tests specified in the acceptance and testing procedure document, showing the compliance with the requirements of the current design. The damper physical realization, test bench design, experimental campaign, and model validation will be presented in Part 2.

Pipe vibration attenuation through internal damping and optimal design of vibro-impact systems

Pipelines periodically supported by rack structures (PPRs) are common in chemical and petrochemical plants, among others, and conventional tools such as dampers and hysteretic absorbers are commonly used to mitigate large vibrations in these systems. In this study, we explore two alternative strategies: (i) enhancing the attenuation rate of PPR vibrations through structural internal damping, and (ii) using nonlinear vibro-impact systems (VIS) to reduce seismic vibrations in a PPR. To shed light on the first strategy, we develop analytical dispersion relations for a PPR and show how damping can improve the mitigation capabilities of the periodic system. As for the second strategy, we consider a 9-node beam, i.e., a single span (SS) of a PPR equipped with a VIS, and combine the central composite design (CCD) and Kriging metamodelling to maximize dissipation energy and minimize the number of impacts. This multi-objective optimization problem aims to find the most effective design solution for the VIS in terms of gap and coefficient of restitution (COR). Additionally, we consider the stochastic nature of seismic input and the possible chaotic behavior of the VIS. To account for the sensitive variability of the number of impacts in seismic records, we perform incremental dynamic analyses and calculate fragility functions for various engineering demand parameters, including the number of impacts. We define a 3D surface for selecting the optimal gap-COR pair. When impacts occur, transient results can be chaotic, and we compute the largest Lyapunov exponents of a few representative trajectories.

Viscoelastic damping design – A novel approach for shape optimization of Constrained Layer Damping treatments at different ambient temperatures

Passive damping plays an important role in the vibration mitigation of aeronautic structures. In contrast to active systems, passive damping systems do not require any energy supply. Thus, their readiness is independent, which reduces the failure probability compared to active systems. Constrained Layer Damping (CLD) has become an established treatment for damping bending vibrations. Unlike other passive systems such as shock-mounts, CLD can be compactly integrated into an existing structure as an add-on solution. However, the design scope is limited by mass constraints and the optimal design for maximum damping must be found by optimization. For this purpose, a novel optimization approach is presented. The layer widths of the core and face layers of a CLD structure are treated as design parameters. Compared to the strategy of placing CLD patches on vibration antinodes, the proposed approach provides up to 52 % higher damping. The optimal design of a generic beam structure is determined considering different modes, viscoelastic material stiffnesses and ambient temperatures. Furthermore, the simulated damping is experimentally verified for a shape-optimized beam. The analyses show that the optimal design depends significantly on the viscoelastic material stiffness and is therefore temperature dependent. As a consequence, a generalized design guideline for CLD treatments cannot be derived.

Micro-Scale Mechanical Metamaterial with a Controllable Transition in the Poisson's Ratio and Band Gap Formation.

The ability to significantly change the mechanical and wave propagation properties of a structure without rebuilding it is currently one of the main challenges in the field of mechanical metamaterials. This stems from the enormous appeal that such tunable behavior may offer from the perspective of applications ranging from biomedical to protective devices, particularly in the case of micro-scale systems. In this work, a novel micro-scale mechanical metamaterial is proposed that can undergo a transition from one type of configuration to another, with one configuration having a very negative Poisson's ratio, corresponding to strong auxeticity, and the other having a highly positive Poisson's ratio. The formation of phononic band gaps can also be controlled concurrently which can be very useful for the design of vibration dampers and sensors. Finally, it is experimentally shown that the reconfiguration process can be induced and controlled remotely through application of a magnetic field by using appropriately distributed magnetic inclusions.

Parameters Design of Transverse Seismic Dampers for Complex Bridge Types—an Example of a Double-width Double-tower Cable-stayed Bridge

Large and complex bridges usually have significant nonlinear effects. In the design of seismic and other dynamic characteristics, it is usually impossible to obtain results from simple force calculations. In this paper, taking the mechanical parameters of the complex structure of double wide double tower cable-stayed bridge as an example, a shear damper in seismic field is designed. The experimental results show that: (1) The shear type mild steel damper can improve the lateral seismic performance of cable-stayed bridges. (2) Because the double span cable-stayed bridge is connected by dampers between towers, the mechanical parameters of dampers will affect the natural structure of the bridge, and there is no obvious linear relationship between the yield force of the damper and the bending moment at the bottom of the tower.

Optimal design of SMA damper for vibration control of connected building under random seismic excitation

To alleviate the earthquake induced damages in closely spaced high-rise buildings, linear or non-linear dampers have been frequently employed. Out of different options, the frequently utilized non-linear damper is the yield damper. Yield damper shows good floor displacement control efficiency, but increases peak floor acceleration and leaves large residual deformation at the end of ground motion. Also, it shows degradation in the hysteresis loop; whereas to achieve a good acceleration and displacement control efficiency, it is imperative to have a stable hysteresis loop with negligible residual deformation. In this context, shape memory alloy (SMA) composed damper has been viewed as a potential solution to reduce floor displacement and acceleration, simultaneously. Also, it offers excellent recentering property and good seismic energy dissipation capacity. This research aims to use the above stated superior properties of SMA and investigate the seismic response control efficiency of optimally design SMA damper for connected buildings, and compare with the yield damper. Optimal stochastic responses of connected buildings are estimated under random earthquake, as modeled using the Kanai-Tajimi power spectra. To linearize the non-linear force–displacement behavior of SMA and yield damper, a statistical linearization approach is adopted. The RMS (root mean square) floor acceleration and RMS floor displacement ratios are determined as response outputs for the damper connected buildings. Studies results show that, optimally designed SMA damper is more effective in reducing acceleration of stiff building and displacement of the flexible building than the yield damper. Compared to the yield damper, SMA damper reduces the RMS acceleration ratios by 15 % for the flexible building and 35 % for the stiff building; and RMS displacement by 20 % for the flexible building and 0.5 % for the stiff building. Overall, SMA damper provide much better seismic response control efficiency for connected buildings than yield damper.

Design and Performance Study of Hybrid Channel-valved Magnetorheological Dampers

In order to solve the problem of low damping force caused by low utilization of magnetic field in traditional magnetorheological dampers, a hybrid channel valve type magnetorheological damper with circular channel and disk channel are proposed. The main content of this paper is to design the basic structure of mixed channel valve magnetorheological damper. The mathematical model of damping force based on Bingham plastic model was established from the design of magnetic circuits. The two-dimensional simulation model of MR Damper was established by using EMAG module in ANSYS finite element analysis software, and the magnetic circuit of mixed channel valve MR Damper was simulated and analyzed. The results show that the output damping force of the hybrid channel valve-type magnetorheological damper is 18 KN and the adjustable coefficient is 14.52 with the current I of 3A, the number of coil turns of 560, the axial damping gap of 1 mm and the radial damping gap of 1.5 mm.

Design and Test of Quad-Bundle Spacer Damper Based on a New Rubber Structure

Aiming at improving the handling efficiency and acquiring the satisfactory antivibration effect and damping performance, a quad-bundle spacer damper of 500 kV extra high voltage transmission lines was designed and developed based on a new rubber structure. Firstly, a mathematical vibration model of the spacer damper was constructed, and the structures of the defect-prone parts of the spacer damper were analyzed. Then, the structure was optimized based on the defect analysis, the clamp with fast installation as well as removal and the damper joint with superior performance were designed. On this basis, a new quad-bundle spacer damper was developed. Last but not least, the handling efficiency of the new quad-bundle spacer damper was evaluated, and performance tests were conducted according to the IEC standards. The evaluation and test results show that the handling efficiency, antivibration effect, and damping performance of the new quad-bundle spacer damper are significantly improved compared with those of the regular quad-bundle spacer damper, which provides a guarantee for the safe operation of 500 kV extra high voltage transmission lines.

Energy absorbing multilayered self-recovering metamaterials with chiral topology

A novel energy absorbing material is proposed for the design of shock absorbers and vibrational dampers. A layered architectured microstructure is put forward consisting of the repetition of plane lattices having hexachiral topology with alternate chirality, each being designed as a periodic assembly of rigid disks connected by elastic ligaments. Because of the chiral topology of the single layer, the rotation of the rigid disks takes place when in-plane stress states are applied so implying a relative rotation between the disks of adjacent lattices with opposite chirality. Pins passing through for each stacking of disks impose them the same in-plane displacement. Moreover, frictional dissipative mechanisms at the interface between adjacent disks according to two different compression modes orthogonal to the layers make the metamaterial suitable for either reusing or self-recovering the initial configuration. In the first case the pre-tensioning of the pins implies the compression of plane frictional interfaces. The frictional sliding compatible with the disk relative rotation implies an overall hysteretic bilinear response with remarkable energy dissipation. The metamaterial may be reused once the pins are relaxed and re-tensioned. In the latter case no pre-tension is applied to the pins and the compressive force between the disks is obtained through saw-tooth shaped interfaces between adjacent disks to get elastically constrained transverse dilation when the relative rotations at the interfaces take place. The overall response turns out to be highly dissipative and self-recovering, i.e. able to return to the initial configuration when removing the applied stresses. As shown in the examples the quasi-static behavior of the proposed metamaterial makes it a candidate as an efficient vibration damper and a shock absorber characterized by i) hysteretic response with remarkable energy dissipation under biaxial stress states; ii) reuse or self-recovering after the energy absorption event; iii) bilateral response, i.e. equal behavior under both tension and compression.

A broadband metamaterial damper design based on synergetic coupling among multi-cells

This paper proposes a broadband damping method to achieve broadband vibration absorption by superposition of the working bands of several damping units. The device composes of several local resonant metamaterial dampers with gradient elastic wave band gaps via weak coupling. By integrating the units with band gaps in different frequency ranges in parallel, a linear superposition of the absorption bandwidth can be achieved. This property overcomes the shortcomings of the traditional dynamic vibration absorbers (DVAs) or metamaterial dampers with narrow working bands, and provides a solution for broadband low-frequency vibration attenuation. Compared to conventional multi-degree-of-freedom (MDOF) DVAs, this design belongs to a special metamaterial-based MDOF damper that could satisfy both low damping ratio and weak coupling conditions. As the working bandwidth of each sub-unit could be optimized by changing structural parameters and structural forms, the available design parameters are significantly increased. Moreover, the sizes of the damper device and each sub-unit are sub-wavelength, so the additional mass is greatly lower than that of the traditional DVA. The design method and device proposed in this paper are expected to be widely used in the broadband low-frequency vibration suppression of various types of machinery and equipment.

Optimal design of negative-stiffness dampers for improved efficiency of structural seismic isolation

Over the past two decades, negative-stiffness devices have attracted increasing interest in the community of structural vibration isolation and control. They are typically used in combination with supplemental damping devices, and the combined systems are often referred to as negative-stiffness dampers (NSDs). Different types of NSDs have been developed and studied using both theoretical and experimental methods. However, comprehensive comparative studies between optimally designed NSDs for improving the efficiency of structural seismic isolation are inadequate. In this paper, three types of NSDs, i.e., the negative-stiffness viscous damper (NSVD), negative-stiffness viscoelastic damper (NSVeD), and negative-stiffness inertoviscous damper (NSiVD) are considered and compared in terms of their efficiencies for structural seismic isolation. Analytical formulas are derived to calculate the optimal damping coefficients of the NSVeD and NSiVD to maximize the modal damping ratio, thus minimizing the peak transmissibility. Frequency- and time-domain responses of low-frequency structures separately equipped with the three types of NSDs are compared when they are designed to achieve equal modal damping ratios. Moreover, based on the derived analytical optimal formulas, a multi-objective minimization design method is presented to determine the optimal characteristic parameters of NSDs, and simultaneous reduction of isolator displacement and floor response acceleration of a benchmark base-isolated building structures under a suit of design-level ground motions is achieved. The results indicate that the three types of NSDs can be more effective than conventional viscous dampers in reducing floor response accelerations of base-isolated structures without compromising the isolator displacement, and the NSVeD has superior performance over the NSVD and NSiVD in terms of improved efficiency of structural seismic isolation.

A novel multi-objective optimization of mass dampers for controlling the vortex-induced vibration in bridges

This paper investigates an optimization framework of the four mass dampers for controlling the vortex-induced vibration (VIV) in long-span bridges, including the tuned mass damper (TMD), the series double tuned mass dampers (DTMD) and the inerter-equipped tuned mass damper (ITMD). The equations of motion of the bridge-damper system subjected to the vortex-induced force are established. The vortex-induced amplitude of the girder is analytically given. Furthermore, the optimal design is implemented by taking the vortex-induced amplitude as the constraint condition. Introducing two optimization objectives, the stroke index and the robustness index, a novel bi-objective optimization framework with constraints is proposed and then solved by multiple objective particle swarm optimization (MOPSO). A comparative analysis of the four mass dampers with varying total mass ratios is performed. The results show that the vortex-induced amplitude of the girder is greatly reduced to satisfy the requirement after installing the four optimized mass dampers. Both performances of the two optimization objectives are improved with the increase of the total mass ratio. The inertial device parallel to the spring and dashpot provides no advantage in controlling the VIV in bridges. The DTMD has dramatic robustness to changes in the bridge natural frequency and cannot strongly amplify its stroke, especially under the condition of a small mass ratio. The framework provides an excellent balance between control effect and stability in the VIV of bridges for the optimal design of the mass dampers.

A Damped Double Dipole Antenna for UHF RFID Sensing in the Frequency Domain

Ultrahigh frequency (UHF) radio frequency identification (RFID) tags provide an inexpensive framework for distributed sensing, yet for the most cost-effective implementation, it is necessary to consider antenna design in concert with the capabilities of responsive materials that can be coupled to the tag response. Materials, such as functionalized carbon nanotubes (CNTs), have been engineered to change in resistance when exposed to a variety of analytes and have been incorporated in RFID tags to create low-cost sensors that work at a fixed reader–tag separation distance. This article presents a damped double dipole antenna design enabling UHF RFID tags that are able to sense changes in resistance of a sensing element (with a conductivity similar to that of printed CNT networks) regardless of reader–tag distance within the far-field read range. Simulations of the proposed design show two methods of operation, either by comparing the damping between two resonant peaks or by shifting the resonant frequency of the RFID tag. The first method is validated experimentally with surface mount resistors, showing a relative change in the effective antenna transmission coefficient, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{e}$ </tex-math></inline-formula> , of 0.2 for a 35% change in resistance of the sensing element.

Design and dynamic performance research of MR hydro-pneumatic spring based on multi-physics coupling model

Aiming at the problem that the damping coefficient of the traditional hydro-pneumatic spring cannot be adjusted in real-time, the magnetorheological (MR) damping technology was introduced into the traditional hydro-pneumatic spring with single gas chamber. A new shear-valve mode MR hydro-pneumatic spring was proposed. And its dynamic performance was analyzed based on multi-physical coupling simulation and mechanical property test. Firstly, a structural scheme of MR hydro-pneumatic suspension was proposed to ensure the original height adjustment function based on the working principle of traditional hydro-pneumatic suspension with single gas chamber. Secondly, based on the design requirements, the parameter of MR hydro-pneumatic spring damping structure was designed by using MR damper design method. Thirdly, the multi-physical coupling dynamic performance of the MR hydro-pneumatic spring damping structure was analyzed based on the electromagnetic field analysis theory, flow field analysis theory and thermal field analysis theory. The analysis results showed that the designed MR hydro-pneumatic spring has reasonable magnetic circuit structure and excellent working performance. Then, the mechanical properties of MR hydro-pneumatic spring were tested. The results showed that the maximum damping force can reach 20 kN, and the dynamic adjustable multiple can reach 6.4 times. It has good controllability and meets the design requirements. Finally, a nonlinear model of MR hydro-pneumatic spring was established based on the elastic force calculation model of the gas and the Bouc–Wen model. The simulation results of the established model agree well with the experimental results, which can accurately describe the dynamic properties of the hydro-pneumatic spring. The proposed design and modeling method of the MR hydro-pneumatic spring can provide a theoretical basis for the related vibration damping devices.

Construction of motional phase maps for granular dampers

Harmonically vibrated granular media exhibit a variety of motional behaviours depending on amplitude, frequency, and vibration-to-gravity directional orientation. Motional behaviour defines the physical interactions of particles in the granular media and therefore the energy dissipation performance. A "phase map" that describes motional behaviour over broad ranges of frequency and amplitude is therefore a very useful tool in damper design. However, at present, identification of the operating motional conditions within the granular media has only been conducted by visual observation of the particles following a particle-level simulation or a specifically designed experiment. Because of this, design optimisation over a broad range of amplitude and frequency becomes costly. This paper aims to help reduce this cost through the development of approximate phase maps based on expected dissipative interactions of particles. Three-dimensional discrete element method simulations are conducted over a wide range of excitation intensities under two different vibration-to-gravity directional orientations (i.e., perpendicular, and parallel to the standard gravity direction) to allow the observation of as many motional phases as possible. The effect of particle size, volume filling ratio and particle shape on granular energy dissipation sources are also investigated.

Design and experimental characterization of a bypass magnetorheological damper featuring variable stiffness and damping

Magnetorheological (MR) fluid dampers (MRFDs) with variable stiffness and variable damping capability (VSVD-MRFDs) have demonstrated excellent vibration mitigation performance. However, there are limited studies on the development of bypass VSVD-MRFDs which offer both higher dynamic range and output force, apart from simple maintenance and straightforward assembly. In this study, a novel large-capacity VSVD-MRFD with an annular-radial bypass MR valve, as opposed to the typical practice of implementing the valve within the traveling piston in the hydraulic cylinder of the MRFD, is proposed. The main contribution of the present work includes: (a) providing the conceptional design and experimental dynamic characterization of the proposed VSVD-MRFD; (b) investigating the feasibility of the proposed damper for realizing the VSVD characteristics under wide ranges of loading conditions. A test rig was, thus, designed to perform experimental characterization of the proposed VSVD-MRFD under wide ranges of mechanical loading and magnetic field conditions. A qualitative analysis including force-displacement, and force-velocity characteristics, together with a quantitative analysis including dynamic range, equivalent viscous and stiffness coefficients, were conducted as a function of loading frequency, displacement amplitude, and applied current. Results showed a maximum dynamic range and maximum output force of 4.5 and 7.8 kN, respectively. Also, the maximum relative increase in the equivalent viscous and stiffness coefficients were obtained, respectively, as 425% and 488%, when the applied current is increased from zero to 2 A. The results confirm the potential of the proposed VSVD-MRFD for applications in off-road suspension systems. The externally designed bypass MR valve permits a straightforward design modification for realizing wide scalability of damping force in different applications (e.g., off-road vehicle suspension systems).

Tuned Mass Damper Design of Substation Post Switchgear in Gale Area

Post switchgear of substation in a gale area is a typical wind-sensitive structure. In order to reduce the wind-induced response of substation post switchgear in a gale area, in this paper, according to the theoretical formula of the optimal frequency ratio and the optimal damping ratio of TMD given by Den Hartog, a tuned mass damper (TMD) is proposed to reduce the vibration of the first-order vibration mode outside the plane of the structure. The Simulink simulation model of the simplified structure with TMD is established and the fluctuating wind speed of the equipment is simulated by the Kaimal wind speed spectrum. The wind vibration control effect of TMD is checked, and the rationality of the TMD design is verified.