Structural Damping Research Articles

Enhancing stiffness and damping characteristics in nacreous composites through functionally graded tablet design

Nacreous composites offer significant potential for applications in structural damping materials, which require simultaneous high stiffness and damping properties. In this study, we propose that the incorporation of functionally graded tablets into nacreous composites can further enhance both stiffness and damping energy dissipation concurrently. Analytical formulae for the loss modulus, storage modulus, and loss factor, validated through a series of finite element analyses, were derived to investigate the effects of variations in tablet modulus, structural geometry, and constituent properties. Our analyses demonstrate that designing a parabolic modulus distribution in the tablets can yield optimal strengthening and damping results. Furthermore, the characteristic modulus variation degree, overlap length, and frequency emerged from the systematic optimization of loss and storage moduli. Additionally, numerical experiments and model predictions demonstrate that the loss modulus of functionally graded nacreous composites surpasses the predetermined design limit and is five times greater than that of existing homogeneous nacreous composites. Combining the developed theoretical model presented here with advanced 3D printing techniques would offer effective guidelines for designing and fabricating high-performance bio-inspired structural damping composites.

Multiple Tuned Mass Dampers and Double Tuned Mass Dampers for Soft Story Structures: A Comparative Study

Recent seismic events have highlighted the vulnerability of reinforced concrete buildings, especially soft-story structures, to damage and collapse during strong earthquakes due to the ground's vibrational response. This study aims to mitigate these adverse vibrations using passive control mechanisms, particularly tuned mass dampers (TMDs). Conventional TMDs require a substantial mass to effectively influence the structure's lateral reactions. The research explores the use of multi-tuned mass dampers (MTMDs) and double-tuned mass dampers (DTMDs) in a soft-story building. The study uses MATLAB to estimate TMD parameters and subject the models to seismic loading. The comparative assessment of these models reveals the potential benefits of using MTMD and DTMD systems to enhance the seismic resilience of soft-story structures.

Thermal Conductivity and Temperature Dependency of Magnetorheological Fluids and Application Systems-A Chronological Review.

Many studies on magnetorheological fluid (MRF) have been carried out over the last three decades, highlighting several salient advantages, such as a fast phase change, easy control of the yield stress, and so forth. In particular, several review articles of MRF technology have been reported over the last two decades, summarizing the development of MRFs and their applications. As specific examples, review articles have been published that include the optimization of the particles and carrier liquid to achieve minimum off-state viscosity and maximum yield stress at on-state, the formulation of many constitutive models including the Casson model and the Herschel-Bulkley (H-B) model, sedimentation enhancement using additives and nanosized particles, many types of dampers for automotive suspension and civil structures, medical and rehabilitation devices, MRF polishing technology, the methods of magnetic circuit design, and the synthesis of various controllers. More recently, the effect of the temperature and thermal conductivity on the properties of MRFs and application systems are actively being investigated by several works. However, there is no review article on this issue so far, despite the fact that the thermal problem is one of the most crucial factors to be seriously considered for the development of advanced MRFs and commercial products of application systems. In this work, studies on the thermal conductivity and temperature in MRFs themselves and their temperature-dependent application systems are reviewed, respectively, and principal results are summarized, emphasizing the following: how to reduce the temperature effect on the field-dependent properties of MRFs and how to design an application system that minimizes the thermal effect. It is noted here that the review summary is organized in a chronological format using tables.

Experiment and optimization of a damping structure system with distributed multiple unidirectional single-particle dampers

Although particle dampers are characterized by a wide damping frequency band, flexible arrangement, and applicability to harsh environments, they have three shortcomings: their performance is difficult to simulate, insufficient research has been conducted on the damping effect they exert on multi-story structures, and there are no methods for evaluating their performance. Therefore, the aim of this research was to develop a Multiple Unidirectional Single-Particle Damper (MUSPD). Firstly, the simulation element of the MUSPD was established by analyzing its damping mechanism, following which the values of the parameters in the element were determined. Secondly, a series of shaking table tests were performed to investigate the damping effect of the MUSPD and demonstrate the accuracy of the simulation. Thirdly, the optimal layout of the MUSPD was proposed based on an analysis of the relationship between particle mass, particle movement distance, and damping effect. Fourthly, a dynamic method for evaluating the damping effect of the MUSPD was proposed. Finally, the rationality and feasibility of the optimal layout scheme and the method for evaluating the MUSPD in multi-story structures were verified by a case analysis. The test results demonstrated that the damping rate of MUSPD for displacement peaks in multi-story structures reached 21.40 %, with a root mean square damping rate of 36.50 %. Additionally, for acceleration peaks, MUSPD achieved a damping rate of 25.12 %, with a root mean square damping rate of 38.10 %. MUSPD exhibited a significant damping effect on multi-story structures. The comparison between test results and simulation results showed that the simulation element of the MUSPD exhibited good accuracy; Simulation analysis results revealed that the optimal layout scheme and dynamic evaluation method were reasonable and effective.

Large-Strain Vibrations of Axially Stretched Hyperelastic Rods

Fast-moving soft robotics usually suffer large-strain deformation with a relatively high velocity. To improve their performance, it is necessary to study the underly dynamical mechanism. However, the inherent strong material nonlinearity brings considerable difficulties in modeling and calculating the soft structure’s nonlinear dynamics. This work focuses on the large-strain vibrations of the hyperelastic rod under an axial tensile force. Several typical hyperelastic models, including the neo-Hookean, Mooney, and Yeoh models, are used to derive the equations governing the rod’s dynamics. The equations based on these models are relatively complex, and their corresponding numerical calculation diverges in some cases. Therefore, a reference stretch ratio(s) polynomial fitting (RSRPF) model is proposed to derive the concise governing equation. Such a governing equation is effectively solved by the combination of the Galerkin discretization and the fourth-order Runge–Kutta integration algorithm. The correctness of the developed model and the employed algorithm is verified by comparing with the previous data of a hyperelastic membrane. In most cases, the rod periodically vibrates under a periodic tensile force. However, when the structural damping is small and the load frequency approaches the resonant frequency, the hyperelastic rod may quasi-periodically vibrate. The revealed large-strain vibration mechanism is supposed to be useful for guiding the dynamical design of soft structures.

Evaluation of the damping characteristics of a hybrid piezo-shunt nanocomposite using a two-step homogenization approach

Composite materials containing piezoelectric particles have attracted remarkable attention because of their distinctive electromechanical conversion characteristics. These supreme properties lead to their applications in various fields, such as vibration damping of structures. The damping parameter of dynamic systems is crucial, especially when they undergo resonance phenomena. Multi-phase polymer matrix composites consisting of piezoelectric particles are innovative material systems that have been recently introduced to convert the mechanical vibrations into electrical energy, and subsequently dissipate into heat through an internal electrical circuit. The present study aims to analytically investigate the viscoelastic characteristics of a shunted three-phase composite composed of a polymer matrix, electrically conductive nanoparticles and piezoelectric particles. The effective viscoelastic characteristics of a shunted composite are calculated using one- and two-step homogenization procedures and by considering the viscoelastic characteristics of constituent materials. The influence of several key parameters, namely, the non-dimensional frequency, the volume fraction of electrically conductive nanoparticles and piezoelectric particles, and the shape of the inclusions, on viscoelastic characteristics, such as phase angles, the storage modulus and loss modulus, are examined. The viscoelastic characteristics are considerably affected by these parameters, and the perceived behavior is justified by the governing equations. The assessment of results confirms that the damping characteristics can be improved by careful selection of a volume fraction of constituent materials and control of the excitation frequency of the smart composite, while avoiding additional costs and likely inconveniences in the fabrication process.

Longtime behavior of the weakly coupled Euler-Bernoulli plate system with structural damping

In this paper, we study the longtime behavior of the weakly coupled Euler-Bernoulli plate system with one structural damping. The system consists of two plate equations coupled by zero order terms. First, we show that when the coupling coefficient function is a nonzero constant and the damping coefficient function is a positive constant, the optimal energy decay rate of the system is t−23. Then we consider the case that the coupling and damping coefficient functions have compact supports. By Carleman estimate and the frequency domain method, we show that the energy of the system decays logarithmically when the supports of the coupling and damping coefficient functions satisfy suitable assumptions.

Numerical-Computational Model for Dynamic Nonlinear Analysis of Frames With Semi-Rigid Connection Considering the Damping Effect

Objective: the scope of this work is to present a numerical-computational model for transient dynamic nonlinear analysis of frames with geometric nonlinearity and semi-rigid connection. Methodology: the equation of motion, which describes the structural dynamical system, is solved by the a-Generalized direct integration method associated with the standard Newton-Raphson method. The structures are discretized through the co-rotational formulation of the Finite Element Method considering the Euler-Bernoulli beam theory. The semi-rigid connection of structural members (beam-column and beam-support) is simulated by a connection element with zero length, which is described in terms of axial, translational and rotational stiffness. Results and conclusion: From the numerical results of three structural systems (bi-fixed beam, L-shaped frame, and single-story frame) obtained with the free Scilab program, it is concluded that the definition of the type of connection is an important factor to be considered in the analysis of frames subjected to dynamic loads. Furthermore, structural damping, which is a measure of energy dissipation, drives the structure from a vibrating state to a resting state. Research implications: Structural Engineering has been designing systems that cannot be analyzed and dimensioned without dynamic effects being considered. lack of knowledge of the levels and characteristics of the dynamic response can lead to system failure during the application of repetitive loading due to accumulation of structural damage. In this sense, the numerical model can represent a valuable engineering tool when it comes to the dynamic analysis of plane metallic structures with geometric nonlinearity.

On the influence of joining processes on the vibration of structures

The joining of new and dissimilar materials in the transportation sector, to meet the demands for lighter structures, requires the use of alternative joining processes. However, it is not clear how different types of structural joints compare in terms of their contribution to the vibration and damping of structures. The present work aims to provide a comprehensive experimental and numerical analysis on the contribution of three structural joints – butt friction stir welding, single lap adhesive joint and hole hemmed joint – to the vibration and damping of two joined aluminium sheets. For this purpose, experimental analysis is performed to study the free-free vibration of the three structural joints. In addition, finite element models are developed to better understand the behaviour of these joints and discuss the challenges of the numerical modelling procedure. The first four natural frequencies, experimentally obtained for each structure, suggest that the adhesive joint has significantly higher natural frequencies, due to the thickness increase at overlap, while the hole hemmed joint presents the most significant contribution to damping, owing to sliding at the overlap region. The numerical models show a very good agreement with the experimental results in terms of the natural frequencies and mode shapes, with simple modelling providing accurate results. In conclusion, the main findings are that the adhesive joints allow for a stiffer structure, with the natural frequencies increasing with the overlap dimension, while hole hemming enhances damping. The butt-butt friction stir welding has a small effect on the structural behaviour, showing a similar dynamic stiffness and damping when compared to a solid sheet of the same dimension.

Research on Vibration Damping Analysis of UHV Suspended Converter Valve Model

The UHV (ultra high voltage) suspended converter valve is hinged to the top of the valve hall, so the equipment has a long structural period, the suspended converter valve is displaced under the action of earthquakes, and the valve tower is susceptible to damage due to interaction with the important equipment connected to it. The high cost, large size, and weight of the real type of UHV suspended converter valve make it difficult to carry out shaking table test studies of the real type of equipment. In this paper, a numerical model of a UHV-suspended converter valve scaling device and its damping structure model are established, and a damping analysis study with damping at the top of the converter valve model is carried out. The analysis showed that the maximum displacement of the converter tower was 136.3 mm under the action of a 0.4 g El-Centro earthquake. With horizontal damping at the top, the maximum displacement of the converter tower is 62.9 mm, a reduction of 53.9% compared to the undamped case. This study proposes a vibration damping design for UHV suspended converter valve, laying the foundation for subsequent shaker test studies of the scaled-down model vibration damping structure of the UHV suspended converter valve and the productization of vibration dampers for the equipment.

Increased modal damping of undamped single and multiscale acoustic black hole panels.

The acoustic black hole (ABH) effect has been shown to increase damping of structures by focusing energy into a tapered-thickness region with added damping material. This paper illustrates that enhanced damping can be achieved without the use of damping material. Three panels were designed with different ABH grid patterns and parameters and compared to a baseline panel. Increased damping is shown to exist for two of the three ABH panels even though no damping material was applied. The panel modes which exhibited increased damping were local to the ABH grid while global modes did not exhibit increased damping.

Analiza mehanizma disipacije energije međukatno izolirane konstrukcije utemeljena na zaostajanju u fazi

Owing to the existence of the isolation layer, a phase lag phenomenon occurs between the superstructure and substructure of a story isolation structure. This phenomenon causes a phase difference between the superstructure and substructure; furthermore, the generated phase difference has a significant impact on the structural damping effect. To study this effect, we established a two-mass model of an inter-story isolated structure, derived the phase difference formula, analysed the impact of the phase difference on the damping effect of the modelled inter-story isolated structure and obtained the optimal phase difference to achieve the best damping effect; in addition, we combined the principle of minimum base shear and optimal phase difference to optimise the damping of the structural isolation layer with different mass ratios. Based on the optimal damping, an energy balance equation was established from the viewpoint of energy. The energy transfer and consumption under different phase differences were analysed to further discuss the relationship between phase differences and the damping effect of the inter-story isolated structure.

Finite element model updating of a plate type structure made of composite material using a network of PZT

Ambient vibrations are one of the most unpredicted, undesired, and uncontrolled destructive causes of sudden failure for many types of structural systems, predominantly those made of FRP thin plates. FRP thin plates may undergo dramatic collapse beneath the periodic ambient loads associated with frequencies, particularly those approaching natural frequencies. Much research has been done over the last few decades to enhance the structural damping behaviour capabilities of thin plates against ambient vibrations via several means and systems of active vibration control. Recent, exceptional advancements in the field of smart materials and their applications in the field of active vibration control have provided a viable alternative to conventional vibration control tools (sensors/actuators). For instance, the coupled properties inherited by PWAS were utilised to develop durable, compact, and efficient actuators/sensors. To minimize the influence of the disparity between the theoretical and actual dynamic structure performances, the numerical FEM has to be updated using real structural data. In the present study, a model update of the structural parameters of a smart beam is carried out by employing PWAS as smart vibration control tools (sensor/actuator) that have been previously installed on the substrate structure. A finite element model is developed to mimic this intelligent beam. Then, laboratory experiments are undertaken to determine system parameters, which are used to update the finite element model. Finally, optimization is done to minimize the FEM variance in the designated structure vibration response from the real one.

The effect of structural damping on flow-induced vibration of a thin elliptical cylinder

This study experimentally investigates the influence of structural damping on the transverse flow-induced vibration (FIV) of an elastically mounted thin elliptical cylinder. The cylinder tested has an elliptical ratio of $\varepsilon = b/a = 5$ , where $a$ and $b$ are the streamwise and cross-flow dimensions, respectively, and a mass ratio (i.e. the total oscillating mass/the displaced fluid mass) of $17.4$ . The FIV response was characterised over a reduced velocity range of $2.30 \leq U^* = U/(\,{{f_{{nw}}}} b) \leq 10.00$ (corresponding to a Reynolds number range of $300 \leq \textit {Re} =(U b)/\nu \leq 1300$ ) and a structural damping ratio range of $3.62\times 10^{-3}\leq \zeta \leq 1.87\times 10^{-1}$ . Here, $U$ is the free stream velocity, ${{f_{{nw}}}}$ is the natural frequency of the system in quiescent fluid (water) and $\nu$ is the kinematic viscosity of the fluid. The FIV response was characterised by four wake–body synchronisation regimes (defined as the matching of the dominant fluid forcing and oscillation frequencies, and labelled regime I, regime II, regime III and the hyper branch) and a desynchronisation region, with the hyper branch representing a high amplitude regime not observed for a circular cylinder. Interestingly, the major vortex shedding mode was predominately two single opposite-signed vortices shed per body vibration cycle. Moreover, hydrogen-bubble-based flow visualisations revealed a secondary vortex street forming in the elongated shear layers associated with largest-scale vibration amplitudes ( $A^* = A/b$ up to $7.7$ ) in the hyper branch and regime II. As the structural damping ratio was increased beyond $1.92 \times 10^{-2}$ , the hyper branch was found to be suppressed. The results have potential ramifications for the efficient extraction of energy from free-flowing water sources, which has become increasingly topical over the last decade.

Design, analysis and optimization of a hybrid fluid flow magnetorheological damper based on multiphysics coupling model

Magnetorheological (MR) dampers are widely used in industrial applications due to its simple structure, fast response and adjustable damping performance. However, the volume of the MR damper will be limited by the installation space, which hinders the application to some extent. In this paper, a hybrid fluid flow MR damper which can be used in antiseismic building is designed to achieve better damping performance under constrained volume size. The multiphysics coupling simulation model and circuit simulation model are also established. Numerical results show the output damping force is 6.367 kN, the dynamic adjustable range is 50.768, and the current input time is 31 ms under the applied current of 2.0 A. In order to improve the dynamic performance of the designed MR damper under constrained volume size, a multi-objective structural optimization method based on theoretical calculation model is proposed. Experiments are also conducted to investigate the dynamic performance of the initial and optimal MR damper. Compared with the initial MR damper, the output damping force and the dynamic adjustable range of the optimal damper are improved by 6.6 % and 46.3 %, while the energy consumption is reduced by 10.7 %, respectively.

An artificial intelligence approach to design periodic nonlinear oscillator chains under external excitation with stable damped solitons

In this paper, an artificial intelligence approach is developed to create a metamodel of damped solitons in periodic nonlinear oscillator chains under external excitation. Unlike resonators subjected to parametric excitation, chains subjected exclusively to external excitation do not have known analytical solutions for Intrinsic Localized Modes (ILMs) when damping is pondered. The proposed metamodel is a quick design tool of nonlinear damped periodic structures describing effectively the behavior of solitonic solutions, demonstrating a computational cost considerably lower than that of the Newton method. The results of this work highlight the potential of ANN regression models in the description of physical phenomena represented by the Nonlinear Schrödinger Equation when damping is considered.

Active Vibration Control Using Loudspeaker-Based Inertial Actuator with Integrated Piezoelectric Sensor

With the evolution of the aerospace industry, structures have become larger and more complex. These structures exhibit significant characteristics such as extensive flexibility, low natural frequencies, numerous modes, and minimal structural damping. Without implementing vibration control measures, the risk of premature structural fatigue failure becomes imminent. In present times, the installation of inertial actuators and control signal acquisition units typically requires independent setups, which can be cumbersome for practical engineering purposes. To address this issue, this study introduces a novel approach: an independent control unit combining a loudspeaker-based inertial actuator (LBIA) with an integrated piezoelectric ceramic sensor. This unit enables autonomous vibration control, offering the advantages of ease of use, low cost, and lightweight construction. Experimental verification was performed to assess the mechanical properties of the LBIA. Additionally, a mathematical model for the LBIA with an integrated piezoelectric ceramic sensor was developed, and its efficacy as a control unit for thin plate structure vibration control was experimentally validated, showing close agreement with numerical results. Furthermore, the LBIA’s benefits as an actuator for low-frequency mode control were verified through experiments using external sensors. To further enhance control effectiveness, a mathematical model of the strain differential feedback controller based on multi-bandpass filtering velocity improvement was established and validated through experiments on the clamp–clamp thin plate structure. The experimental results demonstrate that the designed LBIA effectively reduces vibration in low-frequency bands, achieving vibration energy suppression of up to 12.3 dB and 23.6 dB for the first and second modes, respectively. Moreover, the LBIA completely suppresses the vibration of the fourth mode. Additionally, the improved control algorithm, employing bandpass filtering, enhances the effectiveness of the LBIA-integrated sensor, enabling accurate multimodal damping control of the structure’s vibrations for specified modes.

A novel response-amplified shape memory alloy-based damper: Theory, experiment and numerical simulation

The energy dissipation capacity of shape memory alloy (SMA) dampers can be effectively improved owing to the success of response amplification technology. However, conventional response-amplified SMA dampers for building structures still face a risk of failure during extremely rare earthquake events. In this study, a novel response-amplified SMA damper (RASD) is proposed with the advantages of fully exploiting the energy dissipation characteristics of SMA materials and avoiding material failure. First, the components, configuration, and working principles of the proposed damper were described. Subsequently, a restoring-force model of the RASD was established, and its accuracy was verified through cyclic loading tests. Finally, seismic performance mitigation of a single-degree-of-freedom (SDOF) system under different hazard levels was conducted to evaluate the effectiveness and advantages of the proposed RASD quantitatively. The results reveal that the RASD has a good force amplification effect and excellent damping enhancement effect and thus conspicuously mitigates the seismic response of the SDOF system. In particular, the proposed RASD can effectively reduce the force and displacement demand of SMA materials without the risk of SMA failure, while significantly mitigating the structural response.

Vibration Attenuation in a Beam Structure with a Periodic Free-Layer Damping Treatment

In order to improve the vibration reduction performance of damping treatments, a new damping structure consisting of a uniform base layer and two periodically alternating free layers was examined in this study. Closed-form solutions for both the band structure and the forced response of the periodic bi-layer beam were theoretically derived and verified via numerical solutions using the finite-element method. The results showed that the structure with periodic free-layer damping (PFLD) treatment reduced broadband vibrations, and the levels of reduction were dominated by Bragg scattering in the band gaps and damping in the passbands. The vibration experiment verified the derived theory’s accuracy and showed that the PFLD treatment could increase vibration reduction levels in low-frequency band gaps compared with traditional free-layer damping treatments. The effects of the parameters—cell lengths, sub-cell-length ratios, and thickness ratios—were also discussed, providing further understanding of the vibration reduction performance of the bi-layer beam with the PFLD treatment, and this can be used to help designers optimize the periodic bi-layer beam to achieve better performance.

Structural damping estimation from live monitoring of a tall modular building

AbstractThe damping ratio is a key indicator of an individual structure's susceptibility to dynamic loads, including the level of discomfort experienced by the occupants of a tall building subjected to wind loading. While computational models, laboratory studies and empirical data can provide estimates of structural damping, the most reliable way to evaluate true damping ratio values is through modal identification using data from field tests on full‐scale finished structures. As an innovative form of construction, high‐rise modular buildings have not been the subject of previous vibration monitoring investigations, implying an absence of essential structural dynamics information. This paper assesses the reliability of four modal identification methods for estimating the damping ratio of a structure using ambient acceleration response data recorded from the world's tallest modular structure, the Ten Degrees building in Croydon, South London. The methods considered are two implementations of the Bayesian fast Fourier transform (BFFT), the random decrement technique (RDT), and a hybrid of the RDT which first decomposes the ambient data into sub‐signals using analytical mode decomposition (AMD‐RDT). Each method is applied to response data collected during 10 significant wind loading events to evaluate the inherent modal properties of the structure, with the computed damping ratio values compared between methods and events. By reporting the first measured damping ratios for a tall modular structure, the paper makes an important contribution to knowledge about the vibration properties of an emerging form of construction.