Design Of Damper Research Articles

Prediction of Beyond Design and Residual Performances of Viscoelastic Dampers by a Simplified Fractional Derivative Model

When subjected to excessive shear deformation, viscoelastic (VE) dampers may inevitably suffer from damages, due to their VE material layers with limited thickness. Under the circumstance, their stiffness and energy dissipation capabilities may deteriorate but not totally vanish. To estimate the seismic performances of viscoelastically damped structures, the beyond design and residual performances of damaged VE dampers are crucial to protect structures from severe failure during the following main shock or aftershocks. On the other hand, for new viscoelastically damped structures under the normal design earthquakes, neglecting the residual performance of damaged VE dampers may result in nonconservative design. Thus, this study aims to provide approaches to analytically characterize the beyond design and residual performances of damaged full-scale VE dampers. Based on the simplified fractional derivative model, the analytical predictions have been compared with the experimental results. The proposed model works well for the design performance of the intact full-scale VE dampers. Particularly, it can also reproduce the beyond design and residual performances of damaged full-scale VE dampers, if due consideration is taken of the effects of excitation frequencies, ambient temperatures, temperature rises, softening, and hardening.

Influence of mild steel damper design parameters on energy dissipation performance of low-damage self-centering precast concrete frame connections

Based on the characteristics of replaceable energy dissipating devices of low-damage self-centering precast concrete frame connections (LDSCPC), an LDSCPC joint specimen and five mild steel dampers with different design parameters are designed. The effects of design parameters of mild steel dampers on mechanical properties and energy dissipating performance of LDSCPC joints are studied by cyclic load tests and finite element (FE) analysis. The results shows that the residual deformation of mild steel damper is mainly concentrated in the horizontal energy dissipation strip and its internal angle connected with the vertical energy dissipation strip; increasing the size of the energy dissipation strip can further improve the bearing capacity of mild steel damper, but the performance improvement is more evident after 1.5% drift; the mild steel damper with thickness of 12 mm can save material and play a better role than the thickness of 10 mm and 14 mm; The detailed FE model has enough accuracy in predicting the behavior of LDSCPC connections. The pinching behavior of the damper can be avoided by a preload of 155 kN, which can improve the energy dissipation performance by at least 40%. The corner of horizontal and vertical energy dissipation strips is the area with relatively severe damage. The element damage on the horizontal energy dissipation strip may cause the damper to fracture, which should be paid attention to in the further analysis and optimization design.

Design and Optimization of the High Order Modes Damper for a 1.5 GHz Superconducting Harmonic Cavity

The installation of a superconducting radio-frequency (SRF) cavity can improve the beam lifetime via increasing the electron bunch length. A prototype 1.5-GHz SRF passive harmonic cavity working at 4.5 K was designed for The Taiwan Photon Source (TPS). As the beam might become unstable because of the coupled-bunch instability resulting from Higher Order Modes (HOMs) of the SRF harmonic cavity, HOMs damping of this cavity is an important issue. Ferrite absorbers placed in the beam tubes are designed to damp the HOMs. A theoretical calculation for the instability threshold for the HOMs is given. A tracking method is used to simulate the instabilities for operation with this HOMs-damped SRF harmonic cavity. The design and optimization of the HOMs damper, as well as the results of instability studies for this SRF harmonics cavity, are presented here.

Применение вихревого струйного устройства при разработке активных гидропневмодемпферов, используемых в технических средствах реабилитации

The paper overviews and analyses the current status of the development and research of active hydro-pneumatic dampers, which are used in rehabilitation equipment, where vortex jet devices can be applied as control valves. The study focuses on a vortex jet device whose distinctive feature is the absence of mechanically moving parts, describes the principle of its operation, and gives the rationale for using it in the active hydro-pneumatic damper of the knee module prosthesis. From a review of scientific and technical literature, a conclusion is drawn that active hydro-pneumatic dampers are used not only in rehabilitation equipment but also in vehicle shock absorbers. The experience gained in the design and development of active hydro-pneumatic dampers for vehicle shock absorbers was applied in the design and development of an active hydro-pneumatic damper for the knee module. In order to identify the advantages and disadvantages, we examined some designs of active hydro-pneumatic dampers for vehicle shock absorbers. Analysis of technical solutions showed the advantage of vortex jet devices, e.g. high reliability, the ability to work with various working environments, low manufacturing and operating costs; enabled us to recommend a vortex jet device to be used as an actuator, i.e., a vortex valve, in the valve assembly of an active hydro-pneumatic damper. The use of a vortex jet device increases the reliability of the structure and reduces the energy consumption for the control of the structure. The proposed design of the hydro-pneumatic damper allows the use of interactive damping control. The study is the first to introduce the concept and describe the principle of operation of an active hydro-pneumatic damper using a vortex jet device

Finite element reduction modeling and vibration analysis of mistuned coating thickness blisk

The application of hard coating damping technology to the blades ofblisk can effectively reduce the vibration stress and improve its service life. In this paper, a three-dimensional eight-node laminated incompatible element is proposed, which only needs the node coordinates of the structure without the coating. In the coating damping design process, it could avoid reconstructing the finite element mesh when changes the coating thickness. Based on the cyclic symmetry algorithm and the SNM method, a finite element reduction model to analyze the vibration characteristics of the coated blisk with coating thickness mistuning was established andverified by ANSYS. The results indicate that the proposed finite element model can be used to analyze the vibration characteristics with the changed coating thicknessand it shows great consistence with the result of ANSYS. On the other side, the SNM still has high accuracy when the coating thickness varies from 0 mm to 0.3 mm.

Optimization of torsional vibration damper of cranktrain system using a hybrid damping approach

The focus of this research is to develop the optimum design of torsional vibration damper using hybrid damping approach to decrease the torsional vibrations in the cranktrain system of internal combustion engines (ICE). For this purpose, a double mass rubber and viscous torsional vibration damper (DMRV-TVD) are combined. The optimization procedure is carried out using genetic algorithm (GA) to determine the best hybrid damping performance on cranktrain system of a four stroke and four cylinder diesel engine. Accordingly, twelve degrees of freedom lumped mass mathematical model of the proposed cranktrain system is created. The stiffness and damping coefficients of viscous and rubber materials used in DMRV-TVD model are verified by modal test and finite element natural frequency analysis. Then, the excitation torque is calculated considering the inertia forces and gas force, and Fourier series expansion is performed to obtain the harmonics of driven torque as the input load on the relevant masses. The relative angular deflection of the front end point of the crankshaft is determined. Additionally, in order to decrease the torsional vibrations of the crankshaft, DMRV-TVD model is optimized depending on the viscous material parameters by defining the boundary conditions and objective function of the genetic algorithm. The comparative results show that the developed hybrid design of optimized DMRV-TVD reduced the torsional vibrations by 50.17% when compared to the non-optimized DMRV-TVD. This achieved reduction in the torsional vibrations is expected to increase the engine performance and its durability as well as providing a better driving comfort and fuel efficiency.

Optimal Design of Dampers for Multi-Mode Cable Vibration Control Based on Genetic Algorithm

Cables in cable-stayed bridges are subjected to the problem of multi-mode vibrations. Particularly, the first ten modes of long cables can have a frequency less than 3[Formula: see text]Hz and hence are vulnerable to wind-rain induced vibrations. In practice, mechanical dampers are widely used to mitigate such cable vibrations and thus they have to be designed to provide sufficient damping for all the concerned vibration modes. Meanwhile, the behaviors of practical dampers are complicated and better to be described by mechanical models with many parameters. Furthermore, additional mechanical components such as inerters and negative stiffness devices have been proposed to enhance the damper performance on cables. Therefore, it is increasingly difficult to optimize the damper parameters for suppressing multi-mode cable vibrations. To address this issue, this study proposes a novel damper design method based on the genetic algorithm (GA). The procedure of the method is first introduced where the damper performance optimization is formulated as a single-objective multi-parameter optimization problem. The effectiveness of the method is then verified by considering a viscous damper on a stay cable. Subsequently, the method is applied to optimize three typical dampers for cable vibration control, i.e. the positive stiffness damper, the negative stiffness damper, and the viscous inertial mass damper. The results show that the GA-based method is effective and efficient for cable damper design to achieve best multi-mode control effect and it is particularly useful for dampers with more parameters.

Comprehensive Review of Optimal and Smart Design of Nonlinear Building Structures With and Without Passive Dampers Subjected to Earthquake Loading

The optimal and smart design of nonlinear building structures with and without passive dampers subjected to earthquake loading is of great concern in the structural design of building structures. The research started around 1980 and many investigations have been conducted. A comprehensive review on this subject is made in this article. After the description of essential features of the optimal design problem of nonlinear building structures under earthquake ground motions, analysis types of optimization problems are explained and the significance of the dynamic pushover analysis is discussed from the viewpoint of analysis of limit states under earthquake ground motions of magnitude larger than the code-specified level. Then, the categorization by the response of frames and dampers was made. In this categorization, several subjects are discussed first: 1) Optimal design of bare nonlinear building frames under seismic loading, 2) Optimal design of nonlinear dampers for elastic building frames under seismic loading, 3) Optimal design of linear dampers for nonlinear building frames under seismic loading, 4) Optimal design of nonlinear building frames with specified nonlinear dampers under seismic loading, 5) Optimal design of nonlinear dampers for specified nonlinear building frames under seismic loading, 6) Simultaneous optimization of elastic-plastic building structures and passive dampers. Finally, the classification of researches in view of solution strategies is conducted for providing another viewpoint.

A Method for the Design and Optimization of Nonlinear Tuned Damping Concepts to Mitigate Self-Excited Drill String Vibrations Using Multiple Scales Lindstedt-Poincaré

In downhole drilling systems, self-excited torsional vibrations caused by the bit-rock interactions can affect the drilling process and lead to the premature failure of components. Especially self-excited oscillations of higher-order modes lead to critical dynamic loads. The slim drill string design and the naturally limited drilled borehole diameter limit the installation space, power supply and lead to numerous potentially critical self-excited torsional modes. Consequently, small and robust passive damping concepts are required. The variety of possible downhole boundary conditions and potential damper designs necessitates analytical solutions for effective damper design and optimization. In this paper, two nonlinear passive damper concepts are investigated regarding design and effectiveness to reduce self-excited high-frequency torsional oscillations in drill string dynamics. Based on a finite element model of a drill string, a suitable minimal model based on the identified critical mode is generated and solved analytically using the Multiple Scales Lindstedt-Poincaré (MSLP) method. The advantages of MSLP compared to conventional MS methods are shown for this example. On the basis of the analytical solution, parameter influences are determined, and design equations are derived. The analytical results are transferred to self-excited drill string vibrations and discussed using time domain simulations of the drill string model.

Theoretical investigations on the linear and nonlinear damping force for an eddy current damper combining with rack and gear

To study the damping characteristics of a new type of eddy current damper with rack and gear recently proposed by the authors, the damping torque for the eddy current damper with rack and gear was theoretically investigated based on some fundamental assumptions, including evenly distributed magnetic field on a conductor plate and no magnetic leakage. A linear relationship between damping torque and velocity was obtained. Numerical simulations by using COMSOL Multiphysics were conducted to evaluate the accuracy of the linear theoretical formula. When angular velocity is less than 30 rad/s, it seems that the linear theoretical results agree well with the numerical results, and maximum relative error between them is about 6.58%. Then, by using COMSOL Multiphysics, a series of parametric studies on damping torque, including the effects of the air gap, the thickness of a back iron plate, the location and number of permanent magnets, and the thickness of a conductor plate, were carried out to further examine the linear theoretical formula. The results show the effects of the air gap and back iron plate on the relative error between linear theoretical and numerical results can be ignored, whereas the location and number of permanent magnets and the thickness of the conductor plate have significant influences on the relative error. Finally, a nonlinear theoretical formula was obtained by introducing three modified coefficients into the linear theoretical formula, and its accuracy was verified in some typical cases. It is proved that there is sufficient accuracy to adopt the nonlinear theoretical formula in preliminary design of the eddy current damper with rack and gear to determine the main structural parameters.

The friction and wear mechanism of O-rings in magnetorheological damper: Numerical and experimental study

In this paper, the friction and wear mechanisms of O-ring, commonly used sealing element of magnetorheological damper, were revealed, which has reference significance for seal design, fault diagnosis and life prediction of damper. A series of models of frictional force were established, through calculation and analysis, it was found that the piston rod velocity, particle size and particle mass fraction have certain rules that affect the friction coefficient and the film thickness. Subsequently, the friction and wear test bench of the sealing element of the magnetorheological damper was built, verifying the correctness of the theoretical model. In addition, through the observation of O-rings after the tests under different experimental conditions, the wear mechanism of O-ring is mainly abrasive wear.

Contact nonlinear analysis for the under-platform dampers of blade based on a frictional energy dissipation model

The under-platform dampers of blade in an aero-engine can reduce the vibration through friction energy dissipation, which is generally regarded as a kind of foundation vibration model subjected to fluctuant pressure. The possible unstable air-flow and complex changes in aero-engine’s speed at service result in the consequence that the tangential pressure originated from blade vibration as well as the centrifugal force applied on the foundation vibration model appear fluctuating. These fluctuant parameters are often assumed in the sinusoidal form. Meanwhile, the frequency ratio and phase difference between them also change during the operation process. To explore the effects of the changes in frictional energy dissipation and nonlinear contact response, a differential equation for a frictional energy model with the vibrational foundation is deduced and proposed in this paper. The equation integrates the complex condition of friction into a simple differential form, through which the hysteresis characteristic for different frequency ratios and phase differences are calculated precisely and efficiently. Additionally, the amplitude-frequency characteristics of the relative displacement between the contact surfaces of the proposed model are further investigated. This study can provide a reference for dynamic tribology design of the under-platform damper for engineering.

Analytic expression of additional damping ratio based on Bouc–Wen model and performance evaluation

SummaryAccurate calculation of the additional damping ratio provided by the damper to the structure is a necessary parameter for evaluating and selecting the optimal damping design scheme. At present, bilinear model is usually adopted to calculate the additional damping ratio of buckling‐restrained brace (BRB) and metal damper, but this method is not accurate. The hysteretic characteristics of the dampers can be simulated accurately by Bouc–Wen model. However, the traditional expression of Bouc–Wen model is implicit, and its energy dissipation cannot directly be quantified. In view of this, the explicit analysis of Bouc–Wen model is carried out, and the analytical solution of energy dissipation of this model is proposed. Furthermore, the formula for calculating the additional damping ratio is obtained. The correctness of the analytical solution is verified by numerical examples, and compared with the bilinear model, the superiority of the proposed method in the calculation accuracy is proved. The effect of the Bouc–Wen model parameters on the additional damping ratio is studied. The difference between Bouc–Wen model and bilinear model with various earthquake excitations is proved by finite element method, and the difference of dynamic response between the damping structures based on different damper models is shown and compared.

Конструкторско-технологическое обеспечение износостойкости поверхности эластомера резинокордных оболочек демпфирующих устройств

Two main factors are considered that determining the friction between non-lubricated surfaces of an elastomer and a solid base during their relative motion. The first one is adhesion in the areas of real (actual) catalysis and the second factor is the deformation component, which is due to the delay of recovery of the elastomer after the irregularity is introduced and it is called the hysteresis component of friction. One of the main problems of increasing the resource of pneumatic dampers is minimizing the wear of the covering layer of the rubber-cord casing (RCC). The wear of the RCC is due to the fact that sliding friction occurs in the process of contact between the metal surface and the surface of the RCC, as a result of which the cover layer of the RCC (in some cases with the first cord layer) wears out, depending on the chemical composition of the rubber and the features of the operation of the pneumatic shock absorber. In order to minimize the wear of rubber, it is proposed to change the design of the pneumatic damper so that rolling friction dominates in the contact between the surfaces of rubber and metal

Design of multiple dynamic dampers for a beam structure

Design of multiple dynamic dampers for a beam structure

Generalized dynamic model of hydrodynamic vibration dampener subject to viscous damping

Use as an elastic body of the working fluid improves the efficiency of the hydraulic damper, reliability, and durability, in this case, the issues of improving the reliability of existing locomotives hydraulic dampers by upgrading separate the components for major repairs with the extension of the useful life are relevant. To increase the efficiency of damping dynamic vibrations and reduce the load on the support units and running gear elements, a modernized design of a hydro friction damper with improved damping properties was developed, for which an application was filed for the Patent of the Republic of Uzbekistan for Invention No. IAP 2021 0002.

Design of multiple dynamic dampers for a three-layered structure

Design of multiple dynamic dampers for a three-layered structure

Simulation of the Dynamic Response to Sinusoidal Excitation of the Elastic Porous Metal Mesh Damper

As a promising device of vibration isolation for rocket engine turbopumps, turbine engines, and other kinds of rotordynamic applications, the elastic porous metal mesh damper (MMD) has drawn large attention from researchers. It exhibits higher load capacity and environmental adaptivity than traditional viscoelastic damping materials owing to the excellent combination of metallic properties and the rubber‐like damping performance. However, the design of a metal mesh damper relies heavily on the trial‐and‐error methodology for tuning fabrication parameters, which prevents it from widespread use in rotor‐bearing applications. Therefore, efforts are directed toward forging an explicit link between fabrication parameters and the dynamic behaviors of MMDs in the present work. Quasistatic and dynamic mechanical tests are carried out to help determine the primary factor that influences the damping performance of the MMD and to demonstrate how the dynamic behaviors of MMDs evolve with the fabrication parameters. Furthermore, two different modeling methodologies, i.e., the FE method and the mixed damping approach, are used to predict the hysteresis behaviors of the dampers. The latter method not only properly reproduces the experimental results but also makes it possible to build an intuitive connection between the fabrication procedures and the dynamic mechanical behaviors of the MMDs. The orthogonal test results determine that the mesh density plays a dominant role in controlling both the load capacity and damping performance of the MMDs. By integrating mesh density and motion amplitude into the expression of parameters including stiffness coefficient, damping coefficient, and damping component factor, the mixed damping model demonstrates excellent predictive accuracy under different excitation conditions.

Optimization of Multiple Tuned Mass Dampers for Road Bridges Taking into Account Bridge‐Vehicle Interaction, Random Pavement Roughness, and Uncertainties

Road bridge designs are based on technical standards, which, to date, consider dynamic loading as equivalent static loads. Additionally, the few engineers who perform a dynamic analysis typically do not consider the effects of bridge‐vehicle interaction and also simplify the road’s irregularity profile. Moreover, often, even when a simplified dynamic analysis is carried out and shows that there will be a high dynamic amplification factor (DAF), designers prefer to solve this problem by adopting high safety factors and thereby oversizing the bridge, rather than using energy dissipation devices that would allow reducing the amplitude of vibration. In this context, the present work proposes a complete methodology to minimize the dynamic response of road bridges by optimizing multiple tuned mass dampers (MTMD), taking into account the bridge‐vehicle interaction, the random profile of pavement irregularities, and the uncertainties present in the coupled system and in the excitation. For illustrative purposes, the coupled vibration problem of a regular truck traveling on a random road profile over a typical Brazilian bridge is analyzed. Three different scenarios for the MTMD are considered. The proposed optimization problem is solved by employing the Whale Optimization Algorithm (WOA). The results showed the excellent ability of the proposed methodology, reducing the bridge’s DAF to acceptable values for all analyzed cases, considering or not the uncertainties present in the system. Furthermore, the results obtained by the proposed methodology are compared with results obtained using classical tuned mass damper (TMD) design methods, showing the best performance of the proposed optimization method. Thus, the proposed method can be employed to optimize MTMD, improving bridge design.

ОПРЕДЕЛЕНИЕ ОПТИМАЛЬНЫХ ПАРАМЕТРОВ ДЕМПФИРОВАНИЯ ЗЕМЛЯНОГО ПОЛОТНА ЖЕЛЕЗНЫХ ДОРОГ В СЕЙСМИЧЕСКИ АКТИВНЫХ РАЙОНАХ

The paper considers a damping layer design for roadbed with parameters that provide safety of railway traffic in seismically dangerous regions. It presents a theoretical study of seismic forces on railway roadbed on the basis of analysis of earthquake influence parameters on stressed and strained state of railway track construction. For the investigations the author has applied methods of multifactorial experimental design. The author has developed a method for determination of optimal parameters for damping depending on main parameters of an earthquake (magnitude, distance from hypocenter, physical and mechanical characteristics of the Earth crust) and geological characteristics of a railway section (capability of layers, deformational and elastic properties of the Earth crust, foundation and roadbed). As a result, the author suggests designs of a damping layer that has a layered-geterogenous compositional structure with given properties. Moreover, he has established a possibility to increase an aseismic stability of railway roadbed by construction of the damping layer with given properties.