Performance Of Damper Research Articles

Experimental study on frictional behavior of different structural materials

Friction dampers were widely applied to the beam-column connections to dissipate earthquake energy. The damage of buildings under earthquake could then be reduced obviously. To ensure the good performance of the friction dampers, the appropriate selection of the materials for the friction pads was important. This paper investigated the coefficient of friction of different materials under cyclic loading. Four types of materials which included steel, galvanized steel, brass, and aluminum were chosen. The studied variables were the surface cleaning process, the bolt pretension, and the loading protocols. The test results showed that the shot blasting process significantly enhanced the coefficient of friction and the energy dissipation ability. Friction dampers with friction pads made of these four materials offered high initial stiffness. They could provide the needed stiffness for the structures. The coefficient of friction was largely affected by the bolt pretension and the loading protocols. Except for the friction damper with friction pads made of aluminum, the other three friction dampers exhibited satisfactory energy dissipation ability without obvious strength degradation. Mathematical models were proposed to predict the variation of the coefficient of friction for different materials. Good agreement was found between the prediction and the test data.

A grid-side multi-modal adaptive damping control of super-/sub-synchronous oscillations in type-4 wind farms connected to weak AC grid

• A multi-modal damping control (MADC) is proposed to damp multiple oscillation modes independently. • A general design framework for damping multiple oscillation modes is given. • MADC is validated to damp sub-synchronous and super-synchronous oscillations in Type-4 wind farms. Type-4 wind farms connected to weak AC grids have the risk of sub-synchronous oscillation/interaction (SSO/SSI) with multiple oscillation modes, which can lead to unplanned outages and system destabilization. This paper first presents the magnitude and frequency characteristics of the oscillations followed by the control design requirements. Then, it gives a general design of grid-side multi-modal adaptive damping control (MADC) to stabilize multiple oscillation modes. The MADC utilizes an FFT-based inter-harmonic phasor measurement algorithm, which can detect and track multiple oscillation modes simultaneously. The MADC uses bus voltages and line currents as inputs to extract and control each oscillation mode without considering the coupling of the modes due to the frequency coupling effect. The unstable modes are stabilized by injecting phase-shifted currents with multiple frequencies such that the impedance response of the whole system around the concerned frequencies is reshaped. Notable features of the proposed damping control include automatic and independent detection, tracking and suppression of multiple oscillation modes. The proposed MADC's damping performance is validated through extensive electromagnetic transient (EMT) simulations of type-4 wind farms connected to a weak ac grid causing super-/sub-synchronous oscillations. The system model and the proposed damping control are designed and tested in commercial EMT software.

Improved Data-Driven Model-Free Adaptive Damping Controller Design for Interconnected Power Systems With Stochastic Communication Delays

The original model-based wide-area damping control (WADC) is difficult to obtain good damping performance due to the complex structure of interconnected power systems. In this paper, an improved data-driven model-free adaptive control (ID-MFAC) algorithm is proposed to design WADC for interconnected power systems with stochastic communication delays. First, the multiple-input multiple-output power system can be decoupled as multiple single-input single-output subsystems by considering controller interactions and system disturbances. Second, a step-size vector is designed to adjust the pseudo-partial derivative and make the algorithm more flexible by considering both input and output data adequately. Furthermore, an adaptive delay compensator is designed to compensate stochastic communication delays. Last, simulations are conducted to verify that the ID-MFAC algorithm can efficiently suppress multiple inter-area oscillations modes under various stochastic communication delays.

Five Years' Monitoring Data on Rail Damper Performance

Roughness in rail surface accumulates with train operations and grows faster on curved tracks than tangent tracks. Higher roughness leads to higher noise radiation. In Hong Kong, railway noise prediction includes a 3dB correction for rail surface deterioration. Depending on rate of deterioration, different rail grinding cycles (typically between 3 and 24 months) are scheduled to ensure train operations without excessive noise radiation. Before rail dampers installation, noise levels were monitored for 1.5 years and around the noise limit with variation +/- 3dB(A) due to rail roughness variation. After installation of rail damper, railway noise was generally maintained at 7dB(A) below the noise limit with variation +/-1.5dB(A) for more than 3 years. Noise reduction at dominant frequencies 630 Hz and 800 Hz were more than 10dB in 1/3 Octave analysis. The rail dampers were installed at alternative spaces such that additional rail dampers can be installed to double the amount in case further noise reduction is required. This paper examines the five years' monitoring data in detail, showing the noise levels with smaller variations over grinding cycles after rail damper installation, and explores rail damper potential ability to slow down the growth rate of rail roughness levels.

Tool vibration isolation in hard turning process with magnetorheological fluid damper

Tool vibration in metal cutting significantly influences the surface finish and machining stability. Suppressing the tool vibration to enhance the finished product quality is the need of the hour. The current study proposes the augmentation of a Magnetorheological (MR) fluid damper to suppress tool vibration in hard tuning with easy installation without structural modification. The MR fluid damper changes its damping coefficient with the magnetic field to regulate variable cutting conditions. An optimal composition of MR fluid has been prepared in-house to be used in the damper. The in-house MR fluid is compared with commercial MR fluid. The comparison shows that in-house prepared MR fluid performs equally well compared to commercial fluid. The MR damper effectively damps high-amplitude vibration at aggressive cutting conditions. The L9 Taguchi design of the experiment opted to arrive at minimal machining parameters to evaluate the damper's performance in machining two workpiece materials, namely oil-hardened nickel steel (OHNS) and high carbon high chromium (HCHCR D2) die steel. The surface roughness and tool vibration are reduced with the damper. It is noted that in-house MR fluid performed equally well as commercial MR fluid. The tool wear study is also carried out to monitor the influence of external damping over tool life. The stability lobe diagram is obtained analytically with experimental validation to mark the stability limit of the machining condition. The stability boundary increases with the damper enabling aggressive cutting conditions.

Seismic Performance and Parametric Study of a Winding Rope Fluid Viscous Damper (WRFVD) for Continuous Girder Bridges

ABSTRACT To decrease the seismic response of continuous girder bridges, the seismic performance of a novel winding rope fluid viscous damper (WRFVD) was investigated. This device was installed between the sliding piers and superstructure, and connected to the superstructure by winding ropes. WRFVD can accommodate the thermal deformation of superstructure under service condition, and make the fixed pier and sliding piers bear the seismic loads together by establishing the friction connection between the sliding piers and superstructure under earthquake action. In this study, the theoretical mechanism of WRFVD is derived, and verified by a dynamic performance test. A shaking table test was conducted on a scaled three-span continuous girder bridge employing WRFVD. The test results showed that WRFVD can effectively reduce the seismic response of continuous girder bridges. The parametric study of WRFVD on a five-span continuous girder bridge was investigated. The parametric study shows that the seismic response of multi-span continuous girder bridge equipped with WRFVD decrease with the increasing damping coefficient and friction coefficient, and the decreasing damping index.

Theoretical and experimental study on performance of compound-driven MR valve-controlled damper

A compound-driven magnetorheological (MR) valve is designed to cope with the low reliability and high energy consumption of traditional MR valves. The operating magnetic field of the valve is applied by both the excitation coil and ring magnet, maintaining excellent pressure drop performance even at zero current. To analyze the performance and obtain the variation law of the magnetic flux density and pressure drop, a pressure drop mathematical model and a magnetic field simulation model are established. The key parameters of the MR valve are also optimized using non-dominated sorting genetic algorithms-II. A dynamic performance test system is built, and the influence of the load on the pressure drop and hysteresis characteristics of the MR valve is studied. The results show that the optimized pressure drop and adjustable coefficient are improved by 4.7% and 8.6% respectively. The pressure drop grows nonlinearly with the electric current and reaches saturation at a current of 1.5 A, and a pressure drop of 1485 kPa is still generated at zero current. The output damping force of the compound-driven MR valve-controlled damper can be continuously adjustable, indicating that the dynamic performance of the damper can be controlled by adjusting the input current.

Damping performance of the degraded fluid viscous damper due to oil leakage

As a typical passive energy dissipation device, fluid viscous dampers (FVDs) are widely employed to alleviate seismic-induced structural vibration. However, oil leakage often occurs in FVDs, which has been identified as a critical factor that may cause deterioration in their mechanical behaviors. This study aims to evaluate the damping performance of the leaked FVD. To obtain the mechanical properties, a series of cyclic tests were conducted on a large-tonnage FVD with different oil leakage levels. The performance degradation mechanism was revealed through the finite element method, and analytical models for simulating the hysteresis characteristics of the leaked FVD were established and verified. A long-span cable-stayed bridge subjected to harmonic excitations was used as a case study to show the impact of leakage and load intensity on the bridge responses and the damper performance. The results reveal that oil leakage will cause a “gap” phenomenon in the hysteresis curves (i.e., the damper does not generate damping force), but it will not alter the mechanical parameters of the FVD following the gap has been consumed. The reason for this phenomenon is that air would flow through the orifices prior to silicone oil when being compressed. A negative correlation is found between the vibration mitigation effectiveness of FVD and the leakage level. However, the degree of performance degradation will be minimized when subjected to higher-intensity excitations. A leaked FVD is more prone to force-exceeding and stroke-exceeding failures thus it should be replaced soon.

Design of robust particle dampers using inner structures and coated container walls

Classical particle dampers suffer from their non-robust damping behavior, i.e. they can only be efficiently applied to a specific frequency range and amplitude range. The reason for that is that particle motion, also called motion mode, and damper efficiency show a strong correlation. By changing particle or container properties the motion modes are shifted to other excitation conditions but their efficient range is not much affected. To increase the damping performance and robustness of particle dampers, two approaches are presented here by introducing new motion modes. Therefore, the particle dampers are analyzed experimentally using a shaker setup and numerically using the discrete element method. The first design approach uses inner structures inside the particle damper, manufactured by a 3D printer. The inner structures consist of different numbers of beams, placed perpendicular to the container moving direction. They lead to a much more robust damper as the transition between the motion modes gets smoother. For the second approach, the container walls are equipped with different soft polymers. In this way a new motion mode at low excitation intensities is observed, leading to a high efficiency possibly on a large excitation intensity range. For an easy calculation of the necessary wall’s Young’s modulus an analytical formula based on Hertz impact theory is derived.

Performance analysis of magnetorheological plastomer dampers with different annular shear gaps

Magnetorheological plastomer (MRP) dampers are controllable semi-active smart devices, which are commonly used in the field of vehicle suspension systems, structural engineering, aerospace engineering and military equipment. This study was conducted to numerically investigate the performance of MRP dampers with different annular shear gap sizes. The MRP used in the analysis consisted of 60% Carbonyl Iron Powder (CIP) and 40% Polyurethane Matrix (MRP60). The focus of the analysis was on the MRP60 flow behaviour in the annular shear gap region, where the induced magnetic field generated a range of dynamic damping forces depending on the size of the annular shear gap. The numerical simulation involved an integration of the finite element analysis (FEA) to examine the magnetic field in the annular shear gap region as well as the computational fluid dynamics (CFD) analysis to simulate the damping characteristics of the MRP damper. The relationship between the yield stress and the magnetic flux density for MRP60 was used for the analysis. The results of the FEA showed that as the size of the annular shear gap increased, the magnetic flux density and the yield stress decreased. From the CFD results, it was observed that the damping force decreased as a result of increasing the size of annular shear gap.

Design and experimental research of stepped bypass magnetorheological damper

In order to meet the damper performance requirements of heavy vehicles, a stepped-bypass magnetorheological damper is proposed. The mathematical model of damping force is deduced, and its mechanical properties are numerically simulated. Then the damper is manufactured, and the mechanical properties of the stepped bypass magnetorheological damper are experimentally studied. The simulation are consistent with the experimental results. The damper is optimized by orthogonal optimization design test. Finally, it is concluded that the maximum output damping force of the stepped bypass magnetorheological damper is about 4500 N, and the adjustable coefficient K is about 5.4. After optimization, the damping force of the stepped bypass magnetorheological damper is increased by at least 5.3%, and the adjustable coefficient K is at least 1.37 times that before optimization, which is 13% wider than that before optimization.

Mechanical property of cylindrical sandwich shell with gradient core of entangled wire mesh

To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components, the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper. Firstly, the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine, and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing. Secondly, to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores, quasi-static and dynamic mechanical experiments were carried out. The primary evaluations of mechanical properties include secant stiffness, natural frequency, Specific Energy Absorption (SEA), vibration acceleration level, and so on. The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin. The axial gradient material has almost no influence on the vibration frequencies of the shell, whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin. Moreover, compared to the conventional sandwich shells, the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction, stiffness designing, and energy dissipation.

Experimental Investigation of the Vibration Reduction of the Pipeline System with a Particle Impact Damper under Random Excitation

In the engineering field, severe vibration of the pipeline system occurs under random excitation, which leads to vibration failure of the pipeline system due to overload. The traditional method is to increase the rigidity of the pipeline system, and to avoid low-frequency resonance by using clamps or damping materials. However, due to structural limitations, it is difficult to apply clamps and damping materials. Particle damping technology has been applied in many fields, and the vibrational energy in the broadband frequency domain could be dissipated based on nonlinear particle collision damping. In this paper, a particle impact damper is designed for vibration reduction of the pipeline system. The damping capability is identified to investigate the effects of particle material, filling rate, particle size, damper structure, and boundary conditions. The results indicate that the ideal damping performance can be obtained by properly selecting particle parameters. Based on applying particle damping on the pipeline system, the proposed particle impact damper showed excellent damping capability under random excitation.

A Control Bandwidth Optimized Active Damping Scheme for LC and LCL Filter-Based Converters

Control bandwidth and damping performance are two key specifications for high-order LC and LCL filter-based converters. The damping of high-order filter-based converters has been extensively studied. However, the control bandwidth issue was ignored. The quantitative relationship between the control gains and bandwidth is still unclear. Moreover, the delay compensator was designed independently without considering the interactions with the main controller. This paper proposes a control bandwidth-optimized active damping control strategy for the LC and LCL filter-based converters to overcome these shortcomings. With the proposed generalized controller, the close loop transfer function of the N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> order filter-based converter can be simplified to an N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> order low pass filter with an adjustable cutoff frequency. This greatly simplifies the control bandwidth optimization. To alleviate the negative influence of the computational delay on the control bandwidth, a novel delay compensator is proposed. To reach an overall optimized control performance, the particle swarm optimization (PSO) method is used to optimize the controller and delay compensator parameters simultaneously to realize both high control bandwidth and good damping performance. Experimental results verify the effectiveness of the proposed novel controller.

Mitigating Subsynchronous Oscillation Using Model-Free Adaptive Control of DFIGs

Incorporating subsynchronous damping controllers (SSDCs) into the control loops of doubly-fed induction generators (DFIGs) is one of the most cost-effective methods to suppress subsynchronous oscillation (SSO). However, it is difficult to achieve satisfactory control performance of SSDCs due to the time-varying structure and operating conditions of wind integrated power systems. In this paper, an improved model-free adaptive control (MFAC) method is developed for DFIGs to overcome the limitations of conventional methods for SSO mitigation. First, the structure of the MFAC-based SSDC (M-SSDC) for DFIGs is designed. Then, an improved MFAC predictive control algorithm is proposed to achieve SSO mitigation. Moreover, the stability of the closed-loop system with the proposed M-SSDC is analyzed, which provides some guidelines for determining controller parameters. Additionally, the input-output signal pair of M-SSDC is selected by using geometric measure for the optimum damping performance. Case studies under various operating conditions of the test power system validate the effectiveness of the proposed M-SSDC as well as its superior damping performance over conventional approaches.

Shrinkage of frame polymer concretes in road construction

It is known that with the same raw material composition, it is possible to obtain different structures of composite materials. So, for example, polymer concretes can be made using traditional technology and the method of phase-by-phase forming. At the same time, frame technology reduces material consumption without loss of strength properties and increases durability. Polymer composite materials of phase-forming by combining properties viscoelastic binder and rigid matrix. It has highly damping performance. The article considers the possibility of using the frame structure polymer composite material in road construction. The composition is also considered, the advantages are determined and a comparison with traditional materials is made. The shrinkage stresses of polymer concrete that occur during the polycondensation reaction of furan resin are quite large and can exceed the permissible ones, which leads to a violation of the monolithic nature of the structure due to the appearance of micro- and macrocracks. In this work, the kinetics of shrinkage within 28 days was studied. The composition of the frame polymer composite material includes the following components: furfural acetone monomer (FAM resin), benzosulfonic acid, granite crushed stone, andesite flour, quartz sand. Theshrinkage of phase-formed polymer concrete was measured on samples hardening under normal temperature-humidity conditions. The generally accepted technique was used, shrinkage deformations were installed along the axis of the sample on two opposite faces with a clock-type indicator with a division price of 0.001 mm. Also in the work is a diagram of the device for determining the deformations of the shrinkage of samples and the results of the study are given. Experimentally established the intensity of shrinkage, which manifests itself in the first three days of curing, in the future its change is insignificant and by the seventh day it fades. According to the test results, it was established that the linear shrinkage of frame polymer concretes is three times less than the shrinkage of polymer concretes with a conventional structure.

Study on elastohydrodynamic lubrication performance of double-layer composite water-lubricated bearings

Double-layer composite water-lubricated bearing is a new type of water-lubricated bearing which can integrate the good damping performance of low elastic under-layer bush and good tribological performance of plastic layer bush. This paper analyzes its elastohydrodynamic lubrication performance by fluid–structure interaction (FSI) method, and studies the effects of eccentricity ratio, rotational speed, elastic modulus distribution and thickness distribution of bearing bush on its lubrication performance. Results show that the lubrication performance of double-layer bearing is more like that of plastic bearing. As rotational speed and eccentricity ratio increase, the maximum water film pressure, the load carrying capacity and the maximum bush deformation increase significantly. As the elastic modulus of the low elastic under-layer bush decreases, the total bush deformation increases significantly, but the load carrying capacity decreases slightly. The bush thickness distribution influences the deformation distribution of both low elastic under-layer bush and plastic layer bush, but have little impact on the total bush deformation and bearing lubrication performance.

Passive attitude stabilization of ionic-wind-powered micro air vehicles

The ionic-wind-powered Micro Air Vehicles (MAVs) can achieve a higher thrust-to-weight ratio than other MAVs. However, this kind of MAV has not yet achieved controlled flight because of the unstable thrust produced by the ionic wind and the dynamic instability related to the small size. In this paper, a passive attitude stabilization method of the ionic-wind-powered MAV using air dampers is introduced. The key factors that influence the performance of the air dampers, including the layout, position, and area of the air dampers, are theoretically studied. The appropriate optimal position of the air dampers is also obtained by Monte Carlo stochastic simulations. Then the proposed passive attitude stabilization method is applied to the ionic-wind-powered MAVs of different wingspan (2 cm and 6.3 cm). Finally, the experimental results show that using the proposed method, attitude stabilization is achieved for the first time for the ionic-wind-powered MAV. Moreover, the altitude control of an ionic-wind-powered MAV with a wingspan of 6.3 cm is also demonstrated.

Performance of wire rope damper in vibration reduction of stay cable

This paper systematically investigates the novel application of wire ropes as a damper rather than as an isolator to reduce the wind-induced high-mode vibration of stay cables. Three-direction cyclic loading tests, including tension–compression direction, shear direction, and roll direction, are conducted to clarify the damping behavior of the proposed wire rope damper. The wire rope damper exhibits asymmetric hysteretic characteristics in the tension–compression direction, while the hysteresis loops in the shear and roll directions are symmetrical. A modified normalized Bouc-Wen model is presented to describe the multi-directional hysteretic characteristics of the wire rope damper. An analysis method considering the nonlinear damping behavior is developed in this study to overcome the limitations of the traditional analysis using an equivalent damping coefficient. The proposed analysis method is validated against the physical experiments. The proposed wire rope damper system was installed on the Su-Tong Yangtze River Bridge to reduce the high-mode vortex-induced vibration of the stay cable. The field monitoring data demonstrate that the proposed wire rope damper can significantly reduce the in-plane and out-of-plane vibrations. The effect of the wire rope damper on the cable vibration control is further examined using the proposed analysis method. The finite element results further demonstrate the effectiveness of the wire rope damper in high-mode vibration reduction of stay cables. The features of the wire rope damper, such as multi-directional damping, broadband applicability, and simple configuration, are beneficial to its application in cable vibration control.

Vibration behavior of a carbon fiber‐reinforced polymer composite sandwich panel: Rhombus core versus elliptical core

AbstractExploring lightweight sandwich structures with excellent load‐bearing and vibration damping performances is one of the important topics in structural and functional applications. The aim of the present research is to design, fabricate carbon fiber‐reinforced polymer (CFRP) sandwich panels with rhombus cores and investigate their modal characteristics by comparing with the traditional elliptical sandwich structure experimentally and numerically. In order to obtain modal properties including natural frequencies, damping ratio, mode shapes, and frequency responses of the fabricated structure, modal experiment is performed using a modal hammer with an acceleration sensor. Furthermore, a finite element method is developed to validate the precision of the experimental data. It is recognized that the finite element results are in remarkably great agreement with those obtained by modal experiment. The experimental results showed that the natural frequencies of the sandwich structures with rhombus are much higher than that of the elliptical sandwich structures under free–free boundary conditions and equal relative density of the truss cores.