Concept Of Damping Research Articles

Amortiguamiento Viscoso Equivalente en el Diseño Basado en Desplazamientos

A comienzos de siglo comienza el desarrollo de métodos de diseño basados en desempeño para estructuras sometidas a acción sísmica, destacándose entre ellos el método de diseño directo basado en desplazamientos (DDBD). Este método caracteriza el comportamiento no lineal de una estructura sometida a acción sísmica mediante un sistema lineal equivalente, donde se utiliza el concepto de amortiguamiento viscoso equivalente (AVE) para representar el comportamiento no lineal, así como todas las fuentes de disipación de energía elásticas e inelásticas en la estructura. El AVE tiene sus comienzos a principios del siglo pasado y con el advenimiento del DDBD se han realizado números estudios numéricos y experimentales para aproximar el comportamiento lineal de la estructura. Este artículo presenta los principales avances del AVE, se abordan distintos ciclos de histéresis, y característicos de diversas tipologías estructurales, se concluye que es un tema abierto sobre todo en la parte experimental.

Application of Tuned Vibration Absorber Concept to Blisk Ring Dampers: A Nonlinear Study

AbstractIn this study, a novel design for ring dampers is proposed, where the concept of tuned vibration absorbers is leveraged to substantially increase damper effectiveness while minimizing potential stresses near the blade root. Tuned absorbers have been used in the past to reduce the forced response amplitudes of both mechanical and civil structures. The absorber natural frequency is tuned to the targeted frequency of the host structure where it is attached. The vibration reduction mechanism relies on energy transfer from the host structure to the absorber. The novel design technique proposed here uses a vibration absorber approach to achieve energy transfer from the blisk to the damper, which leads to larger damper motion. This enables energy dissipation due to friction, reducing vibrations even in blade-dominated modes. An academic finite element model of a blisk with a ring damper is used to demonstrate the novel tuned damper concept and design technique. The geometric mistuning of the damper due to the presence of a gap in the ring structure is also taken into account. The results demonstrate the validity of the proposed tuned damper concept, showing a substantial vibration amplitude reduction compared to the linear baseline results, in which the damper is not tuned or absent.

Dynamic Behaviour Adaptation of Lightweight Structures by Compressible Constrained Layer Damping with Embedded Polymeric Foams and Nonwovens

Evanescent morphing in combination with an original concept of Compressible Constrained Layer Damping (CCLD) is a novel and promising approach for dynamic behaviour adaptation. The crucial component of the CCLD is a compressible intermediate layer with its thickness and material properties controlled by fluid actuation, enabling the adjustment of the damping and stiffness of the overall system. To estimate the potential of the CCLD, an analytical model was developed which describes the vibration behaviour of the overall structure, taking into account the compression-driven properties of the intermediate layer. The results confirm the principal correctness of the initial theoretical assumptions regarding the adaptive dynamic behaviour of structures with CCLD treatment. A significant vibration mitigation as well as a high adaptability of dynamic behaviour were observed, however, they show a complex dependence on the system configuration. Nevertheless, the developed analytical modelling approach can already be used for a preliminary system design. Besides the analysed polymer-based foams as the intermediate layer, nonwovens also exhibit compression-dependent shear properties and can therefore be used in CCLD. First preliminary investigations show that the damping performance is on average about ten times better than that of the polymeric foams.

Nonlinear Electromagnetic Shunt Damping for Nonlinear Vibration Isolators

This paper presents the concept of nonlinear electromagnetic shunt damping (N-EMSD) and employs it for the vibration isolation enhancement of nonlinear vibration isolators. A nonlinear electromagnetic vibration isolator (NEVI) is designed. Two configurations of the permanent magnets and coils are constructed to illustrate the damping mechanisms of linear electromagnetic shunt damping (L-EMSD) and N-EMSD, respectively. The nonlinear electromagnetic coupling coefficient of the NEVI is modeled. The theoretical models of the NEVI with L-EMSD and N-EMSD are established. Both the numerical simulation and experimental efforts are performed to verify the vibration isolation performance of the NEVI with L-EMSD and N-EMSD. The results demonstrate that the proposed N-EMSD can provide wonderful nonlinear damping to reduce vibration in the resonance region but do not affect the isolation performance in the isolation region. L-EMSD has a better vibration suppression performance than N-EMSD in the resonance region; however, the vibration isolation performance becomes worse in the isolation region. Furthermore, the effect of the isolation mass is also studied experimentally. This work opens a new opportunity to further study EMSD technique in linear and nonlinear systems.

A New Generation of Magnetorheological Vehicle Suspension System With Tunable Stiffness and Damping Characteristics

As the concept of variable stiffness (VS) and variable damping (VD) has increasingly drawn attention because of its superiority on reducing unwanted vibrations, dampers with property of varying stiffness and damping have been an attractive method to further improve vehicle performance and driver comfort. This paper presents the design, prototyping, modeling, and experimental evaluation of a VS and VD magnetorheological (MR) vehicle suspension system. It was first characterized by an INSTRON machine. Then, a phenomenological model was proposed to capture the characteristics of the damper and TS fuzzy approach was used to model the quarter car system where the proposed damper was installed. Different controllers, including skyhook, short-time Fourier transform and state observer based controller were designed to control the damper. Experimental results demonstrate that the quarter car system with the VS and VD suspension performs best in terms of reducing the sprung mass accelerations comparing with other suspensions.

Design and experimental characterization of a twin-tube MR damper for a passenger van

The smart behavior of magneto-rheological (MR) fluid is used in the present work in designing, experimentally characterizing and analyzing a MR damper for automotive application using the twin-tube damper concept. A commercially available passive damper of a passenger van was tested to find the characteristic damping requirement of the vehicle. With this as reference, a twin-tube MR damper working in valve mode was designed and fabricated. The magnetic flux density induced in the fluid flow gap is maximized using Taguchi analysis and finite element method magnetics (FEMM) software. The FEMM results are validated by verifying with results obtained analytically using electromagnetic circuit theory. The MR damper filled with commercially available MR fluid was experimentally tested in damper testing machine. The results demonstrate that the force developed by the MR damper is indeed increasing with the value of the current supplied. At various frequencies of input oscillation, the energy dissipated by the MR damper in a single cycle increases significantly with current supplied. The novelty of this work is that a twin-tube MR damper working in valve mode was designed as a replacement for the passive damper used in a passenger van. The MR damper thus developed is capable of producing practical levels of damping force at actual operating frequencies and amplitudes of the passive damper in the passenger van. For further analysis, the behavior of the MR damper is modeled by using the Bouc–Wen model for hysteretic systems. A proportional–integral–derivative controller is used to track the desired damping force in time domain to demonstrate the application of the MR damper in a semi-active suspension system.

Parametric study of a novel nose landing gear shimmy damper concept

Shimmy dampers are passive solutions for undesired shimmy vibration in aircraft landing gears. Although they mitigate shimmy to variable degrees, they can introduce weight, cost, and reliability penalties especially when added to existing landing gear systems. More effective and compact shimmy dampers with reduced maintenance effort and enhanced stability performance can then greatly contribute to light-weighting, as well as lowering the aviation risk and maintenance costs. Moreover, a robust performance analysis and characterization framework based on high-fidelity computational models is absent from the literature while it is essential to quantify the capabilities of a given damper. In this work, analysis of a novel shimmy damper concept is presented along with an effective methodology for evaluating the performance of shimmy dampers based on nonlinear shimmy amplitude maps and stability boundary plots. The new damper concept is suitable for installation on existing and new landing gears and features a multifunctional torque link member including an assembly of beam and damping units to suppress the undesired vibrations. The influence of torque link damper parameters is then thoroughly explored using the nonlinear Multibody Dynamics model of the nose landing gear employed for both generating the shimmy maps and time histories of the vibrations. The novel concept is shown to be capable of effectively mitigating the rotational shimmy given that the parameters are chosen appropriately based on the systematic approach laid out. The insights from the analysis are then distilled in the form of recommendation for designing next generation shimmy dampers. Moreover, the novel framework introduced for characterizing shimmy dampers offers great benefit to the shimmy suppression research and development practice.

Numerical and experimental studies on a new variable stiffness and damping magnetorheological fluid damper

This article describes a new magnetorheological fluid damper; its damping and stiffness are variable and controllable through the compact structure of two damping units and a spring. The ability of variable stiffness and damping enables it to be used for more effective vibration control in wide-band excitation wave occasions. First, the effective stiffness and output damping force are calculated in theory. Then, the magnetic field is simulated by finite element analysis. After the prototype of the new magnetorheological fluid damper is developed and machined, the damper’s performances are tested in a hydraulic actuated MTS machine, including stiffness variability and damping variability in different current. The successful development, numerical calculation, and experimental testing shows that the new damper not only outputs a controllable damping force but also occurs as the great variable stiffness in a certain range, which makes the true design and implementation of the concept of variable stiffness and damping.

Multi‐DFIG aggregated model based SSR analysis considering wind spatial distribution

This study investigates the impact of wind spatial distribution on sub-synchronous resonance (SSR), considering wind speed difference and wind turbine division. For a doubly-fed induction generator (DFIG) wind farm, two equivalent aggregated models, i.e. a one-DFIG model and a multi-DFIG model, are established and both simplified to impedance model for investigation. In one-DFIG model, the SSR mechanism in DFIG wind farm, and the impact of wind speed on SSR are discussed. The concept of damping is introduced to explain how DFIG SSR current changes under the negative resistance of wind farm. Then, in multi-DFIG model, DFIGs are divided into different groups based on their wind speed, and the interaction between DFIG groups is investigated. Simulations are used to validate the proposed analysis, and the results show that, multi-DFIG model performances a higher accuracy when dealing with DFIG wind spatial distribution problems compared with one-DFIG model.

An integrated finite particle method with perfectly matched layer for modeling wave-structure interaction

ABSTRACTNumerical simulation of wave-structure interaction is an important but challenging topic due to the movement, deformation and even breakup of free surface, and strong fluid-structure interaction. The implementation of far-field boundary condition is crucial for numerical simulations of wave-structure interaction to avoid the disturbance of reflected waves. In this paper, an integrated finite particle method (FPM) with perfectly matched layer (PML) is developed for modeling wave-structure interaction problems. The PML uses a fictitious layer based on the concept of physical damping to control the wave reflection in a wave tank. The FPM with PML is first used to model the regular wave propagation and it is found that the obtained numerical results are in good agreement with analytical solutions or existing reference results. It is further proved that PML with a properly selected length of wave tank can effectively remove the traveling waves and reproduce the far-field effects. The FPM with PML is then used to model the oscillating wave surge converter (OWSC). The results show that the time-averaged power of OWSC strongly depends on the PTO damping coefficients, the wave periods and the distance between the OWSCs.

A compact perfectly matched layer algorithm for acoustic simulations in the time domain with smoothed particle hydrodynamic method.

This paper focuses on the development of absorbing boundary conditions and their implementation in the smoothed particle hydrodynamics (SPH) method for wave propagation problems. A compact perfectly matched layer (C-PML) approach is formulated for transient acoustic problems in an infinite space using SPH models with a computational domain of finite dimensions. The proposed approach is based on the concept of fictitious physical damping acting within the additional perfectly matched layers (PMLs) to absorb outgoing waves to practically eliminate the reflection of waves from the boundary of the finite computational domain. To reduce the amount of computations resulting from the layers and improve the computational stability with respect to time, the C-PML algorithm uses the time exponential differencing scheme with small PML domains implemented in an SPH code for transient analyses of waves propagating in acoustic media. Tests of Gaussian pulse sound wave propagation are conducted to demonstrate the effectiveness of the proposed algorithm. The results show that the C-PML algorithm with SPH can absorb the outgoing wave with fewer layers than the conventional PML algorithm. The influence of the thickness of the PML layers, attenuation coefficient, and smoothing length on the C-PML algorithm are analyzed.

The concept of vibration damping of the variable mass assembly

An innovative method of damping vibrations using a variable mass assembly will be presented in this article. The concept was based on a physical pendulum model consisting of two connected elements. Mass exchange between the upper and lower member of the pendulum is modelled as a gravity a fluid flow. With the passage of time, the mass of the upper member of pendulum decreases and the mass of the lower member of pendulum increases. It is assumed preserve the mass of the whole system. The article will also present the application possibilities and a review of currently used vibration dampers.

Hermetically Sealed Squeeze Film Damper for Operation in Oil-Free Environments

The following work advances a new concept for a hermetically sealed squeeze film damper (HSFD), which does not require an open-flow lubrication system. The hermetically sealed concept utilizes a submersed plunger within a contained fluidic cavity filled with incompressible fluid and carefully controlled end plate clearances to generate high levels of viscous damping. Although the application space for a hermetic damper can be envisioned to be quite broad, the context here will target the use of this device as a rotordynamic bearing support damper in flexibly mounted gas bearing systems. The effort focused on identifying the stiffness and damping behavior of the damper while varying test parameters such as excitation frequency, vibration amplitude, and end plate clearance. To gain further insight to the damper behavior, key dynamic pressure measurements in the damper land were used for identifying the onset conditions for squeeze film cavitation. The HSFD performance is compared to existing gas bearing support dampers and a conventional open-flow squeeze film dampers (SFD) used in turbomachinery. The damper concept yields high viscous damping coefficients an order of magnitude larger than existing oil-free gas bearing supports dampers and shows comparable damping levels to current state of the art open-flow SFD. The force coefficients were shown to contribute frequency-dependent stiffness and damping coefficients while exhibiting amplitude independent behavior within operating regimes without cavitation. Finally, using experimentally based force density calculations, the data revealed threshold cavitation velocities, approximated for the three end seal clearance cases. To complement the experimental work, a Reynolds-based fluid flow model was developed and is compared to the HSFD damping and stiffness results.

DIII-D Research to Prepare for Steady State Advanced Tokamak Power Plants

We review progress made on the advanced tokamak path to fusion energy by the DIII-D National Fusion Facility (Luxon et al. in Nucl Fusion 42:614, 2002). The advanced tokamak represents a highly attractive approach for a future steady state fusion power plant. In this concept, there is a natural alignment between high pressure operation, favorable stability and transport properties, and a highly self-driven (‘bootstrap’) plasma current to sustain operation efficiently and without disruptions. Research on DIII-D has identified several promising plasma configurations for fully non-inductive operation with potential applications to a range of future devices, from ITER to nuclear science facilities, to compact or large scale fusion power plants. Significant progress has been made toward realizing these scenarios, with the demonstration of high β access, off-axis current drive techniques, model based profile control, and stability and ELM control in reactor relevant physics regimes. Radiative techniques have also been pioneered to develop improved compatibility with divertor requirements, and simultaneous access to high performance pedestals. Research has also developed major advances in physics understanding, validating concepts of kinetic damping of ideal MHD instabilities that enable high β operation, identifying how current profile and β influence plasma turbulence in order to validate and improve turbulent transport models, and understanding the physics of energetic particle redistribution due to Alfvénic and other instabilities. These advances have been partnered with development of a rigorous integrated modeling framework used to interpret and validate individual physics models of the various aspects of plasma behavior, and to guide development of improved regimes and upgrades. These tools are also being used to develop and validate concepts for future reactors directly. Having established these foundations, DIII-D is now undergoing a substantial upgrade to raise power, current drive, electron heating and 3-D field capabilities in order to validate this physics and test conceptual solutions in reactor-relevant physics regimes, with a goal to resolve the key scientific and technology questions to enable a decision on a future steady state fusion power plant.

Modeling and Operational Analysis of an Automotive Shock Absorber with a Tuned Mass Damper

Abstract Recently, the topic of energy dissipation efficiency of vehicle suspension dampers has become a research and engineering problem due to structural requirements of vehicle manufacturers and the introduction of electric/hybrid cars. By principle, any disturbances in the damping force generation process translate into pressure fluctuations to be then transferred to the body of the vehicle. The effect known as rattling within the damper engineering community is perceived as detrimental to ride comfort. To improve the performance of a vehicle damper several methods can be devised and used. One approach is to optimize the settings of the valves in the damper. The approach, however, often influences the force output of the damper. Another technique involves the application of add-on systems. One such system is the tuned mass damper concept originally developed by Frahm for structural engineering applications. In the paper the author proposes a damper concept equipped with an external/internal tuned mass damper component for improving the dynamic characteristics of vehicle dampers. The author presents modeling details followed by simulations of the damper with the tuned mass damper concept subjected to oscillatory inputs, and a critical analysis of the presented results.

Semi-Active Vortex Induced Vibration Control of an Elastic Elliptical Cylinder with Energy Regeneration Capability

The concept of energy-regenerative damping is adopted in semi-active vortex-induced vibration (VIV) suppression of an elastically supported inclined impenetrable elliptical cylinder modeled as a two degree-of-freedom (DOF) system in laminar cross-flow at low Reynolds numbers (Re = 210). It is based on the intelligent (model free) adaptive fuzzy sliding mode control (AFSMC) strategy in conjunction with switch-based energy regenerating circuit of a tunable electromagnetic (EM) damper. The semi-active damper is linked to the plant model in a multi-field co-simulation framework via MATLAB/Simulink coupled with a user defined function in a CFD package. The AFSM controller initially calculates the desired transverse control force for suppression of the cylinder VIV. Consequently, by smart adjustment of the variable circuit load resistance, the current flow through EM damper circuit is adaptively modulated in such a way that the damping force continually tracks its active counterpart in a semi-active manner. Furthermore, when the damper is operating in the regeneration mode, the mechanical vibration energy that is traditionally dissipated as heat in conventional viscous dampers will be stored as electric charge in a capacitor. Numerical simulations demonstrate that the regenerative semi-active EM-based VIV control system can effectively suppress the cylinder motion while recovering a certain portion of mechanical vibration energy through the cooperative action of two distinct operation modes of the EM damper. Unlike conventional active control systems, the proposed system does not require a large external power supply, and at least part of the required power may be provided by the recovered energy.

Simulation based optimization of torsional vibration dampers in automotive powertrains

In this paper, an approach for the automated design of isolation elements as used in automotive powertrains is presented. The method is based on 1D-MBS models representing various drivetrain configurations and damper concepts. This allows for a dynamical analysis in typical design relevant driving situations like full load acceleration or engine start. The concept design is carried out in a numerical optimization process in order to find a set of geometric parameters with minimal design space requirements and weight. Especially the specifications imposed on the drivetrain’s vibrational behavior lead to a complex optimization problem which requires robust and carefully tuned algorithms. A search method that has been successfully applied to constrained design problems in engineering is the Augmented Lagrangian Particle Swarm Optimization procedure. The dimensioning of a dual mass flywheel with an additional internal damper for an all-wheel drive sports car is used as a test case to evaluate the algorithm’s suitability for this particular application. Several control parameter settings are compared regarding their influence on the optimizer performance.

Analysis, Prototyping, and Experimental Characterization of an Adaptive Hybrid Electromagnetic Damper for Automotive Suspension Systems

In this paper, the concept of hybrid electromagnetic damping is explored and experimentally evaluated. The aim of the hybrid electromagnetic damping concept is to address the adaptive damping problem in vehicle suspension systems. In order to reach optimal performance, the damping characteristics of the vehicle suspension system must be capable of adaptively increasing or decreasing the amount of energy being absorbed by the system. For the sake of having the requisite functionality of variable damping, a multitude of solutions have been implemented, proposed, and evaluated at both the commercial and academic research levels. These solutions have met the variable damping requirements, but still, there are several crucial drawbacks associated with them. To overcome the shortcomings associated with the aforementioned variable damping solutions, a hybrid design consisting of a conventional hydraulic damper and a linear motor topology is fused together to build a hybrid variable damper. In the proposed hybrid electromagnetic design, the oil in the system acts as bias to provide fail-safe operation for the system, and the linear motor topology allows the requisite variable damping requirement to be achieved with the additional capacity for recovering energy from the system. We present an extended analysis of the electromagnetic damping component of the hybrid damper that can serve as a potent tool for the designers who seek to maximize the adaptability (and regeneration capacity) of the hybrid damper. Afterwards, based on the proposed hybrid electromagnetic concept, the design and fabrication of the first prototype are illustrated. An experimental setup and a test protocol are prepared, and different experiments are conducted to characterize the damping properties of hydraulic and electromagnetic components. Furthermore, friction forces, as well as power capacities, are scrutinized. The results indicate that the hybrid electromagnetic damper prototype is capable of providing a variable damping coefficient in a range of 1302–1540 N $\cdot$ s/m.

Thermally activated energy dissipation in semi-crystalline polymer nanocomposites

In this manuscript, we demonstrate the concept of active damping in semi-crystalline thermoplastics which are reinforced with a percolated network of CNTs, where the damping of the composite was augmented considerably, controllably and reversibly via Joule heating. The Joule heating triggered relaxation mechanisms in the amorphous phase of the matrix. To this end, semi-crystalline poly ether ether ketone (PEEK) polymer and PEEK/carbon nanotube (CNT) composites were fabricated and their viscoelastic properties were studied. The damping performance was experimentally tested by dynamic mechanical analysis. The polymer relaxation resulting from an increase in temperature, triggered by the Joule heating of the nanoparticles, demonstrated the potential for damping enhancement in the composite. A considerable enhancement in damping (by as much as 400%) was achieved at a significantly lower relative loss in storage modulus (40%), both caused by relaxation mechanisms in Joule heated samples. This enhancement in damping corresponds to a 150% improvement in the figure of merit for damping materials. The non-uniform temperature distribution in the sample was measured experimentally at the macroscale and estimated via continuum models at the microscale. It was concluded that non-uniform temperature distribution in the composite, especially at the microscale, had a large effect on the overall damping enhancement. Based on the microscale models, potential mechanisms by which the active damping can be enhanced were discussed.

DC-Bus Voltage Control Stability Affected by AC-Bus Voltage Control in VSCs Connected to Weak AC Grids

With the wide application of voltage source converters (VSCs) in power system, dc-bus voltage control instabilities increasingly occurred in practical conditions, especially in weak ac grid, which poses challenges on stability and security of power converters applications. This paper aims to give physical insights into the stability of dc-bus voltage control affected by ac-bus voltage control in VSC connected to weak grid. The concepts of damping and restoring components are developed for dc-bus voltage to describe the stability of dc-bus voltage control. The impact of ac-bus voltage control on dc-bus voltage control stability can be revealed by investigating the impact of ac-bus voltage control on damping and restoring components essentially. Furthermore, the detailed analysis for the impact of ac-bus voltage control on damping and restoring components is presented considering varied ac system strengths, operating points, and ac-bus voltage control parameters. The simulation results from 1.5-MW full-capacity wind power generation system are demonstrated which conform well to the analysis. Finally, the experimental results validate the analysis.