Design Of Damper Research Articles

Bounding of earthquake response via critical double impulse for efficient optimal design of viscous dampers for elastic‐plastic moment frames

AbstractAn input velocity adjustment method of the critical double impulse (DI) is presented for efficient design of viscous dampers for elastic‐plastic moment frames. The input velocity is adjusted so that the input energy to the lowest eigenmode under the critical DI is equal to those under the selected recorded ground motions. This adjustment makes the critical DI work as the active earthquake. The response bounding property of the critical DI is supported by, (1) the multi‐modal property of the critical DI, (2) the usual excitation of the lowest mode response under recorded ground motions, (3) the large proportion of the instantaneous input energy to the total input energy in the critical DI. The proposed method can treat not only pulse‐like near‐fault ground motions but also ground motions of random nature. To validate the proposed method, the input energies and the maximum interstory drifts under the recorded ground motions and the critical DI with the adjusted input velocity are investigated for elastic single‐degree‐of‐freedom (SDOF) models, elastic proportionally damped MDOF models, and elastic‐plastic proportionally damped MDOF models. The optimization method presented in the previous paper is extended so that the critical DI can be treated for the design of viscous dampers for elastic‐plastic moment frames.

Dissipation behaviors of granular balls in a shaken closed container

Dissipated power and motion state of granular balls in a quasi-2D closed container subjected to vertical fixed-frequency excitation are investigated by comparing discrete element simulation with experiment test. The verified DEM (Discrete Element Method) model is employed to further study the dissipation characteristics and dynamical behaviors of granular balls under the conditions of different excitation amplitude A and excitation frequency f. Damping contour and phase diagram of vibrated granular balls in the A- f plane of external excitation are obtained respectively, which indicate nine different damping phases of vibrated granular balls. An unknown high damping granular phase that we call as Wave-solid state is revealed and the dissipation behaviors of three high damping granular phases including the Wave-solid state are analyzed based on the velocity profile, density profile and loss profile of vibrated granular balls. Further, the dynamical characteristics of the Wave-solid state and the commonality of the three high damping granular phases are preliminary discussed respectively. Finally, based on the previous and present research results, two solutions by controlling the jamming transition of vibrated granular materials in granular dampers for the universal design of granular dampers are presented.

Optimal design of a tunable electromagnetic shunt damper for dynamic vibration absorber

Dynamic vibration absorber (DVA) is an effective device for suppressing resonant vibration of noisy machineries and structures. However, the optimum design of DVA requires precise tuning of the damping force in the DVA, which unfortunately is often not practical and prone to changes of working conditions. In this paper, a tunable electromagnetic shunt damper (EMSD) with different opposing magnet pairs configurations is tested for the optimum design of DVA. The optimum magnet pairs configuration is derived to provide the maximum damping force in the DVA. Both simulations and experiments are conducted to verify the damping coefficient variation with the number of magnet pairs in the EMSD. The experimental optimization procedure of the DVA is designed according to the fixed-points theory. The damping force generated by the EMSD can be readily adjusted by varying the external resistance of the EMSD. This is the first experimental implementation report of the optimization procedure described in the fixed-points theory. The proposed tunable EMSD can conveniently allow for onsite optimal tuning of DVA. The proposed design methodology provides fine tuning of the damping coefficient of EMSD to achieve robust optimal DVA performance, even when subject to changes of external parasitic damping.

Geometric design of friction ring dampers in blisks using nonlinear modal analysis and Kriging surrogate model

Integrally bladed disks (blisk) have been widely used in the turbo-machinery industry due to its high aerodynamic performance and structural efficiency. A friction ring damper (FRD) is usually integrated in the system to improve its low damping. However, the design of the geometry of this FRD become complex and computationally expensive due to the strong nonlinearities from friction interfaces. In this work, we propose an efficient modelling strategy based on advanced nonlinear modal analysis and Kriging surrogate models to design and optimize the geometry of a 3D FRD attached to a high fidelity full-scale blisk. The 3D ring damper is parametrised with a few key geometrical parameters. The impact of each geometric parameter and their sensitivities to nonlinear dynamic response can be efficiently assessed using Kriging meta-modelling based on a few damped nonlinear normal modes. Results demonstrate that the damping performances of ring dampers can be substantially optimized through the proposed modelling strategy whilst key insights for the design of the rings are given. It is also demonstrated that the distribution of the contact normal load on the contact interfaces has a strong influence on the damping performances and can be effectively tuned via the upper surface geometry of the ring dampers.

Optimal design of Magnetorheological damper for seismic response reduction of Base-Isolated structures considering Soil-Structure interaction

The base isolation technique is a well-known strategy used for the seismic protection of structures. It introduces a highly deformable device between the structure and the foundation to isolate the main structure from the ground motions. Despite the continuous enhancement of base isolation techniques, the limitations of this strategy are well known to researchers and engineers. Base isolation systems undergo large displacement under strong earthquake motions, which usually results in structural damage and users’ discomfort. In this study, a magnetorheological (MR) damper is used to improve the performance of a benchmark base-isolated building by placing the MR damper between the base of the structure and the foundation. The soil-structure interaction (SSI) effect is included in the study by considering three types of soil, denoted dense, medium, and soft. The soil is introduced through two degrees of freedom, namely, sway and rocking, based on the cone simplified linear model. The MR damper parameters are optimized using a particle swarm optimization (PSO) algorithm under a set of benchmark earthquake records. The optimal local parameters related to each benchmark earthquake and soil type are averaged to obtain general optimum parameters. The acquired general optimum parameters are then used to study the dynamical response of the benchmark base-isolated building controlled by the MR damper, considering an array of 100 natural earthquake ground motions. The obtained results show an enhancement of the dynamic response under all soils conditions compared to non-optimized and base isolation only scenarios. Several engineering demand parameters (EDP) and response indicators were investigated in this study, including top floor and base displacements, inter-storey drift, storey drift, top floor acceleration, and base shear. The results obtained show the effectiveness of the optimization in improving the response of base-isolated structures. It also demonstrates the dependence of damper parameters on soil typologies.

Design of Particle Dampers for Laser Powder Bed Fusion

Additively manufactured particle dampers can significantly improve component damping. However, if designed incorrectly, the damping can be worsened. For the design of additively manufactured particle dampers, there are not yet sufficient design rules and models to describe the effect due to numerous design parameters. The research question answered in this paper describes how the effect of particle damping can be characterised as a function of excitation force and excitation frequency for different cavity sizes. To characterise the effect of particle damping, a 33 full factorial test plan is constructed, and the damping is determined experimentally. It is shown that the damping can be reliably evaluated with the circle-fit method. The effect of particle damping is investigated for beams made of AlSi10Mg, 1.2709 and Ti6Al4V. As a result, a positive effect of the particle damping in a frequency range from 500 to 30,000 Hz and partly up to the 9th bending mode can be proven. It is shown that, for the first bending mode, there is an optimum at approx. 2000 Hz. For the optimum, the increase of the damping for the tool steel 1.2709 to 28 and for the aluminium alloy AlSi10Mg to 18 can be proven.

Nonlinear Vibration Analysis of Turbine Bladed Disks With Midspan Dampers

Abstract Friction dampers are one of the most common secondary structures utilized to alleviate excessive vibration amplitudes in turbomachinery applications. In this paper, the dynamic behavior of the turbine bladed disks coupled with one of the special damper designs, the so-called Midspan Dampers (MSDs) that is commonly used in steam turbines of Baker Hughes Company, is thoroughly studied. Friction between the blade and the damper is modeled through a large number of contact nodes by using two-dimensional contact elements with a variable normal load. In the solution procedure, the coupled static/dynamic Harmonic Balance approach is utilized for the first time in the assessment of the dissipation capability of MSDs, computationally shown by predicting the forced response levels of the system at different resonances. Moreover, it is demonstrated that the nonlinear dynamic response is non-unique and it may vary considerably even if all the user-controlled inputs are kept identical. This phenomenon is a novel observation for MSDs, and it is explained by an uncertainty present in the contact forces. Contact conditions corresponding to multiple responses are also investigated to unveil the different kinematics of the damper under the same nominal conditions.

Design and Simulation Analysis of an Electromagnetic Damper for Reducing Shimmy in Electrically Actuated Nose Wheel Steering Systems

Based on the technical platform of electrically actuated nose wheel steering systems, a new type of damping shimmy reduction technology is developed to break through the limitations of traditional hydraulic damping shimmy reduction methods, and an electrically actuated nose wheel steering structure scheme is proposed. The mathematical model of the electromagnetic damper is established, the derivation of skin depth, damping torque and damping coefficient is completed, and the design of the shape and size of the electromagnetic damper is combined with the derivation results and the technical index of shimmy reduction. The electromagnetic field finite element simulation results show that the mathematical modeling method of the electromagnetic damper has good accuracy, and its application to the shimmy reduction module of the electrically actuated nose wheel steering system is also feasible and superior. Finally, the key factors influencing the performance of electromagnetic damper shimmy reduction are studied and analyzed, thus forming a complete electromagnetic damper shimmy reduction technology for the electrically actuated system, and laying the foundation for the design of novel all-electric aircraft and landing gear.

Material Damping Prediction in Timber Beams Based on Timoshenko Free-Free Beam Model

Damping in vibrating structures is much less understood than their stiffness and inertial properties and in timber structures it is even less understood how damping is generated in motion characteristic of bending and shear separately. We analyse these contributions through application of the so-called method of complex moduli, arising in constant-hysteretic models of damping. We separate the influences on overall damping due to these independent material properties by considering a partial differential equation of undamped motion and substituting Young's and shear moduli with their complex counterparts. We keep the rotary inertia present in the model to assess its own damping contribution and design an experimental setup in which vibration of a free-free beam is simulated so that no reaction (i.e., no contact damping) should be present, which allows us to assess the contribution due to bending, shear and rotary inertia to material damping only. We show that, in the present model, the overall loss factor is indeed smaller than in the literature, while the damping due to shear effects grows in higher vibration modes and beams with smaller length-to-height ratio. Finally, we propose a damping prediction model built on simple linear regression in which the vibration modes are processed separately.

All-round responses and boundaries of a shaft and dry friction damper assembly

A helicopter tailrotor driveline is equipped with dampers to suppress the resonance of transmission shafts. A dry friction damper and a slender shaft form an assembly The comprehensive understanding of different responses of the assembly provides the basis for a more reasonable parameter configuration of the damper. To this end, the assembly is modeled as a dynamic system with rub impact between a rotor with continuous parameter distribution and a suspended elastic stator. Boundaries of rub impact and condition of Hopf bifurcation are derived. Pinned natural frequencies and backward whirl frequencies are solved by analytical deduction. The critical speed for triggering a backward whirl with consideration of eccentric excitation is obtained by the multiple scale perturbation method. Then, all-round responses and boundaries are solved by both analytical and numerical approaches based on the parameters of a helicopter. The effects of friction coefficient, internal damping, suspension stiffness, variable impact stiffness, etc. on the boundaries are presented in detail with the discussion of relationships between physical reasons and analytical conditions. Results show that smaller impact stiffness difference and friction coefficient, a greater mass damping ring, moderate suspension stiffness, greater internal and external damping are the key factors for the damper design. This study has reference significance not only for the assembly in a helicopter but also for similar mechanical systems.

Multiparameter Optimization Design of Self-centering Friction Damper Using Shape Memory Alloy Bars

ABSTRACT In this study, the superelasticity of shape memory alloy (SMA) bars was used to develop a new self-centering friction damper (SCFD). A modified SMA constitutive model was established and verified using cyclic tensile test results of the SMA bars to establish the theoretical model of the SCFD. An effective method for the multiparameter optimization design of the SCFD was developed, which is applicable to other hybrid dampers. This optimal method using the genetic algorithm was based on defining an optimization calculation that reflects the dissipative coefficient and equivalent viscous damping as the evaluation indices and the SCFD design variables as the optimal parameters.

Integral Methodology for the Multiphysics Design of an Automotive Eddy Current Damper

The present work reports an integrated (experimental and numerical) methodology that combines the development of a finite element multiphysics model with an experimental strategy to optimally design an eddy current damper for automotive suspensions. The multiphysics model couples the whole set of time-dependent electromagnetic, thermal, mechanical, and fluid–wall interaction (CFD) partial differential equations. The developed FE model was validated against both literature model predictions and in-house experimental data. The electromagnetic model takes into account the magnetic material characteristics of the ferromagnetic material and iron poles. Loss separation and the Jiles–Atherton hysteresis models were invoked to determine the heat generated in the soft iron parts. The computation of the fluid–wall interaction phenomena in the air gap allowed for the prediction of the temperature field across the solid materials, including the magnets. The design of the EC damper addresses the effects of the geometries of the stator and rotor, as they are the most critical geometries for maximizing the functions of an eddy current damper. The magneto-thermal simulations suggested that the heating of the permanent magnets remains within a safe region over the investigated operational frequency range of the eddy current damper.

Extending the Validity of Squeeze Film Damping Models with Lower Aspect Ratios.

Squeeze film air damping is a significant factor in the design of MEMS devices owing to its great impact on the dynamic performance of vibrating structures. However, the traditional theoretical results of squeeze film air damping are derived from the Reynolds equation, wherein there exists a deviation from the true results, especially in low aspect ratios. While expensive efforts have been undertaken to prove that this deviation is caused by the neglect of pressure change across the film, a quantitative study has remained elusive. This paper focuses on the investigation of the finite size effect of squeeze film air damping and conducts numerical research using a set of simulations. A modified expression is extended to lower aspect ratio conditions from the original model of squeeze film air damping. The new quick-calculating formulas based on the simulation results reproduce the squeeze film air damping with a finite size effect accurately with a maximum error of less than 1% in the model without a border effect and 10.185% in the compact model with a border effect. The high consistency between the new formulas and simulation results shows that the finite size effect was adequately considered, which offers a previously unattainable precise damping design guide for MEMS devices.

Design of a novel seismic retrofitting system for RC structures based on asymmetric friction connections and CLT panels

Friction-based dampers are a valid solution for non-invasive seismic retrofitting interventions of existing structures, particularly reinforced-concrete (RC) structures. The design of friction-based dampers is challenging: underestimating the slip force prevents the full use of the potential of the device, which attains the maximum admissible displacement earlier than expected. By contrast, overestimating the slip force may cause delayed triggering of the device when the structure has suffered extensive damage. Therefore, designing the appropriate slip force is an optimization problem. The optimal slip force guarantees the highest inter-story drift reduction. The authors formulated the optimization problem for designing a specific class of friction-based dampers, the asymmetric friction connection (AFC), devised as part of the ongoing multidisciplinary Horizon 2020 research project e-SAFE (Energy and Seismic AFfordable rEnovation solutions). The seismic retrofitting technology involves the external application of modular prefabricated cross-laminated timber (CLT) panels on existing external walls. Friction dampers connect the CLT panels to the beams of two consecutive floors. The friction depends on the mutual sliding of two metal plates, pressed against each other by preloaded bolts. This study determines the optimal slip force, which guarantees the best seismic performance of an RC structural archetype. The authors investigate the nonlinear dynamic response of a coupled mechanical system (RC frame-friction damper) under a set of strong-motion earthquakes, using non-differential hysteresis models calibrated on the experimental cyclic responses. The solution of the optimization leads to the proposal of a preliminary simplified design procedure, useful for practitioners.

Optimal distribution of friction dampers to improve the seismic performance of steel moment resisting frames

This study aims to develop a low computational cost framework to optimize the seismic performance of the steel moment-resisting frames (SMRFs) equipped with friction dampers at different performance levels. To achieve the optimal design of dampers in a structure, a novel approach called adaptive optimisation technique (AOT) is adopted. The basis of this method is to achieve a uniform distribution of damage (UDD) in the structure to exploit the maximum energy dissipation capacity of the dampers. The optimisation objective is to obtain the best position of friction dampers and minimize their slip-threshold force to satisfy a predefined inter-story drift (i.e. selected performance target). The efficiency of the proposed method is demonstrated through optimum design of 4, 8, and 16-story SMRFs subjected to a set of strong natural earthquake records. The unique features of AOT are examined including the high convergence rate, the independence of the optimal solution from an arbitrary starting point, and also the ability to perform multi-level performance optimisation. Finally, the dependency of the seismic optimisation methods to the selected design acceleration record, as a challenge in the practical seismic design process, is addressed by proposing a modification in the proposed adaptive formula. In addition, the results of the proposed method are compared with iterative, non-iterative, and some metaheuristic optimisation methods such as genetic algorithm (GA), particle swarm optimisation algorithm (PSO), and simulated annealing algorithm (SA). It is shown that the AOT can lead to optimum design solutions with significantly less computational costs (up to 98%) compared to the conventional techniques.

Design, characterization and control of MR damper for two-wheeler applications

The research on Automotive systems is always an ongoing process with varied advancements in different sectors. One such sector is suspension system and the recent trends in vehicular suspension has taken a turn towards semiactive suspension considering its salient features like cost effectiveness and low power consumption with variable damping force. This research work presents the design of radial flux Magneto Rheological damper (MRD) with magnetic field analyzed using the FEMM tool. The designed MR damper has fabricated and characterized for modelling the damper in order to simulate the quarter car model of two wheeler rear suspension. The entire simulation was carried out using MATLAB/SIMULINK.

Performance evaluation of friction dampers for building with soil-structure interaction

From ancient times, earthquakes have been considered the most devastating natural disaster. Many times, the damages caused by earthquakes are irrecoverable due to the static design of building structures. For the reduction of these damages, friction dampers are widely used as passive energy dissipation devices. As the friction dampers are designed with fixed base assumption, the effect of soil-structure interaction is totally neglected. Hence, the present study deals with the design methodology of friction damper incorporating soil-structure interaction effect. The slip load of friction dampers has been calculated by assuming a fixed base and flexible base (i.e. the linear and nonlinear behavior). The different models of a soil-foundation system were constructed using multilinear elements. The pushover analysis has been carried out to design the friction damper and the comparison of the same has also been done. Finally, a numerical study over different models was carried out to evaluate the performance of the friction dampers. The response was compared based on storey drift, member forces, and energy dissipated by friction dampers. It was found that the design of friction dampers by considering the non-linearity of soil leads to a realistic approach to seismic design.

Design of a Novel Magnetorheological Damper with Large Damping Force and its Nonlinear Modeling at High Velocity

Design of a Novel Magnetorheological Damper with Large Damping Force and its Nonlinear Modeling at High Velocity

Study Case: Electromechanical Design of a Magnetic Damper for Robotic Systems

Study Case: Electromechanical Design of a Magnetic Damper for Robotic Systems

Optimal design of passive momentum exchange impact damper using mechanical singularity

Optimal design of passive momentum exchange impact damper using mechanical singularity