Design Of Damper Research Articles

Experimental Study of Friction and Wear Behaviour of Ni Based Superalloy Material

Nickel based superalloy material is used for the design of dampers in steam and gas turbine. Parametric study of rubbing velocity, contact pressure and contact temperature influence on Nickel based superalloy material coefficient of friction and wear analysis. Friction is not desirable in machines, but it is desirable in design parameter for brakes and clutches. In the present paper, an experimental investigation is carried to find out the coefficient of friction and wear rate of Nickel based superalloy material. Experiments are carried by using a pin on disk apparatus on different diameter pins and disks of the same material. The experiments are carried on normal load ranging from 10 to 200N, speed varies from 200 to 2000 rpm and, wear track diameter ranging from 5 to 160 mm. Thus, the coefficient of friction and wear rate were studied with varying normal load at a constant rubbing velocity for different diameter pins. Thereafter the coefficient of friction and wear rate studied at a constant normal load with varying rubbing velocities for different diameter pins. By varying normal load at constant rubbing velocity it is observed that coefficient of friction decreases and wear rate increases for all diameter pins

Design of a composite viscous damper and application on cylindrical thin-walled part milling

Chatter vibration is apt to occur when machining thin-walled parts with insufficient rigidity. The harmful excitation of periodical cutting forces can be mitigated by enhancing the dynamic stiffness or increasing the damping of the part. A composite viscous damper including air damping and eddy current damping is designed, which can be attached on the thin-walled part by the vacuum. Based on the formulations of air damping and eddy current damping, the optimal equivalent viscous damping is derived for achieving the maximum critical depth of cut. Furthermore, the geometries of the damper are determined for damping a specific thin-walled part after investigating its relationship with viscous damping. The modal test indicates that the damper can suppress multiple modes of the cylindrical thin-walled part, and the amplitude of the first mode of the frequency response function (FRF) is reduced by 57%. The composite viscous damper is applied to suppress the chatter and resonant vibration of the thin-walled part during machining. Milling tests demonstrate that the machining vibration is reduced by 55% and 76% after employing single damper and four dampers, respectively.

Design and Analysis of a Hybrid Annular Radial Magnetorheological Damper for Semi-Active In-Wheel Motor Suspension.

In this study, a novel hybrid annular radial magnetorheological damper (HARMRD) is proposed to improve the ride comfort of an electric vehicle (EV) powered by an in-wheel motor (IWM). The model primarily comprises annular-radial ducts in series with permanent magnets. Mathematical models representing the governing motions are formulated, followed by finite element analysis of the HARMRD to investigate the distribution of the magnetic field density and intensity of the magnetorheological (MR) fluid in both the annular and radial ducts. The optimized model generates a damping force of 87.3–445.7 N at the off-state (zero input current) with the excitation velocity ranging between 0 and 0.25 m/s. By contrast, the generated damping force varies from 3386.4 N to 3753.9 N at an input current of 1.5 A with the same velocity range as the off state. The damping forces obtained using the proposed model are 31.4% and 19.2% higher for the off-field and on-field states, respectively, compared with those of the conventional annular radial MR damper. The efficiency of the proposed model is evaluated by adopting two different vehicles: a conventional vehicle powered by an engine and an EV powered by an IWM. The simulation results demonstrate that the proposed HARMRD along with the skyhook controller significantly improves both the ride comfort and road-holding capability for both types of vehicles.

Design and optimization of a magnetorheological damper based on B-spline curves

Taking advantage of the magnetically controllable rheological properties of magnetorheological (MR) fluid, MR dampers are widely used in many engineering fields. Much effort has been made to improve the performance of MR dampers. Structural optimization is one of the popular methods to effectively improve the performance parameters of MR dampers. Most MR damper optimizations are focused on parts with regular shape, but shapes governed by equations can bring out more possibilities and further optimal results. Therefore, in this paper, a new MR damper is designed and optimized based on B-spline curves in order to maximize the controllable output damping force while saving the input power for the prosthetic knee. First, design principle of dividing the parts of the MR damper into two categories is introduced. Then, B-spline curves are used to form the piston shape, which is one of the crucial parts inside the magnetic circuit. Later, the optimal B-spline curve and other geometric parameters inside the magnetic circuit are obtained through simulation and optimization. Furthermore, the optimized MR damper is fabricated, assembled and tested. Finally, the proposed MR damper is compared with the ones in our previous work. Experimental results match well with the simulation ones. When working at the frequency of 1.0 Hz and the amplitude of 10 mm, the proposed MR damper has large maximum damping force and dynamic ratio, with acceptable equivalent damping. The proposed MR damper also performs better than the prototypes in our previous work in terms of maximum damping force, field dependent force, equivalent damping, dynamic range, and force-to-power ratio.

Risk-Based Optimal Design of Seismic Protective Devices for a Multicomponent Bridge System Using Parameterized Annual Repair Cost Ratio

Base isolators and fluid viscous dampers are viable protective devices that have been commonly considered in the seismic protection of civil engineering structures. However, the optimal design of these devices remains a tedious and iterative undertaking due to the uncertainty of ground motions, the nonlinear behavior of the structure, and its change of dynamic characteristics (i.e., effective stiffness and damping ratio) under each new design. The optimal design problem becomes more challenging concerning a multiresponse bridge system where conflicting damage potential is often expected among multiple bridge components (e.g., column, bearing, shear key, deck unseating, foundation). In this respect, this study develops a risk-based optimization strategy that directly links the expected annual repair cost ratio (ARCR) of the bridge to the design parameters of base isolators and fluid dampers. This strategy is achieved by devising a multistep workflow that integrates a seismic hazard model, a design of experiment for bearings and dampers, a logistic regression towards parameterized component-level fragility models, and a bridge system-level seismic loss assessment. The developed ARCR is parameterized as a convex function of the influential parameters of seismic protective devices. As such, optimal bearing and damper designs can be pinpointed by directly visualizing the global minimum of the parameterized ARCR surface. The optimal design is carried out against a typical reinforced concrete highway bridge in California that is installed with the fluid dampers and three types of widely-used isolation bearings—the elastomeric bearing, lead-rubber bearing, and friction pendulum system. It is shown that optimal design parameters can be obtained to significantly reduce the expected ARCR of the bridge, whereas combining optimally designed bearings and dampers can provide the minimum seismic risk.

Physics-informed deep neural networks for simulating S-shaped steel dampers

Numerical simulation that combines finite element methods and experimental data has been recognized as effective in modeling hysteretic behaviors and capturing the principle mechanical trend of passive energy dissipation devices. However, the seismic design and mechanical characteristics assessment for passive energy dissipation devices require a laborious effort and massive computational resources to tune mechanical-oriented parameters. Particularly, the potential risk of departure from the actual system is rising for the desirable seismic design of dampers due to the numerical model simplification and assumption. To eliminate the potential weakness of numerical models, this paper explores a surrogate model by implementing physics-informed deep neural networks (DNNs) to approximate hysteretic behaviors of S-shaped steel dampers. The proposed physics-informed DNNs mainly consists of recurrent neural networks (RNNs) and long short-term networks (LSTMs), which can encode the Bouc-Wen model into the direct graph and incorporate the effect of design-oriented geometry parameters. To validate the generality of the network, the optimization model was calibrated numerically and experimentally, respectively, which exhibits good performance in predicting nonlinear behaviors of different dampers with reasonable accuracy. The proposed physics-informed DNNs can be an alternative to relieve the laboriousness of the seismic design and mechanical characteristics assessment of passive energy dissipation devices.

Research on Damping Contribution Rate of Key Parameters of Valve-Controlled Damping Adjustable Damper

Valve-controlled damping adjustable damper has the characteristics of simple structure and adjustable damping, and it has always been a hot research topic. This paper establishes a mathematical model of damping characteristics of the valve-controlled damping adjustable damper and designs the experiment of the damping characteristics of the compression stroke and the recovery stroke. Through simulation and experiment, the accuracy of the mathematical model is verified, and the damping contribution rate of different key parameters under different excitation speeds is analyzed. The results show that the mathematical model of the damping characteristics can well describe the working state of the damper. The damping contribution rate of key parameters under different excitation speeds is obtained. The damping contribution of the constant through-hole diameter decreases gradually after the valve is opened for the first time. With the increase of the excitation speed, the valve plate equivalent thickness and the valve plate maximum limit clearance of the check valve gradually play a major role in the damping contribution rate. The research results can screen out the key parameters, improve the development efficiency of the damper, and provide guidance for the damper design and optimization.

Piezoelectric active damper for surface roughness improvement in hard turning processes

Surface roughness and profile accuracy on rolling or sliding surfaces are critical for the wear and fatigue of a component. A high roughness or poor profile accuracy results in higher friction and higher wear rate of the surface. One of the major factors affecting the surface roughness is chatter vibrations. This paper presents a novel design and development of an active damper for chatter suppression of hard turning processes using a piezoelectric actuator and strain signal for chatter detection. The active damper consists of a piezoelectric actuator with an embedded strain gauge for measuring the vibration displacement. In this work, the radial strain signal as a result of radial chatter vibrations from the strain gauge is used as a feedback signal to the actuator using a feedback controller. A fixture was designed using special stiffeners such that it limited the tool displacements in the tangential and feed directions to only 0.2 µm and 0.4 µm, respectively, while allowing for movement in the radial direction in the actuator’s force direction. The experimental results showed a significant suppression in chatter vibrations and improvement of surface roughness using the proposed active damper. A reduction of 83% in surface roughness (Ra) was observed during the cutting process. The details of the tool design, control design, hardware implementation and system validation are given hereinafter.

Optimization Design of the Magnetic Multi-Mass Damper for Multi-Frequency Vibration Suppression

It is widely demonstrated that the tuned mass dampers (TMDs) are efficient to suppress resonant vibration, but the effective bandwidth is narrow and the robustness of the system is not enough, especially applied to variable frequency excitation. This paper presents an optimization design method of multi-mass damper (MMD) for variable multi-frequency vibration control. The dampers mounted on the primary system are made up of one main TMD and two MMDs, and each MMD is made up of three mass dampers, whose damping is provided by magnetic dampers, whose analytical model is established for optimization. The optimization objective function proposed is based on the variance, the difference between the maximum and the minimum values, root-mean-square values of the primary system vibration, which can help attenuate the vibration and improve the robustness of the primary system theoretically. The simulation results indicate that the vibration of the primary system under multi-frequency is suppressed 6[Formula: see text]dB by the designed dampers. In the experiments, the optimized damping ratios of every mass damper are realized using the magnetic dampers. The vibration amplitude of the primary system can be suppressed more than 50% when the main TMD and MMDs start work, the dramatic fluctuation of frequency response is replaced by gentle transition, and the experimental results are consistent with the simulation results well.

Energy dissipation in horizontally driven particle dampers of low acceleration intensities

The energy dissipation in sinusoidally driven particle dampers is highly dependent on the motion mode of the particle bed. Especially, for applications of low acceleration intensity, i.e., acceleration amplitude below gravitational acceleration, only small energy dissipation rates are obtained so far, due to sticking of particles. Here, a new and more efficient design of particle dampers is introduced for such applications, whereby the focus is on horizontal vibrations. The proposed design makes use of the rolling property of spheres inside particle containers with flat bases. First, a cuboid container shape is studied. Two different motion modes are observed experimentally within this container shape. For low driving amplitudes, the particle bed is showing a scattered behavior resulting in a low damping efficiency. For high driving amplitudes instead, the rolling collect-and-collide state is observed resulting in much higher efficiency. Analytical descriptions for the energy dissipation are derived for both motion modes, being in good agreement with experimental measurements. It is obtained that the optimal working point of such dampers, i.e., the optimal stroke, is only depending on the filling ratio of the damper. Additionally, the optimal working point separates both motion modes. For lower strokes as the optimal one, the scattered state is observed, while for higher strokes the rolling collect-and-collide mode is seen. Sensitivity analyses are performed using the experimental setup and discrete element simulations. It is obtained that especially a low friction coefficient and a high particle radius are beneficial. On the other hand, a small tilt around the container’s longitudinal or pitch axis might significantly decrease the efficiency of the damper. Besides the cuboid container, the effect of a cylindrical container heading against gravity is analyzed. While the particle bed motion modes are only little influenced, the efficiency of the damper becomes independent of the excitation direction in the horizontal plane. Thus, such dampers could be applied to a large field of applications in mechanical and civil engineering.

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.