Damping Ring Research Articles

An innovative two-level yielding knee-braced frame with deformation-controlled ring damper

Previous earthquake experiences have shown that conventional yielding dampers designed for an earthquake intensity cannot perform adequately at higher intensity levels. This paper addresses this issue by proposing a two-level yielding configuration for knee-braced steel frames having an innovative deformation-controlled ring damper (CRD). The proposed configuration includes a knee element damper (KED) and a CRD with a deformation-control device. In weak or moderate earthquakes, the CRD serves as the primary energy absorber. In contrast, in higher-intensity earthquakes, the deformation of the CRD is controlled and the KED acts as a secondary fuse for energy dissipation. In this study, four traditional ring dampers with different geometric properties and two CRD were experimentally tested and their numerical models in Abaqus were successfully verified. The results demonstrated stable and asymmetric hysteretic curves with satisfactory ductility and energy absorption of the ring dampers. Additionally, the CRD revealed a proper control of deformation. Subsequently, a previously tested knee-braced frame specimen with the common ring damper was numerically modeled. After verifying the validity of the model, the behavior of a typical knee-braced frame equipped with a deformation-controlled multi-ring damper (CRD-KBF) was investigated and compared with a common KBF and ring-braced frame (RBF). The obtained results confirmed the expected two-level yielding behavior of the proposed configuration. The numerical analyses demonstrated higher ductility and energy dissipation capacity of the CRD-KBF compared to the other frames.

Experimental and numerical investigation of a steel yielding arc and ring damper

The use of yield steel dampers in structures improves seismic resilience by efficiently absorbing energy, reducing the impact of seismic forces, and enhancing overall safety and stability. This paper introduces Arc and Ring Dampers (ARDs), a replaceable structural fuse system with the goal of improving seismic performance of structures against earthquakes. The ARD configuration consists of a central ring surrounded by four arcs. For the first time, an experimental study is carried out on full-scale damper specimens to determine seismic performance and failure mechanisms under cyclic loading. Nonlinear finite element method (FEM) analysis is employed for numerical validation and parametric exploration, taking into account variables such as arc and ring thickness, ring and arc radius, and stiffener width. According to the results, by carefully selecting and designing the geometric characteristics of this damper, it would offer a remarkably efficient energy absorption capacity and a significant load-bearing ability, resulting in a 36 % increase in its equivalent damping ratio. This study also describes these geometric features in detail, including the arcs' and ring's width-to-thickness ratios. Furthermore, this damper maintains structural stiffness without degradation under cyclic loading conditions, showing good ductility up to a value of 5.5. The theoretical predictions here are in good agreement with the experimental outcomes.

Intentional Blade Mistuning to Emulate the Dynamic Influence of Split Ring Damper

Abstract A novel methodology to predict responses of bladed disks incorporated with a split ring damper is proposed. To account for the dynamic characteristics of a split ring damper, intentional blade stiffness mistuning is presented. It is assumed that the mistuning is proportional to the blade stiffness matrix and uniformly distributed to all blades. Therefore, responses of bladed disks integrated with a split ring damper are captured by the detuned bladed disk integrated with a continuous ring damper. The proposed method is demonstrated through a lumped parameter model and validated using a complete finite element model. A key advantage of the proposed approach is that the dynamic characteristics of a split ring damper are emulated by a continuous ring damper in the detuned bladed disk. Moreover, the approach holds the potential to facilitate reduced-order modeling (ROM) by employing sector-level calculations. This results in substantial reductions in computational efforts while maintaining accurate predictions of forced responses.

A parametric study on the effect of ring damper on wheel damping

Ring dampers have been widely applied to control vibration of, and noise from, train wheels due to the simple structure, negligible impact on operational safety and potential in vibration and noise reduction. Yet, parameters affecting the vibro-acoustic performance of a ring-damped wheel are not adequately studied. In this paper, the apparent modal damping ratios of a ring-damped wheel are studied numerically using a finite element model allowing for frictional nonlinearity. Studied parameters include the impact force used to excite the wheel, the preload in the ring, the friction coefficient of the interface between the ring and the wheel, and the number of rings installed. Several findings can be drawn from the study. Installation of one or two rings to the wheel does not change the resonance frequencies (they are also termed the modal frequencies of the ring-damped wheel) but reduces the resonance responses by generating extra damping to the modes. The ring is more effective for radial excitation than for axial excitation. At most modal frequencies, damping with double rings is higher than with a single ring. Although there are few modal frequencies at which the modal damping ratios are reduced by installing the second ring, the average damping ratio with two rings is much higher, by a factor of 2.37 for axial excitation and 1.73 for radial excitation, than that with a single ring. The apparent damping of the ring-damped wheel increases with the level of the impact force, especially for radial excitation. There is an optimal combination of the preload in the ring and the frictional coefficient with which damping induced by the ring is the highest. Besides, the average damping ratios of the modes above 2000 Hz are proposed to be an indicator of the effectiveness of the performance of a ring-damped wheel in noise reduction.

Beam Loading Compensation of Traveling Wave Linac to a Multi-bunch Pulse with Gaps

In the electron driven ILC (International Linear Collider) positron source, the beam is generated and accelerated in a multi-bunch format with mini-trains. The macro-pulse contains 2 to 4 mini-trains with several gaps, because the pulse format is a copy of a part of the bunch storage pattern in DR (Damping Ring). This pulse format causes a variation of the accelerator field in the pulse due to the transient beam loading and an intensity fluctuation of captured positron. The beam loading is compensated by amplitude modulation on the input RF in the positron booster composed from L-band and S-band traveling wave RF cavity. In this article, we derive the exact solution for the compensation with the gaps. In addition, we evaluate the effect of the time constant (delay) of the input RF modulation due to klystron Q-value.

SuperKEKB personnel protection system

The Super-KEKB[1] personnel protection system (PPS) takes care of not only Super-KEKB accelerator, but also Photon Factory - Advanced Ring (PF-AR), Positron Damping Ring (PDR)[2] and their beam transport lines (BT)[3]. The logic of the PPS has been changed to adapt the new accelerator operation scheme. The Experimental Physics and Industrial Control System (EPICS) was introduced into the PPS. Many tools developed under EPICS environment are used.

Traveling-wave vibration modelling for thin-walled gear with ring damper

The harmful resonances of the thin-walled gears for aviation high-speed gear transmission systems, especially the traveling-wave vibration (TWV), frequently occur under complex excitations. The ring damper is an excellent and widely used damping technology for TWV reduction. However, lacking the TWV predictive method, there are few theoretical bases for the damper optimization. In this paper, firstly, assuming that the external input energy, the gear damping energy dissipation, and the ring damper energy dissipation form an energy balance, a novel model of TWV response based on energy dissipation (TRED) is proposed for the thin-walled gear with ring damper. Secondly, to solve the complex nonlinear TRED model, using the Rayleigh damping theory, the discrete expression of TRED model is innovatively given instead of traditional equation solving methods. Considering that the TRED model is established based on the vibrational displacement, a method for the conversion of gear vibration strain and displacement is given under different TWV directions and vibration strain measurements, and the solving method is proposed for the TRED model based on the above established theories. Finally, to validate the TRED model and its solutions, the speed-up experiments are conducted, and the experimental results are compared with the TRED prediction. Results show that the experimental and theoretical results are consistent, and the maximum predictive error is 8.7 %, which validates the feasibility of the proposed theories and methods.

Special-shape ring dampers for thin-walled gears subjected to traveling-wave vibration

Ring dampers are solutions to the traveling-wave vibration (TWV), a threat to high-speed thin-walled gears. But a complete design method for them is lacking, and normal dampers have contact problems, which make TWV mitigation less effective. So, a novel design method is proposed for the special-shape ring damper (SSRD), which is an improved type that aims to have good energy dissipation and contact performance. The methodology starts by estimating the optimal contact pressure, which acts on the SSRD to achieve the maximum frictional dissipation. Then its deformation is calculated based on the stress function method to get the shape that can perform the desired pressure. Furthermore, high-speed experiments are made to validate the TWV attenuation of the experimental SSRD. And its contact features are investigated by light transmission tests and finite element models. The results show that the SSRD can maintain almost complete contact with the gear, avoiding energy dissipation loss due to uncontacted parts. It also makes the contact pressure more even, which fits better with the uniform pressure assumption in the design methodology. Moreover, the SSRD effectively suppresses the TWV, and after damper installation, the strain peak reduction for the experimental gear exceeds 67.5%. The proposed methodology provides a theoretical basis for the ring damper design, and can be applied to ensure safe operation of aero-engine gears by suppressing their harmful dynamics behavior, TWV.

ANALYSIS OF NONLINEAR RIGIDITY CHARACTERISTICS OF AIR BLOWER COMPRESSOR ELASTIC SUPPORTS

Vibrations of rotor systems are largely determined by elastic characteristics of supports. In the general case, the dependence of displacements on force for such supports is nonlinear. This applies to bearing supports of various types. In addition to bearings, elastic elements are also used in supports of rotor systems. They are designed to change the overall stiffness of the supports. The paper analyzes the radial stiffness of flexible ring dampers used in rotor supports. For this, two main approaches are proposed. The first is a conventional simulation of this problem of contact mechanics using the finite element method. The second is an analytical method that can be used as an alternative to expensive numerical calculations. This method is based on the principle of minimum additional energy. A special closed-form variational formulation is developed using the Euler-Bernoulli beam approximation for an elastic ring and a simplified model of normal contact on the ring flanges. It was shown that the surface tolerances of parts have a significant effect on the radial response of a flexible ring, which can become nonlinear. Tight fit of the ring on both sides makes it much stiffer, and non-tight fit leads to free movement of the rotor and much weaker damping of its movement. Both methods gave results that are consistent for the considered cases. By varying their design parameters, it is possible to adjust the rotor systems from critical modes of operation. Keywords: rotor system, elastic support, rigidity, finite element analysis, stress-strain state, contact interaction, principle of minimum additional energy

A Study of the Collective Beam Instabilities in the Damping Ring of the VEPP-5 Injection Complex

A Study of the Collective Beam Instabilities in the Damping Ring of the VEPP-5 Injection Complex

Numerical and experimental investigations on a friction ring damper for a flywheel

A damping strategy using a friction ring damper for an industrial flywheel was numerically and experimentally investigated. The friction ring damper, located on the arms of the flywheel, was experimentally found to effectively reduce the vibration amplitude of the flywheel. The vibration energy was dissipated when relative motions occur at the friction contact interfaces. Nonlinear dynamic analysis based on a lumped-parameter model of a flywheel equipped with a friction ring damper was conducted. The normal load, N, was used to evaluate the damping performance of the friction ring damper. For several values of N, steady-state responses under harmonic excitation and nonlinear modes were obtained using the harmonic balance method combined with the alternating frequency–time domain method. The forced response analysis proved the existence of an optimal value of N, which could minimize the vibration amplitude of the flywheel. The nonlinear modal analysis showed that all the damping ratio–frequency curves were completely coincident even for different values of N, and the frequency corresponding to the maximum damping ratio was equal to the frequency at the intersection of the forced response curves under the fully slip state and the fully stick state of the friction contact interface. By analyzing the behaviors of the friction contact interface, it was shown that the friction contact interface provides damping in the combined stick–slip state. The forced response under random excitation was calculated using the Runge–Kutta method, and the friction interface behaviors were analyzed. Finally, spectral testing was conducted to verify the numerical results.

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.

An Evaluation Method for Dry Friction Damping of Ring Damper in Gas Turbine Engines under Axial Vibration

The blisks and labyrinth seals in gas turbine engines are typical rotating periodic structures. Vibration problems will inevitably occur during the operation, which can easily lead to High Cycle Fatigue failure of the structure. Adding ring damper is an effective means of structural vibration reduction. The damper uses the dry friction of the contact surface to dissipate the vibration energy, improve the damping of the system, and then reduce the vibration response of the structure. The structures have a nodal diameter and modal shape, and the forced vibration often presents the characteristics of traveling wave. In this paper, an evaluation method for dry friction damping of ring damper under the axial component of traveling wave vibration is established. For the given vibration stress at the critical location, the equivalent damping ratio provided by the ring damper is calculated based on the friction energy dissipation and the damping characteristic curve that is the equivalent damping ratio varying with the vibration stress is obtained. This method can avoid calculating the nonlinear dry friction forced response and is suitable for the design stage. The damping of split ring dampers with rectangular section for one blisk and labyrinth seal is analyzed in this paper. It is shown that rotating speed, friction coefficient, section area and material density significantly influence the damping characteristics. There are many factors affecting the damping characteristics of the damping, so it is necessary to comprehensively consider various factors and multiple modes for vibration reduction design.

Steel dual-ring dampers: Micro-finite element modelling and validation of cyclic behavior

Extensive studies have been performed by researchers to increase the ductility and energy-absorption of concentrically braced frames. One of the most widely used strategies for increasing ductility and energy-absorbing is the utilization of energy-dissipation systems. In this regard, the energy-dissipation system consisting of a steel dual-ring damper (SDRD) with different construction details is presented, to improve hysteresis behavior and performance of steel ring dampers (SRD). The most important cause of energy-dissipation in SRDs are the development of bending plastic hinges in the rings. Therefore, by adding an inner ring to the SDR system, it increases the number of moment plastic hinges and in turn increases energy dissipation. Parametric studies havse been performed applying the nonlinear micro-finite element (MFE) procedure to investigate the improved models. The parametric studies comprise examining the efficacy of thickness parameters and the inner ring diameters of the improved models. The SRD models was selected as the base model for comparing and evaluating the effects of improved dampers. MFE models were then analyzed under cyclic loading and nonlinear static methods. Confirmation of the results of the MFE models were performed against the test results. The results indicated that the diameter to the thickness ratio of inner ring of SDRDs has a considerable influence on determining the hysteresis behavior, ductility, ultimate capacity and performance, as well as energy dissipation. Also, the results show that the details of the construction of the internal and external ring connections were a considerable effect on the performance and hysteresis behavior of SDRDs.

Analysis and stabilization of AC line synchronized timing system for superKEKB

A timing system provides high-precision signals to allow the controls over a variety of hardware and software components in the accelerator complex. This is guaranteed by the radio frequency (RF) synchronization and trigger signal transmission for subsystems such as klystrons, pulsed magnets, and beam monitors. This trigger signal is usually generated at the same phase of an AC power line to follow the source of the fluctuation of an electrical grid and reduce unwanted variation of the beam quality. A long bucket selection cycle that is necessary for the SuperKEKB damping ring (DR) and main ring (MR) increases the complexity of the timing system. Uncertainty in the timing system and the trigger signal delivery failure caused by a drastic AC power line drift are observed. The cause and effect of timing system failures are analyzed. The solutions to improve the reliability of the timing system by upgrading the software are presented.

RF parameters design for a Circular Electron–Positron Collider

Radio frequency (RF) parameters design is an important part in RF system design. In this paper we will introduce a general method of choosing appropriate RF parameters for a circular [Formula: see text] collider. The RF parameters are determined with several analytical formulas. With this method, the RF parameters of the Circular Electron–Positron Collider (CEPC) for Conceptual Design Report (CDR) are verified. A new set of RF parameters for the CEPC with 1-cell LG Nb cavities is also designed. Besides, the RF parameters of the CEPC Advanced Partial Double Ring (APDR) and the CEPC Damping Ring (DR) are designed for the first time, and a preliminary study of the beam loading effects of APDR and DR is also carried out.

Nonlinear Modal Analysis of Frictional Ring Damper for Compressor Blisk

Abstract The use of integrally blisk is becoming popular because of the advantages in aerodynamic efficiency and mass reduction. However, in an integrally blisk, the lack of the contact interface leads to a low structural damping compared to an assembled bladed disk. One emerging damping technique for the integrally blisk is based on the use of friction ring damper, which exploits the contact interfaces at the underneath of the disk. In this paper, three different geometries of the ring dampers are investigated for damping enhancement of a blisk. A full-scale compressor blisk is considered as a case study where a node-to-node contact model is used to compute the contact forces. The dynamic behavior of the blisk with the ring damper is investigated by using nonlinear modal analysis, which allows a direct estimation of the damping generated by the friction interface. The damping performance for the different ring dampers is evaluated and compared. It appears that the damping efficiency as well as the shift in the resonant frequency for the different geometries is highly related to the nodal diameter and contact pressure/gap distributed within contact interface. The geometry of the ring damper has significant impact on the damping performance.

A Study of the Contact Interface for Compressor Blisks with Ring Dampers Using Nonlinear Modal Analysis

The integrally bladed disks, also known as blisks, have been widely used in industrial turbomachinery because of their benefits in aerodynamic performance and mass reduction. Friction damping is considered as the major damping sources in turbomachinery. However, in blisks, the friction damping is negligible due to the lack of the contact interfaces. The friction ring dampers are one of the emerging external damping sources for blisks. In this paper, a full-scale blisk with a friction ring damper is studied, where a 3D contact element is used to compute the contact frictions. The blisk and ring damper is investigated using their damped nonlinear normal modes. The modal damping can be directly calculated and used to quantify the friction damping generated by the ring damper. The contact behaviour within the contact interface is further analysed. The nodes with initial gap show less damping ability. The separations within the contact interface are expected to be avoided to achieve a better damping performance.

Intestines of non-uniform stiffness mold the corners of wombat feces.

The bare-nosed wombat (Vombatus ursinus) is a fossorial, herbivorous, Australian marsupial, renowned for its cubic feces. However, the ability of the wombat's soft intestine to sculpt flat faces and sharp corners in feces is poorly understood. In this combined experimental and numerical study, we show one mechanism for the formation of corners in a highly damped environment. Wombat dissections show that cubes are formed within the last 17 percent of the intestine. Using histology and tensile testing, we discover that the cross-section of the intestine exhibits regions with a two-fold increase in thickness and a four-fold increase in stiffness, which we hypothesize facilitates the formation of corners by contractions of the intestine. Using a mathematical model, we simulate a series of azimuthal contractions of a damped elastic ring composed of alternating stiff and soft regions. Increased stiffness ratio and higher Reynolds number yield shapes that are more square. The corners arise from faster contraction in the stiff regions and relatively slower movement in the center of the soft regions. These results may have applications in manufacturing, clinical pathology, and digestive health.

Numerical Investigation of Cyclic Behaviour of Stainless Steel Ring Damper

Numerical Investigation of Cyclic Behaviour of Stainless Steel Ring Damper