WorldWideScience

Sample records for fluid damping effects

  1. Electroresponsive Aqueous Silk Protein As “Smart” Mechanical Damping Fluid

    Science.gov (United States)

    2015-01-01

    Here we demonstrate the effectiveness of an electroresponsive aqueous silk protein polymer as a smart mechanical damping fluid. The aqueous polymer solution is liquid under ambient conditions, but is reversibly converted into a gel once subjected to an electric current, thereby increasing or decreasing in viscosity. This nontoxic, biodegradable, reversible, edible fluid also bonds to device surfaces and is demonstrated to reduce friction and provide striking wear protection. The friction and mechanical damping coefficients are shown to modulate with electric field exposure time and/or intensity. Damping coefficient can be modulated electrically, and then preserved without continued power for longer time scales than conventional “smart” fluid dampers. PMID:24750065

  2. Design guide for calculating fluid damping for circular cylindrical structures

    International Nuclear Information System (INIS)

    Chen, S.S.

    1983-06-01

    Fluid damping plays an important role for structures submerged in fluid, subjected to flow, or conveying fluid. This design guide presents a summary of calculational procedures and design data for fluid damping for circular cylinders vibrating in quiescent fluid, crossflow, and parallel flow

  3. Characterization of hydrofoil damping due to fluid-structure interaction using piezocomposite actuators

    Science.gov (United States)

    Seeley, Charles; Coutu, André; Monette, Christine; Nennemann, Bernd; Marmont, Hugues

    2012-03-01

    Hydroelectric power generation is an important non-fossil fuel power source to help meet the world’s energy needs. Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Although the effects of fluid mass loading are well documented, fluid damping is also a critical quantity that may limit vibration amplitudes during service, and therefore help to avoid premature failure of the turbines. However, fluid damping has received less attention in the literature. This paper presents an experimental investigation of damping due to FSI. Three hydrofoils were designed and built to investigate damping due to FSI. Piezoelectric actuation using macrofiber composites (MFCs) provided excitation to the hydrofoil test structure, independent of the flow conditions, to overcome the noisy environment. Natural frequency and damping estimates were experimentally obtained from sine sweep frequency response functions measured with a laser vibrometer through a window in the test section. The results indicate that, although the natural frequencies were not substantially affected by the flow, the damping ratios were observed to increase in a linear manner with respect to flow velocity.

  4. Effect of Temperature and Electric Field on the Damping and Stiffness Characteristics of ER Fluid Short Squeeze Film Dampers

    Directory of Open Access Journals (Sweden)

    H. P. Jagadish

    2013-01-01

    Full Text Available Squeeze film dampers are novel rotor dynamic devices used to alleviate small amplitude, large force vibrations and are used in conjunction with antifriction bearings in aircraft jet engine bearings to provide external damping as these possess very little inherent damping. Electrorheological (ER fluids are controllable fluids in which the rheological properties of the fluid, particularly viscosity, can be controlled in accordance with the requirements of the rotor dynamic system by controlling the intensity of the applied electric field and this property can be utilized in squeeze film dampers, to provide variable stiffness and damping at a particular excitation frequency. The paper investigates the effect of temperature and electric field on the apparent viscosity and dynamic (stiffness and damping characteristics of ER fluid (suspension of diatomite in transformer oil using the available literature. These characteristics increase with the field as the viscosity increases with the field. However, these characteristics decrease with increase in temperature and shear strain rate as the viscosity of the fluid decreases with temperature and shear strain rate. The temperature is an important parameter as the aircraft jet engine rotors are located in a zone of high temperature gradients and the damper fluid is susceptible to large variations in temperature.

  5. Damping system immersed in a fluid

    International Nuclear Information System (INIS)

    1980-01-01

    The invention relates to a damping system which is immersed in a fluid and allows slow motion, while opposing fast motion of a mobile or deformable system immersed in a fluid. Nuclear reactors utilize fabricated assemblies immmersed in the spent fuel storage pool to support the fuel elements placed in the pool, e.g., when refueling the reactor. These fabricated assemblies must be held in position, relative to the concrete walls of the pool, so as to allow slow deformation of the assemblies due to thermal expansion, while curbing fast motion, e.g., earthquake-induced motion. Such fast motion due to earthquakes might be the cause of resonance phenomena involving the fuel storage rack structure and the pool walls, should the rack structure and pool walls have the same resonant frequency. In the event of an earthquake, the damping system would provide for fast curbing of structure motion to prevent uncontrolled deformation which might result in breaks and destruction [fr

  6. Fluid Damping Variation of a Slender Rod in Axial Flow Field

    Energy Technology Data Exchange (ETDEWEB)

    Park, Nam-Gyu; Yoo, Jong-Sung; Jung, Yil-Sup [KEPCO Nuclear Fuel Co., Daejeon (Korea, Republic of)

    2016-10-15

    This study proposed an analytic damping model considering the axial flow condition. In addition, the specific damping values with respect to the flow speeds are calculated. The flow induced damping is beneficial to fuel integrity in that impact energy due to severe accidents such as earthquake dissipates rapidly. A nuclear fuel bundle is composed of many slender fuel rods which contain fission material. The slender rod is typical structure in the fuel, therefore fluid damping estimation on the rod should be an important clue leading to fuel bundle damping identification. Severe accidents could cause fuel assembly vibration in the core, but large motion could be damped out rapidly when a strong damping mechanism is involved. This paper suggested a mathematical model of the slender structure. The physical meaning of the model is described, and the simulation results with the model are also provided. Actual damping due to the fluid is nonlinear, therefore further works are required to explain the detail behavior with the nonlinearity. The model validation test is on-going in KEPCO Nuclear Fuel, but it is believed that performance of the model is well correlated to the published work.

  7. Nonlinear damping for vibration isolation of microsystems using shear thickening fluid

    Science.gov (United States)

    Iyer, S. S.; Vedad-Ghavami, R.; Lee, H.; Liger, M.; Kavehpour, H. P.; Candler, R. N.

    2013-06-01

    This work reports the measurement and analysis of nonlinear damping of micro-scale actuators immersed in shear thickening fluids (STFs). A power-law damping term is added to the linear second-order model to account for the shear-dependent viscosity of the fluid. This nonlinear model is substantiated by measurements of oscillatory motion of a torsional microactuator. At high actuation forces, the vibration velocity amplitude saturates. The model accurately predicts the nonlinear damping characteristics of the STF using a power-law index extracted from independent rheology experiments. This result reveals the potential to use STFs as adaptive, passive dampers for vibration isolation of microelectromechanical systems.

  8. The investigation of added masses and damping factors for vibrations of tube and tube bundles in fluid

    International Nuclear Information System (INIS)

    Sinyavskii, V.F.; Fedotovskii, V.S.; Kukhtin, A.B.

    1977-01-01

    The vibrations of single cylinders in fluid being surrounded by the solid walls of different form as well as the bundles of cylindric rods have been considered in this report. A model is proposed for hydrodynamic damping of vibrations and the analytic solution of a problem concerning damping of cylinder vibrations in fluid surrounded by a concentric shell. It has been shown that the fluid viscosity and vibration frequency influence the value of the fluid added mass and the damping factor of vibrations

  9. Damping measurements in flowing water

    Science.gov (United States)

    Coutu, A.; Seeley, C.; Monette, C.; Nennemann, B.; Marmont, H.

    2012-11-01

    Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.

  10. Damping measurements in flowing water

    International Nuclear Information System (INIS)

    Coutu, A; Monette, C; Nennemann, B; Marmont, H; Seeley, C

    2012-01-01

    Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.

  11. Pipe damping

    International Nuclear Information System (INIS)

    Ware, A.G.

    1985-01-01

    Studies are being conducted at the Idaho National Engineering Laboratory to determine whether an increase in the damping values used in seismic structural analyses of nuclear piping systems is justified. Increasing the allowable damping would allow fewer piping supports which could lead to safer, more reliable, and less costly piping systems. Test data from availble literature were examined to determine the important parameters contributing to piping system damping, and each was investigated in separate-effects tests. From the combined results a world pipe damping data bank was established and multiple regression analyses performed to assess the relative contributions of the various parameters. The program is being extended to determine damping applicable to higher frequency (33 to 100 Hz) fluid-induced loadings. The goals of the program are to establish a methodology for predicting piping system damping and to recommend revised guidelines for the damping values to be included in analyses

  12. Damping characteristics and flow behaviors of an ER fluid with a piston sine vibration in a viscous damper

    International Nuclear Information System (INIS)

    Yamaguchi, Hiroshi; Zhang, Xin-Rong; Niu, Xiao-Dong

    2010-01-01

    The damping characteristics and flow behaviors of ER fluids inside a piston–cylinder viscous damper subjected to external electric fields are studied based on experiment, theoretical analysis and numerical simulation. The viscous damper is a closed system with an inner piston and an outer cylinder, which is designed and constructed in our laboratory. In the experiment, the test ER fluid is enclosed in the gap of a piston–cylinder system. To examine the damping characteristics of the test ER fluid, a piston sine vibration experiment is performed with accompanying theoretical analyses. In addition, in order to investigate the ER flow behaviors inside the damper, a numerical simulation is carried out. The present study discloses the damping characteristics and the fluid mechanism of the ER fluid in the piston–cylinder damper with an applied external electric field

  13. Pressure Feedback in Fluid Power Systems--Active Damping Explained and Exemplified

    DEFF Research Database (Denmark)

    Pedersen, Henrik Clemmensen; Andersen, Torben O.

    2018-01-01

    Fluid power systems are inherently nonlinear and typically suffer from very poor damping. Despite these characteristics, it is not uncommon that traditional linear type controllers are applied. This typically results in conservative adjustment of the controllers, or when more advanced controllers...... a given system, and how to adjust the parameters of the pressure feedback to obtain the best results. This is done for both a traditional symmetric cylinder servo system and a system with a differential cylinder using both pressure and nonpressure compensated proportional valves. Based on the presented...

  14. Characterization of hydrofoil damping due to fluid–structure interaction using piezocomposite actuators

    International Nuclear Information System (INIS)

    Seeley, Charles; Coutu, André; Monette, Christine; Nennemann, Bernd; Marmont, Hugues

    2012-01-01

    Hydroelectric power generation is an important non-fossil fuel power source to help meet the world’s energy needs. Fluid–structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Although the effects of fluid mass loading are well documented, fluid damping is also a critical quantity that may limit vibration amplitudes during service, and therefore help to avoid premature failure of the turbines. However, fluid damping has received less attention in the literature. This paper presents an experimental investigation of damping due to FSI. Three hydrofoils were designed and built to investigate damping due to FSI. Piezoelectric actuation using macrofiber composites (MFCs) provided excitation to the hydrofoil test structure, independent of the flow conditions, to overcome the noisy environment. Natural frequency and damping estimates were experimentally obtained from sine sweep frequency response functions measured with a laser vibrometer through a window in the test section. The results indicate that, although the natural frequencies were not substantially affected by the flow, the damping ratios were observed to increase in a linear manner with respect to flow velocity. (paper)

  15. Damping of the radial impulsive motion of LMFBR core components separated by fluid squeeze films

    International Nuclear Information System (INIS)

    Liebe, R.; Zehlein, H.

    1977-01-01

    The core deformation of a liquid metal cooled fast breeder reactor (LMFBR) due to local pressure propagation from rapid energy releases is a complex three-dimensional fluid-structure-interaction problem. High pressure transients of short duration cause structural deformation of the closely spaced fuel elements, which are surrounded by the flowing coolant. Corresponding relative displacements give rise to squeezing fluid motion in the thin layers between the subassemblies. Therefore significant backpressures are produced and the resulting time and space dependent fluid forces are acting on the structure as additional non-conservative external loads. Realistic LMFBR safety analysis of several clustered fuel elements have to account for such flow induced forces. Several idealized models have been proposed to study some aspects of the complex problem. As part of the core mechanics activities at GfK Karlsruhe this paper describes two fluid flow models (model A, model B), which are shown to be suitable for physically coupled fluid-structure analyses. Important assumptions are discussed in both cases and basic equations are derived for one- and two-dimensional incompressible flow fields. The interface of corresponing computer codes FLUF (model A) and FLOWAX (model B) with structural dynamics programs is outlined. Finally fluid-structure interaction problems relevant to LMFBR design are analyzed; parametric studies indicate a significant cushioning effect, energy dissipation and a strongly nonlinear as well as timedependent damping of the structural response. (Auth.)

  16. Damping Measurements of Plasma Modes

    Science.gov (United States)

    Anderegg, F.; Affolter, M.; Driscoll, C. F.

    2010-11-01

    For azimuthally symmetric plasma modes in a magnesium ion plasma, confined in a 3 Tesla Penning-Malmberg trap with a density of n ˜10^7cm-3, we measure a damping rate of 2s-1plasma column, alters the frequency of the mode from 16 KHz to 192 KHz. The oscillatory fluid displacement is small compared to the wavelength of the mode; in contrast, the fluid velocity, δvf, can be large compared to v. The real part of the frequency satisfies a linear dispersion relation. In long thin plasmas (α> 10) these modes are Trivelpiece-Gould (TG) modes, and for smaller values of α they are Dubin spheroidal modes. However the damping appears to be non-linear; initially large waves have weaker exponential damping, which is not yet understood. Recent theoryootnotetextM.W. Anderson and T.M. O'Neil, Phys. Plasmas 14, 112110 (2007). calculates the damping of TG modes expected from viscosity due to ion-ion collisions; but the measured damping, while having a similar temperature and density dependence, is about 40 times larger than calculated. This discrepancy might be due to an external damping mechanism.

  17. Characterization of Slosh Damping for Ortho-Grid and Iso-Grid Internal Tank Structures

    Science.gov (United States)

    Westra, Douglas G.; Sansone, Marco D.; Eberhart, Chad J.; West, Jeffrey S.

    2016-01-01

    Grid stiffened tank structures such as Ortho-Grid and Iso-Grid are widely used in cryogenic tanks for providing stiffening to the tank while reducing mass, compared to tank walls of constant cross-section. If the structure is internal to the tank, it will positively affect the fluid dynamic behavior of the liquid propellant, in regard to fluid slosh damping. As NASA and commercial companies endeavor to explore the solar system, vehicles will by necessity become more mass efficient, and design margin will be reduced where possible. Therefore, if the damping characteristics of the Ortho-Grid and Iso-Grid structure is understood, their positive damping effect can be taken into account in the systems design process. Historically, damping by internal structures has been characterized by rules of thumb and for Ortho-Grid, empirical design tools intended for slosh baffles of much larger cross-section have been used. There is little or no information available to characterize the slosh behavior of Iso-Grid internal structure. Therefore, to take advantage of these structures for their positive damping effects, there is much need for obtaining additional data and tools to characterize them. Recently, the NASA Marshall Space Flight Center conducted both sub-scale testing and computational fluid dynamics (CFD) simulations of slosh damping for Ortho-Grid and Iso-Grid tanks for cylindrical tanks containing water. Enhanced grid meshing techniques were applied to the geometrically detailed and complex Ortho-Grid and Iso-Grid structures. The Loci-STREAM CFD program with the Volume of Fluid Method module for tracking and locating the water-air fluid interface was used to conduct the simulations. The CFD simulations were validated with the test data and new empirical models for predicting damping and frequency of Ortho-Grid and Iso-Grid structures were generated.

  18. Variable stiffness and damping MR isolator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X Z; Wang, X Y; Li, W H; Kostidis, K [University of Wollongong, School of Mechanical, Materials and Mechatronic Engineering, NSW 2522 (Australia)], E-mail: weihuali@uow.edu.au

    2009-02-01

    This paper presents the development of a magnetorheological (MR) fluid-based variable stiffness and damping isolator for vibration suppressions. The MR fluid isolator used a sole MR control unit to achieve the variable stiffness and damping in stepless and relative large scope. A mathematical model of the isolator was derived, and a prototype of the MR fluid isolator was fabricated and its dynamic behavior was measured in vibration under various applied magnetic fields. The parameters of the model under various magnetic fields were identified and the dynamic performances of isolator were evaluated.

  19. Experimental and Theoretical Analysis for a Fluid-Loaded, Simply Supported Plate Covered by a Damping and Decoupling Composite Acoustic Coating

    Directory of Open Access Journals (Sweden)

    Baihua Yuan

    2017-01-01

    Full Text Available This work presents a vibroacoustic response model for a fluid-loaded, simply supported rectangular plate covered by a composite acoustic coating consisting of damping and decoupling layers. The model treated the damping layer and base plate as a unified whole under pure bending moments and the decoupling layer as a three-dimensional, isotropic, linear elastic solid. The validity of the model was verified by both numerical analysis and experiments and was shown to accurately extend previous studies that were limited to a plate covered by a single damping or decoupling layer with an evaluation confined solely to numerical analysis. The trends of the numerical and experimental results are generally consistent, with some differences due to the influences of water pressure and the frequency dependence of the material parameters, which are not taken into account by the numerical analysis. Both experimental and numerical results consistently show that the radiated noise reduction effect of the composite coating is superior to that of single-type coatings, which is attributed to the fact that the composite coating combines the merits of both the high vibration suppression performance of the damping layer and the superior vibration isolation performance of the decoupling layer.

  20. DAMPING OF MAGNETOHYDRODYNAMIC TURBULENCE IN PARTIALLY IONIZED PLASMA: IMPLICATIONS FOR COSMIC RAY PROPAGATION

    International Nuclear Information System (INIS)

    Xu, Siyao; Yan, Huirong; Lazarian, A.

    2016-01-01

    We study the damping processes of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in a partially ionized medium. We start from the linear analysis of MHD waves, applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and the cutoff boundary of linear MHD waves is investigated. We find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow MHD turbulence, and offer a thorough discussion of their propagation and dissipation behavior. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and the solar chromosphere. The importance of neutral viscosity in damping the Alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. As a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified.

  1. Simplified Model of Nonlinear Landau Damping

    International Nuclear Information System (INIS)

    Yampolsky, N.A.; Fisch, N.J.

    2009-01-01

    The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.

  2. Bryan's effect and anisotropic nonlinear damping

    Science.gov (United States)

    Joubert, Stephan V.; Shatalov, Michael Y.; Fay, Temple H.; Manzhirov, Alexander V.

    2018-03-01

    In 1890, G. H. Bryan discovered the following: "The vibration pattern of a revolving cylinder or bell revolves at a rate proportional to the inertial rotation rate of the cylinder or bell." We call this phenomenon Bryan's law or Bryan's effect. It is well known that any imperfections in a vibratory gyroscope (VG) affect Bryan's law and this affects the accuracy of the VG. Consequently, in this paper, we assume that all such imperfections are either minimised or eliminated by some known control method and that only damping is present within the VG. If the damping is isotropic (linear or nonlinear), then it has been recently demonstrated in this journal, using symbolic analysis, that Bryan's law remains invariant. However, it is known that linear anisotropic damping does affect Bryan's law. In this paper, we generalise Rayleigh's dissipation function so that anisotropic nonlinear damping may be introduced into the equations of motion. Using a mixture of numeric and symbolic analysis on the ODEs of motion of the VG, for anisotropic light nonlinear damping, we demonstrate (up to an approximate average), that Bryan's law is affected by any form of such damping, causing pattern drift, compromising the accuracy of the VG.

  3. Phase shift effects for fluid conveying pipes with non-ideal supports

    DEFF Research Database (Denmark)

    Dahl, Jonas; Thomsen, Jon Juel

    2008-01-01

    Vibrations of a fluid-conveying pipe with non-ideal supports are investigated with respect to phase shift effects. A numerical Galerkin approach is developed for this general problem, and the use of it exemplified with a investigation of phase shift effects from rotational damping at supports...

  4. Effects of ion-atom collisions on the propagation and damping of ion-acoustic waves

    DEFF Research Database (Denmark)

    Andersen, H.K.; D'Angelo, N.; Jensen, Vagn Orla

    1968-01-01

    Experiments are described on ion-acoustic wave propagation and damping in alkali plasmas of various degrees of ionization. An increase of the ratio Te/Ti from 1 to approximately 3-4, caused by ion-atom collisions, results in a decrease of the (Landau) damping of the waves. At high gas pressure and....../or low wave frequency a "fluid" picture adequately describes the experimental results....

  5. Size effect related to damping caused by water submersion

    International Nuclear Information System (INIS)

    Dong, R.G.

    1981-01-01

    An important effect of water submersion on the dynamic response of a structure is the increase in effective damping. The dynamic response of submerged structures is of interest in the nuclear power industry for reasons of operational safety during seismic and other dynamic excitations. In this paper, the added damping contribution that results from the viscosity of water and the dependence of the contribution on structural size are examined. Other factors considered are the applicable range of viscous damping with respect to displacement amplitude and, as far as damping is concerned, how far neighboring members must be from each other to respond as if in open water. An expression is derived for relating the damping value to structural size. Estimated added-damping values for representative fuel elements, fuel bundles, and main steam-pressure-relief-valve lines are given based on our derived expression for added damping

  6. Hydro-dynamic damping theory in flowing water

    Science.gov (United States)

    Monette, C.; Nennemann, B.; Seeley, C.; Coutu, A.; Marmont, H.

    2014-03-01

    Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid-head to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon always has to be considered carefully during the design phase to avoid operational issues later on. The RSI dynamic response amplitudes are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. The prediction of the two first factors has been largely documented in the literature. However, the prediction of fluid damping has received less attention in spite of being critical when the runner is close to resonance. Experimental damping measurements in flowing water on hydrofoils were presented previously. Those results showed that the hydro-dynamic damping increased linearly with the flow. This paper presents development and validation of a mathematical model, based on momentum exchange, to predict damping due to fluid structure interaction in flowing water. The model is implemented as an analytical procedure for simple structures, such as cantilever beams, but is also implemented in more general ways using three different approaches for more complex structures such as runner blades: a finite element procedure, a CFD modal work based approach and a CFD 1DOF approach. The mathematical model and all three implementation approaches are shown to agree well with experimental results.

  7. Electromagnetic damping of neutron star oscillations

    International Nuclear Information System (INIS)

    McDermott, P.N.; Savedoff, M.P.; Van Horn, H.M.; Zweibel, E.G.; Hansen, C.J.

    1984-01-01

    Nonradial pulsations of a neutron star with a strong dipole magnetic field cause emission of electromagnetic radiation. Here we compute the power radiated to vacuum by neutron star g-mode pulsations and by torsional oscillations of the neutron star crust. For the low-order quadrupole fluid g-modes we have considered, we find electromagnetic damping to be considerably more effective than gravitational radiation. For example, a 0.5 M/sub sun/ neutron star with a core temperature approx.10 7 K has a g 1 -mode period of 371 ms; for this mode were find the electromagnetic damping time to be tau/sub FM/approx.0.3 s, assuming the surface magnetic field strength of the neutron star to be B 0 approx.10 12 gauss. This is considerably less than the corresponding gravitational radiation time tau/sub GR/approx.3 x 10 17 yr. For dipole g-mode oscillations, there is no gravitational radiation, but electromagnetic damping and ohmic dissipation are efficient damping mechanisms. For dipole torsional oscillations, we find that electromagnetic damping again dominates, with tau/sub EM/approx.5 yr. Among the cases we have studied, quadrupole torsional oscillations appear to be dominated by gravitational radiation damping, with tau/sub GR/approx.10 4 yr, as compared with tau/sub EM/approx.2 x 10 7 yr

  8. Water confinement effects on fuel assembly motion and damping

    International Nuclear Information System (INIS)

    Brenneman, B.; Shah, S.J.; Williams, G.T.; Strumpell, J.H.

    2003-01-01

    It has been established by other authors that the accelerations of the water confined by the reactor core baffle plates has a significant effect on the responses of all the fuel assemblies during LOCA or seismic transients. This particular effect is a consequence of the water being essentially incompressible, and thus experiencing the same horizontal accelerations as the imposed baffle plate motions. These horizontal accelerations of the fluid induce lateral pressure gradients that cause horizontal buoyancy forces on any submerged structures. These forces are in the same direction as the baffle accelerations and, for certain frequencies at least, tend to reduce the relative displacements between the fuel and baffle plates. But there is another confinement effect - the imposed baffle plate velocities must also be transmitted to the water. If the fuel assembly grid strips are treated as simple hydro-foils, these horizontal velocity components change the fluid angle of attack on each strip, and thus may induce large horizontal lift forces on each grid in the same direction as the baffle plate velocity. There is a similar horizontal lift due to inclined flow over the rods when axial flow is present. These combined forces appear to always reduce the relative displacements between the fuel and baffle plates for any significant axial flow velocity. Modeling this effect is very simple. It was shown in previous papers that the mechanism for the large fuel assembly damping due to axial flow may be the hydrodynamic forces on the grid strips, and that this is very well represented by discrete viscous dampers at each grid elevation. To include the imposed horizontal water velocity effects, on both the grids and rods, these dampers are simply attached to the baffle plate rather than 'ground'. The large flow-induced damping really acts in a relative reference frame rather than an absolute or inertial reference frame, and thus it becomes a flow-induced coupling between the fuel

  9. Effects of Damping Plate and Taut Line System on Mooring Stability of Small Wave Energy Converter

    Directory of Open Access Journals (Sweden)

    Zhen Liu

    2015-01-01

    Full Text Available Ocean wave energy can be used for electricity supply to ocean data acquisition buoys. A heaving buoy wave energy converter is designed and the damping plate and taut line system are used to provide the mooring stability for better operating conditions. The potential flow assumption is employed for wave generation and fluid structure interactions, which are processed by the commercial software AQWA. Effects of damping plate diameter and taut line linking style with clump and seabed weights on reduction of displacements in 6 degrees of freedom are numerically studied under different operating wave conditions. Tensile forces on taut lines of optimized mooring system are tested to satisfy the national code for wire rope utilization.

  10. Damping of liquid sloshing by foams

    Science.gov (United States)

    Sauret, A.; Boulogne, F.; Cappello, J.; Dressaire, E.; Stone, H. A.

    2015-02-01

    When a container is set in motion, the free surface of the liquid starts to oscillate or slosh. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rims of the container. However, beer does not slosh as readily as water, which suggests that foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of a liquid foam placed on top of a liquid bath. We generate a monodisperse two-dimensional liquid foam in a rectangular container and track the motion of the foam. The influence of the foam on the sloshing dynamics is experimentally characterized: only a few layers of bubbles are sufficient to significantly damp the oscillations. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient through viscous dissipation on the walls of the container. Then we extend our study to confined three-dimensional liquid foam and observe that the behavior of 2D and confined 3D systems are very similar. Thus, we conclude that only the bubbles close to the walls have a significant impact on the dissipation of energy. The possibility to damp liquid sloshing using foam is promising in numerous industrial applications such as the transport of liquefied gas in tankers or for propellants in rocket engines.

  11. A novel two-way-controllable magneto-rheological fluid damper

    International Nuclear Information System (INIS)

    Aydar, Gokhan; Wang, Xiaojie; Gordaninejad, Faramarz

    2010-01-01

    In this paper, a disc type, radial flow-mode magneto-rheological (MR) fluid damper comprising a permanent magnet and an electromagnet is designed, built and tested. The proposed MR fluid damper has an MR valve with which two-way controllability through cancellation or enhancement of the magnetic field is obtained. This added feature provides damping forces less than or greater than that of a passive viscous original equipment manufacturer damper. A three-dimensional electromagnetic finite element analysis has been performed to realize this unique function in the proposed design. Experimental and theoretical studies have been conducted in order to demonstrate that this new design can provide softer damping properties by cancelling the effect of the permanent magnet, while at the same time enhancing the field effect, resulting in a harder damping device. Softer and harder damping refer to decrease and increase in the damping, respectively

  12. Effective damping for SSR analysis of parallel turbine-generators

    International Nuclear Information System (INIS)

    Agrawal, B.L.; Farmer, R.G.

    1988-01-01

    Damping is a dominant parameter in studies to determine SSR problem severity and countermeasure requirements. To reach valid conclusions for multi-unit plants, it is essential that the net effective damping of unequally loaded units be known. For the Palo Verde Nuclear Generating Station, extensive testing and analysis have been performed to verify and develop an accurate means of determining the effective damping of unequally loaded units in parallel. This has led to a unique and simple algorithm which correlates well with two other analytic techniques

  13. A review of damping of two-phase flows

    International Nuclear Information System (INIS)

    Hara, Fumio

    1993-01-01

    Damping of two-phase flows has been recognized as one of the most unknown parameters in analyzing vibrational characteristics of structures subjected to two-phase flows since it seems to be influenced by many physical parameters involved in the physics of dynamic energy dissipation of a vibrating structure, for example, liquid viscosity, surface tension, flow velocity, mass ratio, frequency, void fraction, flow regime and so forth. This paper deals with a review of scientific works done to date on the damping of two phase flows and discussions about what has been clarified and what has not been known to us, or what kinds of research are needed about two-phase flow damping. The emphasis is put on the definition of two-phase fluid damping, damping measurement techniques, damping characteristics in relation to two phase flow configurations, and damping generation mechanisms

  14. Preliminary Study on the Damping Effect of a Lateral Damping Buffer under a Debris Flow Load

    Directory of Open Access Journals (Sweden)

    Zheng Lu

    2017-02-01

    Full Text Available Simulating the impact of debris flows on structures and exploring the feasibility of applying energy dissipation devices or shock isolators to reduce the damage caused by debris flows can make great contribution to the design of disaster prevention structures. In this paper, we propose a new type of device, a lateral damping buffer, to reduce the vulnerability of building structures to debris flows. This lateral damping buffer has two mechanisms of damage mitigation: when debris flows impact on a building, it acts as a buffer, and when the structure vibrates due to the impact, it acts as a shock absorber, which can reduce the maximum acceleration response and subsequent vibration respectively. To study the effectiveness of such a lateral damping buffer, an impact test is conducted, which mainly involves a lateral damping buffer attached to a two-degree-of-freedom structure under a simulated debris flow load. To enable the numerical study, the equation of motion of the structure along with the lateral damping buffer is derived. A subsequent parametric study is performed to optimize the lateral damping buffer. Finally, a practical design procedure is also provided.

  15. Fuel Assembly Damping Summary

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kanghee; Kang, Heungseok; Oh, Dongseok; Yoon, Kyungho; Kim, Hyungkyu; Kim, Jaeyong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    This paper summary the fuel assembly damping data in air/in still water/under flow, released from foreign fuel vendors, compared our data with the published data. Some technical issues in fuel assembly damping measurement testing are also briefly discussed. Understanding of each fuel assembly damping mechanisms according to the surrounding medium and flow velocity can support the fuel design improvement in fuel assembly dynamics and structural integrity aspect. Because the upgraded requirements of the newly-developed advanced reactor system will demands to minimize fuel design margin in integrity evaluation, reduction in conservatism of fuel assembly damping can contribute to alleviate the fuel design margin for sure. Damping is an energy dissipation mechanism in a vibrating mechanical structure and prevents a resonant structure from having infinite vibration amplitudes. The sources of fuel assembly damping are various from support friction to flow contribution, and it can be increased by the viscosity or drag of surrounding fluid medium or the average velocity of water flowing. Fuel licensing requires fuel design evaluation in transient or accidental condition. Dynamic response analysis of fuel assembly is to show fuel integrity and requires information on assembly-wise damping in dry condition and under wet or water flowing condition. However, damping measurement test for the full-scale fuel assembly prototype is not easy to carry out because of the scale (fuel prototype, test facility), unsteadiness of test data (scattering, random sampling and processing), instrumentation under water flowing (water-proof response measurement), and noise. LWR fuel technology division in KAERI is preparing the infra structure for damping measurement test of full-scale fuel assembly, to support fuel industries and related research activities. Here is a preliminary summary of fuel assembly damping, published in the literature. Some technical issues in fuel assembly damping

  16. Transit-Time Damping, Landau Damping, and Perturbed Orbits

    Science.gov (United States)

    Simon, A.; Short, R. W.

    1997-11-01

    Transit-time damping(G.J. Morales and Y.C. Lee, Phys. Rev. Lett. 33), 1534 (1974).*^,*(P.A. Robinson, Phys. Fluids B 3), 545 (1991).** has traditionally been obtained by calculating the net energy gain of transiting electrons, of velocity v, to order E^2* in the amplitude of a localized electric field. This necessarily requires inclusion of the perturbed orbits in the equation of motion. A similar method has been used by others(D.R. Nicholson, Introduction to Plasma Theory) (Wiley, 1983).*^,*(E.M. Lifshitz and L.P. Pitaevskifi, Physical Kinetics) (Pergamon, 1981).** to obtain a ``physical'' picture of Landau damping in a nonlocalized field. The use of perturbed orbits seems odd since the original derivation of Landau (and that of Dawson) never went beyond a linear picture of the dynamics. We introduce a novel method that takes advantage of the time-reversal invariance of the Vlasov equation and requires only the unperturbed orbits to obtain the result. Obviously, there is much reduction in complexity. Application to finite slab geometry yields a simple expression for the damping rate. Equivalence to much more complicated results^2* is demonstrated. This method allows us to calculate damping in more complicated geometries and more complex electric fields, such as occur in SRS in filaments. See accompanying talk.(R.W. Short and A. Simon, this conference.) This work was supported by the U.S. DOE Office of Inertial Confinement Fusion under Co-op Agreement No. DE-FC03-92SF19460.

  17. Model identification methodology for fluid-based inerters

    Science.gov (United States)

    Liu, Xiaofu; Jiang, Jason Zheng; Titurus, Branislav; Harrison, Andrew

    2018-06-01

    Inerter is the mechanical dual of the capacitor via the force-current analogy. It has the property that the force across the terminals is proportional to their relative acceleration. Compared with flywheel-based inerters, fluid-based forms have advantages of improved durability, inherent damping and simplicity of design. In order to improve the understanding of the physical behaviour of this fluid-based device, especially caused by the hydraulic resistance and inertial effects in the external tube, this work proposes a comprehensive model identification methodology. Firstly, a modelling procedure is established, which allows the topological arrangement of the mechanical networks to be obtained by mapping the damping, inertance and stiffness effects directly to their respective hydraulic counterparts. Secondly, an experimental sequence is followed, which separates the identification of friction, stiffness and various damping effects. Furthermore, an experimental set-up is introduced, where two pressure gauges are used to accurately measure the pressure drop across the external tube. The theoretical models with improved confidence are obtained using the proposed methodology for a helical-tube fluid inerter prototype. The sources of remaining discrepancies are further analysed.

  18. Fluid transport due to nonlinear fluid-structure interaction

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1997-01-01

    This work considers nonlinear fluid-structure interaction for a vibrating pipe containing fluid. Transverse pipe vibrations will force the fluid to move relative to the pipe creating unidirectional fluid flow towards the pipe end. The fluid flow induced affects the damping and the stiffness...... of the pipe. The behavior of the system in response to lateral resonant base excitation is analysed numerically and by the use of a perturbation method (multiple scales). Exciting the pipe in the fundamental mode of vibration seems to be most effective for transferring energy from the shaker to the fluid......, whereas higher modes of vibration can be used to transport fluid with pipe vibrations of smaller amplitude. The effect of the nonlinear geometrical terms is analysed and these terms are shown to affect the response for higher modes of vibration. Experimental investigations show good agreement...

  19. Allergy and respiratory health effects of dampness and dampness-related agents in schools and homes

    DEFF Research Database (Denmark)

    Holst, G; Høst, A; Doekes, G

    2016-01-01

    was identified based on technical inspection and bedroom dampness on parents' self-report. Classroom and bedroom dust was analysed for seven microbial components. Skin-prick-testing determined atopic sensitisation. Lung function was expressed as z-scores for forced expiratory volume in one second (zFEV1...... ), forced vital capacity (zFVC) and the ratio zFEV1 /zFVC using GLI-2012-prediction-equations. The parents reported children's allergies, airway symptoms and doctor-diagnosed asthma. High classroom dampness, but not bedroom dampness, was negatively associated with zFEV1 (β-coef. -0.71; 95%CI -1.17 - -0...... (ETS) decreased zFEV1 (β-coef. -0.22; 95%CI -0.42- -0.02) and zFEV1 /zFVC-ratio (β-coef. -0.26; 95%CI -0.44 - -0.07) and increased upper airway symptoms (OR1.66; 95%CI 1.03-2.66). In conclusion, dampness in classrooms may have adverse respiratory health effects in pupils, but microbial agents...

  20. Eddy damping effect of additional conductors in superconducting levitation systems

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Zhao-Fei; Gou, Xiao-Fan, E-mail: xfgou@hhu.edu.cn

    2015-12-15

    Highlights: • In this article, for the eddy current damper attached to the HTSC, we • quantitatively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. • presented four different arrangements of the copper damper, and comparatively studied their damping effects and Joule heating, and finally proposed the most advisable arrangement. - Abstract: Passive superconducting levitation systems consisting of a high temperature superconductor (HTSC) and a permanent magnet (PM) have demonstrated several fascinating applications such as the maglev system, flywheel energy storage. Generally, for the HTSC–PM levitation system, the HTSC with higher critical current density J{sub c} can obtain larger magnetic force to make the PM levitate over the HTSC (or suspended below the HTSC), however, the process of the vibration of the levitated PM, provides very limited inherent damping (essentially hysteresis). To improve the dynamic stability of the levitated PM, eddy damping of additional conductors can be considered as the most simple and effective approach. In this article, for the HTSC–PM levitation system with an additional copper damper attached to the HTSC, we numerically and comprehensively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. Furthermore, we comparatively studied four different arrangements of the copper damper, on the comprehensive analyzed the damping effect, efficiency (defined by c/V{sub Cu}, in which V{sub Cu} is the volume of the damper) and Joule heating, and finally presented the most advisable arrangement.

  1. Possibility of Landau damping of gravitational waves

    International Nuclear Information System (INIS)

    Gayer, S.; Kennel, C.F.

    1979-01-01

    There is considerable uncertainty in the literature concerning whether or not transverse traceless gravitational waves can Landau damp. Physically, the issue is whether particles of nonzero mass can comove with surfaces of constant wave phase, and therefore, loosely, whether gravitational waves can have phase speeds less than that of light. We approach the question of Landau damping in various ways. We consider first the propagation of small-amplitude gravitational waves in an ideal fluid-filled Robertson-Walker universe of zero spatial curvature. We argue that the principle of equivalence requires those modes to be lightlike. We show that a freely moving particle interacting only with the collective fields cannot comove with such waves if it has nonzero mass. The equation for gravitational waves in collisionless kinetic gases differs from that for fluid media only by terms so small that deviations from lightlike propagation are unmeasurable. Thus, we conclude that Landau damping of small-amplitude, transverse traceless gravitational waves is not possible

  2. Nuclear power plant piping damping parametric effects

    International Nuclear Information System (INIS)

    Ware, A.G.

    1983-01-01

    The NRC and EG and G Idaho are engaged in programs to evaluate piping-system damping, in order to provide realistic and less conservative values to be used in seismic analyses. To generate revised guidelines, solidly based on technical data, new experimental data need to be generated and assessed, and the parameters which influence piping-system damping need to be quantitatively identified. This paper presents the current state-of-the-art knowledge in the United States on parameters which influence piping-system damping. Examples of inconsistencies in the data and areas of uncertainty are explained. A discussion of programs by EG and G Idaho and other organizations to evaluate various effects are included, and both short-and long-range goals of the program are outlined

  3. Fluid-structure interaction in tube bundles: homogenization methods, physical analysis

    International Nuclear Information System (INIS)

    Broc, D.; Sigrist, J.F.

    2009-01-01

    It is well known that the movements of a structure may be strongly influenced by fluid. This topic, called 'Fluid Structure Interaction' is important in many industrial applications. Tube bundles immersed in fluid are found in many cases, especially in nuclear industry: (core reactors, steam generators,...). The fluid leads to 'inertial effects' (with a decrease of the vibration frequencies) and 'dissipative effects' (with higher damping). The paper first presents the methods used for the simulation of the dynamic behaviour of tube bundles immersed in a fluid, with industrial examples. The methods used are based on the Euler equations for the fluid (perfect fluid), which allow to take into account the inertial effects. It is possible to take into account dissipative effects also, by using a Rayleigh damping. The conclusion focuses on improvements of the methods, in order to take into account with more accuracy the influence of the fluid, mainly the dissipative effects, which may be very important, especially in the case of a global fluid flow. (authors)

  4. Vibration Control of Sandwich Beams Using Electro-Rheological Fluids

    Science.gov (United States)

    Srikantha Phani, A.; Venkatraman, K.

    2003-09-01

    Electro-rheological (ER) fluids are a class of smart materials exhibiting significant reversible changes in their rheological and hence mechanical properties under the influence of an applied electric field. Efforts are in progress to embed ER fluids in various structural elements to mitigate vibration problems. The present work is an experimental investigation of the behaviour of a sandwich beam with ER fluid acting as the core material. A starch-silicone-oil-based ER fluid is used in the present study. Significant improvements in the damping properties are achieved in experiments and the damping contributions by viscous and non-viscous forces are estimated by force-state mapping (FSM) technique. With the increase in electric field across the ER fluid from 0 to 2 kV, an increase of 25-50% in equivalent viscous damping is observed. It is observed that as concentration of starch is increased, the ER effect grows stronger but eventually is overcome by applied stresses.

  5. Damping in heat exchanger tube bundles. A review

    International Nuclear Information System (INIS)

    Iqbal, Qamar; Khushnood, Shahab; Ghalban, Ali Roheim El; Sheikh, Nadeem Ahmed; Malik, Muhammad Afzaal; Arastu, Asif

    2007-01-01

    Damping is a major concern in the design and operation of tube bundles with loosely supported tubes in baffles for process shell and tube heat exchangers and steam generators which are used in nuclear, process and power generation industries. System damping has a strong influence on the amplitude of vibration. Damping depends upon the mechanical properties of the tube material, geometry of intermediate supports and the physical properties of shell-side fluid. Type of tube motion, number of supports, tube frequency, vibration amplitude, tube mass or diameter, side loads, support thickness, higher modes, shell-side temperature etc., affect damping in tube bundles. The importance of damping is further highlighted due to current trend of larger exchangers with increased shell-side velocities in modern units. Various damping mechanisms have been identified (Friction damping, Viscous damping, Squeeze film damping, Support damping. Two-Phase damping, and very recent-Thermal damping), which affect the performance of process exchangers and steam generators with respect to flow induced vibration design, including standard design guidelines. Damping in two-phase flow is very complex and highly void fraction, and flow-regime dependent. The current paper focuses on the various known damping mechanisms subjected to both single and two-phase cross-flow in process heat exchangers and steam generators and formulates the design guidelines for safer design. (author)

  6. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    Some nontrivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial (depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based...... on a slightly modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical...

  7. Nuclear power plant piping damping parametric effects

    International Nuclear Information System (INIS)

    Ware, A.G.

    1983-01-01

    The present NRC guidelines for structural damping to be used in the dynamic stress analyses of nuclear power plant piping systems are generally considered to be overly conservative. As a result, plant designers have in many instances used a considerable number of seismic supports to keep stresses calculated by large scale piping computer codes below the allowable limits. In response to this problem, the NRC and EG and G Idaho are engaged in programs to evaluate piping system damping, in order to provide more realistic and less conservative values to be used in seismic analyses. To generate revised guidelines, solidly based on technical data, new experimental data need to be generated and assessed, and the parameters which influence piping system damping need to be quantitatively identified. This paper presents the current state-of-the-art knowledge in the United States on parameters which influence piping system damping. Examples of inconsistencies in the data and areas of uncertainty are explained. A discussion of programs by EG and G Idaho and other organizations to evaluate various effects is included, and both short and long range goals of the program are outlined

  8. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    2008-01-01

    Some non-trivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based on a slightly...... modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical optimally...

  9. Landau damping in bi-dust ion-acoustic waves

    International Nuclear Information System (INIS)

    Castro, E.; Puerta, J.; Martin, P.; Cereceda, C.

    2006-01-01

    Ion acoustic dust waves in a bi-dust plasma are analyzed in this paper. In order to model this system, we assume the existence of two different kinds of grains, each characterized by a different radius. Relative velocities between grains and charge fluctuations are neglected. In order to derive the dispersion relation of this system, we use the well known hybrid fluid-kinetic model, in which ions are treated kinetically and other species as fluids. In this plasma, waves with non-relative velocities between species leads to damped waves with frequency modes, defined by the grain radius. The induced damping ratio is studied as a function of the grain and ion densities. (Author)

  10. Geometric size effect on the extrinsic Gilbert damping in laterally confined magnetic structures

    Energy Technology Data Exchange (ETDEWEB)

    Song, Hyon-Seok [Department of Emerging Materials Science, DGIST, Daegu 42988 (Korea, Republic of); Lee, Kyeong-Dong [Department of Materials Science and Engineering, KAIST, Daejeon 34141 (Korea, Republic of); You, Chun-Yeol [Department of Physics, Inha University, Incheon 22212 (Korea, Republic of); Park, Byong-Guk [Department of Materials Science and Engineering, KAIST, Daejeon 34141 (Korea, Republic of); Hong, Jung-Il, E-mail: jihong@dgist.ac.kr [Department of Emerging Materials Science, DGIST, Daegu 42988 (Korea, Republic of); Research Centre for Emerging Materials, DGIST, Daegu 42988 (Korea, Republic of)

    2016-05-15

    We investigated spin dynamics in micron-length scale patterned thin films using the GPU-based micromagnetic simulation program. Spin precessional motion was induced by a Gaussian-pulse magnetic field. The effective Gilbert damping was examined by tracking the precessional motion of the spins, and we found that the damping constant depends on the size and shape of the pattern as well as the externally applied magnetic field. Additional extrinsic damping generated around the edge region was attributed to the dephasing effect between the fundamental spin wave and other spin wave modes. We find that the effect of extrinsic damping could be eliminated by proper adjustments of sample size, external bias field, position, and area of observation. - Highlights: • GPU based micromagnetic simulation of spin dynamics in the micropatterned ferromagnetic films. • Effect of edge regions of the pattern on the Gilbert damping behaviors. • Guide for the analyses of intrinsic magnetic damping in the micron scale patterned films.

  11. Analytical Solution and Physics of a Propellant Damping Device

    Science.gov (United States)

    Yang, H. Q.; Peugeot, John

    2011-01-01

    NASA design teams have been investigating options for "detuning" Ares I to prevent oscillations originating in the vehicle solid-rocket main stage from synching up with the natural resonance of the rest of the vehicle. An experimental work started at NASA MSFC center in 2008 using a damping device showed great promise in damping the vibration level of an 8 resonant tank. However, the mechanisms of the vibration damping were not well understood and there were many unknowns such as the physics, scalability, technology readiness level (TRL), and applicability for the Ares I vehicle. The objectives of this study are to understand the physics of intriguing slosh damping observed in the experiments, to further validate a Computational Fluid Dynamics (CFD) software in propellant sloshing against experiments with water, and to study the applicability and efficiency of the slosh damper to a full scale propellant tank and to cryogenic fluids. First a 2D fluid-structure interaction model is built to model the system resonance of liquid sloshing and structure vibration. A damper is then added into the above model to simulate experimentally observed system damping phenomena. Qualitative agreement is found. An analytical solution is then derived from the Newtonian dynamics for the thrust oscillation damper frequency, and a slave mass concept is introduced in deriving the damper and tank interaction dynamics. The paper will elucidate the fundamental physics behind the LOX damper success from the derivation of the above analytical equation of the lumped Newtonian dynamics. Discussion of simulation results using high fidelity multi-phase, multi-physics, fully coupled CFD structure interaction model will show why the LOX damper is unique and superior compared to other proposed mitigation techniques.

  12. Non-Destructive Damping Measurement for Wafer-Level Packaged Microelectromechanical System (MEMS) Acceleration Switches

    Science.gov (United States)

    2014-09-01

    small geometries and inertial forces are often negligible, so the behavior of fluids is based primarily on the viscous effects.3 Experimental...system modeling. In isolated environments filled with a working fluid that dissipates energy, damping between parallel and sliding plates that are... damper in a second-order differential equation. Fig. 1 Example of the data taken by the data acquisition device The impact table will produce high

  13. Eddy damping effect of additional conductors in superconducting levitation systems

    Science.gov (United States)

    Jiang, Zhao-Fei; Gou, Xiao-Fan

    2015-12-01

    Passive superconducting levitation systems consisting of a high temperature superconductor (HTSC) and a permanent magnet (PM) have demonstrated several fascinating applications such as the maglev system, flywheel energy storage. Generally, for the HTSC-PM levitation system, the HTSC with higher critical current density Jc can obtain larger magnetic force to make the PM levitate over the HTSC (or suspended below the HTSC), however, the process of the vibration of the levitated PM, provides very limited inherent damping (essentially hysteresis). To improve the dynamic stability of the levitated PM, eddy damping of additional conductors can be considered as the most simple and effective approach. In this article, for the HTSC-PM levitation system with an additional copper damper attached to the HTSC, we numerically and comprehensively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. Furthermore, we comparatively studied four different arrangements of the copper damper, on the comprehensive analyzed the damping effect, efficiency (defined by c/VCu, in which VCu is the volume of the damper) and Joule heating, and finally presented the most advisable arrangement.

  14. Piping system damping data at higher frequencies

    International Nuclear Information System (INIS)

    Ware, A.G.

    1987-01-01

    Research has been performed at the Idaho National Engineering Laboratory (INEL) for the United States Nuclear Regulatory Commission (USNRC) to determine best-estimate damping values for dynamic analyses of nuclear piping systems excited in the 20 to 100 Hz frequency range. Vibrations in this frequency range are typical of fluid-induced transients, for which no formal pipe damping guidelines exist. The available data found in the open literature and the USNRC/INEL nuclear piping damping data bank were reviewed, and a series of tests on a straight 3-in. (76-mm) piping system and a 5-in. (127-mm) system with several bends and elbows were conducted as part of this research program. These two systems were supported with typical nuclear piping supports that could be changed from test to test during the series. The resulting damping values were ≥ those of the Pressure Vessel Research Committee (PVRC) proposal for unisulated piping. Extending the PVRC damping curve from 20 to 100 Hz at 3% of critical damping would give a satisfactory representation of the test data. This position has been endorsed by the PVRC Technical Committee on Piping Systems. 14 refs

  15. Super-Alfvénic Propagation and Damping of Reconnection Onset Signatures

    Science.gov (United States)

    Sharma Pyakurel, P.; Shay, M. A.; Haggerty, C. C.; Parashar, T. N.; Drake, J. F.; Cassak, P. A.; Gary, S. Peter

    2018-01-01

    The quadrupolar out-of-plane Hall magnetic field generated during collisionless reconnection propagates away from the x line as a kinetic Alfvén wave (KAW). While it has been shown that this KAW carries substantial Poynting flux and propagates super-Alfvenically, how this KAW damps as it propagates away from the x line is not well understood. In this study, this damping is examined using kinetic particle-in-cell simulations of antiparallel symmetric magnetic reconnection in a one-dimensional current sheet equilibrium. In the reconnection simulations, the KAW wave vector has a typical magnitude comparable to an inverse fluid Larmor radius (effectively an inverse ion Larmor radius) and a direction of 85-89° relative to the local magnetic field. We find that the damping of the reconnection KAW is consistent with linear Landau damping results from a numerical Vlasov dispersion solver. This knowledge allows us to generalize our damping predictions to regions in the magnetotail and solar corona where the magnetic geometry can be approximated as a current sheet. For the magnetotail, the KAW from reconnection will not damp away before propagating the approximately 20 Earth radii associated with global magnetotail distances. For the solar corona, on the other hand, these KAWs will completely damp before reaching the distances comparable to the flare loop length.

  16. Parameter identification in a generalized time-harmonic Rayleigh damping model for elastography.

    Directory of Open Access Journals (Sweden)

    Elijah E W Van Houten

    Full Text Available The identifiability of the two damping components of a Generalized Rayleigh Damping model is investigated through analysis of the continuum equilibrium equations as well as a simple spring-mass system. Generalized Rayleigh Damping provides a more diversified attenuation model than pure Viscoelasticity, with two parameters to describe attenuation effects and account for the complex damping behavior found in biological tissue. For heterogeneous Rayleigh Damped materials, there is no equivalent Viscoelastic system to describe the observed motions. For homogeneous systems, the inverse problem to determine the two Rayleigh Damping components is seen to be uniquely posed, in the sense that the inverse matrix for parameter identification is full rank, with certain conditions: when either multi-frequency data is available or when both shear and dilatational wave propagation is taken into account. For the multi-frequency case, the frequency dependency of the elastic parameters adds a level of complexity to the reconstruction problem that must be addressed for reasonable solutions. For the dilatational wave case, the accuracy of compressional wave measurement in fluid saturated soft tissues becomes an issue for qualitative parameter identification. These issues can be addressed with reasonable assumptions on the negligible damping levels of dilatational waves in soft tissue. In general, the parameters of a Generalized Rayleigh Damping model are identifiable for the elastography inverse problem, although with more complex conditions than the simpler Viscoelastic damping model. The value of this approach is the additional structural information provided by the Generalized Rayleigh Damping model, which can be linked to tissue composition as well as rheological interpretations.

  17. Validity of Miles Equation in Predicting Propellant Slosh Damping in Baffled Tanks at Variable Slosh Amplitude

    Science.gov (United States)

    Yang, H. Q.; West, Jeff

    2018-01-01

    Determination of slosh damping is a very challenging task as there is no analytical solution. The damping physics involves the vorticity dissipation which requires the full solution of the nonlinear Navier-Stokes equations. As a result, previous investigations were mainly carried out by extensive experiments. A systematical study is needed to understand the damping physics of baffled tanks, to identify the difference between the empirical Miles equation and experimental measurements, and to develop new semi-empirical relations to better represent the real damping physics. The approach of this study is to use Computational Fluid Dynamics (CFD) technology to shed light on the damping mechanisms of a baffled tank. First, a 1-D Navier-Stokes equation representing different length scales and time scales in the baffle damping physics is developed and analyzed. Loci-STREAM-VOF, a well validated CFD solver developed at NASA MSFC, is applied to study the vorticity field around a baffle and around the fluid-gas interface to highlight the dissipation mechanisms at different slosh amplitudes. Previous measurement data is then used to validate the CFD damping results. The study found several critical parameters controlling fluid damping from a baffle: local slosh amplitude to baffle thickness (A/t), surface liquid depth to tank radius (d/R), local slosh amplitude to baffle width (A/W); and non-dimensional slosh frequency. The simulation highlights three significant damping regimes where different mechanisms dominate. The study proves that the previously found discrepancies between Miles equation and experimental measurement are not due to the measurement scatter, but rather due to different damping mechanisms at various slosh amplitudes. The limitations on the use of Miles equation are discussed based on the flow regime.

  18. The damped wave equation with unbounded damping

    Science.gov (United States)

    Freitas, Pedro; Siegl, Petr; Tretter, Christiane

    2018-06-01

    We analyze new phenomena arising in linear damped wave equations on unbounded domains when the damping is allowed to become unbounded at infinity. We prove the generation of a contraction semigroup, study the relation between the spectra of the semigroup generator and the associated quadratic operator function, the convergence of non-real eigenvalues in the asymptotic regime of diverging damping on a subdomain, and we investigate the appearance of essential spectrum on the negative real axis. We further show that the presence of the latter prevents exponential estimates for the semigroup and turns out to be a robust effect that cannot be easily canceled by adding a positive potential. These analytic results are illustrated by examples.

  19. The damped wave equation with unbounded damping

    Czech Academy of Sciences Publication Activity Database

    Freitas, P.; Siegl, Petr; Tretter, C.

    2018-01-01

    Roč. 264, č. 12 (2018), s. 7023-7054 ISSN 0022-0396 Institutional support: RVO:61389005 Keywords : damped wave equation * unbounded damping * essential spectrum * quadratic operator funciton with unbounded coefficients * Schrodinger operators with complex potentials Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 1.988, year: 2016

  20. Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects

    Science.gov (United States)

    Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.

    2011-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.

  1. Application of fluid-structure coupling to predict the dynamic behavior of turbine components

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, B; Seidel, U [Voith Hydro Holding GmbH and Co. KG, Alexanderstr. 11, 89522 Heidenheim (Germany); Roth, S, E-mail: bjoern.huebner@voith.co [Laboratory for Hydraulic Machines, EPFL, Avenue de Cour 33 Bis, 1007 Lausanne (Switzerland)

    2010-08-15

    In hydro turbine design, fluid-structure interaction (FSI) may play an important role. Examples are flow induced inertia and damping effects, vortex induced vibrations in the lock-in vicinity, or hydroelastic instabilities of flows in deforming gaps (e.g. labyrinth seals). In contrast to aeroelasticity, hydroelastic systems require strongly (iteratively) coupled or even monolithic solution procedures, since the fluid mass which is moving with the structure (added-mass effect) is much higher and changes the dynamic behavior of submerged structures considerably. Depending on the mode shape, natural frequencies of a turbine runner in water may be reduced to less than 50% of the corresponding frequencies in air, and flow induced damping effects may become one or two orders of magnitude higher than structural damping. In order to reduce modeling effort and calculation time, the solution strategy has to be adapted precisely to a given application. Hence, depending on the problem to solve, different approximations may apply. Examples are the calculation of natural frequencies and response spectra in water using an acoustic fluid formulation, the determination of flow induced damping effects by means of partitioned FSI including complex turbulent flows, and the identification of hydroelastic instabilities using monolithic coupling of non-linear structural dynamics and water flow.

  2. Evaluation of damping loss factor of flat laminates by sound transmission

    Science.gov (United States)

    Parrinello, A.; Ghiringhelli, G. L.

    2018-06-01

    A novel approach to investigate and evaluate the damping loss factor of a planar multilayered structure is presented. A statistical analysis reveals the connection between the damping properties of the structure and the transmission of sound through the thickness of its laterally infinite counterpart. The obtained expression for the panel loss factor involves all the derivatives of the transmission and reflection coefficients of the layered structure with respect each layer damping. The properties of the fluid for which the sound transmission is evaluated are chosen to fulfil the hypotheses on the basis of the statistical formulation. A transfer matrix approach is used to compute the required transmission and reflection coefficients, making it possible to deal with structures having arbitrary stratifications of different layers and also granting high efficiency in a wide frequency range. Comparison with alternative formulations and measurements demonstrates the effectiveness of the proposed methodology.

  3. Dynamic characteristics of Non Newtonian fluid Squeeze film damper

    Science.gov (United States)

    Palaksha, C. P.; Shivaprakash, S.; Jagadish, H. P.

    2016-09-01

    The fluids which do not follow linear relationship between rate of strain and shear stress are termed as non-Newtonian fluid. The non-Newtonian fluids are usually categorized as those in which shear stress depends on the rates of shear only, fluids for which relation between shear stress and rate of shear depends on time and the visco inelastic fluids which possess both elastic and viscous properties. It is quite difficult to provide a single constitutive relation that can be used to define a non-Newtonian fluid due to a great diversity found in its physical structure. Non-Newtonian fluids can present a complex rheological behaviour involving shear-thinning, viscoelastic or thixotropic effects. The rheological characterization of complex fluids is an important issue in many areas. The paper analyses the damping and stiffness characteristics of non-Newtonian fluids (waxy crude oil) used in squeeze film dampers using the available literature for viscosity characterization. Damping and stiffness characteristic will be evaluated as a function of shear strain rate, temperature and percentage wax concentration etc.

  4. Damping Effects of Drogue Parachutes on Orion Crew Module Dynamics

    Science.gov (United States)

    Aubuchon, Vanessa V.; Owens, D. Bruce

    2016-01-01

    Because simulations of the Orion Crew Module (CM) dynamics with drogue parachutes deployed were under-predicting the amount of damping seen in free-flight tests, an attach-point damping model was applied to the Orion system. A key hypothesis in this model is that the drogue parachutes' net load vector aligns with the CM drogue attachment point velocity vector. This assumption seems reasonable and has historically produced good results, but has never been experimentally verified. The wake of the CM influences the drogue parachutes, which makes performance predictions of the parachutes difficult. Many of these effects are not currently modeled in the simulations. A forced oscillation test of the CM with parachutes was conducted in the NASA LaRC 20-Ft Vertical Spin Tunnel (VST) to gather additional data to validate and refine the attach-point damping model. A second loads balance was added to the original Orion VST model to measure the drogue parachute loads independently of the CM. The objective of the test was to identify the contribution of the drogues to CM damping and provide additional information to quantify wake effects and the interactions between the CM and parachutes. The drogue parachute force vector was shown to be highly dependent on the CM wake characteristics. Based on these wind tunnel test data, the attach-point damping model was determined to be a sufficient approximation of the parachute dynamics in relationship to the CM dynamics for preliminary entry vehicle system design. More wake effects should be included to better model the system.

  5. Concerning the Effect of a Viscoelastic Foundation on the Dynamic Stability of a Pipeline System Conveying an Incompressible Fluid

    Directory of Open Access Journals (Sweden)

    Vincent Olunloyo

    2016-12-01

    Full Text Available In this paper, we present an analytical method for solving a well-posed boundary value problem of mathematical physics governing the vibration characteristics of an internal flow propelled fluid-structure interaction where the pipeline segment is idealized as an elastic hollow beam conveying an incompressible fluid on a viscoelastic foundation. The effect of Coriolis and damping forces on the overall dynamic response of the system is investigated. In actuality, for a pipe segment supported at both ends and subject to a free motion, these two forces generate conjugate complex frequencies for all flow velocities. On employing integral transforms and complex variable functions, a closed form analytical expression is derived for the overall dynamic response. It is demonstrated that a concise mathematical expression for the natural frequency associated with any mode of vibration can be deduced from the algebraic product of the complex frequency pairs. By a way of comparative analysis for damping decrement physics reminiscent with laminated structures, mathematical expressions are derived to illustrate viscoelastic damping effects on dynamic stability for any flow velocity. The integrity of the analytical solution is verified and validated by confirming theresults in literature in appropriate asymptotic limits.

  6. Dynamics of two coaxial cylindrical shells containing viscous fluid

    International Nuclear Information System (INIS)

    Yeh, T.T.; Chen, S.S.

    1976-09-01

    This study was motivated by the need to design the thermal shield in reactor internals and other system components to avoid detrimental flow-induced vibrations. The system component is modeled as two coaxial shells separated by a viscous fluid. In the analysis, Flugge's shell equations of motion and linearized Navier-Stokes equation for viscous fluid are employed. First, a traveling-wave type solution is taken for shells and fluid. Then, from the interface conditions between the shells and fluid, the solution for the fluid medium is expressed in terms of shell displacements. Finally, using the shell equations of motion gives the frequency equation, from which the natural frequency, mode shape, and modal damping ratio of coupled modes can be calculated. The analytical results show a fairly good qualitative agreement with the published experimental data. Some important conclusions are as follows: (1) In computing the natural frequencies and mode shapes of uncoupled modes and coupled modes, the fluid may be considered inviscid and incompressible. (2) There exists out-of-phase and in-phase modes. The lowest natural frequency is always associated with the out-of-phase mode. (3) The lowest natural frequency of coupled modes is lower than the uncoupled modes. (4) The fluid viscosity contributes significantly to damping, in particular, the modal damping of the out-of-phase modes isrelatively large for small gaps. (5) If the fluid gap is small, or the fluid viscosity is relatively high, the simulation of the vibration Reynolds number should be included to ensure that modal damping of the model is properly accounted for. With the presented analysis and results, the frequency and damping characteristics can be analyzed and design parameters can be related to frequency and damping

  7. Wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes with surface and nonlocal effects

    Science.gov (United States)

    Zhen, Ya-Xin

    2017-02-01

    In this paper, the transverse wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes is investigated based on nonlocal elasticity theory with consideration of surface effect. The governing equation is formulated utilizing nonlocal Euler-Bernoulli beam theory and Kelvin-Voigt model. Explicit wave dispersion relation is developed and wave phase velocities and frequencies are obtained. The effect of the fluid flow velocity, structural damping, surface effect, small scale effects and tube diameter on the wave propagation properties are discussed with different wave numbers. The wave frequency increases with the increase of fluid flow velocity, but decreases with the increases of tube diameter and wave number. The effect of surface elasticity and residual surface tension is more significant for small wave number and tube diameter. For larger values of wave number and nonlocal parameters, the real part of frequency ratio raises.

  8. Investigation of Damping Physics and CFD Tool Validation for Simulation of Baffled Tanks at Variable Slosh Amplitude

    Science.gov (United States)

    Yang, H. Q.; West, Jeff

    2016-01-01

    Determination of slosh damping is a very challenging task as there is no analytical solution. The damping physics involves the vorticity dissipation which requires the full solution of the nonlinear Navier-Stokes equations. As a result, previous investigations were mainly carried out by extensive experiments. A systematical study is needed to understand the damping physics of baffled tanks, to identify the difference between the empirical Miles equation and experimental measurements, and to develop new semi-empirical relations to better represent the real damping physics. The approach of this study is to use Computational Fluid Dynamics (CFD) technology to shed light on the damping mechanisms of a baffled tank. First, a 1-D Navier-Stokes equation representing different length scales and time scales in the baffle damping physics is developed and analyzed. Loci-STREAM-VOF, a well validated CFD solver developed at NASA MSFC, is applied to study the vorticity field around a baffle and around the fluid-gas interface to highlight the dissipation mechanisms at different slosh amplitudes. Previous measurement data is then used to validate the CFD damping results. The study found several critical parameters controlling fluid damping from a baffle: local slosh amplitude to baffle thickness (A/t), surface liquid depth to tank radius (d/R), local slosh amplitude to baffle width (A/W); and non-dimensional slosh frequency. The simulation highlights three significant damping regimes where different mechanisms dominate. The study proves that the previously found discrepancies between Miles equation and experimental measurement are not due to the measurement scatter, but rather due to different damping mechanisms at various slosh amplitudes. The limitations on the use of Miles equation are discussed based on the flow regime.

  9. Numerical studies of shear damped composite beams using a constrained damping layer

    DEFF Research Database (Denmark)

    Kristensen, R.F.; Nielsen, Kim Lau; Mikkelsen, Lars Pilgaard

    2008-01-01

    Composite beams containing one or more damping layers are studied numerically. The work is based on a semi-analytical model using a Timoshenko beam theory and a full 2D finite element model. The material system analysed, is inspired by a train wagon suspension system used in a EUREKA project Sigma......!1841. For the material system, the study shows that the effect of the damping layer is strongly influenced by the presence of a stiff constraining layer, that enforces large shear strain amplitudes. The thickness of the damping rubber layer itself has only a minor influence on the overall damping....... In addition, a large influence of ill positioned cuts in the damping layer is observed....

  10. Damping in LMFBR pipe systems

    International Nuclear Information System (INIS)

    Anderson, M.J.; Barta, D.A.; Lindquist, M.R.; Renkey, E.J.; Ryan, J.A.

    1983-06-01

    LMFBR pipe systems typically utilize a thicker insulation package than that used on water plant pipe systems. They are supported with special insulated pipe clamps. Mechanical snubbers are employed to resist seismic loads. Recent laboratory testing has indicated that these features provide significantly more damping than presently allowed by Regulatory Guide 1.61 for water plant pipe systems. This paper presents results of additional in-situ vibration tests conducted on FFTF pipe systems. Pipe damping values obtained at various excitation levels are presented. Effects of filtering data to provide damping values at discrete frequencies and the alternate use of a single equivalent modal damping value are discussed. These tests further confirm that damping in typical LMFBR pipe systems is larger than presently used in pipe design. Although some increase in damping occurred with increased excitation amplitude, the effect was not significant. Recommendations are made to use an increased damping value for both the OBE and DBE seismic events in design of LMFBR pipe systems

  11. Magnetic Damping For Maglev

    Directory of Open Access Journals (Sweden)

    S. Zhu

    1998-01-01

    Full Text Available Magnetic damping is one of the important parameters that control the response and stability of maglev systems. An experimental study to measure magnetic damping directly is presented. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters, such as conductivity, gap, excitation frequency, and oscillation amplitude, on magnetic damping. The experimental technique is capable of measuring all of the magnetic damping coefficients, some of which cannot be measured indirectly.

  12. Effects of Active Sting Damping on Common Research Model Data Quality

    Science.gov (United States)

    Acheson, Michael J.; Balakrishna, S.

    2011-01-01

    Recent tests using the Common Research Model (CRM) at the Langley National Transonic Facility (NTF) and the Ames 11-foot Transonic Wind Tunnel (11' TWT) produced large sets of data that have been used to examine the effects of active damping on transonic tunnel aerodynamic data quality. In particular, large statistically significant sets of repeat data demonstrate that the active damping system had no apparent effect on drag, lift and pitching moment repeatability during warm testing conditions, while simultaneously enabling aerodynamic data to be obtained post stall. A small set of cryogenic (high Reynolds number) repeat data was obtained at the NTF and again showed a negligible effect on data repeatability. However, due to a degradation of control power in the active damping system cryogenically, the ability to obtain test data post-stall was not achieved during cryogenic testing. Additionally, comparisons of data repeatability between NTF and 11-ft TWT CRM data led to further (warm) testing at the NTF which demonstrated that for a modest increase in data sampling time, a 2-3 factor improvement in drag, and pitching moment repeatability was readily achieved not related with the active damping system.

  13. Damping of Quasi-stationary Waves Between Two Miscible Liquids

    Science.gov (United States)

    Duval, Walter M. B.

    2002-01-01

    Two viscous miscible liquids with an initially sharp interface oriented vertically inside a cavity become unstable against oscillatory external forcing due to Kelvin-Helmholtz instability. The instability causes growth of quasi-stationary (q-s) waves at the interface between the two liquids. We examine computationally the dynamics of a four-mode q-s wave, for a fixed energy input, when one of the components of the external forcing is suddenly ceased. The external forcing consists of a steady and oscillatory component as realizable in a microgravity environment. Results show that when there is a jump discontinuity in the oscillatory excitation that produced the four-mode q-s wave, the interface does not return to its equilibrium position, the structure of the q-s wave remains imbedded between the two fluids over a long time scale. The damping characteristics of the q-s wave from the time history of the velocity field show overdamped and critically damped response; there is no underdamped oscillation as the flow field approaches steady state. Viscous effects serve as a dissipative mechanism to effectively damp the system. The stability of the four-mode q-s wave is dependent on both a geometric length scale as well as the level of background steady acceleration.

  14. Non-Linear Slosh Damping Model Development and Validation

    Science.gov (United States)

    Yang, H. Q.; West, Jeff

    2015-01-01

    Propellant tank slosh dynamics are typically represented by a mechanical model of spring mass damper. This mechanical model is then included in the equation of motion of the entire vehicle for Guidance, Navigation and Control (GN&C) analysis. For a partially-filled smooth wall propellant tank, the critical damping based on classical empirical correlation is as low as 0.05%. Due to this low value of damping, propellant slosh is potential sources of disturbance critical to the stability of launch and space vehicles. It is postulated that the commonly quoted slosh damping is valid only under the linear regime where the slosh amplitude is small. With the increase of slosh amplitude, the critical damping value should also increase. If this nonlinearity can be verified and validated, the slosh stability margin can be significantly improved, and the level of conservatism maintained in the GN&C analysis can be lessened. The purpose of this study is to explore and to quantify the dependence of slosh damping with slosh amplitude. Accurately predicting the extremely low damping value of a smooth wall tank is very challenging for any Computational Fluid Dynamics (CFD) tool. One must resolve thin boundary layers near the wall and limit numerical damping to minimum. This computational study demonstrates that with proper grid resolution, CFD can indeed accurately predict the low damping physics from smooth walls under the linear regime. Comparisons of extracted damping values with experimental data for different tank sizes show very good agreements. Numerical simulations confirm that slosh damping is indeed a function of slosh amplitude. When slosh amplitude is low, the damping ratio is essentially constant, which is consistent with the empirical correlation. Once the amplitude reaches a critical value, the damping ratio becomes a linearly increasing function of the slosh amplitude. A follow-on experiment validated the developed nonlinear damping relationship. This discovery can

  15. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    International Nuclear Information System (INIS)

    Hwa-Min, Kim; Young-Dae, Jung

    2007-01-01

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle θ L = π/4. (authors)

  16. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hwa-Min, Kim [Daegu Univ. Catholic, Dept. of Electronics Engineering (Korea, Republic of); Young-Dae, Jung [Hanyang Univ., Dept. of Applied Physics, Seoul (Korea, Republic of)

    2007-07-15

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle {theta}{sub L} = {pi}/4. (authors)

  17. Effect of T6 heat treatment on damping characteristics of Al/RHA ...

    Indian Academy of Sciences (India)

    Abstract. In the present work, effect of T6 heat treatment on the damping behaviour of aluminum/rice husk ash .... alloy-based composites, there is dearth of information on the damping ... fication. Using the process 4, 6 and 8% by weight, RHA.

  18. Damping of liquid sloshing by foams: from everyday observations to liquid transport

    Science.gov (United States)

    Sauret, Alban; Boulogne, Francois; Cappello, Jean; Stone, Howard

    2014-11-01

    When a liquid-filled container is set in motion, the free surface of the liquid starts to slosh, i.e. oscillate. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rim of the container. However, beer does not slosh as readily, which suggests that the presence of foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of liquid foam placed on top of a liquid bath in a Hele-Shaw cell. We generate a monodisperse 2D liquid foam and track its motion. The influence of the foam on the sloshing dynamics is characterized: 2 to 3 layers of bubbles are sufficient to significantly damp the oscillations. For more than 5 layers of bubbles, the original vertical motion of the foam becomes mainly horizontal. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient. This study motivated by everyday observations has promising applications in numerous industrial applications such as the transport of liquid in cargoes.

  19. Overview of collective effects in the NLC main damping rings

    International Nuclear Information System (INIS)

    Wolski, A.; Santis, S. de

    2002-01-01

    The present design for the NLC Main Damping Rings (MDRs) meets the specifications for acceptance and extracted emittance, in the limit of zero current. However, the relatively large bunch charge and moderate energy mean that a variety of collective effects can impact the beam dynamics, leading to loss of stability or increase of equilibrium emittance. These effects include intrabeam scattering, impedance from numerous sources, fast ion instability, and (in the positron ring) electron cloud. In this note, we survey the expected impact on damping ring performance from each of a number of collective effects, and discuss the priorities for future studies in this area

  20. Calculations of emittance and damping time effects in the SLC damping rings

    International Nuclear Information System (INIS)

    Limberg, T.; Moshammer, H.; Raubenheimer, T.; Spencer, J.; Siemann, R.

    1992-03-01

    In a recent NDR machine experiment the transverse emittance was studied as a function of store time and tune. To explain the observed transverse emittance damping time constants, the magnetic measurement data of the longitudinal field of the bending magnets had to be taken into account. The variation of the transverse emittances with tune due to misalignments and the associated anomalous dispersion is studied as well as the effect of synchrobetatron coupling due to dispersion in the RF cavities

  1. Theoretical study of flow ripple for an aviation axial-piston pump with damping holes in the valve plate

    OpenAIRE

    Guan, Changbin; Jiao, Zongxia; He, Shouzhan

    2014-01-01

    Based on the structure of a certain type of aviation axial-piston pump’s valve plate which adopts a pre-pressurization fluid path (consisting a damping hole, a buffer chamber, and an orifice) to reduce flow ripple, a single-piston model of the aviation axial-piston pump is presented. This single-piston model comprehensively considers fluid compressibility, orifice restriction effect, fluid resistance in the capillary tube, and the leakage flow. Besides, the instantaneous discharge areas used ...

  2. Laboratory piping system vibration tests to determine parametric effects on damping in the seismic frequency range

    International Nuclear Information System (INIS)

    Ware, A.G.

    1987-01-01

    A pipe damping research program is being conducted for the United States Nuclear Regulatory Commission at the Idaho National Engineering Laboratory to establish more realistic, best-estimate damping values for use in dynamic structural analyses of piping systems. As part of this program, tests were conducted on a 5-in. (128 mm ID) laboratory piping system to determine the effects of pressure, support configuration, insulation and response amplitude on damping. The tests were designed to produce a wide range of damping values, from very low damping in lightly excited uninsulated systems with few supports, to higher damping under conditions of either/or insulation, high level excitation, and various support arrangements. The effect of pressure at representative seismic levels was considered to be minimal. The supports influence damping at all excitation levels; damping was highest when a mechanical snubber was present in the system. The addition of insulation produced a large increase in damping for the hydraulic shaker excitation tests, but there was no comparable increase for the snapback excitation tests. Once a response amplitude of approximately one-half yield stress was reached, overall damping increased to relatively high levels (>10% of critical)

  3. Effect of milling on the damping behavior of nano-structured copper

    Energy Technology Data Exchange (ETDEWEB)

    Srikanth, Narasimalu; Thein, Maung Aye; Gupta, Manoj

    2004-02-05

    In the present study, elemental Cu powder was mechanically milled (MMed) for 10 h to reduce the grain (crystalline) size in the nano-range (<100 nm). The mechanically milled powder (10 h-MMed) and elemental powder without mechanical milling (MM) (0 h-MMed) was consolidated by die-cold compaction and were further hot extruded at different temperatures to maintain a crystallite size within the nano-range. Further, the specimen was tested by a novel free-free type suspended beam arrangement, coupled with circle-fit approach to determine damping characteristics. The characterization results help to understand the effect of the nano-size grains on the overall damping capacity of the bulk samples compared to a normal micro-crystalline sample. Results show that the damping capacity of the nano-grained material increases due to the presence of process induced microstructural changes similar to the damping behavior of a micro-grain sized specimen.

  4. Process Damping Parameters

    International Nuclear Information System (INIS)

    Turner, Sam

    2011-01-01

    The phenomenon of process damping as a stabilising effect in milling has been encountered by machinists since milling and turning began. It is of great importance when milling aerospace alloys where maximum surface speed is limited by excessive tool wear and high speed stability lobes cannot be attained. Much of the established research into regenerative chatter and chatter avoidance has focussed on stability lobe theory with different analytical and time domain models developed to expand on the theory first developed by Trusty and Tobias. Process damping is a stabilising effect that occurs when the surface speed is low relative to the dominant natural frequency of the system and has been less successfully modelled and understood. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the cut surface, with material properties and the relief geometry of the tool believed to be key factors governing performance. This study combines experimental trials with Finite Element (FE) simulation in an attempt to identify and understand the key factors influencing process damping performance in titanium milling. Rake angle, relief angle and chip thickness are the variables considered experimentally with the FE study looking at average radial and tangential forces and surface compressive stress. For the experimental study a technique is developed to identify the critical process damping wavelength as a means of measuring process damping performance. For the range of parameters studied, chip thickness is found to be the dominant factor with maximum stable parameters increased by a factor of 17 in the best case. Within the range studied, relief angle was found to have a lesser effect than expected whilst rake angle had an influence.

  5. A numerically efficient damping model for acoustic resonances in microfluidic cavities

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, P., E-mail: hahnp@ethz.ch; Dual, J. [Institute of Mechanical Systems (IMES), Department of Mechanical and Process Engineering, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich (Switzerland)

    2015-06-15

    Bulk acoustic wave devices are typically operated in a resonant state to achieve enhanced acoustic amplitudes and high acoustofluidic forces for the manipulation of microparticles. Among other loss mechanisms related to the structural parts of acoustofluidic devices, damping in the fluidic cavity is a crucial factor that limits the attainable acoustic amplitudes. In the analytical part of this study, we quantify all relevant loss mechanisms related to the fluid inside acoustofluidic micro-devices. Subsequently, a numerical analysis of the time-harmonic visco-acoustic and thermo-visco-acoustic equations is carried out to verify the analytical results for 2D and 3D examples. The damping results are fitted into the framework of classical linear acoustics to set up a numerically efficient device model. For this purpose, all damping effects are combined into an acoustofluidic loss factor. Since some components of the acoustofluidic loss factor depend on the acoustic mode shape in the fluid cavity, we propose a two-step simulation procedure. In the first step, the loss factors are deduced from the simulated mode shape. Subsequently, a second simulation is invoked, taking all losses into account. Owing to its computational efficiency, the presented numerical device model is of great relevance for the simulation of acoustofluidic particle manipulation by means of acoustic radiation forces or acoustic streaming. For the first time, accurate 3D simulations of realistic micro-devices for the quantitative prediction of pressure amplitudes and the related acoustofluidic forces become feasible.

  6. Nonlinear modeling of tuned liquid dampers (TLDs) in rotating wind turbine blades for damping edgewise vibrations

    DEFF Research Database (Denmark)

    Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit

    2015-01-01

    Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit......Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g...... free-surface elevation equally well, the one-mode model can still be utilized for the design of TLD. Parametric optimization of the TLD is carried out based on the one-mode model, and the optimized damper effectively improves the dynamic response of wind turbine blades....

  7. Design of a new adaptive fuzzy controller and its implementation for the damping force control of a magnetorheological damper

    International Nuclear Information System (INIS)

    Phu, Do Xuan; Shah, Kruti; Choi, Seung-Bok

    2014-01-01

    This paper presents a new adaptive fuzzy controller and its implementation for the damping force control of a magnetorheological (MR) fluid damper in order to validate the effectiveness of the control performance. An interval type 2 fuzzy model is built, and then combined with modified adaptive control to achieve the desired damping force. In the formulation of the new adaptive controller, an enhanced iterative algorithm is integrated with the fuzzy model to decrease the time of calculation (D Wu 2013 IEEE Trans. Fuzzy Syst. 21 80–99) and the control algorithm is synthesized based on the H ∞ tracking technique. In addition, for the verification of good control performance of the proposed controller, a cylindrical MR damper which can be applied to the vibration control of a washing machine is designed and manufactured. For the operating fluid, a recently developed plate-like particle-based MR fluid is used instead of a conventional MR fluid featuring spherical particles. To highlight the control performance of the proposed controller, two existing adaptive fuzzy control algorithms proposed by other researchers are adopted and altered for a comparative study. It is demonstrated from both simulation and experiment that the proposed new adaptive controller shows better performance of damping force control in terms of response time and tracking accuracy than the existing approaches. (papers)

  8. The effect of microstructure at interface between coating and substrate on damping capacity of coating systems

    International Nuclear Information System (INIS)

    Wang, Xueqin; Pei, Yanling; Ma, Yue

    2013-01-01

    Samples with various interface microstructures between the coating and the substrate were designed and fabricated in this paper. Dynamic mechanical thermal analyzer (DMTA) was utilized to investigate the dynamic mechanical properties of the samples and scanning electron microscopy (SEM) was used to observe the interface microstructure between the substrate and coating. The effect of the interface microstructure on damping was studied, and results indicated that the larger the coating/substrate interface thickness was and the more interface defects were, the higher interface system damping was. When the micro-hardness ratio of substrate to coating was increased, the damping of coating system was enhanced. The effect of the APS and EB-PVD coating on damping capacity was investigated. There was a dramatic increase in the damping value of the APS coating when the strain was higher than 20 ppm, while the damping amplitude effect of the EB-PVD coating was not so obvious, which could mainly be caused by the different energy dissipation mechanisms of the two coatings.

  9. Reduction of inward momentum flux by damped eigenmodes

    International Nuclear Information System (INIS)

    Terry, P. W.; Baver, D. A.; Hatch, D. R.

    2009-01-01

    The inward momentum flux driven by the off-diagonal pressure gradient in a fluid model for ion temperature gradient turbulence with large Richardson number is significantly reduced by the excitation of stable eigenmodes. This is accomplished primarily through the amplitude autocorrelation of the damped eigenmode, which, in the flux, directly counteracts the quasilinear contribution of the unstable eigenmode. Stable eigenmode cross correlations also contribute to the flux, but the symmetry of conjugate pairing of growing and damped eigenmodes leads to significant cancellations between cross correlation terms. Conjugate symmetry is a property of unstable wavenumbers but applies to the whole of the saturated state because damped eigenmodes in the unstable range prevent the spread of energy outside that range. The heat and momentum fluxes are nearly isomorphous when expressed in terms of the eigenmode correlations. Due to this similarity of form, the thermodynamic constraint, which keeps the heat flux outward even when significantly reduced by the damped eigenmode, results in a momentum flux that remains inward, even though it is also reduced by the damped eigenmode. The isomorphism is not perfect. When the contribution of stable eigenmode cross correlations to the flux do not cancel, the momentum flux can reverse sign and become outward.

  10. Study on the development of passive MR damper with displacement-dependent damping characteristics

    International Nuclear Information System (INIS)

    Murakami, Takahiro; Sakai, Michiya; Nakano, Masami

    2010-01-01

    In this paper, we propose a new concept of a magneto-rheological (MR) fluid damper, which is a passive MR fluid damper. The passive MR damper has no electrical devices, such as a sensor, power supply and controller, and hence, it has an advantage in reliability and cost compared with semi-active MR dampers. Moreover, the proposed MR damper can be designed to have a variable damping force in response to its displacement. In this paper, the dynamic performance of the passive MR damper is experimentally demonstrated. The prototype of the proposed damper has been manufactured in order to verify the dynamic performance. The displacement excitation test result of the damper demonstrates that the damping characteristics depend on its displacement amplitude, that is, the damper behaves as a linear viscous damper under small vibrations and develops much higher damping performance under large vibrations. (author)

  11. Magneto-induced large deformation and high-damping performance of a magnetorheological plastomer

    International Nuclear Information System (INIS)

    Liu, Taixiang; Gong, Xinglong; Xu, Yangguang; Pang, Haoming; Xuan, Shouhu

    2014-01-01

    A magnetorheological plastomer (MRP) is a new kind of soft magneto-sensitive polymeric composite. This work reports on the large magneto-deforming effect and high magneto-damping performance of MRPs under a quasi-statical shearing condition. We demonstrate that an MRP possesses a magnetically sensitive malleability, and its magneto-mechanical behavior can be analytically described by the magneto-enhanced Bingham fluid-like model. The magneto-induced axial stress, which drives the deformation of the MRP with 70 wt % carbonyl iron powder, can be tuned in a large range from nearly 0.0 kPa to 55.4 kPa by an external 662.6 kA m −1 magnetic field. The damping performance of an MRP has a significant correlation with the magnetic strength, shear rate, carbonyl iron content and shear strain amplitude. For an MRP with 60 wt % carbonyl iron powder, the relative magneto-enhanced damping effect can reach as high as 716.2% under a quasi-statically shearing condition. Furthermore, the related physical mechanism is proposed, and we reveal that the magneto-induced, particle-assembled microstructure directs the magneto-mechanical behavior of the MRP. (paper)

  12. Nuclear piping system damping data studies

    International Nuclear Information System (INIS)

    Ware, A.G.; Arendts, J.G.

    1985-01-01

    A programm has been conducted at the Idaho National Engineering Laboratory to study structural damping data for nuclear piping systems and to evaluate if changes in allowable damping values for structural seismic analyses are justified. The existing pipe damping data base was examined, from which a conclusion was made that there were several sets of data to support higher allowable values. The parameters which most influence pipe damping were identified and an analytical investigation demonstrated that increased damping would reduce the required number of seismic supports. A series of tests on several laboratory piping systems was used to determine the effect of various parameters such as types of supports, amplitude of vibration, frequency, insulation, and pressure on damping. A multiple regression analysis was used to statistically assess the influence of the various parameters on damping, and an international pipe damping data bank has been formed. (orig.)

  13. Development of new damping devices for piping

    International Nuclear Information System (INIS)

    Kobayashi, Hiroe

    1991-01-01

    An increase of the damping ratio is known to be very effective for the seismic design of a piping system. Increasing the damping ratio and reducing the seismic response of the piping system, the following three types of damping devices for piping systems are introduced: (1) visco-elastic damper, (2) elasto-plastic damper and (3) compact dynamic damper. The dynamic characteristics of these damping devices were investigated by the component test and the applicability of them to the piping system was confirmed by the vibration test using a three dimensional piping model. These damping devices are more effective than mechanical snubbers to reduce the vibration of the piping system. (author)

  14. Effect of wall compliance on peristaltic transport of a Newtonian fluid in an asymmetric channel

    Directory of Open Access Journals (Sweden)

    Mohamed H. Haroun

    2006-01-01

    Full Text Available Peristaltic transport of an incompressible viscous fluid in an asymmetric compliant channel is studied. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phases. The fluid-solid interaction problem is investigated by considering equations of motion of both the fluid and the deformable boundaries. The driving mechanism of the muscle is represented by assuming the channel walls to be compliant. The phenomenon of the “mean flow reversal” is discussed. The effect of wave amplitude ratio, width of the channel, phase difference, wall elastance, wall tension, and wall damping on mean-velocity and reversal flow has been investigated. The results reveal that the reversal flow occurs near the boundaries which is not possible in the elastic symmetric channel case.

  15. Damping of Resonantly Forced Density Waves in Dense Planetary Rings

    Science.gov (United States)

    Lehmann, Marius; Schmidt, Jürgen; Salo, Heikki

    2016-10-01

    We address the stability of resonantly forced density waves in dense planetary rings.Already by Goldreich and Tremaine (1978) it has been argued that density waves might be unstable, depending on the relationship between the ring's viscosity and the surface mass density. In the recent paper (Schmidt et al. 2016) we have pointed out that when - within a fluid description of the ring dynamics - the criterion for viscous overstability is satisfied, forced spiral density waves become unstable as well. In this case, linear theory fails to describe the damping.We apply the multiple scale formalism to derive a weakly nonlinear damping relation from a hydrodynamical model.This relation describes the resonant excitation and nonlinear viscous damping of spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients. The model consistently predicts linear instability of density waves in a ring region where the conditions for viscous overstability are met. In this case, sufficiently far away from the Lindblad resonance, the surface mass density perturbation is predicted to saturate to a constant value due to nonlinear viscous damping. In general the model wave damping lengths depend on a set of input parameters, such as the distance to the threshold for viscous overstability and the ground state surface mass density.Our new model compares reasonably well with the streamline model for nonlinear density waves of Borderies et al. 1986.Deviations become substantial in the highly nonlinear regime, corresponding to strong satellite forcing.Nevertheless, we generally observe good or at least qualitative agreement between the wave amplitude profiles of both models. The streamline approach is superior at matching the total wave profile of waves observed in Saturn's rings, while our new damping relation is a comparably handy tool to gain insight in the evolution of the wave amplitude with distance from resonance, and the different regimes of

  16. Barotropic FRW cosmologies with Chiellini damping

    Energy Technology Data Exchange (ETDEWEB)

    Rosu, Haret C., E-mail: hcr@ipicyt.edu.mx [IPICyT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San José 2055, Col. Lomas 4a Sección, 78216 San Luis Potosí, SLP (Mexico); Mancas, Stefan C., E-mail: stefan.mancas@erau.edu [Department of Mathematics, Embry–Riddle Aeronautical University, Daytona Beach, FL 32114-3900 (United States); Chen, Pisin, E-mail: pisinchen@phys.ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics (LeCosPA) and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

    2015-05-08

    It is known that barotropic FRW equations written in the conformal time variable can be reduced to simple linear equations for an exponential function involving the conformal Hubble rate. Here, we show that an interesting class of barotropic universes can be obtained in the linear limit of a special type of nonlinear dissipative Ermakov–Pinney equations with the nonlinear dissipation built from Chiellini's integrability condition. These cosmologies, which evolutionary are similar to the standard ones, correspond to barotropic fluids with adiabatic indices rescaled by a particular factor and have amplitudes of the scale factors inverse proportional to the adiabatic index. - Highlights: • Chiellini-damped Ermakov–Pinney equations are used in barotropic FRW cosmological context. • Chiellini-damped scale factors of the barotropic FRW universes are introduced. • These scale factors are similar to the undamped ones.

  17. Temperature effects on MIPs in the BGO calorimeters of DAMPE

    Science.gov (United States)

    Wang, Yuan-Peng; Wen, Si-Cheng; Jiang, Wei; Yue, Chuan; Zhang, Zhi-Yong; Wei, Yi-Feng; Zhang, YunLong; Zang, Jing-Jing; Wu, Jian

    2017-10-01

    In this paper, we present a study of temperature effects on BGO calorimeters using proton MIPs collected in the first year of operation of DAMPE. By directly comparing MIP calibration constants used by the DAMPE data production pipe line, we find an experimental relation between the temperature and signal amplitudes of each BGO bar: a general deviation of -1.162%/°C, and -0.47%/°C to -1.60%/°C statistically for each detector element. During 2016, DAMPE’s temperature changed by ˜8°C due to solar elevation angle, and the corresponding energy scale bias is about 9%. By frequent MIP calibration operation, this kind of bias is eliminated to an acceptable value. This work was supported by National Key Program for Research and Development (No. 2016YFA0400200) and by NSFC (11303105, 11673021). The DAMPE mission was funded by the strategic priority science and technology projects in space science of the Chinese Academy of Sciences (No. XDA04040000 and No. XDA04040400)

  18. Design, Analysis, and Experimental Evaluation of a Double Coil Magnetorheological Fluid Damper

    Directory of Open Access Journals (Sweden)

    Guoliang Hu

    2016-01-01

    Full Text Available A magnetorheological (MR damper is one of the most advanced devices used in a semiactive control system to mitigate unwanted vibration because the damping force can be controlled by changing the viscosity of the internal magnetorheological (MR fluids. This study proposes a typical double coil MR damper where the damping force and dynamic range were derived from a quasistatic model based on the Bingham model of MR fluid. A finite element model was built to study the performance of this double coil MR damper by investigating seven different piston configurations, including the numbers and shapes of their chamfered ends. The objective function of an optimization problem was proposed and then an optimization procedure was constructed using the ANSYS parametric design language (APDL to obtain the optimal damping performance of a double coil MR damper. Furthermore, experimental tests were also carried out, and the effects of the same direction and reverse direction of the currents on the damping forces were also analyzed. The relevant results of this analysis can easily be extended to the design of other types of MR dampers.

  19. Locked magnetic island chains in toroidally flow damped tokamak plasmas

    International Nuclear Information System (INIS)

    Fitzpatrick, R; Waelbroeck, F L

    2010-01-01

    The physics of a locked magnetic island chain maintained in the pedestal of an H-mode tokamak plasma by a static, externally generated, multi-harmonic, helical magnetic perturbation is investigated. The non-resonant harmonics of the external perturbation are assumed to give rise to significant toroidal flow damping in the pedestal, in addition to the naturally occurring poloidal flow damping. Furthermore, the flow damping is assumed to be sufficiently strong to relax the pedestal ion toroidal and poloidal fluid velocities to fixed values determined by neoclassical theory. The resulting neoclassical ion flow causes a helical phase-shift to develop between the locked island chain and the resonant harmonic of the external perturbation. Furthermore, when this phase-shift exceeds a critical value, the chain unlocks from the resonant harmonic and starts to rotate, after which it decays away and is replaced by a helical current sheet. The neoclassical flow also generates an ion polarization current in the vicinity of the island chain which either increases or decreases the chain's radial width, depending on the direction of the flow. If the polarization effect is stabilizing, and exceeds a critical amplitude, then the helical island equilibrium becomes unstable, and the chain again decays away. The critical amplitude of the resonant harmonic of the external perturbation at which the island chain either unlocks or becomes unstable is calculated as a function of the pedestal ion pressure, the neoclassical poloidal and toroidal ion velocities and the poloidal and toroidal flow damping rates.

  20. System and method for damping vibration in a drill string

    Science.gov (United States)

    Wassell, Mark Ellsworth; Turner, William Evans; Burgess, Daniel E; Perry, Carl Allison

    2014-03-04

    A system for damping vibration in a drill string can include a valve assembly having a supply of a fluid, a first member, and a second member capable of moving in relation to first member in response to vibration of the drill bit. The first and second members define a first and a second chamber for holding the fluid. Fluid can flow between the first and second chambers in response to the movement of the second member in relation to the first member. The valve assembly can also include a coil or a valve for varying a resistance of the fluid to flow between the first and second chambers.

  1. Phenomenology of chiral damping in noncentrosymmetric magnets

    KAUST Repository

    Akosa, Collins Ashu; Miron, Ioan Mihai; Gaudin, Gilles; Manchon, Aurelien

    2016-01-01

    A phenomenology of magnetic chiral damping is proposed in the context of magnetic materials lacking inversion symmetry. We show that the magnetic damping tensor acquires a component linear in magnetization gradient in the form of Lifshitz invariants. We propose different microscopic mechanisms that can produce such a damping in ferromagnetic metals, among which local spin pumping in the presence of an anomalous Hall effect and an effective “s-d” Dzyaloshinskii-Moriya antisymmetric exchange. The implication of this chiral damping in terms of domain-wall motion is investigated in the flow and creep regimes.

  2. Phenomenology of chiral damping in noncentrosymmetric magnets

    KAUST Repository

    Akosa, Collins Ashu

    2016-06-21

    A phenomenology of magnetic chiral damping is proposed in the context of magnetic materials lacking inversion symmetry. We show that the magnetic damping tensor acquires a component linear in magnetization gradient in the form of Lifshitz invariants. We propose different microscopic mechanisms that can produce such a damping in ferromagnetic metals, among which local spin pumping in the presence of an anomalous Hall effect and an effective “s-d” Dzyaloshinskii-Moriya antisymmetric exchange. The implication of this chiral damping in terms of domain-wall motion is investigated in the flow and creep regimes.

  3. A Weakly Nonlinear Model for the Damping of Resonantly Forced Density Waves in Dense Planetary Rings

    Science.gov (United States)

    Lehmann, Marius; Schmidt, Jürgen; Salo, Heikki

    2016-10-01

    In this paper, we address the stability of resonantly forced density waves in dense planetary rings. Goldreich & Tremaine have already argued that density waves might be unstable, depending on the relationship between the ring’s viscosity and the surface mass density. In the recent paper Schmidt et al., we have pointed out that when—within a fluid description of the ring dynamics—the criterion for viscous overstability is satisfied, forced spiral density waves become unstable as well. In this case, linear theory fails to describe the damping, but nonlinearity of the underlying equations guarantees a finite amplitude and eventually a damping of the wave. We apply the multiple scale formalism to derive a weakly nonlinear damping relation from a hydrodynamical model. This relation describes the resonant excitation and nonlinear viscous damping of spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients. The model consistently predicts density waves to be (linearly) unstable in a ring region where the conditions for viscous overstability are met. Sufficiently far away from the Lindblad resonance, the surface mass density perturbation is predicted to saturate to a constant value due to nonlinear viscous damping. The wave’s damping lengths of the model depend on certain input parameters, such as the distance to the threshold for viscous overstability in parameter space and the ground state surface mass density.

  4. The influence of the current intensity on the damping characteristics for a magneto-rheological damper of passenger car

    Science.gov (United States)

    Dobre, A.; Andreescu, C. N.; Stan, C.

    2016-08-01

    Due to their simplicity and controllability, adaptive dampers became very popular in automotive engineering industry, especially in the passenger cars industry, in spite of technological obstacles inherent and the high cost of the magnetic fluid. “MagneRide” is the first technology which uses smart fluids in the shock absorbers of the vehicles adaptive suspensions. Since the discovery of the magneto-rheological effect there is a consistent progress regarding the control algorithms and hardware part itself. These magneto-rheological devices have a major potential which can be explored in various fields of applications. At present many companies make researches for the improvement of the response time and for obtaining a better response at low frequency and amplitude of the body car oscillations. The main objective of this paper is to determine the damping characteristic of a magnetorheological shock absorber of a passenger car. The authors aim to observe how to modify the damping characteristic by changing the intensity of the electric current. The experimental researches have being carried out on a complex and modern test bench especially built for testing shock absorbers, in order to compare the damping characteristic of the classical damper with the magneto-rheological damper.

  5. Pipe damping

    International Nuclear Information System (INIS)

    Ware, A.G.; Arendts, J.G.

    1984-01-01

    A program has been developed to assess the available piping damping data, to generate additional data and conduct seperate effects tests, and to establish a plan for reporting and storing future test results into a data bank. This effort is providing some of the basis for developing higher allowable damping values for piping seismic analyses, which will potentially permit removal of a considerable number of piping supports, particularly snubbers. This in turn will lead to more flexible piping systems which will be less susceptible to thermal cracking, will be easier to maintain and inspect, as well as less costly

  6. Damped least square based genetic algorithm with Gaussian distribution of damping factor for singularity-robust inverse kinematics

    International Nuclear Information System (INIS)

    Phuoc, Le Minh; Lee, Suk Han; Kim, Hun Mo; Martinet, Philippe

    2008-01-01

    Robot inverse kinematics based on Jacobian inversion encounters critical issues of kinematic singularities. In this paper, several techniques based on damped least squares are proposed to lead robot pass through kinematic singularities without excessive joint velocities. Unlike other work in which the same damping factor is used for all singular vectors, this paper proposes a different damping coefficient for each singular vector based on corresponding singular value of the Jacobian. Moreover, a continuous distribution of damping factor following Gaussian function guarantees the continuous in joint velocities. A genetic algorithm is utilized to search for the best maximum damping factor and singular region, which used to require ad hoc searching in other works. As a result, end effector tracking error, which is inherited from damped least squares by introducing damping factors, is minimized. The effectiveness of our approach is compared with other methods in both non-redundant robot and redundant robot

  7. Damped least square based genetic algorithm with Gaussian distribution of damping factor for singularity-robust inverse kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Phuoc, Le Minh; Lee, Suk Han; Kim, Hun Mo [Sungkyunkwan University, Suwon (Korea, Republic of); Martinet, Philippe [Blaise Pascal University, Clermont-Ferrand Cedex (France)

    2008-07-15

    Robot inverse kinematics based on Jacobian inversion encounters critical issues of kinematic singularities. In this paper, several techniques based on damped least squares are proposed to lead robot pass through kinematic singularities without excessive joint velocities. Unlike other work in which the same damping factor is used for all singular vectors, this paper proposes a different damping coefficient for each singular vector based on corresponding singular value of the Jacobian. Moreover, a continuous distribution of damping factor following Gaussian function guarantees the continuous in joint velocities. A genetic algorithm is utilized to search for the best maximum damping factor and singular region, which used to require ad hoc searching in other works. As a result, end effector tracking error, which is inherited from damped least squares by introducing damping factors, is minimized. The effectiveness of our approach is compared with other methods in both non-redundant robot and redundant robot

  8. An Empirical Method for Particle Damping Design

    Directory of Open Access Journals (Sweden)

    Zhi Wei Xu

    2004-01-01

    Full Text Available Particle damping is an effective vibration suppression method. The purpose of this paper is to develop an empirical method for particle damping design based on extensive experiments on three structural objects – steel beam, bond arm and bond head stand. The relationships among several key parameters of structure/particles are obtained. Then the procedures with the use of particle damping are proposed to provide guidelines for practical applications. It is believed that the results presented in this paper would be helpful to effectively implement the particle damping for various structural systems for the purpose of vibration suppression.

  9. Experimental observation of fluid echoes in a non-neutral plasma

    International Nuclear Information System (INIS)

    Yu, Jonathan H.; Driscoll, C. Fred

    2002-01-01

    Experimental observation of a nonlinear fluid echo is presented which demonstrates the reversible nature of spatial Landau damping, and that non-neutral plasmas behave as nearly ideal 2D fluids. These experiments are performed on UCSD's CamV Penning-Malmberg trap with magnetized electron plasmas. An initial m i =2 diocotron wave is excited, and the received wall signal damps away in about 5 wave periods. The density perturbation filaments are observed to wrap up as the wave is spatially Landau damped. An m t =4 'tickler' wave is then excited, and this wave also Landau damps. The echo consists of a spontaneous appearance of a third m e =2 wave after the responses to the first two waves have inviscidly damped away. The appearance time of the echo agrees with theory, and data suggests the echo is destroyed at least partly due to saturation

  10. Effect of domain variations on damping capacity of Fe-16Cr-2.5Mo alloy solution annealed at 1373 K and 1473 K

    International Nuclear Information System (INIS)

    Xu Yonggang; Ning Li; Wen Yuhua

    2011-01-01

    The damping capacity of Fe-16Cr-2.5Mo alloy heat-treated at different temperatures was investigated. A water-based magnetic fluid was used to analyze domain morphologies. The experimental results show that there is a maximum value of damping capacity when the solution annealing temperature of the material is 1373 K. When the annealing temperature is higher, the damping capacity of the alloy drops quickly. The change in damping capacity with the solution annealing temperature is believed to be due to different domain morphologies. The domains are larger and the domain-wall area is smaller in the alloy annealed at a higher temperature. The wedge-shaped domains acted as obstacles for pinning the domain-wall movement, even though movement of the 90 o domains is easy. As a result, the damping capacity of the alloys drops when the annealing temperature is very high. - Research Highlights: →The change in damping capacity with solution annealing temperature is believed to be due to different domain morphologies. →The domains are larger and the domain-wall area is smaller in the alloy annealed at a higher temperature. →The wedge-shaped domains acted as obstacles for pinning the domain-wall movement, even though movement of the 90 o domains is easy.

  11. Modeling and control of magnetorheological fluid dampers using neural networks

    Science.gov (United States)

    Wang, D. H.; Liao, W. H.

    2005-02-01

    Due to the inherent nonlinear nature of magnetorheological (MR) fluid dampers, one of the challenging aspects for utilizing these devices to achieve high system performance is the development of accurate models and control algorithms that can take advantage of their unique characteristics. In this paper, the direct identification and inverse dynamic modeling for MR fluid dampers using feedforward and recurrent neural networks are studied. The trained direct identification neural network model can be used to predict the damping force of the MR fluid damper on line, on the basis of the dynamic responses across the MR fluid damper and the command voltage, and the inverse dynamic neural network model can be used to generate the command voltage according to the desired damping force through supervised learning. The architectures and the learning methods of the dynamic neural network models and inverse neural network models for MR fluid dampers are presented, and some simulation results are discussed. Finally, the trained neural network models are applied to predict and control the damping force of the MR fluid damper. Moreover, validation methods for the neural network models developed are proposed and used to evaluate their performance. Validation results with different data sets indicate that the proposed direct identification dynamic model using the recurrent neural network can be used to predict the damping force accurately and the inverse identification dynamic model using the recurrent neural network can act as a damper controller to generate the command voltage when the MR fluid damper is used in a semi-active mode.

  12. Quadratic Damping

    Science.gov (United States)

    Fay, Temple H.

    2012-01-01

    Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…

  13. Process Damping and Cutting Tool Geometry in Machining

    Science.gov (United States)

    Taylor, C. M.; Sims, N. D.; Turner, S.

    2011-12-01

    Regenerative vibration, or chatter, limits the performance of machining processes. Consequences of chatter include tool wear and poor machined surface finish. Process damping by tool-workpiece contact can reduce chatter effects and improve productivity. Process damping occurs when the flank (also known as the relief face) of the cutting tool makes contact with waves on the workpiece surface, created by chatter motion. Tool edge features can act to increase the damping effect. This paper examines how a tool's edge condition combines with the relief angle to affect process damping. An analytical model of cutting with chatter leads to a two-section curve describing how process damped vibration amplitude changes with surface speed for radiussed tools. The tool edge dominates the process damping effect at the lowest surface speeds, with the flank dominating at higher speeds. A similar curve is then proposed regarding tools with worn edges. Experimental data supports the notion of the two-section curve. A rule of thumb is proposed which could be useful to machine operators, regarding tool wear and process damping. The question is addressed, should a tool of a given geometry, used for a given application, be considered as sharp, radiussed or worn regarding process damping.

  14. Process Damping and Cutting Tool Geometry in Machining

    International Nuclear Information System (INIS)

    Taylor, C M; Sims, N D; Turner, S

    2011-01-01

    Regenerative vibration, or chatter, limits the performance of machining processes. Consequences of chatter include tool wear and poor machined surface finish. Process damping by tool-workpiece contact can reduce chatter effects and improve productivity. Process damping occurs when the flank (also known as the relief face) of the cutting tool makes contact with waves on the workpiece surface, created by chatter motion. Tool edge features can act to increase the damping effect. This paper examines how a tool's edge condition combines with the relief angle to affect process damping. An analytical model of cutting with chatter leads to a two-section curve describing how process damped vibration amplitude changes with surface speed for radiussed tools. The tool edge dominates the process damping effect at the lowest surface speeds, with the flank dominating at higher speeds. A similar curve is then proposed regarding tools with worn edges. Experimental data supports the notion of the two-section curve. A rule of thumb is proposed which could be useful to machine operators, regarding tool wear and process damping. The question is addressed, should a tool of a given geometry, used for a given application, be considered as sharp, radiussed or worn regarding process damping.

  15. Revisiting the Landau fluid closure.

    Science.gov (United States)

    Hunana, P.; Zank, G. P.; Webb, G. M.; Adhikari, L.

    2017-12-01

    Advanced fluid models that are much closer to the full kinetic description than the usual magnetohydrodynamic description are a very useful tool for studying astrophysical plasmas and for interpreting solar wind observational data. The development of advanced fluid models that contain certain kinetic effects is complicated and has attracted much attention over the past years. Here we focus on fluid models that incorporate the simplest possible forms of Landau damping, derived from linear kinetic theory expanded about a leading-order (gyrotropic) bi-Maxwellian distribution function f_0, under the approximation that the perturbed distribution function f_1 is gyrotropic as well. Specifically, we focus on various Pade approximants to the usual plasma response function (and to the plasma dispersion function) and examine possibilities that lead to a closure of the linear kinetic hierarchy of fluid moments. We present re-examination of the simplest Landau fluid closures.

  16. Unsteady flow damping force prediction of MR dampers subjected to sinusoidal loading

    Science.gov (United States)

    Yu, M.; Wang, S. Q.; Fu, J.; Peng, Y. X.

    2013-02-01

    So far quasi-steady models are usually used to design magnetorheological (MR) dampers, but these models are not sufficient to describe the MR damper behavior under unsteady dynamic loading, for fluid inertia is neglected in quasi-steady models, which will bring more error between computer simulation and experimental results. Under unsteady flow model, the fluid inertia terms will bring error calculated upto 10%, so it is necessary to be considered in the governing equation. In this paper, force-stroke behavior of MR damper with flow mode due to sinusoidal loading excitation is mainly investigated, to simplify the analysis, the one-dimensional axisymmetric annular duct geometry of MR dampers is approximated as a rectangular duct. The rectangular duct can be divided into 3 regions for the velocity profile of the incompressible MR fluid flow, in each region, a partial differential equation is composed of by Navier-Stokes equations, boundary conditions and initial conditions to determine the velocity solution. In addition, in this work, not only Bingham plastic model but the Herschel—Bulkley model is adopted to analyze the MR damper performance. The damping force resulting from the pressure drop of unsteady MR dampers can be obtained and used to design or size MR dampers. Compared with the quasi-steady flow damping force, the damping force of unsteady MR dampers is more close to practice, particularly for the high-speed unsteady movement of MR dampers.

  17. Unsteady flow damping force prediction of MR dampers subjected to sinusoidal loading

    International Nuclear Information System (INIS)

    Yu, M; Fu, J; Wang, S Q; Peng, Y X

    2013-01-01

    So far quasi-steady models are usually used to design magnetorheological (MR) dampers, but these models are not sufficient to describe the MR damper behavior under unsteady dynamic loading, for fluid inertia is neglected in quasi-steady models, which will bring more error between computer simulation and experimental results. Under unsteady flow model, the fluid inertia terms will bring error calculated upto 10%, so it is necessary to be considered in the governing equation. In this paper, force-stroke behavior of MR damper with flow mode due to sinusoidal loading excitation is mainly investigated, to simplify the analysis, the one-dimensional axisymmetric annular duct geometry of MR dampers is approximated as a rectangular duct. The rectangular duct can be divided into 3 regions for the velocity profile of the incompressible MR fluid flow, in each region, a partial differential equation is composed of by Navier-Stokes equations, boundary conditions and initial conditions to determine the velocity solution. In addition, in this work, not only Bingham plastic model but the Herschel—Bulkley model is adopted to analyze the MR damper performance. The damping force resulting from the pressure drop of unsteady MR dampers can be obtained and used to design or size MR dampers. Compared with the quasi-steady flow damping force, the damping force of unsteady MR dampers is more close to practice, particularly for the high-speed unsteady movement of MR dampers.

  18. Effects of high-frequency damping on iterative convergence of implicit viscous solver

    Science.gov (United States)

    Nishikawa, Hiroaki; Nakashima, Yoshitaka; Watanabe, Norihiko

    2017-11-01

    This paper discusses effects of high-frequency damping on iterative convergence of an implicit defect-correction solver for viscous problems. The study targets a finite-volume discretization with a one parameter family of damped viscous schemes. The parameter α controls high-frequency damping: zero damping with α = 0, and larger damping for larger α (> 0). Convergence rates are predicted for a model diffusion equation by a Fourier analysis over a practical range of α. It is shown that the convergence rate attains its minimum at α = 1 on regular quadrilateral grids, and deteriorates for larger values of α. A similar behavior is observed for regular triangular grids. In both quadrilateral and triangular grids, the solver is predicted to diverge for α smaller than approximately 0.5. Numerical results are shown for the diffusion equation and the Navier-Stokes equations on regular and irregular grids. The study suggests that α = 1 and 4/3 are suitable values for robust and efficient computations, and α = 4 / 3 is recommended for the diffusion equation, which achieves higher-order accuracy on regular quadrilateral grids. Finally, a Jacobian-Free Newton-Krylov solver with the implicit solver (a low-order Jacobian approximately inverted by a multi-color Gauss-Seidel relaxation scheme) used as a variable preconditioner is recommended for practical computations, which provides robust and efficient convergence for a wide range of α.

  19. Optimizing parameter of particle damping based on Leidenfrost effect of particle flows

    Science.gov (United States)

    Lei, Xiaofei; Wu, Chengjun; Chen, Peng

    2018-05-01

    Particle damping (PD) has strongly nonlinearity. With sufficiently vigorous vibration conditions, it always plays excellent damping performance and the particles which are filled into cavity are on Leidenfrost state considered in particle flow theory. For investigating the interesting phenomenon, the damping effect of PD on this state is discussed by the developed numerical model which is established based on principle of gas and solid. Furtherly, the numerical model is reformed and applied to study the relationship of Leidenfrost velocity with characteristic parameters of PD such as particle density, diameter, mass packing ratio and diameter-length ratio. The results indicate that particle density and mass packing ratio can drastically improve the damping performance as opposed as particle diameter and diameter-length ratio, mass packing ratio and diameter-length ratio can low the excited intensity for Leidenfrost state. For discussing the application of the phenomenon in engineering, bound optimization by quadratic approximation (BOBYQA) method is employed to optimize mass packing ratio of PD for minimize maximum amplitude (MMA) and minimize total vibration level (MTVL). It is noted that the particle damping can drastically reduce the vibrating amplitude for MMA as Leidenfrost velocity equal to the vibrating velocity relative to maximum vibration amplitude. For MTVL, larger mass packing ratio is best option because particles at relatively wide frequency range is adjacent to Leidenfrost state.

  20. Damping in aerospace composite materials

    Science.gov (United States)

    Agneni, A.; Balis Crema, L.; Castellani, A.

    Experimental results are presented on specimens of carbon and Kevlar fibers in epoxy resin, materials used in many aerospace structures (control surfaces and wings in aircraft, large antennas in spacecraft, etc.). Some experimental methods of estimating damping ratios are first reviewed, either in the time domain or in the frequency domain. Some damping factor estimates from experimental tests are then shown; in order to evaluate the effects of the aerospace environment, damping factors have been obtained in a typical range of temperature, namely between +120 C and -120 C, and in the pressure range from room pressure to 10 exp -6 torr. Finally, a theoretical approach for predicting the bounds of the damping coefficients is shown, and prediction data are compared with experimental results.

  1. Damping and fluidelastic instability in two-phase cross-flow heat exchanger tube arrays

    Science.gov (United States)

    Moran, Joaquin E.

    flux, and its dependency is a function of void fraction. A dimensional analysis was carried out to investigate the relationship between damping and two-phase flow related parameters. As a result, the inclusion of surface tension in the form of the Capillary number appears to be useful when combined with the two-phase component of the damping ratio (interfacial damping). A strong dependence of damping on flow regime was observed when plotting the interfacial damping versus the void fraction, introducing an improvement over the previous result obtained by normalizing the two-phase damping, which does not exhibit this behaviour. The interfacial velocity model was selected to represent the fluidelastic data in two-phase experiments, due to the inclusion of the tube array geometry and density ratio effects, which does not exist for the pitch velocity approach. An essential component in reliably establishing the velocity threshold for fluidelastic instability, is a measure of the energy dissipation available in the system to balance the energy input from the flow. The present analysis argues that the damping in-flow is not an appropriate measure and demonstrates that the use of quiescent fluid damping provides a better measure of the energy dissipation, which produces a much more logical trend in the stability behaviour. This value of damping, combined with the RAD density and the interfacial velocity, collapses the available data well and provides the expected trend of two-phase flow stability data over the void fraction range from liquid to gas flows. The resulting stability maps represent a significant improvement over existing maps for predicting fluidelastic instability of tube bundles in two-phase flows. This result also tends to confirm the hypothesis that the basic mechanism of fluidelastic instability is the same for single and two-phase flows.

  2. Modeling meniscus rise in capillary tubes using fluid in rigid-body motion approach

    Science.gov (United States)

    Hamdan, Mohammad O.; Abu-Nabah, Bassam A.

    2018-04-01

    In this study, a new term representing net flux rate of linear momentum is introduced to Lucas-Washburn equation. Following a fluid in rigid-body motion in modeling the meniscus rise in vertical capillary tubes transforms the nonlinear Lucas-Washburn equation to a linear mass-spring-damper system. The linear nature of mass-spring-damper system with constant coefficients offers a nondimensional analytical solution where meniscus dynamics are dictated by two parameters, namely the system damping ratio and its natural frequency. This connects the numerous fluid-surface interaction physical and geometrical properties to rather two nondimensional parameters, which capture the underlying physics of meniscus dynamics in three distinct cases, namely overdamped, critically damped, and underdamped systems. Based on experimental data available in the literature and the understanding meniscus dynamics, the proposed model brings a new approach of understanding the system initial conditions. Accordingly, a closed form relation is produced for the imbibition velocity, which equals half of the Bosanquet velocity divided by the damping ratio. The proposed general analytical model is ideal for overdamped and critically damped systems. While for underdamped systems, the solution shows fair agreement with experimental measurements once the effective viscosity is determined. Moreover, the presented model shows meniscus oscillations around equilibrium height occur if the damping ratio is less than one.

  3. Evaluation of TLCD Damping Factor from FRF Measurement Due to Variation of the Fluid Viscosity

    OpenAIRE

    Son, Lovely

    2016-01-01

    Tuned Liquid Column Damper (TLCD) has become an alternative solution for reducing low frequency vibration response of machines and structures. This is not surprisingly that the damper has simply structure and low maintenance cost. The main disadvantage of using TLCD is the complexity in controlling TLCD damping factor experimentally. Theoretically, damping factor can be controlled by adjusting the orifice dimension. However, this method is time consuming and not appropriate conducted in the r...

  4. Fast damping in mismatched high intensity beam transportation

    Directory of Open Access Journals (Sweden)

    V. Variale

    2001-08-01

    Full Text Available A very fast damping of beam envelope oscillation amplitudes was recently observed in simulations of high intensity beam transport, through periodic FODO cells, in mismatched conditions [V. Variale, Nuovo Cimento Soc. Ital. Fis. 112A, 1571–1582 (1999 and T. Clauser et al., in Proceedings of the Particle Accelerator Conference, New York, 1999 (IEEE, Piscataway, NJ, 1999, p. 1779]. A Landau damping mechanism was proposed at the origin of observed effect. In this paper, to further investigate the source of this fast damping, extensive simulations have been carried out. The results presented here support the interpretation of the mechanism at the origin of the fast damping as a Landau damping effect.

  5. Contribution of the active control to the measurement of fluid-elastic coupling strengths; Apport du controle actif pour la mesure des forces de couplage fluide-elastique

    Energy Technology Data Exchange (ETDEWEB)

    Legendre, S

    1999-06-30

    A precise dimensioning of the tubes inside a steam generator requires a better knowledge of the fluid-elastic coupling phenomena. The direct method for the determination of fluid-elastic coupling coefficients allows to explore only a reduced range of flow velocities and is unsuitable for the low velocities and for velocities close to the critical instability velocity. The active damping control method has been validated both with air and water and offers the possibility to extend the range of flow velocities using an artificial supply of damping: 50% of increase in single-phase flow conditions with measurements performed beyond the critical instability velocity, a doubling of the explored range of velocities in two-phase flow conditions. For a 25% two-phase flow, a stabilization of the damping of the coupled fluid-structure system is observed beyond the critical instability velocity. Finally, the calculation of fluid-elastic dimensionless coefficients has permitted to show the influence of the reduced velocity on the fluid-elastic coupling in two-phase flow conditions. (J.S.)

  6. Magnetic damping phenomena in ferromagnetic thin-films and multilayers

    Science.gov (United States)

    Azzawi, S.; Hindmarch, A. T.; Atkinson, D.

    2017-11-01

    Damped ferromagnetic precession is an important mechanism underpinning the magnetisation processes in ferromagnetic materials. In thin-film ferromagnets and ferromagnetic/non-magnetic multilayers, the role of precession and damping can be critical for spintronic device functionality and as a consequence there has been significant research activity. This paper presents a review of damping in ferromagnetic thin-films and multilayers and collates the results of many experimental studies to present a coherent synthesis of the field. The terms that are used to define damping are discussed with the aim of providing consistent definitions for damping phenomena. A description of the theoretical basis of damping is presented from early developments to the latest discussions of damping in ferromagnetic thin-films and multilayers. An overview of the time and frequency domain methods used to study precessional magnetisation behaviour and damping in thin-films and multilayers is also presented. Finally, a review of the experimental observations of magnetic damping in ferromagnetic thin-films and multilayers is presented with the most recent explanations. This brings together the results from many studies and includes the effects of ferromagnetic film thickness, the effects of composition on damping in thin-film ferromagnetic alloys, the influence of non-magnetic dopants in ferromagnetic films and the effects of combining thin-film ferromagnets with various non-magnetic layers in multilayered configurations.

  7. Decoherence and Landau-Damping

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K.Y.; /Fermilab

    2005-12-01

    The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.

  8. Damping values for nuclear power plant piping during seismic events and fluid-induced transients

    International Nuclear Information System (INIS)

    Ware, A.G.

    1986-01-01

    For several years the Idaho National Engineering Laboratory (INEL) has been assisting the United States Nuclear Regulatory Commission (USNRC) in efforts to establish best-estimate damping values for use in the dynamic analysis of nuclear power plant piping systems. Data from a number of piping vibration tests conducted at facilities worldwide (including the INEL) have been collected, evaluated, reported, and placed in a nuclear piping data bank at the INEL. These data are being used to justify changes in allowable damping values for use in nuclear piping design, thus making piping systems safer, less costly, and easier to inspect and maintain

  9. Dynamic characteristics of a novel damped outrigger system

    Science.gov (United States)

    Tan, Ping; Fang, Chuangjie; Zhou, Fulin

    2014-06-01

    This paper presents exact analytical solutions for a novel damped outrigger system, in which viscous dampers are vertically installed between perimeter columns and the core of a high-rise building. An improved analytical model is developed by modeling the effect of the damped outrigger as a general rotational spring acting on a Bernoulli-Euler beam. The equivalent rotational spring stiffness incorporating the combined effects of dampers and axial stiffness of perimeter columns is derived. The dynamic stiffness method (DSM) is applied to formulate the governing equation of the damped outrigger system. The accuracy and efficiency are verified in comparison with those obtained from compatibility equations and boundary equations. Parametric analysis of three non-dimensional factors is conducted to evaluate the influences of various factors, such as the stiffness ratio of the core to the beam, position of the damped outrigger, and the installed damping coefficient. Results show that the modal damping ratio is significantly influenced by the stiffness ratio of the core to the column, and is more sensitive to damping than the position of the damped outrigger. The proposed analytical model in combination with DSM can be extended to the study of structures with more outriggers.

  10. Effect of oscillation mode on the free-molecule squeeze-film air damping

    KAUST Repository

    Gang Hong,

    2010-01-01

    A 3D Monte Carlo (MC) simulation approach is developed and employed to study the effect of the oscillation mode on the squeeze-film air damping in the free-molecule regime. By tracking individual gas molecule\\'s motion and its interaction with the resonator, the MC approach is by far the most accurate modeling approach for the modeling of squeeze-film damping in the free-molecule regime. The accuracy of this approach is demonstrated on several cases in which either analytical solutions or experimental measurements are available. It has been found that unlike the case when resonators oscillate in an unbounded domain, squeeze film damping is very sensitive to the mode shape, which implies that some of the existing modeling approaches based on rigid-resonator assumption may not be accurate when applied to model resonators oscillating at their deformed shape. ©2010 IEEE.

  11. Gamma irradiation induced effects of butyl rubber based damping material

    Science.gov (United States)

    Chen, Hong-Bing; Wang, Pu-Cheng; Liu, Bo; Zhang, Feng-Shun; Ao, Yin-Yong

    2018-04-01

    The effects of gamma irradiation on the butyl rubber based damping material (BRP) at various doses in nitrogen were investigated in this study. The results show that irradiation leads to radiolysis of BRP, with extractives increasing from 14.9 ± 0.8% of control to 37.2 ± 1.2% of sample irradiated at 350 kGy, while the swelling ratio increasing from 294 ± 3% to 766 ± 4%. The further investigation of the extractives with FTIR shows that the newly generated extractives are organic compounds containing C-H and C˭C bonds, with molecular weight ranging from 26,500 to 46,300. SEM characterization shows smoother surface with holes disappearing with increasing absorbed doses, consistent with "softer" material because of radiolysis. Dynamic mechanical study of BRP show that tan δ first slightly then obviously increases with increasing absorbed dose, while storage modulus slightly decreases. The tensile testing shows that the tensile strength decreases while the elongation at break increases with increasing dose. The positron annihilation lifetime spectroscopy show no obvious relations between free volume parameters and the damping properties, indicating the complicated influencing factors of damping properties.

  12. Study for ILC Damping Ring at KEKB

    Energy Technology Data Exchange (ETDEWEB)

    Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; /KEK, Tsukuba; Pivi, M.; /SLAC

    2011-11-04

    ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

  13. Overview on methods for formulating explicit damping matrices for non-classically damped structures

    International Nuclear Information System (INIS)

    Xu, J.

    1998-04-01

    In computing the dynamic response of a connected system with multiple components having dissimilar damping characteristics, which is often referred to as nonclassically damped system such as nuclear power plant piping systems supported by stiff structures, one needs to define the system-level damping based upon the damping information of components. This is frequently done in practice using approximate methods expressed as composite modal damping with weighting functions. However, when the difference in damping among components is substantial, the composite modal damping may become inappropriate in the characterization of the damping behavior of such systems. In recent years, several new methods have emerged with the expectation that they could produce more exact system-level damping for a group of nonclassically damped structures which are comprised of components that possess classical modal damping. In this paper, an overview is presented to examine these methods in the light of their theoretical basis, the technical merits, and practical applications. To this end, a synthesis method is described, which was shown to reduce to the other methods in the literature

  14. Damping in building structures during earthquakes: test data and modeling

    International Nuclear Information System (INIS)

    Coats, D.W. Jr.

    1982-01-01

    A review and evaluation of the state-of-the-art of damping in building structures during earthquakes is presented. The primary emphasis is in the following areas: 1) the evaluation of commonly used mathematical techniques for incorporating damping effects in both simple and complex systems; 2) a compilation and interpretation of damping test data; and 3) an evaluation of structure testing methods, building instrumentation practices, and an investigation of rigid-body rotation effects on damping values from test data. A literature review provided the basis for evaluating mathematical techiques used to incorporate earthquake induced damping effects in simple and complex systems. A discussion on the effectiveness of damping, as a function of excitation type, is also included. Test data, from a wide range of sources, has been compiled and interpreted for buidings, nuclear power plant structures, piping, equipment, and isolated structural elements. Test methods used to determine damping and frequency parameters are discussed. In particular, the advantages and disadvantages associated with the normal mode and transfer function approaches are evaluated. Additionally, the effect of rigid-body rotations on damping values deduced from strong-motion building response records is investigated. A discussion of identification techniques typically used to determine building parameters (frequency and damping) from strong motion records is included. Finally, an analytical demonstration problem is presented to quantify the potential error in predicting fixed-base structural frequency and damping values from strong motion records, when rigid-body rotations are not properly accounted for

  15. Binary non-additive hard sphere mixtures: fluid demixing, asymptotic decay of correlations and free fluid interfaces

    International Nuclear Information System (INIS)

    Hopkins, Paul; Schmidt, Matthias

    2010-01-01

    Using a fundamental measure density functional theory we investigate both bulk and inhomogeneous systems of the binary non-additive hard sphere model. For sufficiently large (positive) non-additivity the mixture phase separates into two fluid phases with different compositions. We calculate bulk fluid-fluid coexistence curves for a range of size ratios and non-additivity parameters and find that they compare well to simulation results from the literature. Using the Ornstein-Zernike equation, we investigate the asymptotic, r→∞, decay of the partial pair correlation functions, g ij (r). At low densities a structural crossover occurs in the asymptotic decay between two different damped oscillatory modes with different wavelengths corresponding to the two intra-species hard-core diameters. On approaching the fluid-fluid critical point there is a Fisher-Widom crossover from exponentially damped oscillatory to monotonic asymptotic decay. Using the density functional we calculate the density profiles for the planar free fluid-fluid interface between coexisting fluid phases. We show that the type of asymptotic decay of g ij (r) not only determines the asymptotic decay of the interface profiles, but is also relevant for intermediate and even short-ranged behaviour. We also determine the surface tension of the free fluid interface, finding that it increases with non-additivity, and that on approaching the critical point mean-field scaling holds.

  16. Effect of moisture absorption on damping and dynamic stiffness of carbon fiber/epoxy composites

    Energy Technology Data Exchange (ETDEWEB)

    Zai, Behzad Ahmed; Park, M. K.; Mehboob, Hassan; Ali, Rashid [Myongji University, Yongin (Korea, Republic of); Choi, H. S. [Korean Air Daejeon (Korea, Republic of)

    2009-11-15

    In this paper, the damping and dynamic stiffness of UHN125C carbon fiber/epoxy composite beam was experimentally measured. The effect of fiber orientation angle and stacking sequences on damping, resonance frequency, and dynamic stiffness was discussed with a focus on the effect of moisture absorption. Dried specimens were immersed in distilled water for a certain period to absorb water for 8, 16, and 24 d, respectively, and the moisture content absorbed in the specimen was measured. Furthermore, using the impact hammer technique, the measurements of dynamic responses were conducted on a cantilever beam specimen with one end clamped by bolts and metal plates. The damping properties in terms of loss factor were approximated by half-power bandwidth technique. The dynamic stiffness was evaluated using resonance frequency as a function of moisture content. The damping increased with the increase of moisture content: however, the dynamic stiffness reduced with the reduction of resonance frequency. The results of the dynamic stiffness were aided by measuring the dynamic strain using DBU-120A strain-indicating software. The increment in the dynamic strain strengthened the results obtained for dynamic stiffness

  17. Temporal Damping Effect of the Yucca Mountain Fractured Saturated Rock on Transient Infiltration Pulses

    International Nuclear Information System (INIS)

    K. Zhang; Y.S. Wu; L. Pan

    2006-01-01

    Performance assessment of the Yucca Mountain unsaturated zone (UZ) as the site for an underground repository of high-level radioactive waste relies on the crucial assumption that water percolation processes in the unsaturated zone can be approximated as a steady-state condition. Justification of such an assumption is based on temporal damping effects of several geological units within the unsaturated tuff formation. In particular, the nonwelded tuff of the Paintbrush Group (PTn unit) at Yucca Mountain, because of its highly porous nature, has been conceptualized to have a significant capacity for temporally damping transient percolation fluxes. The objective of this study is to investigate these damping effects, using a three-dimensional (3-D) mountain-scale model as well as several one-dimensional (1-D) models. The 3-D model incorporates a wide variety of the updated field data for the highly heterogeneous unsaturated formation at Yucca Mountain. The model is first run to steady state and calibrated using field-measured data and then transient pulse infiltrations are applied to the model top boundary. Subsequent changes in percolation fluxes at the bottom of and within the PTn unit are examined under episodic infiltration boundary conditions. The 1-D model is used to examine the long-term response of the flow system to higher infiltration pulses, while the damping effect is also investigated through modeling tracer transport in the UZ under episodic infiltration condition. Simulation results show the existence of damping effects within the PTn unit and also indicate that the assumption of steady-state flow conditions below the PTn unit is reasonable. However, the study also finds that some fast flow paths along faults exist, causing vertical-flux quick responses at the PTn bottom to the episodic infiltration at the top boundary

  18. Analysis of Skylab IV fluid mechanic science demonstration

    Science.gov (United States)

    Klett, M. G.; Bourgeois, S. V.

    1975-01-01

    Several science demonstrations performed on Skylab III and IV were concerned with the behavior of fluid drops free floating in microgravity. These demonstrations, with large liquid drops, included the oscillation, rotation, impact and coalescence, and air injection into the drops. Rayleigh's analysis of the oscillation of spherical drops of a liquid predicts accurately the effect of size and surface tension on the frequency of vibrated water globules in the Skylab demonstration. However, damping occurred much faster than predicted by Lamb's or Scriven's analyses of the damping time for spherical drops. The impact demonstrations indicated that a minimum velocity is necessary to overcome surface forces and effect a coalescence, but a precise criterion for the coalescence of liquids in low g could not be determined.

  19. Effect of PVRC damping with independent support motion response spectrum analysis of piping systems

    International Nuclear Information System (INIS)

    Wang, Y.K.; Bezler, P.; Shteyngart, S.

    1986-01-01

    The Technical Committee for Piping Systems of the Pressure Vessel Research Committee (PVRC) has recommended new damping values to be used in the seismic analyses of piping systems in nuclear power plants. To evaluate the effects of coupling these recommendations with the use of independent support motion analyses methods, two sets of seismic analyses have been carried out for several piping systems. One set based on the use of uniform damping as specified in Regulatory Guide 1.61, the other based on the PVRC recommendations. In each set the analyses were performed using independent support motion time history and response spectrum methods as well as the envelope spectrum method. In the independent response spectrum analyses, 14 response estimates were in fact obtained by considering different combination procedures between the support group contributions and all sequences of combinations between support groups, modes and directions. For each analysis set, the response spectrum results were compared with time history estimates of those results. Comparison tables were then prepared depicting the percentage by which the response spectrum estimates exceeded the time history estimates. By comparing the result tables between both analysis sets, the impact of PVRC damping can be observed. Preliminary results show that the degree of exceedance of the response spectrum estimates based on PVRC damping is less than that based on uniform damping for the same piping problem. Expressed differently the results obtained if ISM methods are coupled with PVRC damping are not as conservative as those obtained using uniform damping

  20. Damping Wiggler Study at KEK-ATF

    CERN Document Server

    Naito, Takashi; Honda, Yosuke; Korostelev, Maxim S; Kubo, Kiyoshi; Kuriki, Masao; Kuroda, Shigeru; Muto, Toshiya; Nakamura, Norio; Ross, Marc; Sakai, Hiroshi; Terunuma, Nobuhiro; Urakawa, Junji; Zimmermann, Frank

    2005-01-01

    The effects by damping wiggler magnets have been studied at KEK-ATF. The damping ring of the KEK-ATF is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. It is significant issue to realize fast damping in the damping ring. The tuning method with 4 sets of wiggler was investigated for the ultra-low emittance beam. The performance on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and dp/p), has been measured by the SR monitor, the laser wire, the streak camera and the energy spread monitor at the extraction line. We report on the operation condition and the measurement results.

  1. Fluid-structure coupling for an oscillating hydrofoil

    Science.gov (United States)

    Münch, C.; Ausoni, P.; Braun, O.; Farhat, M.; Avellan, F.

    2010-08-01

    Fluid-structure investigations in hydraulic machines using coupled simulations are particularly time-consuming. In this study, an alternative method is presented that linearizes the hydrodynamic load of a rigid, oscillating hydrofoil. The hydrofoil, which is surrounded by incompressible, turbulent flow, is modeled with forced and free pitching motions, where the mean incidence angle is 0° with a maximum angle amplitude of 2°. Unsteady simulations of the flow, performed with ANSYS CFX, are presented and validated with experiments which were carried out in the EPFL High-Speed Cavitation Tunnel. First, forced motion is investigated for reduced frequencies ranging from 0.02 to 100. The hydrodynamic load is modeled as a simple combination of inertia, damping and stiffness effects. As expected, the potential flow analysis showed the added moment of inertia is constant, while the fluid damping and the fluid stiffness coefficients depend on the reduced frequency of the oscillation motion. Behavioral patterns were observed and two cases were identified depending on if vortices did or did not develop in the hydrofoil wake. Using the coefficients identified in the forced motion case, the time history of the profile incidence is then predicted analytically for the free motion case and excellent agreement is found for the results from coupled fluid-structure simulations. The model is validated and may be extended to more complex cases, such as blade grids in hydraulic machinery.

  2. Effect of heat treatment on the microstructures and damping properties of biomedical Mg-Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Department of Dentistry, Chang Yin dental clinic, No.46-1, Yangming St., Banqiao City, Taipei County 220, Taiwan (China); Research Center for Biomedical Devices, Taipei Medical University, Taipei 110, Taiwan (China); Chen, May-Show [Research Center for Biomedical Devices, Taipei Medical University, Taipei 110, Taiwan (China); School of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Lin, Ling-Hung [Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Wu, Ching-Zong, E-mail: chinaowu@tmu.edu.tw [Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Ou, Keng-Liang, E-mail: klou@tmu.edu.tw [Research Center for Biomedical Devices, Taipei Medical University, Taipei 110, Taiwan (China); Graduated Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Yu, Chih-Hua [Research Center for Biomedical Devices, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China)

    2011-01-21

    Research highlights: > When the as-quenched Mg-1Zr alloy was aged at temperatures ranging from 200 deg. C to 500 deg. C, a microstructural transformation sequence was found to be {alpha}-Mg {yields} ({alpha}-Mg + twin{sub dense}) {yields} ({alpha}-Mg + twin{sub loose}) {yields} ({alpha}-Mg + {alpha}-Zr). > As the as-quenched Mg-1Zr alloy was subjected to aging treatment at 300 deg. C for 16 h, it exhibited the maximum damping properties. > The twin structure plays a crucial role in increasing the damping capacity of the Mg-1Zr alloy. - Abstract: In this study, we elucidated the effect of heat treatment on the microstructures and damping properties of the biomedical Mg-1 wt% Zr (K1) alloy by optical microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and experimental model analysis. The following microstructural transformation occurred when the as-quenched (AQ, i.e., solution heat treated and quenched) K1 alloy was subjected to aging treatment in the temperature range 200-500 deg. C: {alpha}-Mg {yields} ({alpha}-Mg + twin{sub dense}) {yields} ({alpha}-Mg + twin{sub loose}) {yields} ({alpha}-Mg + {alpha}-Zr). This microstructural transformation was accompanied by variations in the damping capacity. The damping properties of the AQ K1 alloy subjected to aging treatment at 300 deg. C for 16 h were the best among those of the alloys investigated in the present study. The presence of twin structures in the alloy matrix was thought to play a crucial role in increasing the damping capacity of the K1 alloy. Hence, we state that a combination of solution treatment and aging is an effective means of improving the damping capacity of biomedical K1 alloys.

  3. Effect of heat treatment on the microstructures and damping properties of biomedical Mg-Zr alloy

    International Nuclear Information System (INIS)

    Tsai, Ming-Hung; Chen, May-Show; Lin, Ling-Hung; Lin, Ming-Hong; Wu, Ching-Zong; Ou, Keng-Liang; Yu, Chih-Hua

    2011-01-01

    Research highlights: → When the as-quenched Mg-1Zr alloy was aged at temperatures ranging from 200 deg. C to 500 deg. C, a microstructural transformation sequence was found to be α-Mg → (α-Mg + twin dense ) → (α-Mg + twin loose ) → (α-Mg + α-Zr). → As the as-quenched Mg-1Zr alloy was subjected to aging treatment at 300 deg. C for 16 h, it exhibited the maximum damping properties. → The twin structure plays a crucial role in increasing the damping capacity of the Mg-1Zr alloy. - Abstract: In this study, we elucidated the effect of heat treatment on the microstructures and damping properties of the biomedical Mg-1 wt% Zr (K1) alloy by optical microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and experimental model analysis. The following microstructural transformation occurred when the as-quenched (AQ, i.e., solution heat treated and quenched) K1 alloy was subjected to aging treatment in the temperature range 200-500 deg. C: α-Mg → (α-Mg + twin dense ) → (α-Mg + twin loose ) → (α-Mg + α-Zr). This microstructural transformation was accompanied by variations in the damping capacity. The damping properties of the AQ K1 alloy subjected to aging treatment at 300 deg. C for 16 h were the best among those of the alloys investigated in the present study. The presence of twin structures in the alloy matrix was thought to play a crucial role in increasing the damping capacity of the K1 alloy. Hence, we state that a combination of solution treatment and aging is an effective means of improving the damping capacity of biomedical K1 alloys.

  4. Assessment of effect of SSSC stabilizer in different control channels on damping inter-area oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Shakarami, M.R., E-mail: shakarami@iust.ac.i [Centre of Excellence for Power System Automation and Operation, Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Kazemi, A. [Centre of Excellence for Power System Automation and Operation, Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of)

    2011-03-15

    A static synchronous series compensator (SSSC) is one of the series flexible ac transmission system (FACTS) devices that injects a balanced three-phase voltage in quadrature with the transmission line current. There are two channels for controlling of phase and magnitude of the voltage. When the SSSC is used for damping of inter-area oscillations, a SSSC-based stabilizer can be included in both channels. In this paper, the best location and suitable input control signal for SSSC in order to enhance the damping of inter-area oscillations are selected by residue analysis. A method by quadratic mathematic programming has been presented to the design of the stabilizer. By this method, the effect of the stabilizer in both control channels of the SSSC on damping of inter-area oscillations has been assessed. By considering the gain of stabilizer as a criterion, obtained results from studying on a small and a large multi-machine power system show that the stabilizer in the phase control channel is more effective for damping inter-are oscillations.

  5. Optimal design of high damping force engine mount featuring MR valve structure with both annular and radial flow paths

    International Nuclear Information System (INIS)

    Nguyen, Q H; Choi, S B; Lee, Y S; Han, M S

    2013-01-01

    This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption. (paper)

  6. Optimal design of high damping force engine mount featuring MR valve structure with both annular and radial flow paths

    Science.gov (United States)

    Nguyen, Q. H.; Choi, S. B.; Lee, Y. S.; Han, M. S.

    2013-11-01

    This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption.

  7. Damped nonlinear Schrodinger equation

    International Nuclear Information System (INIS)

    Nicholson, D.R.; Goldman, M.V.

    1976-01-01

    High frequency electrostatic plasma oscillations described by the nonlinear Schrodinger equation in the presence of damping, collisional or Landau, are considered. At early times, Landau damping of an initial soliton profile results in a broader, but smaller amplitude soliton, while collisional damping reduces the soliton size everywhere; soliton speeds at early times are unchanged by either kind of damping. For collisional damping, soliton speeds are unchanged for all time

  8. A review of experimental soil-structure interaction damping

    International Nuclear Information System (INIS)

    Tsai, N.C.

    1981-01-01

    In soil-structure interaction analysis, the foundation soil is usually represented by impedance springs and dampers. The impedance damping includes the effect of both the material damping and the radiation damping. Because the impedance theory normally assumes a rigid structural base and an elastic bond between the soil and structure, it is generally held that the radiation damping has been overestimated by the theory. There are some published information on the dynamic tests of footings and structures that allow direct or indirect assessments of the validity of the analytical radiation damping. An overview of such information is presented here. Based on these limited test data, it is concluded that for horizontal soil-structure interaction analysis the analytical radiation damping alone is sufficient to represent the combined material and radiation damping in the field. On the other hand, for vertical analysis it appears that the theory may have overestimated the radiation damping and certain reduction is recommended. (orig.)

  9. Test and evaluation about damping characteristics of hanger supports for nuclear power plant piping systems (Seismic Damping Ratio Evaluation Program)

    International Nuclear Information System (INIS)

    Shibata, H.; Ito, A.; Tanaka, K.; Niino, T.; Gotoh, N.

    1981-01-01

    Generally, damping phenomena of structures and equipments is caused by very complex energy dissipation. Especially, as piping systems are composed of many components, it is very difficult to evaluate damping characteristics of its system theoretically. On the other hand, the damping value for aseismic design of nuclear power plants is very important design factor to decide seismic response loads of structures, equipments and piping systems. The very extensive studies titled SDREP (Seismic Damping Ratio Evaluation Program) were performed to establish proper damping values for seismic design of piping as a joint work among a university, electric companies and plant makers. In SDREP, various systematic vibration tests were conducted to investigate factors which may contribute to damping characteristics of piping systems and to supplement the data of the pre-operating tests. This study is related to the component damping characteristics tests of that program. The object of this study is to clarify damping characteristics and mechanism of hanger supports used in piping systems, and to establish the evaluation technique of dispersing energy at hanger support points and its effect to the total damping ability of piping system. (orig./WL)

  10. Fluid-elastic force measurements acting on a tube bundle in two-phase cross flow

    International Nuclear Information System (INIS)

    Inada, Fumio; Kawamura, Koji; Yasuo, Akira

    1996-01-01

    Fluid-elastic force acting on a square tube bundle of P/D = 1.47 in air-water two-phase cross flow was measured to investigate the characteristics and to clarify whether the fluid elastic vibration characteristics could be expressed using two-phase mixture characteristics. Measured fluid elastic forces were separated into fluid-elastic force coefficients such as added mass, added stiffness, and added damping coefficient. The added damping coefficient was separated into a two-phase damping and a flow-dependent component as in previous research (Carlucci, 1981 and 1983; Pettigrew, 1994). These coefficients were nondimensionalized with two-phase mixture characteristics such as void fraction, mixture density and mixture velocity, which were obtained using the drift-flux model with consideration given to the model. The result was compared with the result obtained with the homogeneous model. It was found that fluid-elastic force coefficients could be expressed with two-phase flow mixture characteristics very well in the experimental result, and that better result can be derived using the slip model as compared to the homogeneous model. Added two-phase flow, which could be expressed as a function of void fraction, where two-phase damping was nondimensionalized with the relative velocity between the gas and liquid phases used as a reference velocity. Using these, the added stiffness coefficient and flow-dependent component of damping could be expressed very well as a function of nondimensional mixture velocity

  11. A new magnetorheological mount featured by changeable damping gaps using a moved-plate valve structure

    International Nuclear Information System (INIS)

    Phu, Do Xuan; Shah, Kruti; Choi, Seung-Bok

    2014-01-01

    In this work, a new type of a magnetorheological (MR) fluid mount is proposed and its performances are experimentally investigated. The design of this MR mount is based on two operating modes of MR fluid: flow mode and shear mode. These modes are applied to the mechanism design consisting of two components: a fixed plate for applying the flow mode, and a moved plate for applying the shear mode of MR fluid motion. These plates belong to the valve-type structure of MR mount. The primary objective using the moved plate is to overcome the block-up phenomenon which frequently occurs in the conventional-type MR mount, in which there is no flow of MR fluid through the damping gap. In this research, a laboratorial fluid (MRF140) is used in the design and optimization of MR mount. This fluid features plate-like particles unlike the sphere particles. The yield stress of the fluid is measured as a function of the magnetic field and the theoretical analysis for the mount design is undertaken using the properties of the MR fluid, followed by design optimization. The objective function is concentrated on maximal damping force of the MR mount subjected to parameter constraints. Based on the results of optimization, the proposed MR mount is manufactured and tested for the performance evaluation. Vibration control capability and block-up phenomenon are investigated and compared between the proposed and conventional MR mounts. (paper)

  12. Effect of eddy current damping on phononic band gaps generated by locally resonant periodic structures

    Science.gov (United States)

    Ozkaya, Efe; Yilmaz, Cetin

    2017-02-01

    The effect of eddy current damping on a novel locally resonant periodic structure is investigated. The frequency response characteristics are obtained by using a lumped parameter and a finite element model. In order to obtain wide band gaps at low frequencies, the periodic structure is optimized according to certain constraints, such as mass distribution in the unit cell, lower limit of the band gap, stiffness between the components in the unit cell, the size of magnets used for eddy current damping, and the number of unit cells in the periodic structure. Then, the locally resonant periodic structure with eddy current damping is manufactured and its experimental frequency response is obtained. The frequency response results obtained analytically, numerically and experimentally match quite well. The inclusion of eddy current damping to the periodic structure decreases amplitudes of resonance peaks without disturbing stop band width.

  13. Method and apparatus for simultaneous determination of fluid mass flow rate, mean velocity and density

    International Nuclear Information System (INIS)

    Hamel, W.R.

    1984-01-01

    This invention relates to a new method and new apparatus for determining fluid mass flow rate and density. In one aspect of the invention, the fluid is passed through a straight cantilevered tube in which transient oscillation has been induced, thus generating Coriolis damping forces on the tube. The decay rate and frequency of the resulting damped oscillation are measured, and the fluid mass flow rate and density are determined therefrom. In another aspect of the invention, the fluid is passed through the cantilevered tube while an electrically powered device imparts steady-state harmonic excitation to the tube. This generates Coriolis tube-damping forces which are dependent on the mass flow rate of the fluid. Means are provided to respond to incipient flow-induced changes in the amplitude of vibration by changing the power input to the excitation device as required to sustain the original amplitude of vibration. The fluid mass flow rate and density are determined from the required change in power input. The invention provides stable, rapid, and accurate measurements. It does not require bending of the fluid flow

  14. Lubrication pressure and fractional viscous damping effects on the spring-block model of earthquakes

    Science.gov (United States)

    Tanekou, G. B.; Fogang, C. F.; Kengne, R.; Pelap, F. B.

    2018-04-01

    We examine the dynamical behaviours of the "single mass-spring" model for earthquakes considering lubrication pressure effects on pre-existing faults and viscous fractional damping. The lubrication pressure supports a part of the load, thereby reducing the normal stress and the associated friction across the gap. During the co-seismic phase, all of the strain accumulated during the inter-seismic duration does not recover; a fraction of this strain remains as a result of viscous relaxation. Viscous damping friction makes it possible to study rocks at depth possessing visco-elastic behaviours. At increasing depths, rock deformation gradually transitions from brittle to ductile. The fractional derivative is based on the properties of rocks, including information about previous deformation events ( i.e., the so-called memory effect). Increasing the fractional derivative can extend or delay the transition from stick-slip oscillation to a stable equilibrium state and even suppress it. For the single block model, the interactions of the introduced lubrication pressure and viscous damping are found to give rise to oscillation death, which corresponds to aseismic fault behaviour. Our result shows that the earthquake occurrence increases with increases in both the damping coefficient and the lubrication pressure. We have also revealed that the accumulation of large stresses can be controlled via artificial lubrication.

  15. Fluid structure interaction in piping systems

    Energy Technology Data Exchange (ETDEWEB)

    Svingen, Bjoernar

    1996-12-31

    The Dr. ing. thesis relates to an analysis of fluid structure interaction in piping systems in the frequency domain. The governing equations are the water hammer equations for the liquid, and the beam-equations for the structure. The fluid and structural equations are coupled through axial stresses and fluid continuity relations controlled by the contraction factor (Poisson coupling), and continuity and force relations at the boundaries (junction coupling). A computer program has been developed using the finite element method as a discretization technique both for the fluid and for the structure. This is made for permitting analyses of large systems including branches and loops, as well as including hydraulic piping components, and experiments are executed. Excitations are made in a frequency range from zero Hz and up to at least one thousand Hz. Frequency dependent friction is modelled as stiffness proportional Rayleigh damping both for the fluid and for the structure. With respect to the water hammer equations, stiffness proportional damping is seen as an artificial (bulk) viscosity term. A physical interpretation of this term in relation to transient/oscillating hydraulic pipe-friction is given. 77 refs., 72 figs., 4 tabs.

  16. Impedance effects in the CLIC damping rings

    CERN Document Server

    Koukovini-Platia, E; Mounet, N; Rumolo, G; Salvant, B

    2011-01-01

    Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings (DR) is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity showed that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive wall wake fields on the transverse impedance budget is finally discussed.

  17. Analysis of suspension with variable stiffness and variable damping force for automotive applications

    Directory of Open Access Journals (Sweden)

    Lalitkumar Maikulal Jugulkar

    2016-05-01

    Full Text Available Passive shock absorbers are designed for standard load condition. These give better vibration isolation performance only for the standard load condition. However, if the sprung mass is lesser than the standard mass, comfort and road holding ability is affected. It is demonstrated that sprung mass acceleration increases by 50%, when the vehicle mass varies by 100 kg. In order to obtain consistent damping performance from the shock absorber, it is essential to vary its stiffness and damping properties. In this article, a variable stiffness system is presented, which comprises of two helical springs and a variable fluid damper. Fluid damper intensity is changed in four discrete levels to achieve variable stiffness of the prototype. Numerical simulations have been performed with MATLAB Simscape and Simulink which have been with experimentation on a prototype. Furthermore, the numerical model of the prototype is used in design of real size shock absorber with variable stiffness and damping. Numerical simulation results on the real size model indicate that the peak acceleration will improve by 15% in comparison to the conventional passive solution, without significant deterioration of road holding ability. Arrangement of sensors and actuators for incorporating the system in a vehicle suspension has also been discussed.

  18. System and method for damping vibration in a drill string using a magnetorheological damper

    Science.gov (United States)

    Wassell, Mark Ellsworth; Burgess, Daniel E.; Barbely, Jason R.; Thompson, Fred Lamar

    2018-05-22

    A system for damping vibration in a drill string can include a magnetorheological fluid valve assembly having a supply of a magnetorheological fluid. A remanent magnetic field is induced in the valve during operation that can be used to provide the magnetic field for operating the valve so as to eliminate the need to energize the coils except temporarily when changing the amount of damping required. The current to be supplied to the coil for inducing a desired magnetic field in the valve is determined based on the limiting hysteresis curve of the valve and the history of the magnetization of the value using a binary search methodology. The history of the magnetization of the valve is expressed as a series of sets of current and it resulting magnetization at which the current experienced a reversal compared to prior values of the current.

  19. Contribution of the active control to the measurement of fluid-elastic coupling strengths

    International Nuclear Information System (INIS)

    Legendre, S.

    1999-01-01

    A precise dimensioning of the tubes inside a steam generator requires a better knowledge of the fluid-elastic coupling phenomena. The direct method for the determination of fluid-elastic coupling coefficients allows to explore only a reduced range of flow velocities and is unsuitable for the low velocities and for velocities close to the critical instability velocity. The active damping control method has been validated both with air and water and offers the possibility to extend the range of flow velocities using an artificial supply of damping: 50% of increase in single-phase flow conditions with measurements performed beyond the critical instability velocity, a doubling of the explored range of velocities in two-phase flow conditions. For a 25% two-phase flow, a stabilization of the damping of the coupled fluid-structure system is observed beyond the critical instability velocity. Finally, the calculation of fluid-elastic dimensionless coefficients has permitted to show the influence of the reduced velocity on the fluid-elastic coupling in two-phase flow conditions. (J.S.)

  20. Landau fluid model for weakly nonlinear dispersive magnetohydrodynamics

    International Nuclear Information System (INIS)

    Passot, T.; Sulem, P. L.

    2005-01-01

    In may astrophysical plasmas such as the solar wind, the terrestrial magnetosphere, or in the interstellar medium at small enough scales, collisions are negligible. When interested in the large-scale dynamics, a hydrodynamic approach is advantageous not only because its numerical simulations is easier than of the full Vlasov-Maxwell equations, but also because it provides a deep understanding of cross-scale nonlinear couplings. It is thus of great interest to construct fluid models that extended the classical magnetohydrodynamic (MHD) equations to collisionless situations. Two ingredients need to be included in such a model to capture the main kinetic effects: finite Larmor radius (FLR) corrections and Landau damping, the only fluid-particle resonance that can affect large scales and can be modeled in a relatively simple way. The Modelization of Landau damping in a fluid formalism is hardly possible in the framework of a systematic asymptotic expansion and was addressed mainly by means of parameter fitting in a linearized setting. We introduced a similar Landau fluid model but, that has the advantage of taking dispersive effects into account. This model properly describes dispersive MHD waves in quasi-parallel propagation. Since, by construction, the system correctly reproduces their linear dynamics, appropriate tests should address the nonlinear regime. In a first case, we show analytically that the weakly nonlinear modulational dynamics of quasi-parallel propagating Alfven waves is well captured. As a second test we consider the parametric decay instability of parallel Alfven waves and show that numerical simulations of the dispersive Landau fluid model lead to results that closely match the outcome of hybrid simulations. (Author)

  1. Amplitude dependent damping in single crystalline high purity molybdenum

    International Nuclear Information System (INIS)

    Zelada-Lambri, G.I; Lambri, O.A; Garcia, J.A; Lomer, J.N

    2004-01-01

    Amplitude dependent damping measurements were performed on high purity single crystalline molybdenum at several different constant temperatures between room temperature and 1273K. The employed samples were single crystals with the orientation, having a residual resistivity ratio of about 8000. Previously to the amplitude dependent damping tests, the samples were subjected to different thermomechanical histories. Amplitude dependent damping effects appear only during the first heating run in temperature where the samples have the thermomechanical state of the deformation process at room temperature. In the subsequent run-ups in temperature, i.e, after subsequent annealings, amplitude dependent damping effects were not detected (au)

  2. Evaluation of dynamic loads induced by transient regimes of fluid flows in the pipe systems and devices of reducing the loads and their effects

    International Nuclear Information System (INIS)

    Serban, Viorel; Chirita, Alexandru Mihai; Androne, Marian; Alexandru, Constantin; Ciuca, Camelia; Badara, Janina; Alexandru, Carmen

    1995-01-01

    The paper presents the analytic methods for estimating the dynamic effects induced in pipe systems in transient regimes. They are based on computation programs developed in order to check the behaviour of ECCS and EWS under 'water hammer effect' and the behaviour of the primary circuit system under stresses caused by pipe cracks. Computation examples are presented in order to emphasize the capabilities of the programs to model transient phenomena in complex pipe networks. The overpressure induced by the water hammer effect, as revealed by comparing several transient regimes, depends on the fluid viscosity, the initial speed, the duration of starting the transient regime, the system rigidity, etc. Values several ten times higher that the initial one could be thus reached. An overview of new types of devices designed for damping the effect of water hammer phenomenon, as well as of sustaining supports for pipe systems and equipment able to damp the vibrations produced by the transient regimes of fluid flows and seismic movements is presented. These devices have also to cope with the high shocks produced by pipe breakage as well as high static loads. The paper contains the following sections: 1. Introduction; 2. Evaluating dynamic loads associated to the water hammer phenomenon; 3. Determining loads associated to the water hammer phenomenon for the ECC system of the Cernavoda NPP Unit 1; 4. Device for reducing the water hammer effects; 5. Evaluating dynamic loads associated to pipe cracks; 6. Determining loads associated to pipe cracks in the Cernavoda NPP primary circuit; 7. Devices for absorbing and damping the dynamic loads in pipe systems and equipment; 8. Conclusions. (authors)

  3. Superconducting wiggler magnets for beam-emittance damping rings

    CERN Document Server

    Schoerling, Daniel

    2012-01-01

    Ultra-low emittance beams with a high bunch charge are necessary for the luminosity performance of linear electron-positron colliders, such as the Compact Linear Collider (CLIC). An effective way to create ultra-low emittance beams with a high bunch charge is to use damping rings, or storage rings equipped with strong damping wiggler magnets. The remanent field of the permanent magnet materials and the ohmic losses in normal conductors limit the economically achievable pole field in accelerator magnets operated at around room temperature to below the magnetic saturation induction, which is 2.15 T for iron. In wiggler magnets, the pole field in the center of the gap is reduced further like the hyperbolic cosine of the ratio of the gap size and the period length multiplied by pi. Moreover, damping wiggler magnets require relatively large gaps because they have to accept the un-damped beam and to generate, at a small period length, a large magnetic flux density amplitude to effectively damp the beam emittance....

  4. Wave propagation in fluid-conveying viscoelastic carbon nanotubes under longitudinal magnetic field with thermal and surface effect via nonlocal strain gradient theory

    Science.gov (United States)

    Zhen, Yaxin; Zhou, Lin

    2017-03-01

    Based on nonlocal strain gradient theory, wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes (SWCNTs) is studied in this paper. With consideration of thermal effect and surface effect, wave equation is derived for fluid-conveying viscoelastic SWCNTs under longitudinal magnetic field utilizing Euler-Bernoulli beam theory. The closed-form expressions are derived for the frequency and phase velocity of the wave motion. The influences of fluid flow velocity, structural damping coefficient, temperature change, magnetic flux and surface effect are discussed in detail. SWCNTs’ viscoelasticity reduces the wave frequency of the system and the influence gets remarkable with the increase of wave number. The fluid in SWCNTs decreases the frequency of wave propagation to a certain extent. The frequency (phase velocity) gets larger due to the existence of surface effect, especially when the diameters of SWCNTs and the wave number decrease. The wave frequency increases with the increase of the longitudinal magnetic field, while decreases with the increase of the temperature change. The results may be helpful for better understanding the potential applications of SWCNTs in nanotechnology.

  5. Similar Connotation in Chronic Hepatitis B and Nonalcoholic Fatty Liver Patients with Dampness-Heat Syndrome

    Directory of Open Access Journals (Sweden)

    Jianye Dai

    2013-01-01

    Full Text Available The phenomenon that the same syndrome turns up in different diseases appears in the sight of people around the world, which raises the thought for possibility of “Same Treatment for Different Diseases.” Actually, treatment based on ZHENG classification in Traditional Chinese Medicine could bring revelation for the former finding. The dampness-heat syndrome in chronic hepatitis B and nonalcoholic fatty liver is regarded as the breakthrough point. We discussed the molecular mechanism of similar connotation that exists in chronic hepatitis B and nonalcoholic fatty liver by metabonomics to give the modern understanding of dampness-heat syndrome. Both urine and serum metabolic profiling revealed that obvious differences existed between dampness-heat syndrome and non-dampness-heat syndrome but the commonality was proved to appear in chronic hepatitis B and nonalcoholic fatty liver patients with dampness-heat syndrome. Furthermore, disorder of body fluid metabolism, decline in digestive capacity, and imbalance of intestinal flora were found to be the new guiding for treatment, with the hope to provide the basis for Chinese personalized medicine.

  6. A Research Agenda on Assessing and Remediating Home Dampness and Mold to Reduce Dampness-Related Health Effects

    Energy Technology Data Exchange (ETDEWEB)

    Mendell, Mark J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Cosmology Center

    2015-05-28

    This report briefly summarizes, based on recent review articles and selected more recent research reports, current scientific knowledge on two topics: assessing unhealthy levels of indoor D/M in homes and remediating home dampness-related problems to protect health. Based on a comparison of current scientific knowledge to that required to support effective, evidence-based, health-protective policies on home D/M, gaps in knowledge are highlighted, prior questions and research questions specified, and necessary research activities and approaches recommended.

  7. A Research Agenda on Assessing and Remediating Home Dampness and Mold to Reduce Dampness-Related Health Effects

    Energy Technology Data Exchange (ETDEWEB)

    Mendell, Mark J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-06-01

    This report briefly summarizes, based on recent review articles and selected more recent research reports, current scientific knowledge on two topics: assessing unhealthy levels of indoor D/M in homes and remediating home dampness-related problems to protect health. Based on a comparison of current scientific knowledge to that required to support effective, evidence-based, health-protective policies on home D/M, gaps in knowledge are highlighted, prior questions and research questions specified, and necessary research activities and approaches recommended.

  8. Pipe damping studies

    International Nuclear Information System (INIS)

    Ware, A.G.

    1986-01-01

    The Idaho National Engineering Laboratory (INEL) is conducting a research program to assist the United States Nuclear Regulatory Commission (USNRC) in determining best-estimate damping values for use in the dynamic analysis of nuclear power plant piping systems. This paper describes four tasks in the program that were undertaken in FY-86. In the first task, tests were conducted on a 5-in. INEL laboratory piping system and data were analyzed from a 6-in. laboratory system at the ANCO Engineers facility to investigate the parameters influencing damping in the seismic frequency range. Further tests were conducted on 3- and 5-in. INEL laboratory piping systems as the second task to determine damping values representative of vibrations in the 33 to 100 Hz range, typical of hydrodynamic transients. In the third task a statistical evaluation of the available damping data was conduted to determine probability distributions suitable for use in probabilistic risk assessments (PRAs), and the final task evaluated damping data at high strain levels

  9. Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

    Science.gov (United States)

    Lee, Myoung-Jae; Jung, Young-Dae

    2018-04-01

    The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

  10. Nonequilibrium chiral fluid dynamics including dissipation and noise

    International Nuclear Information System (INIS)

    Nahrgang, Marlene; Herold, Christoph; Bleicher, Marcus; Leupold, Stefan

    2011-01-01

    We present a consistent theoretical approach for the study of nonequilibrium effects in chiral fluid dynamics within the framework of the linear σ model with constituent quarks. Treating the quarks as an equilibrated heat bath, we use the influence functional formalism to obtain a Langevin equation for the σ field. This allows us to calculate the explicit form of the damping coefficient and the noise correlators. For a self-consistent derivation of both the dynamics of the σ field and the quark fluid, we have to employ the 2PI (two-particle irreducible) effective action formalism. The energy dissipation from the field to the fluid is treated in the exact formalism of the 2PI effective action where a conserved energy-momentum tensor can be constructed. We derive its form and comment on approximations generating additional terms in the energy-momentum balance of the entire system.

  11. Preventing Dampness Related Health Risks at the Design Stage of Buildings in Mediterranean Climates: A Cyprus Case Study

    Directory of Open Access Journals (Sweden)

    Ugochukwu Kenechi Elinwa

    2018-05-01

    Full Text Available Dampness is a major building challenge that poses a health risk by aiding the growth of mold and other related microorganisms in very humid areas. Thus, the correction of these post-effects results in high maintenance costs via energy consumption, due to the prolonged heating of damp rooms and post-treatment, especially during the winter. A survey of 2000 valid respondents living in apartment-style buildings was conducted and analyzed using SPSS software. In this study, the AutoDesk Computational Fluid Dynamics (ACFD software was used to perform a simulation for building materials analysis, to evaluate them for suitability in high humidity areas and to select the best building orientation for adequate and natural ventilation. The analysis aimed to observe the indoor air conditions due to environmental air flow conditions. The relationships of the airflow conditions to the material properties were measured. The methodology involves a Failure Modes and Effects Analysis to determine the level and nature of the dampness sources. The Design-Expert Statistical-Software 10 confirmed the simulation results. The simulation revealed a lower percentage of relative humidity and temperature in Adobe walls than in brick walls.

  12. Effect of Landau damping on kinetic Alfven and ion-acoustic solitary waves in a magnetized nonthermal plasma with warm ions

    International Nuclear Information System (INIS)

    Bandyopadhyay, Anup; Das, K.P.

    2002-01-01

    The evolution equations describing both kinetic Alfven wave and ion-acoustic wave in a nonthermal magnetized plasma with warm ions including weak nonlinearity and weak dispersion with the effect of Landau damping have been derived. These equations reduce to two coupled equations constituting the KdV-ZK (Korteweg-de Vries-Zakharov-Kuznetsov) equation for both kinetic Alfven wave and ion-acoustic wave, including an extra term accounting for the effect of Landau damping. When the coefficient of the nonlinear term of the evolution equation for ion-acoustic wave vanishes, the nonlinear behavior of ion-acoustic wave, including the effect of Landau damping, is described by two coupled equations constituting the modified KdV-ZK (MKdV-ZK) equation, including an extra term accounting for the effect of Landau damping. It is found that there is no effect of Landau damping on the solitary structures of the kinetic Alfven wave. Both the macroscopic evolution equations for the ion-acoustic wave admits solitary wave solutions, the former having a sech 2 profile and the latter having a sech profile. In either case, it is found that the amplitude of the ion-acoustic solitary wave decreases slowly with time

  13. Damping rings for CLIC

    CERN Document Server

    Jowett, John M; Zimmermann, Frank; Owen, H

    2001-01-01

    The Compact Linear Colider (CLIC) is designed to operate at 3 TeV centre-of-mass energy with a total luminosity of 10^35 cm^-2 s^-1. The overall system design leads to extremely demanding requirements on the bunch trains injected into the main libac at frequency of 100 Hz. In particular, the emittances of the intense bunches have to be about an order of magnitude smaller than presently achieved. We describe our approach to finding a damping ring design capable of meeting these requirements. Besides lattice design, emittance and damping rate considerations, a number of scattering and instability effects have to be incorporated into the optimisation of parameters. Among these, intra-bem scattering and the electron cloud effect are two of the most significant.

  14. Damping Identification of Bridges Under Nonstationary Ambient Vibration

    Directory of Open Access Journals (Sweden)

    Sunjoong Kim

    2017-12-01

    Full Text Available This research focuses on identifying the damping ratio of bridges using nonstationary ambient vibration data. The damping ratios of bridges in service have generally been identified using operational modal analysis (OMA based on a stationary white noise assumption for input signals. However, most bridges are generally subjected to nonstationary excitations while in service, and this violation of the basic assumption can lead to uncertainties in damping identification. To deal with nonstationarity, an amplitude-modulating function was calculated from measured responses to eliminate global trends caused by nonstationary input. A natural excitation technique (NExT-eigensystem realization algorithm (ERA was applied to estimate the damping ratio for a stationarized process. To improve the accuracy of OMA-based damping estimates, a comparative analysis was performed between an extracted stationary process and nonstationary data to assess the effect of eliminating nonstationarity. The mean value and standard deviation of the damping ratio for the first vertical mode decreased after signal stationarization. Keywords: Damping, Operational modal analysis, Traffic-induced vibration, Nonstationary, Signal stationarization, Amplitude-modulating, Bridge, Cable-stayed, Suspension

  15. Reversible dissipative processes, conformal motions and Landau damping

    International Nuclear Information System (INIS)

    Herrera, L.; Di Prisco, A.; Ibáñez, J.

    2012-01-01

    The existence of a dissipative flux vector is known to be compatible with reversible processes, provided a timelike conformal Killing vector (CKV) χ α =(V α )/T (where V α and T denote the four-velocity and temperature respectively) is admitted by the spacetime. Here we show that if a constitutive transport equation, either within the context of standard irreversible thermodynamics or the causal Israel–Stewart theory, is adopted, then such a compatibility also requires vanishing dissipative fluxes. Therefore, in this later case the vanishing of entropy production generated by the existence of such CKV is not actually associated to an imperfect fluid, but to a non-dissipative one. We discuss also about Landau damping. -- Highlights: ► We review the problem of compatibility of dissipation with reversibility. ► We show that the additional assumption of a transport equation renders such a compatibility trivial. ► We discuss about Landau damping.

  16. Reversible dissipative processes, conformal motions and Landau damping

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, L., E-mail: laherrera@cantv.net.ve [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain); Di Prisco, A., E-mail: adiprisc@fisica.ciens.ucv.ve [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain); Ibáñez, J., E-mail: j.ibanez@ehu.es [Departamento de Física Teórica e Historia de la Ciencia, Universidad del País Vasco, Bilbao (Spain)

    2012-02-06

    The existence of a dissipative flux vector is known to be compatible with reversible processes, provided a timelike conformal Killing vector (CKV) χ{sup α}=(V{sup α})/T (where V{sup α} and T denote the four-velocity and temperature respectively) is admitted by the spacetime. Here we show that if a constitutive transport equation, either within the context of standard irreversible thermodynamics or the causal Israel–Stewart theory, is adopted, then such a compatibility also requires vanishing dissipative fluxes. Therefore, in this later case the vanishing of entropy production generated by the existence of such CKV is not actually associated to an imperfect fluid, but to a non-dissipative one. We discuss also about Landau damping. -- Highlights: ► We review the problem of compatibility of dissipation with reversibility. ► We show that the additional assumption of a transport equation renders such a compatibility trivial. ► We discuss about Landau damping.

  17. Effect of oscillation mode on the free-molecule squeeze-film air damping

    KAUST Repository

    Gang Hong,; Wenjing Ye,

    2010-01-01

    A 3D Monte Carlo (MC) simulation approach is developed and employed to study the effect of the oscillation mode on the squeeze-film air damping in the free-molecule regime. By tracking individual gas molecule's motion and its interaction

  18. Lifetime measurement of ATF damping ring

    International Nuclear Information System (INIS)

    Okugi, T.; Hayano, H.; Kubo, K.; Naito, T.; Terunuma, N.; Urakawa, J.; Zimmermann, F.

    1998-06-01

    The purpose of the ATF damping ring is the development of technologies for producing a low emittance beam required in future linear colliders such as JLC. The lifetime of the damping ring is very short (typically a few minutes). It is limited by elastic beam-gas scattering along with a small dynamic aperture, and by single intra-beam scattering (Touschek effect). The Touschek lifetime strongly depends upon the charge density of the beam, especially, the size of the vertical emittance. In this paper, the authors report the results of beam lifetime measurements in the ATF damping ring and the estimation of the vertical emittance from these measurements

  19. Effect of Stress Amplitude on the Damping of Recycled Aggregate Concrete.

    Science.gov (United States)

    Liang, Chaofeng; Liu, Tiejun; Xiao, Jianzhuang; Zou, Dujian; Yang, Qiuwei

    2015-08-14

    Damping characterizes the energy dissipation capacity of materials and structures, and it is affected by several external factors such as vibrating frequency, stress history, temperature, and stress amplitude. This study investigates the relationship between the damping and the stress amplitude of environment-friendly recycled aggregate concrete (RAC). First, a function model of a member's loss factor and stress amplitude was derived based on Lazan's damping-stress function. Then, the influence of stress amplitude on the loss tangent of RAC was experimentally investigated. Finally, parameters used to determine the newly derived function were obtained by numerical fitting. It is shown that the member's loss factor is affected not only by the stress amplitude but also by factors such as the cross section shapes, boundary conditions, load types, and loading positions. The loss tangent of RAC increases with the stress amplitude, even at low stress amplitude. The damping energy exponent of RAC is not identically equal to 2.0, indicating that the damping is nonlinear. It is also found that the energy dissipation capacity of RAC is superior to that of natural aggregate concrete (NAC), and the energy dissipation capacity can be further improved by adding modified admixtures.

  20. Using magnetorheological fluids in an innovative hybrid bicycle damper

    International Nuclear Information System (INIS)

    Shiao, Y J; Nguyen, T S

    2015-01-01

    Magnetorheological fluids are capable of changing their viscosity quickly. This can provide good controllability and fast dynamic response. A conventional passive suspension system with air spring or hydraulic damper has simple design and financial benefit for bicycles, but its operation is uncontrollable and non-adaptive. This paper presented a semi-active hybrid bicycle suspension system which combines conventional air spring and a new magnetorheological damping brake together to reduce vibration of a bicycle. A multi-layer magnetorheological brake and linkage mechanism are connected to bike fork to form the adaptive damping part of the innovative hybrid suspension system. The simulation results proved that the semi-active suspension system can reduce bike vibration effectively. (paper)

  1. Chiral damping of magnetic domain walls

    KAUST Repository

    Jué, Emilie

    2015-12-21

    Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).

  2. Chiral damping of magnetic domain walls

    KAUST Repository

    Jué , Emilie; Safeer, C.  K.; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stephane; Schuhl, Alain; Manchon, Aurelien; Miron, Ioan Mihai; Gaudin, Gilles

    2015-01-01

    Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).

  3. Power oscillation damping controller

    DEFF Research Database (Denmark)

    2012-01-01

    A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...

  4. Electron beam depolarization in a damping ring

    International Nuclear Information System (INIS)

    Minty, M.

    1993-04-01

    Depolarization of a polarized electron beam injected into a damping ring is analyzed by extending calculations conventionally applied to proton synchrotrons. Synchrotron radiation in an electron ring gives rise to both polarizing and depolarizing effects. In a damping ring, the beam is stored for a time much less than the time for self polarization. Spin flip radiation may therefore be neglected. Synchrotron radiation without spin flips, however, must be considered as the resonance strength depends on the vertical betatron oscillation amplitude which changes as the electron beam is radiation damped. An expression for the beam polarization at extraction is derived which takes into account radiation damping. The results are applied to the electron ring at the Stanford Linear Collider and are compared with numerical matrix formalisms

  5. Effect of loose spring skirt mounting position on vibration damping in a multi segment hanging cantilever

    International Nuclear Information System (INIS)

    Nazeer, M.M.; Khan, A.F.; Shah, R.H; Afzal, M.; Ahmed, N.

    2001-01-01

    The loose spring skirt clearance is the major factor effecting the damping and amplitude control of randomly excited vibrations in a vertically hanging cantilever. However, the spring's mounting position also has an important role to play. In this work, the results of computational model as well as that of experimental set-up for various spring mounting positions having optimum annular clearance between skirted member and the skirt are presented and their vibration damping response is analyzed. It is observed that lower is the mounting position, the better is the damping and its maximum value is attained when the bottom end of spring skirt and the hanging cantilever are mutually flushed. (author)

  6. Effect of radiation damping on the interaction of ultra-intense laser pulses with an overdense plasma

    International Nuclear Information System (INIS)

    Zhidkov, Alexei; Koga, James; Sasaki, Akira; Ueshima, Yutaka

    2001-01-01

    The effect of radiation damping on the interaction of an ultra-intense laser pulse with an overdense plasma is studied via relativistic particle-in-cell simulation. The calculation is performed for a Cu solid slab including ionization. We find a strong effect from radiation damping on the electron energy cut-off at about 150 MeV and on the absorption of a laser pulse with an intensity I=5x10 22 W/cm 2 and duration of 20 fs. Hot electrons reradiate more then 10% of the laser energy during the laser pulse. With the laser intensity, the energy loss due to the radiation damping increases as I 3 . In addition, we observe that the laser pulse may not propagate in the plasma even if ω pl 2 /ω 2 γ<1. The increase of skin depth with the laser intensity due to relativistic effects gives rise to the absorption efficiency. (author)

  7. On the Effect of Thermoelastic Damping in Nonlinear Micro Electro Mechanical Resonators using Differential Quadrature Method

    Directory of Open Access Journals (Sweden)

    A. Karami Mohammadi

    2015-07-01

    Full Text Available : In this paper, a nonlinear model of clamped-clamped microbeam actuated by electrostatic load with stretching and thermoelastic effects is presented. Free vibration frequency is calculated by discretization based on DQ method. Frequency is a complex value due to the thermoelastic effect that dissipates the energy. By separating the real and imaginary parts of frequency, quality factor of thermoelastic damping is calculated. Both stretching and thermoelastic effects are validated against the results of the reference papers. The variations of thermoelastic damping versus elasticity modulus, coefficient of thermal expansion and geometrical parameters such as thickness, gap distance, and length are investigated and these results are compared in the linear and nonlinear models for high values of voltage. Also, this paper shows that since for high values of electrostatic voltage the linear model reveals a large error for calculating the thermoelastic damping, the nonlinear model should be used for this purpose.

  8. Coulomb Damping

    Science.gov (United States)

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  9. Estimating the Effects of Damping Treatments on the Vibration of Complex Structures

    Science.gov (United States)

    2012-09-26

    26 4.3 Literature review 26 4.3.1 CLD Theory 26 4.3.2 Temperature Profiling 28 4.4 Constrained Layer Damping Analysis 29 4.5 Results 35...Coordinate systems and length scales are noted. Constraining layer, viscoelastic layer and base layer pertain to the nomenclature used through CLD ...for vibrational damping 4.1 Introduction Constrained layer damping ( CLD ) treatment systems are widely used in complex structures to dissipate

  10. Damping characteristics of reinforced concrete structures

    International Nuclear Information System (INIS)

    Hisano, M.; Nagashima, I.; Kawamura, S.

    1987-01-01

    Reinforced concrete structures in a nuclear power plant are not permitted to go far into the inelasticity generally, even when subjected to strong ground motion. Therefore it is important to evaluate the damping appropriately in linear and after cracking stage before yielding in the dynamic response analysis. Next three dampings are considered of reinforced concrete structures. 1) Internal damping in linear range material damping of concrete without cracks;2) Hysteretic damping in inelastic range material hysteretic damping of concrete due to cracking and yielding;3) Damping due to the energy dissipation into the ground. Among these damping material damping affects dynamic response of a nuclear power plant on hard rock site where damping due to energy dissipation into the ground is scarcely expected. However material damping in linear and slightly nonlinear range have only been assumed without enough experimental data. In this paper such damping is investigated experimentally by the shaking table tests of reinforced concrete box-walls which modeled roughly the outer wall structure of a P.W.R. type nuclear power plant

  11. Seismic Effects and Static Analysis for the Artificial Damped Outrigger Systems in Tall R.C Buildings

    Directory of Open Access Journals (Sweden)

    Abbas AbdulMajeed Allawi

    2016-06-01

    Full Text Available This paper studies the combination fluid viscous dampers in the outrigger system to add supplementary damping into the structure, which purpose to remove the dependability of the structure to lower variable intrinsic damping. It works by connecting the central core, comprising either shear walls or braced frames, to the outer perimeter columns. The modal considered is a 36 storey square high rise reinforced concrete building. By constructing a discrete lumped mass model, and using frequency-based response function, two systems of dampers, parallel and series systems are studied. The maximum lateral load at the top of the building is calculated, and this load will be applied at every floor of the building, giving a conservative solution. For static study Equivalent Lateral Force (ELF was conducted. MATLAB software, has been used in this study. From analysis data, it is observed that the parallel system of dampers result lower amplitude of vibration and achieved more efficiently compared to the series system, and the horizontal displacement for each configurations by using MATLAB software is less than the analytical solution using a uniformly distributed load of 36 nodal point forces that divided the total height.

  12. Role of Magnetorheological Fluids and Elastomers in Today’s World

    Directory of Open Access Journals (Sweden)

    Skalski Paweł

    2017-12-01

    Full Text Available This paper explains the role of magnetorheological fluids and elastomers in today’s world. A review of applications of magnetorheological fluids and elastomers in devices and machines is presented. Magnetorheological fluids and elastomers belong to the smart materials family. Properties of magnetorheological fluids and elastomers can be controlled by a magnetic field. Compared with magnetorheological fluids, magnetorheological elastomers overcome the problems accompanying applications of MR fluids, such as sedimentation, sealing issues and environmental contamination. Magnetorheological fluids and elastomers, due to their ability of dampening vibrations in the presence of a controlled magnetic field, have great potential present and future applications in transport. Magnetorheological fluids are used e.g. dampers, shock absorbers, clutches and brakes. Magnetorheological dampers and magnetorheological shock absorbers are applied e.g. in damping control, in the operation of buildings and bridges, as well as in damping of high-tension wires. In the automotive industry, new solutions involving magnetorheological elastomer are increasingly patented e.g. adaptive system of energy absorption, system of magnetically dissociable [hooks/detents/grips], an vibration reduction system of the car’s drive shaft. The application of magnetorheological elastomer in the aviation structure is presented as well.

  13. Equivalent viscous damping procedure for multi-material systems

    International Nuclear Information System (INIS)

    Ahmed, H.; Ma, D.

    1979-01-01

    The inclusion of accurate viscous damping effects in the seismic analysis of nuclear power plants is discussed. A procedure to evaluate and use equivalent viscous damping coefficients in conjunction with the substructure method of finite element analysis is outlined in detail

  14. Exploring damping characteristics of composite tower of cable ...

    Indian Academy of Sciences (India)

    SHEHATA E ABDEL RAHEEM

    the seismic design [1–7] by dividing the cable-stayed bridge into several ..... damping characteristics is represented by a simple model to study the effect of ...... lent modal damping of short-span bridges subjected to strong motion. J. Bridge ...

  15. Effect of montmorillonite on carboxylated styrene butadiene rubber/hindered phenol damping material with improved extraction resistance

    International Nuclear Information System (INIS)

    Gao, Yuan; Wang, Xiaoping; Liu, Meijun; Xi, Xue; Zhang, Xin; Jia, Demin

    2014-01-01

    Highlights: • MMT and XSBR display synergic effect on protecting HP1098 from being extracted. • A new hindered phenol HP1098 was used to prepare damping material. • Effects of three preparation methods on the material properties were studied. - Abstract: Three methods of blending, including direct blending, melt blending and latex blending, were introduced to disperse sodium based montmorillonite (Na-MMT) and N,N′-hexane-1,6-diylbis{3-(5-di-tert-butyl-4-hydroxyphenyl-propionamide)} (HP1098) into the carboxylated styrene butadiene (XSBR) matrix. Small angle X-ray Diffraction testing indicated that melting Na-MMT with HP1098 enlarged the d-spacing of Na-MMT, which was further enlarged by mechanical blending with XSBR, and this led to homogeneous dispersion of Na-MMT and HP1098, which was indicated by Transmission Electronic Microscopy; latex blending was found most advantageous in dispersing HP1098 which was essential for improved damping performance. Dynamic Mechanical Analysis was utilized to characterize damping properties, and enhanced static mechanical properties were presumably originated from molecule chains being intercalated into the enlarged galleries of Na-MMT by mechanical blending. Formation of hydrogen bonds was observed by Fourier Transformation Infrared Spectrum and was supposed to be responsible for exceptional damping performance at elevated temperature. Extraction measurement of XSBR/Na-MMT/HP1098 composite indicated that XSBR and Na-MMT showed synergic effect in protecting HP1098 molecules from being extracted, which is a promising method in preparing rubber/hindered phenol damping materials with improved extraction resistance, whereby increasing the performance stability and lifespan of the composite materials. Additional advantage of this type of materials is better processability and shortened vulcanization process

  16. Investigation of local load effect on damping characteristics of synchronous generator using transfer-function block-diagram model

    Directory of Open Access Journals (Sweden)

    Pichai Aree

    2005-07-01

    Full Text Available The transfer-function block-diagram model of single-machine infinite-bus power system has been a popular analytical tool amongst power engineers for explaining and assessing synchronous generator dynamic behaviors. In previous studies, the effects of local load together with damper circuit on generator damping have not yet been addressed because neither of them was integrated into this model. Since the model only accounts for the generator main field circuit, it may not always yield a realistic damping assessment due to lack of damper circuit representation. This paper presents an extended transfer-function block-diagram model, which includes one of the q-axis damper circuits as well as local load. This allows a more realistic investigation of the local load effect on the generator damping. The extended model is applied to assess thegenerator dynamic performance. The results show that the damping power components mostly derived from the q-axis damper and the field circuits can be improved according to the local load. The frequency response method is employed to carry out the fundamental analysis.

  17. Investigation of Squeeze Film Damping and Associated Loads

    DEFF Research Database (Denmark)

    Johansen, Per; Bender, Niels Christian; Hansen, Anders Hedegaard

    2017-01-01

    -viscous case. In consequence, this enable insights concerning the influence of piezo-viscosity on this damping effect. These models are used to investigate the loads, which the approaching surfaces experiences. Based on Hertzian theory, comparisons of impact loads and the dynamic squeeze loading are performed......Digital hydraulics have attracted attention towards fast switching valves and the increased focus on reliable fluid power entail that the lifetime of such valves is of great concern. An inherent feature of most valves for digital hydraulics is that of a mechanical end stop. Consequently...... is reviewed with a focus on maximum surface stresses. Using the Barus relation for viscosity-pressure dependency and different film geometries, the classical lubrication theory is applied together with the equation of motion, to obtain the gap height motion equation, both for the iso-viscous and piezo...

  18. Experimental seismic test of fluid coupled co-axial cylinders

    International Nuclear Information System (INIS)

    Chu, M.L.; Brown, S.J.; Lestingi, J.F.

    1979-01-01

    The dynamic response of fluid coupled coaxial cylindrical shells is of interest to the nuclear industry with respect to the seismic design of the reactor vessel and thermal liner. The experiments described present a series of tests which investigate the effect of the annular clearance between the cylinders (gap) on natural frequency, damping, and seismic response of both the inner and outer cylinders. The seismic input is a time history base load to the flexible fluid filled coaxial cylinders. The outer cylinder is elastically supported at both ends while the inner cylinder is supported only at the base (lower) end

  19. Damping Ring R&D at CESR-TA

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, David L. [Cornell Univ., Ithaca, NY (United States). Dept. of Physics

    2015-01-23

    Accelerators that collide high energy beams of matter and anti-matter are essential tools for the investigation of the fundamental constituents of matter, and the search for new forms of matter and energy. A “Linear Collider” is a machine that would bring high energy and very compact bunches of electrons and positrons (anti-electrons) into head-on collision. Such a machine would produce (among many other things) the newly discovered Higgs particle, enabling a detailed study of its properties. Among the most critical and challenging components of a linear collider are the damping rings that produce the very compact and intense beams of electrons and positrons that are to be accelerated into collision. Hot dilute particle beams are injected into the damping rings, where they are compressed and cooled. The size of the positron beam must be reduced more than a thousand fold in the damping ring, and this compression must be accomplished in a fraction of a second. The cold compact beams are then extracted from the damping ring and accelerated into collision at high energy. The proposed International Linear Collider (ILC), would require damping rings that routinely produce such cold, compact and intense beams. The goal of the Cornell study was a credible design for the damping rings for the ILC. Among the technical challenges of the damping rings; the development of instrumentation that can measure the properties of the very small beams in a very narrow window of time, and mitigation of the forces that can destabilize the beams and prevent adequate cooling, or worse lead to beam loss. One of the most pernicious destabilizing forces is due to the formation of clouds of electrons in the beam pipe. The electron cloud effect is a phenomenon in particle accelerators in which a high density of low energy electrons, build up inside the vacuum chamber. At the outset of the study, it was anticipated that electron cloud effects would limit the intensity of the positron ring

  20. Viscous damping of solitary waves in the mud banks of Kerala, West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Murty, C.S.

    Analysis of wave damping in mud bank region following the process of transfer of wave energy to the interior of fluid column through the boundary layer and the energy loss computations owing to viscous shear beneath the solitary wave over a smooth...

  1. Perturbational blowup solutions to the compressible Euler equations with damping.

    Science.gov (United States)

    Cheung, Ka Luen

    2016-01-01

    The N-dimensional isentropic compressible Euler system with a damping term is one of the most fundamental equations in fluid dynamics. Since it does not have a general solution in a closed form for arbitrary well-posed initial value problems. Constructing exact solutions to the system is a useful way to obtain important information on the properties of its solutions. In this article, we construct two families of exact solutions for the one-dimensional isentropic compressible Euler equations with damping by the perturbational method. The two families of exact solutions found include the cases [Formula: see text] and [Formula: see text], where [Formula: see text] is the adiabatic constant. With analysis of the key ordinary differential equation, we show that the classes of solutions include both blowup type and global existence type when the parameters are suitably chosen. Moreover, in the blowup cases, we show that the singularities are of essential type in the sense that they cannot be smoothed by redefining values at the odd points. The two families of exact solutions obtained in this paper can be useful to study of related numerical methods and algorithms such as the finite difference method, the finite element method and the finite volume method that are applied by scientists to simulate the fluids for applications.

  2. Temporal stability of superposed magnetic fluids in porous media

    International Nuclear Information System (INIS)

    Zakaria, Kadry; Sirwah, Magdy A; Alkharashi, Sameh

    2008-01-01

    The present work deals with the stability properties of time periodically streaming superposed magnetic fluids through porous media under the influence of an oblique alternating magnetic field. The system is composed of a middle fluid sheet of finite thickness embedded between two other bounded layers. The fluids are assumed to be incompressible and there are no volume charges in the layers of the fluids. Such configurations are of relevance in a variety of astrophysical and space configurations. The solutions of the linearized equations of motion and boundary conditions lead to deriving two more general simultaneous Mathieu equations of damping terms with complex coefficients. The method of multiple time scales is used to obtain approximate solutions and analyze the stability criteria for both the non-resonant and resonant cases and hence transition curves are obtained for such cases. The stability criteria are examined theoretically and numerically from which stability diagrams are obtained. It is found that the fluid sheet thickness plays a destabilizing role in the presence of a constant field and velocity, while the damping role is observed for the resonant cases. Dual roles are observed for the fluid velocity and the porosity in the stability criteria

  3. Extended Rayleigh Damping Model

    Directory of Open Access Journals (Sweden)

    Naohiro Nakamura

    2016-07-01

    Full Text Available In dynamic analysis, frequency domain analysis can be used if the entire structure is linear. However, time history analysis is generally used if nonlinear elements are present. Rayleigh damping has been widely used in time history response analysis. Many articles have reported the problems associated with this damping and suggested remedies. A basic problem is that the frequency area across which the damping ratio is almost constant is too narrow. If the area could be expanded while incurring only a small increase in computational cost, this would provide an appropriate remedy for this problem. In this study, a novel damping model capable of expanding the constant frequency area by more than five times was proposed based on the study of a causal damping model. This model was constructed by adding two terms to the Rayleigh damping model and can be applied to the linear elements in the time history analysis of a nonlinear structure. The accuracy and efficiency of the model were confirmed using example analyses.

  4. Nonlinear Dynamics and Chaos of Microcantilever-Based TM-AFMs with Squeeze Film Damping Effects

    Directory of Open Access Journals (Sweden)

    Jie-Yu Chen

    2009-05-01

    Full Text Available In Atomic force microscope (AFM examination of a vibrating microcantilever, the nonlinear tip-sample interaction would greatly influence the dynamics of the cantilever. In this paper, the nonlinear dynamics and chaos of a tip-sample dynamic system being run in the tapping mode (TM were investigated by considering the effects of hydrodynamic loading and squeeze film damping. The microcantilever was modeled as a spring-mass-damping system and the interaction between the tip and the sample was described by the Lennard-Jones (LJ potential. The fundamental frequency and quality factor were calculated from the transient oscillations of the microcantilever vibrating in air. Numerical simulations were carried out to study the coupled nonlinear dynamic system using the bifurcation diagram, Poincaré maps, largest Lyapunov exponent, phase portraits and time histories. Results indicated the occurrence of periodic and chaotic motions and provided a comprehensive understanding of the hydrodynamic loading of microcantilevers. It was demonstrated that the coupled dynamic system will experience complex nonlinear oscillation as the system parameters change and the effect of squeeze film damping is not negligible on the micro-scale.

  5. Differential effects of organic compounds on cucumber damping-off and biocontrol activity of antagonistic bacteria

    DEFF Research Database (Denmark)

    Li, Bin; Ravnskov, Sabine; Guanlin, X.

    2011-01-01

    The influence of the organic compounds tryptic soy broth, cellulose, glucose and chitosan on cucumber damping-off caused by Pythium aphanidermatum and biocontrol efficacy of the biocontrol agents (BCAs) Paenibacillus macerans and P. polymyxa were examined in a seedling emergence bioassay. Results...... showed that the organic compounds differentially affected both pathogen and BCAs. Tryptic soy broth, glucose and chitosan increased Pythium damping-off of cucumber, compared to the control treatment without organic compounds, whereas cellulose had no effect. Both Paenibacillus species had biocontrol...

  6. Damping Analysis of Cylindrical Composite Structures with Enhanced Viscoelastic Properties

    Science.gov (United States)

    Kliem, Mathias; Høgsberg, Jan; Vanwalleghem, Joachim; Filippatos, Angelos; Hoschützky, Stefan; Fotsing, Edith-Roland; Berggreen, Christian

    2018-04-01

    Constrained layer damping treatments are widely used in mechanical structures to damp acoustic noise and mechanical vibrations. A viscoelastic layer is thereby applied to a structure and covered by a stiff constraining layer. When the structure vibrates in a bending mode, the viscoelastic layer is forced to deform in shear mode. Thus, the vibration energy is dissipated as low grade frictional heat. This paper documents the efficiency of passive constrained layer damping treatments for low frequency vibrations of cylindrical composite specimens made of glass fibre-reinforced plastics. Different cross section geometries with shear webs have been investigated in order to study a beneficial effect on the damping characteristics of the cylinder. The viscoelastic damping layers are placed at different locations within the composite cylinder e.g. circumferential and along the neutral plane to evaluate the location-dependent efficiency of constrained layer damping treatments. The results of the study provide a thorough understanding of constrained layer damping treatments and an improved damping design of the cylindrical composite structure. The highest damping is achieved when placing the damping layer in the neutral plane perpendicular to the bending load. The results are based on free decay tests of the composite structure.

  7. Closed-form eigensolutions of nonviscously, nonproportionally damped systems based on continuous damping sensitivity

    Science.gov (United States)

    Lázaro, Mario

    2018-01-01

    In this paper, nonviscous, nonproportional, vibrating structures are considered. Nonviscously damped systems are characterized by dissipative mechanisms which depend on the history of the response velocities via hereditary kernel functions. Solutions of the free motion equation lead to a nonlinear eigenvalue problem involving mass, stiffness and damping matrices. Viscoelasticity leads to a frequency dependence of this latter. In this work, a novel closed-form expression to estimate complex eigenvalues is derived. The key point is to consider the damping model as perturbed by a continuous fictitious parameter. Assuming then the eigensolutions as function of this parameter, the computation of the eigenvalues sensitivity leads to an ordinary differential equation, from whose solution arises the proposed analytical formula. The resulting expression explicitly depends on the viscoelasticity (frequency derivatives of the damping function), the nonproportionality (influence of the modal damping matrix off-diagonal terms). Eigenvectors are obtained using existing methods requiring only the corresponding eigenvalue. The method is validated using a numerical example which compares proposed with exact ones and with those determined from the linear first order approximation in terms of the damping matrix. Frequency response functions are also plotted showing that the proposed approach is valid even for moderately or highly damped systems.

  8. Effectiveness of elastic damping in the pivot joints of cargo boom of crane-manipulating installations at large gaps

    Directory of Open Access Journals (Sweden)

    Lagerev I.A.

    2016-03-01

    Full Text Available The article was the analysis of dynamic processes in the cylindrical hinges with large gaps in the cargo boom crane-manipulating installations of mobile machines in operation. Consider the design of damping device for articulated joints, which creates a braking force of elastic resistance to the displacement of the hinge pin within the large gap. The mechanism of action of the damping devices was considered. Analysis of the effectiveness of damping device for re-ducing the dynamic stress state in the elements of cargo boom metal structures depending on the gap size and the stiff-ness of the damping device was performed. Damping device with an elastic shock absorbing elements substantially reduces the additional impact load at the time of selection of the gap in the joint, slow the growth of clearance in the pivot joint, limit the size of the gap specified value, which must not be exceeded during the entire service life of swivel independently from the intensity of his load.

  9. Landau Damping Revisited

    International Nuclear Information System (INIS)

    Rees, John; Chao, Alexander

    2008-01-01

    Landau damping, as the term is used in accelerator science, is a physical process in which an ensemble of harmonic oscillators--an accelerator beam, for example--that would otherwise be unstable is stabilized by a spread in the natural frequencies of the oscillators. This is a study of the most basic aspects of that process. It has two main goals: to gain a deeper insight into the mechanism of Landau damping and to find the coherent motion of the ensemble and thus the dependence of the total damping rate on the frequency spread

  10. An experimental study on damping characteristics of thermal insulation

    International Nuclear Information System (INIS)

    Chiba, T.; Kobayashi, H.

    1985-01-01

    The damping ratio is one of the most important parameters in seismic analysis of nuclear power plant piping systems. Thermal Insulation is considered to contribute to the damping characteristics of piping systems. In the 6th SMiRT conference and 1983 ASME PVP, the damping effect and damping estimating formula was presented as a result of regression analysis from the component tests of 2'' , 4'', and 8'' diameter piping and the proof model test of 1'', 2'' and 4'' piping. In this study, in order to clarify the damping characteristics of larger diameter piping than 8'', the component test of 12'' and 20'' diameter piping with insulation was performed. From the results of these tests and the data survey of the previous papers it was found that the damping ratio of actual piping system with thermal insulation is at least 1% for all size diameter piping

  11. Theoretical study of flow ripple for an aviation axial-piston pump with damping holes in the valve plate

    Directory of Open Access Journals (Sweden)

    Guan Changbin

    2014-02-01

    Full Text Available Based on the structure of a certain type of aviation axial-piston pump’s valve plate which adopts a pre-pressurization fluid path (consisting a damping hole, a buffer chamber, and an orifice to reduce flow ripple, a single-piston model of the aviation axial-piston pump is presented. This single-piston model comprehensively considers fluid compressibility, orifice restriction effect, fluid resistance in the capillary tube, and the leakage flow. Besides, the instantaneous discharge areas used in the single-piston model have been calculated in detail. Based on the single-piston model, a multi-piston pump model has been established according to the simple hydraulic circuit. The single- and multi-piston pump models have been realized by the S-function in Matlab/Simulink. The developed multi-piston pump model has been validated by being compared with the numerical result by computational fluid dynamic (CFD. The effects of the pre-pressurization fluid path on the flow ripple and the instantaneous pressure in the piston chamber have been studied and optimized design recommendations for the aviation axial-piston pump have been given out.

  12. A semiempirical approach to a viscously damped oscillating sphere

    International Nuclear Information System (INIS)

    Alexander, P; Indelicato, E

    2005-01-01

    A simple model of damped harmonic motion is usually presented in undergraduate physics textbooks and straightforwardly applied for a variety of well-known experiments in student laboratories. Results for the decaying vertical oscillation of a sphere attached to the lower end of a spring in containers with different liquids are analysed here under this standard framework. Some important mismatches between observation and theory are found, which are attributed to oversimplifications in the formulation of the drag force. A more elaborate expression for the latter within a semiempirical approach is then introduced and a more appropriate description of the measurements is shown to be attained. Two coefficients account for experimental corrections, which under certain conditions permit in addition the calculation of specific fluid quantities associated with the oscillating sphere. Rough relations between viscosity and damping factor under appropriate limits are derived. The laboratory experience may also be used to introduce the concept of a semiempirical model and exhibit its utility in physics

  13. The effect of dust size distribution on the damping of the solitary waves in a dusty plasma

    International Nuclear Information System (INIS)

    Yang, Xue; Xu, Yan-Xia; Qi, Xin; Wang, Cang-Long; Duan, Wen-Shan; Yang, Lei

    2013-01-01

    The effect of the dust size distribution on the damping rate of the solitary wave in a dusty plasma is investigated in the present paper. It is found that the damping rate increases as either the mean radius of dust grains increases or as the total number density of the dust grains increases. The damping rate is less for usual dusty plasma (about which the number density of the smaller dust grains is larger than that of the larger dust grains) than that of the unusual dusty plasma (about which the number density of the larger dust grains is larger than that of the smaller dust grains)

  14. Design of Weighted Wide Area Damping Controller (WWADC Based PSS for Damping Inter-Area Low Frequency Oscillations

    Directory of Open Access Journals (Sweden)

    Saleh M. Bamasak

    2017-09-01

    Full Text Available Wide Area Measurement System (WAMS can extend and effectively improve the power system stabilizers (PSS capability in damping the inter-area low frequency oscillations in interconnected bulk power systems. This paper proposes the implementation of Weighted Wide Area Damping Controller (WWADC in which weighted factors are introduced for each remote feedback signals. Modal analysis approach is implemented for the purpose of identifying the optimal location as well as the input signals’ optimal combination of WWADC. Based on the linearized model, Differential Evolution (DE algorithm is applied to search for optimal controller parameters and optimal weighted factors. The successful application of the proposed approach is achieved in two power networks; the two-area 4-machine system and the IEEE-39 bus 10-machine system. The analysis of the eigenvalue and non-linear time domain simulations indicate that damping the inter-area oscillations and improving the system stability irrespective of the severity and the location of the disturbances can be effectively achieved by WADC

  15. Spin transfer in an open ferromagnetic layer: from negative damping to effective temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wegrowe, J-E; Ciornei, M C; Drouhin, H-J [Laboratoire des Solides Irradies, Ecole Polytechnique, CNRS-UMR 7642 and CEA/DSM/DRECAM, 91128 Palaiseau Cedex (France)

    2007-04-23

    Spin transfer is a typical spintronics effect that allows a ferromagnetic layer to be switched by spin injection. All experimental results concerning spin transfer (quasi-static hysteresis loops or AC resonance measurements) are described on the basis of the Landau-Lifshitz-Gilbert equation of the magnetization, in which additional current dependent terms are added, like current dependent effective fields and current dependent damping factors, that can be positive or negative. The origin of these terms can be investigated further by performing stochastic experiments, like one-shot relaxation experiments under spin injection in the activation regime of the magnetization. In this regime, the Neel-Brown activation law is observed which leads to the introduction of a current dependent effective temperature. In order to define these counterintuitive parameters (effective temperature and negative damping), a detailed thermokinetic analysis of the different sub-systems involved is performed. This report presents a thermokinetic description of the different forms of energy exchanged between the electric and the ferromagnetic sub-systems at a normal/ferromagnetic junction. The derivation of the Fokker-Planck equation in the framework of the thermokinetic theory allows the transport parameters to be defined from the entropy variation and refined with the Onsager reciprocity relations and symmetry properties of the magnetic system. The contribution of the spin polarized current is introduced as an external source term in the conservation laws of the ferromagnetic layer. Due to the relaxation time separation, this contribution can be reduced to an effective damping. The flux of energy transferred between the ferromagnet and the spin polarized current can be positive or negative, depending on the spin accumulation configuration. The effective temperature is deduced in the activation (stationary) regime, provided that the relaxation time that couples the magnetization to the

  16. An experimental study on damping characteristics of thermal insulation

    International Nuclear Information System (INIS)

    Chiba, Toshio; Kobayashi, Hiroe; Aida, Shigekazu; Wada, Hidetoshi

    1984-01-01

    The damping ratio is one of the most important parameters in seismic analysis of piping systems in a nuclear power plant. Thermal insulation is considered contributing to the damping characteristics of piping systems. At the 6th SMiRT and 1983 ASME PVP conferences, the damping effect and damping estimating formula were presented as a result of regression analysis using the component test data for 2,4 and 8B diameter piping and the proof model test for 1,2 and 4B piping system. In this study, in order to clarify the damping characteristics of a larger diameter piping than 8B,the component test of 12 and 20B diameter piping with insulation was performed. From the results of these tests and the data survey of the previous papers, it was found that the damping ratio of anactual piping system with thermal insulation is at minimum 1% for all size diameter piping. (author)

  17. Landau damping due to tune spreads in betatron amplitude and momentum

    International Nuclear Information System (INIS)

    Lee, S.Y.; Tran, P.; Weng, W.T.

    1989-01-01

    Due to the large space charge transverse impedance in a low energy synchrotron, the coherent tune shift causes the Landau damping to be ineffective in damping the transverse coherent motion. We analyze the effect of Landau damping that is caused by the tune spreads of the betatron amplitude (space charge and/or octupole) and momentum. We find that the Landau damping becomes more significant in our two dimensional analysis. 5 refs

  18. Frequency Dependence of Damping and Compliance in Loudspeaker Suspensions

    DEFF Research Database (Denmark)

    Thorborg, Knud; Tinggaard, Carsten; Agerkvist, Finn T.

    2010-01-01

    ]. It is an empirical model mathematically describing the effects of visco-elasticity in loudspeaker suspensions. The evaluation is to a high degree based on test loudspeakers with rubber surrounds with a high content of plasticizer combining high compliance and high damping. This is very effective to reduce rim...... resonances, but less used in high quality loudspeakers today – where “Low Loss Rubber Surround” is currently seen as a marketing feature, as it is expected to have positive impact on sound quality. The plasticized type of surround shows significant creep, followed by compliance and damping increasing towards...... - with the additives normally used to adjust stiffness and damping - neither frequency dependency of compliance nor creep are significant problems. Despite this, experience shows that frequency dependent mechanical damping nevertheless might be present. In this paper some modifications to the LOG-model are proposed...

  19. Effective mass and damping of submerged structures

    International Nuclear Information System (INIS)

    Dong, R.G.

    1978-01-01

    Various structures important for safety in nuclear power plants must remain functioning in the event of an earthquake or other dynamic phenomenon. Some of these important structures, such as spent-fuel storage racks, main pressure-relief valve lines, and internal structures in the reactor vessel, are submerged in water. Dynamic analysis must include the force and damping effects of water. This report provides a technical basis for evaluating the wide variety of modeling assumptions currently used in design analysis. Current design analysis techniques and information in the literature form the basis of our conclusions and recommendations. We surveyed 32 industrial firms and reviewed 49 technical references. We compare various theories with published experimental results wherever possible. Our findings generally pertain to idealized structures, such as single isolated members, arrays of members, and coaxial cylinders. We relate these findings to the actual reactor structures through observations and recommendations. Whenever possible we recommend a definite way to evaluate the effect of hydrodynamic forces on these structures

  20. Confirmation of soil radiation damping from test versus analysis

    International Nuclear Information System (INIS)

    Eidinger, J.M.; Mukhim, G.S.; Desmond, T.P.

    1987-01-01

    The work was performed to demonstrate that soil-structure interaction effects for nuclear plant structures can be accurately (and conservatively) predicted using the finite element or soil spring methods of soil-structure interaction analysis. Further, the work was done to investigate the relative importance of soil radiation versus soil material damping in the total soil damping analytical treatment. The analytical work was benchmarked with forced vibration tests of a concrete circular slab resting on the soil surface. The applied loading was in the form of a suddenly applied pulse load, or snapback. The measured responses of the slap represent the free vibration of the slab after the pulse load has been applied. This simplifies the interpretation of soil damping, by the use of the logarithmic decay formulation. To make comparisons with the test results, the damping data calculated from the analytical models is also based on the logarithmic decay formulation. An attempt is made to differentiate the observed damped behavior of the concrete slab as being caused by soil radiation versus soil material damping. It is concluded that both the traditional soil radiation and material damping analytical simplifications are validated by the observed responses. It is concluded that arbitrary 'conservative' assumptions traditionally made in nuclear plant soil-structure interaction analyses are indeed arbitrary, and not born out by physical evidence. The amount of conservatism introduced by limiting total soil damping to values like 5% to 10% can be large. For the test slab sizes investigated, total soil damping is about 25%. For full size nuclear plant foundations, total soil damping is commonly in the 35% to 70% range. The authors suggest that full soil damping values (the combined radiation and material damping) should be used in the design, backfit and margin assessment of nuclear plants. (orig./HP)

  1. Modulated Langmuir waves and nonlinear Landau damping

    International Nuclear Information System (INIS)

    Yajima, Nobuo; Oikawa, Masayuki; Satsuma, Junkichi; Namba, Chusei.

    1975-01-01

    The nonlinear Schroedinger euqation with an integral term, iusub(t)+P/2.usub(xx)+Q/u/ 2 u+RP∫sub(-infinity)sup(infinity)[/u(x',t)/ 2 /(x-x')]dx'u=0, which describes modulated Langmuir waves with the nonlinear Landau damping effect, is solved by numerical calculations. Especially, the effects of nonlinear Landau damping on solitary wave solutions are studied. For both cases, PQ>0 and PQ<0, the results show that the solitary waves deform in an asymmetric way changing its velocity. (auth.)

  2. Damping ring designs and issues

    International Nuclear Information System (INIS)

    Wolski, Andrzej; Decking, Winfried

    2003-01-01

    The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed

  3. Damping Improvement of Multiple Damping Controllers by Using Optimal Coordinated Design Based on PSS and FACTS-POD in a Multi-Machine Power System

    Directory of Open Access Journals (Sweden)

    Ali Nasser Hussain

    2016-09-01

    Full Text Available The aim of this study is to present a comprehensive comparison and assessment of the damping function improvement of power system oscillation for the multiple damping controllers using the simultaneously coordinated design based on Power System Stabilizer (PSS and Flexible AC Transmission System (FACTS devices. FACTS devices can help in the enhancing the stability of the power system by adding supplementary damping controller to the control channel of the FACTS input to implement the task of Power Oscillation Damping (FACT POD controller. Simultaneous coordination can be performed in different ways. First, the dual coordinated designs between PSS and FACTS POD controller or between different FACTS POD controllers are arranged in a multiple FACTS devices without PSS. Second, the simultaneous coordination has been extended to triple coordinated design among PSS and different FACTS POD controllers. The parameters of the damping controllers have been tuned in the individual controllers and coordinated designs by using a Chaotic Particle Swarm Optimization (CPSO algorithm that optimized the given eigenvalue-based objective function. The simulation results for a multi-machine power system show that the dual coordinated design provide satisfactory damping performance over the individual control responses. Furthermore, the triple coordinated design has been shown to be more effective in damping oscillations than the dual damping controllers.

  4. Nonlinear effects in the damping of third-sound pulses

    International Nuclear Information System (INIS)

    Browne, D.A.

    1984-01-01

    We show that nonlinearities in the equations of motion for a third-sound pulse in a thick superfluid film lead to the production of short-wavelength solitons. The soliton damping arises from viscous stresses in the film, rather than from coupling to thermal currents in the vapor and the substrate as in the hydrodynamic regime. These solitons are more strongly damped than a long-wavelength third-sound wave and lead to a larger attenuation of the pulse. We show that this mechanism can account for the discrepancy between attenuation calculated theoretically for the long-wavelength limit and the experimentally observed attenuation of low-amplitude third-sound pulses

  5. Simulations of the effects of a superconducting damping wiggler on a short bunched electron beam at ANKA

    Energy Technology Data Exchange (ETDEWEB)

    Gethmann, Julian; Bernhard, Axel; Blomley, Edmund; Hillenbrand, Steffen; Mueller, Anke-Susanne; Smale, Nigel [Karlsruher Institut fuer Technologie (KIT) (Germany); Zolotarev, Konstantin [Budker Institute of Nuclear Physics (Russian Federation)

    2016-07-01

    (As a part of the CLIC collaboration) A CLIC damping wiggler prototype has been installed at the ANKA synchrotron light source in order to validate the technical design of the 3 T superconducting conduction cooled wiggler and its cryostat and to cary out studies on beam dynamical aspects including collective effects. The latter one will be the main focus in this talk. Collective effects that will occur in damping rings are an issue in ANKA's short bunch operation as well. To simulate these effects the accelerator's model including its insertion device has to be very accurate. Such a model of the ANKA storage ring in short bunch operation mode has been developed in elegant. Simulations with the damping wiggler switched on and off have been performed in order to investigate effects of the wiggler on different machine parameters. These new results will be discussed with regard to the question if on the one hand the wiggler could be used for diagnostic purposes and if on the other hand the wiggler's impact on the beam dynamics is changed by the collective effects.

  6. Significance of non-classical damping in seismic qualification of equipment and piping

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Abhinav, E-mail: agupta1@ncsu.edu; Bose, Mrinal K.

    2017-06-15

    Highlights: • Damping in coupled building-piping or building-equipment systems is nonlclassical. • Significance of nonclassical damping is illustrated. • Classical damping assumption can over predict or under predict response. • Significance of nonclassical damping increases for very light secondary systems. • Composite modal damping is another form of classical damping. - Abstract: This paper presents a discussion on the significance of non-classical damping in coupled primary-secondary systems such as building-equipment or building-piping. Closed-form expressions are used to illustrate that the effect of non-classical damping is significant in systems with tuned or nearly tuned uncoupled modes when the mass-interaction is sufficiently small. Further, simple primary-secondary systems are used to illustrate that composite modal damping is another form of classical damping for which the transformed damping matrix, obtained after pre- and post-multiplication of the damping matrix with the modal matrix, contains only diagonal terms. Both the composite and the classical damping give almost identical results that can be much different from the corresponding results for non-classical damping. Finally, it is shown that consideration of classical damping (ignoring the off-diagonal terms) can give excessively conservative results in nearly tuned primary-secondary systems. For perfectly tuned primary-secondary systems, however, classical damping can give responses that are much lower than what they should be.

  7. Multi-damping earthquake design spectra-compatible motion histories

    International Nuclear Information System (INIS)

    Choi, Dong-Ho; Lee, Sang-Hoon

    2003-01-01

    Two iterative methods of developing time histories compatible with multi-damping spectra are presented. The common method of forcing agreement among design and calculated spectral values at several frequencies and multiple damping values may give poor, even meaningless results. The two simple iterative techniques presented here use acceleration impulse functions for 'correcting' the time histories. In the first method the correction is calculated separately for each frequency and damping value and the maximum corresponding coefficient is used to correct the time history for the iteration. In the second method the solution is further improved by introducing a scale factor at each iteration. The effectiveness of the proposed techniques is illustrated by a comparison of a set of six multi-damping design spectra with spectral responses of a time history

  8. Thermodynamic Damping in Porous Materials with Spherical Cavities

    Directory of Open Access Journals (Sweden)

    Sofia D. Panteliou

    1997-01-01

    Full Text Available When a material is subjected to an alternating stress field, there are temperature fluctuations throughout its volume due to the thermoelastic effect. The resulting irreversible heat conduction leads to entropy production that in turn is the cause of thermoelastic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping factor as a function of the porosity of the material. A homogeneous, isotropic, elastic bar of cylindrical shape is considered with uniformly distributed spherical cavities under alternating uniform axial stress. The analytical calculation of the dynamic characteristics of the porous structure yielded the damping factor of the bar and the material damping factor. Exsperimental results on porous metals are in good correlation with an analysis.

  9. Damping in Timber Structures

    OpenAIRE

    Labonnote, Nathalie

    2012-01-01

    Key point to development of environmentally friendly timber structures, appropriate to urban ways of living, is the development of high-rise timber buildings. Comfort properties are nowadays one of the main limitations to tall timber buildings, and an enhanced knowledge on damping phenomena is therefore required, as well as improved prediction models for damping. The aim of this work has consequently been to estimate various damping quantities in timber structures. In particular, models h...

  10. Investigation into electron cloud effects in the International Linear Collider positron damping ring

    Energy Technology Data Exchange (ETDEWEB)

    Crittenden, J. A.; Conway, J.; Dugan, G. F.; Palmer, M. A.; Rubin, D. L.; Shanks, J.; Sonnad, K. G.; Boon, L.; Harkay, K.; Ishibashi, T.; Furman, M. A.; Guiducci, S.; Pivi, M. T. F.; Wang, L.

    2014-03-01

    We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications

  11. Vibration and Damping Analysis of Composite Fiber Reinforced Wind Blade with Viscoelastic Damping Control

    Directory of Open Access Journals (Sweden)

    Tai-Hong Cheng

    2015-01-01

    Full Text Available Composite materials are increasingly used in wind blade because of their superior mechanical properties such as high strength-to-weight and stiffness-to-weight ratio. This paper presents vibration and damping analysis of fiberreinforced composite wind turbine blade with viscoelastic damping treatment. The finite element method based on full layerwise displacement theory was employed to analyze the damping, natural frequency, and modal loss factor of composite shell structure. The lamination angle was considered in mathematical modeling. The curved geometry, transverse shear, and normal strains were exactly considered in present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The frequency response functions of curved composite shell structure and wind blade were calculated. The results show that the damping ratio of viscoelastic layer is found to be very sensitive to determination of magnitude of composite structures. The frequency response functions with variety of thickness of damping layer were investigated. Moreover, the natural frequency, modal loss factor, and mode shapes of composite fiber reinforced wind blade with viscoelastic damping control were calculated.

  12. Squeeze-Film Air Damping of a Five-Axis Electrostatic Bearing for Rotary Micromotors.

    Science.gov (United States)

    Wang, Shunyue; Han, Fengtian; Sun, Boqian; Li, Haixia

    2017-05-13

    Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics. To accurately characterize the damping effect, a set of multiphysics finite-element simulations are performed by computing both the rotor velocity and the distribution of the viscous damping force acting on the rotor. The damping characteristics varying with several key structure parameters are simulated and discussed to optimize the device structure for desirable rotor dynamics. An electrical measurement method is also proposed and applied to validate the numerical results of the damping coefficients experimentally. Given that the frequency response of the electric bearing is critically dependent on the damping coefficients at atmospheric pressure, a solution to the air-film damping measurement problem is presented by taking approximate curve fitting of multi-axis experimental frequency responses. The measured squeeze-film damping coefficients for the five-axis electric bearing agrees well with the numerical solutions. This indicates that numerical multiphysics simulation is an effective method to accurately examine the air-film damping effect for complex device geometry and arbitrary boundary condition. The accurate damping coefficients obtained by FEM simulation will greatly simplify the design

  13. Damping Effect of an Unsaturated-Saturated System on Tempospatial Variations of Pressure Head and Specific Flux

    Science.gov (United States)

    Yang, C.; Zhang, Y. K.; Liang, X.

    2014-12-01

    Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.

  14. Dynamic soil-pile-interaction effects on eigenfrequency and damping of slender structures

    DEFF Research Database (Denmark)

    Zania, Varvara

    2014-01-01

    after a rigorous solution of horizontal soil – pile vibration, while the modified SSI eigenperiod and damping are calculated accounting for the cross coupling stiffness and damping terms of the soil – pile system. Disregarding the off diagonal terms is considered inappropriate since it results to non...

  15. Unified Power Flow Controller Placement to Improve Damping of Power Oscillations

    OpenAIRE

    M. Salehi; A. A. Motie Birjandi; F. Namdari

    2015-01-01

    Weak damping of low frequency oscillations is a frequent phenomenon in electrical power systems. These frequencies can be damped by power system stabilizers. Unified power flow controller (UPFC), as one of the most important FACTS devices, can be applied to increase the damping of power system oscillations and the more effect of this controller on increasing the damping of oscillations depends on its proper placement in power systems. In this paper, a technique based on controllability is pro...

  16. Improving the Validity of Squeeze Film Air-Damping Model of MEMS Devices with Border Effect

    Directory of Open Access Journals (Sweden)

    Cheng Bai

    2014-01-01

    Full Text Available Evaluation of squeezed film air damping is critical in the design and control of dynamic MEMS devices. The published squeezed film air damping models are generally derived from the analytical solutions of Reynolds equation or its other modified forms under the supposition of trivial pressure boundary conditions on the peripheral borders. These treatments ignoring the border effect can not give faithful result for structure with smaller air venting gap or the double-gimbaled structure in which the inner frame and outer one affect the air venting. In this paper, we use Green’s function to solve the nonlinear Reynolds equation with inhomogeneous boundary conditions. For two typical normal motion cases of parallel plate, the analytical models of squeeze film damping force with border effect are established. The viscous and inertial losses with real values and image values acoustic impedance are all included in the model. These models reduced the time consumption while giving satisfactory result. Without multifield coupling analysis, the estimation of the dynamic behavior of MEMS device is also allowed, and the simulation of the system performance is more convenient.

  17. Nonlinear roll damping of a barge with and without liquid cargo in spherical tanks

    Directory of Open Access Journals (Sweden)

    Wenhua Zhao

    2016-01-01

    Full Text Available Damping plays a significant role on the maximum amplitude of a vessel's roll motion, in particular near the resonant frequency. It is a common practice to predict roll damping using a linear radiation–diffraction code and add that to a linearized viscous damping component, which can be obtained through empirical, semi-empirical equations or free decay tests in calm water. However, it is evident that the viscous roll damping is nonlinear with roll velocity and amplitude. Nonlinear liquid cargo motions inside cargo tanks also contribute to roll damping, which when ignored impedes the accurate prediction of maximum roll motions. In this study, a series of free decay model tests is conducted on a barge-like vessel with two spherical tanks, which allows a better understanding of the nonlinear roll damping components considering the effects of the liquid cargo motion. To examine the effects of the cargo motion on the damping levels, a nonlinear model is adopted to calculate the damping coefficients. The liquid cargo motion is observed to affect both the linear and the quadratic components of the roll damping. The flow memory effect on the roll damping is also studied. The nonlinear damping coefficients of the vessel with liquid cargo motions in spherical tanks are obtained, which are expected to contribute in configurations involving spherical tanks.

  18. Simulation Investigation on Application of Powder Metallurgy Damping Effect in Water Hydraulic Pump

    Directory of Open Access Journals (Sweden)

    Shi Weijie

    2018-01-01

    Full Text Available Over the years, the hydrostatic balance slipper is often used to make the hydraulic lubrication film formed between the swash plate and the slipper. In this paper, a slipper containing the powder metallurgy (PM composite material is proposed. The porous characteristics have an automatic damping effect, which can improve the tribological characteristics of the slipper. Based on the Reynolds equation, porous Darcy law and continuity equation, a lubrication model of PM damper is proposed to analyze the damping effect of PM in this paper. The proposed model is calculated using the finite volume method to capture the water film characteristics. Effects of length, diameter and porosity of the PM damper on the water film thickness are investigated. The results show that the water film can be formed by adopting the PM damper. In order to ensure the slipper with PM damper to form hydrostatic support, the length, diameter and porosity of PM damper is recommended to be 5 mm, 8 mm and 0.7, respectively.

  19. Electronic Contributions to the Phonon Damping in Metals

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rune

    1968-07-15

    An imaginary part of the dielectric matrix is derived based on a first order perturbation expansion of the valence electron states in a local potential model of the crystal. The results are used to estimate the electronic contributions to the phonon damping in aluminum and lead. The corrections which have been obtained are of the same order of magnitude at small phonon momenta as the damping earlier calculated for the free electrons. However, the discrepancies between the theoretical and experimental results still remain. The major contribution to damping seems to originate in anharmonic effects, even at 80 deg K.

  20. Effect of microalloying with rare-earth on recrystallization behaviour and damping properties of Mg sheets

    International Nuclear Information System (INIS)

    Ma, Ning; Peng, Qiuming; Pan, Junling; Li, Hui; Xiao, Wenlong

    2014-01-01

    Highlights: • Rare earth additions accelerate recovery, but retard recrystallization. • Internal peak at mediate temperatures corresponds to grain boundary relaxation. • Internal peak at elevated temperature is a recrystallization peak. • Grain size, basal texture and dislocation density affect damping remarkably. - Abstract: The effect of a small amount of rare earth elements (RE: Nd and Dy, 0.5 wt.%) on recrystallization behaviour, microstructural evolution and damping properties of deformed Mg sheets have been investigated. The recrystallization behaviour was analyzed in terms of the Johnson–Mehl–Avrami–Kolmogorov model via the variation of microhardness. The Avrami exponent of pure Mg sheet ranged from 1.02 to 1.16, and it was reduced by adding REs. The acceleration of recovery and retardation of recrystallization were detected by the presence of REs. Three point bending was carried out to assess damping properties. At the temperature of ∼150 °C, the damping peak corresponds to grain boundary relaxation, which was affected by grain size, basal texture and the variation of dislocation density on basal plane. At elevated temperatures, a non-thermal activated peak was mainly dependent upon annealing condition, where its height and temperature were increased by adding REs, assigning to be a recrystallization peak

  1. A lattice with larger momentum compaction for the NLC main damping rings

    International Nuclear Information System (INIS)

    Wolski, Andrzej; Raubenheimer, Tor O.; Woodley, Mark; Wu, Juhao

    2004-01-01

    Previous lattice designs for the Next Linear Collider Main Damping Rings [1] have met the specifications for equilibrium emittance, damping rate and dynamic aperture. Concerns about the effects of the damping wiggler on the beam dynamics [2] led to the aim of reducing the total length of the wiggler to a minimum consistent with the required damping rate, so high-field dipoles were used to provide a significant energy loss in the arcs. However, recent work has shown that the wiggler effects may not be as bad as previously feared. Furthermore, other studies have suggested the need for an increased momentum compaction (by roughly a factor of four) to raise the thresholds of various collective effects. We have therefore developed a new lattice design in which we increase the momentum compaction by reducing the field strength in the arc dipoles, compensating the loss in damping rate by increasing the length of the wiggler. The new lattice again meets the specifications for emittance, damping rate and dynamic aperture, while having the benefit of significantly higher thresholds for a number of instabilities

  2. Motion of a damped oscillating sphere as a function of the medium viscosity

    International Nuclear Information System (INIS)

    Mendoza-Arenas, J J; Perico, E L D; Fajardo, F

    2010-01-01

    In this paper, an experimental setup for undergraduate courses to study the damped harmonic motion of a sphere inside a fluid as a function of the medium viscosity is presented. To observe the dependence of the oscillation of the sphere on the medium viscosity, different concentrations of glycerin in water were used. The sphere is suspended on the end of a spring and its displacement is indirectly obtained using a force sensor. To describe the sphere motion, a drag force different from that given by Stokes' law is used. Our experimental results fit satisfactorily when semiempirical coefficients are introduced in the model. The frequency and relaxation time of the sphere oscillations diminish as the concentration of glycerin increases. Boundary effects due to the fluid container size are studied. We found that when the container size decreases the oscillations decay more rapidly due to a greater resistance to the motion of the sphere.

  3. RESEARCH ON THE ASEISMIC BEHAVIOR OF LONG-SPAN CABLE-STAYED BRIDGE WITH DAMPING EFFECT

    Directory of Open Access Journals (Sweden)

    Wu Fangwen

    2016-07-01

    Full Text Available The main beam of a cable-stayed bridge with a floating system may have a larger longitudinal displacement subject to earthquake effect. Thus, seismic control and isolation are crucial to bridge safety. This paper takes Huai’an Bridge, which has elastic coupling devices and viscous dampers set at the joint of the tower and the beam, as the research background. Its finite element model is established, and the elastic stiffness of elastic coupling devices and damper parameters are analyzed. Viscous damper and elastic coupling devices are simulated using Maxwell model and spring elements, and their damping effects are analyzed and compared through structural dynamic time-history analysis. Results show that viscous damper and elastic coupling device furnished at the joint of tower and beam of a cable-stayed bridge tower beam can effectively reduce the longitudinal displacement of the key part of the construction subject to earthquake effect, perfect the internal force distribution, and improve the aseismic performance. Between the two, viscous damper has better damping effects.

  4. The Characteristics of Vibration Isolation System with Damping and Stiffness Geometrically Nonlinear

    Science.gov (United States)

    Lu, Ze-Qi; Chen, Li-Qun; Brennan, Michael J.; Li, Jue-Ming; Ding, Hu

    2016-09-01

    The paper concerns an investigation into the use of both stiffness and damping nonlinearity in the vibration isolator to improve its effectiveness. The nonlinear damping and nonlinear stiffness are both achieved by horizontal damping and stiffness as the way of the geometrical nonlinearity. The harmonic balance method is used to analyze the force transmissibility of such vibration isolation system. It is found that as the horizontal damping increasing, the height of the force transmissibility peak is decreased and the high-frequency force transmissibility is almost the same. The results are also validated by some numerical method. Then the RMS of transmissibility under Gaussian white noise is calculated numerically, the results demonstrate that the beneficial effects of the damping nonlinearity can be achieved under random excitation.

  5. Characterization of fluid forces exerted on a cylinder array oscillating laterally in axial flow

    International Nuclear Information System (INIS)

    Divaret, Lise

    2014-01-01

    This thesis presents an experimental and a numerical study of the fluid forces exerted on a cylinder or a cylinder array oscillating laterally in an axial flow. The parameters of the system are the amplitude, the oscillation frequency, the confinement and the length to diameter ratio of the cylinder. The objective is to determine the fluid damping created by the axial flow, i.e. the dissipative force. The industrial application of this thesis is the determination of the fluid damping of the fuel assemblies in the core of a nuclear power plant during an earthquake. The study focuses on the configurations where the oscillation velocity is small compared to the axial flow velocity. In a first part, we study the case of a cylinder with no confinement oscillating in axial flow. Two methods are used: a dynamical and a quasi-static approach. In dynamics, the damping rate is measured during free oscillations of the cylinder. In the quasi-static approach, the damping coefficient is calculated from the normal force measured on a yawed cylinder. The range of the small ratios between the oscillation and the axial flow velocities corresponds to a range of low yaw angle where the cylinder is in near-axial flow in statics. The case of a yawed cylinder has been studied both experimentally with experiments in a wind tunnel and numerically with CFD calculations. The analyses of the fluid forces shows that for yaw angles smaller than 5 degrees, a linear lift with the yaw angle creates the damping. The origin of the lift force is discussed from pressure and velocity measurements. The results of the quasi-static approach are compared to the results of the dynamical experiments. In a second part, an experimental study is performed on a rigid cylinder array made up of 40 cylinders oscillating in an axial flow. The normal force and the displacement of the cylinder array are measured simultaneously. The added mass and damping coefficient are calculated and their variation with the

  6. Anisotropic damping of Timoshenko beam elements

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, M.H.

    2001-05-01

    This report contains a description of a structural damping model for Timoshenko beam elements used in the aeroelastic code HawC developed at Risoe for modeling wind turbines. The model has been developed to enable modeling of turbine blades which often have different damping characteristics for flapwise, edgewise and torsional vibrations. The structural damping forces acting on the beam element are modeled by viscous damping described by an element damping matrix. The composition of this matrix is based on the element mass and stiffness matrices. It is shown how the coefficients for the mass and stiffness contributions can be calibrated to give the desired modal damping in the complete model of a blade. (au)

  7. Comparative Research on Characteristics of the Isolation Systems with Dry Friction Damping and with Vicious Damping under Base Excitation

    Science.gov (United States)

    Hou, Junfang; jing, Min; Zhang, Weihua; Lu, Yahui; He, Haiwen

    2017-12-01

    As for the isolation problem of electronic equipments on vehicle, the vibration response characteristics of dry friction damping isolation system under base displacement excitation was analyzed in theory by harmonic balance method, and the displacement response was compared between the isolation systems with dry friction damping and vicious damping separately. The results show that the isolation system with small dry friction damping can’t meet the demands of displacement reduction close to the natural frequency, and it can realize full-frequency vibration isolation by improving dry friction damping when the lock frequency passes beyond the resonance frequency band. The results imply that the damping mechanism of dry friction isolator can’t be described only by dry friction damping, and the composite damping with dry friction and vicious damping is more appropriate.

  8. Damping layout optimization for ship's cabin noise reduction based on statistical energy analysis

    Directory of Open Access Journals (Sweden)

    WU Weiguo

    2017-08-01

    Full Text Available An optimization analysis study concerning the damping control of ship's cabin noise was carried out in order to improve the effect and reduce the weight of damping. Based on the Statistical Energy Analysis (SEA method, a theoretical deduction and numerical analysis of the first-order sensitivity analysis of the A-weighted sound pressure level concerning the damping loss factor of the subsystem were carried out. On this basis, a mathematical optimization model was proposed and an optimization program developed. Next, the secondary development of VA One software was implemented through the use of MATLAB, while the cabin noise damping control layout optimization system was established. Finally, the optimization model of the ship was constructed and numerical experiments of damping control optimization conducted. The damping installation region was divided into five parts with different damping thicknesses. The total weight of damping was set as an objective function and the A-weighted sound pressure level of the target cabin was set as a constraint condition. The best damping thickness was obtained through the optimization program, and the total damping weight was reduced by 60.4%. The results show that the damping noise reduction effect of unit weight is significantly improved through the optimization method. This research successfully solves the installation position and thickness selection problems in the acoustic design of damping control, providing a reliable analysis method and guidance for the design.

  9. Dampness in buildings and health. Building characteristics as predictors for dampness in 8681 Swedish dwellings

    DEFF Research Database (Denmark)

    Hagerhed, L.; Bornehag, Carl-Gustaf; Sundell, Jan

    2002-01-01

    Questionnaire data on 8681 dwellings included in the Swedish study "Dampness in Buildings and Health" have been analysed for associations between dampness indicators, perceptions of indoor air quality and building characteristics such as time of construction, type of ventilation and type of found......Questionnaire data on 8681 dwellings included in the Swedish study "Dampness in Buildings and Health" have been analysed for associations between dampness indicators, perceptions of indoor air quality and building characteristics such as time of construction, type of ventilation and type...... of "Dry air" in 17.3 and 33.7% respectively. Older buildings and the use of natural ventilation were associated with increased frequency of dampness indicators as well as to increased frequencies of complaints on bad indoor air quality....

  10. Coupling of electromagnetics and structural/fluid dynamics - application to the dual coolant blanket subjected to plasma disruptions

    International Nuclear Information System (INIS)

    Jordan, T.

    1996-01-01

    Some aspects concerning the coupling of quasi-stationary electromagnetics and the dynamics of structure and fluid are investigated. The necessary equations are given in a dimensionless form. The dimensionless parameters in these equations are used to evaluate the importance of the different coupling effects. A finite element formulation of the eddy-current damping in solid structures is developed. With this formulation, an existing finite element method (FEM) structural dynamics code is extended and coupled to an FEM eddy-current code. With this program system, the influence of the eddy-current damping on the dynamic loading of the dual coolant blanket during a centered plasma disruption is determined. The analysis proves that only in loosely fixed or soft structures will eddy-current damping considerably reduce the resulting stresses. Additionally, the dynamic behavior of the liquid metal in the blankets' poloidal channels is described with a simple two-dimensional magnetohydrodynamic approach. The analysis of the dimensionless parameters shows that for small-scale experiments, which are designed to model the coupled electromagnetic and structural/fluid dynamic effects in such a blanket, the same magnetic fields must be applied as in the real fusion device. This will be the easiest way to design experiments that produce transferable results. 10 refs., 7 figs

  11. Application of small panel damping measurements to larger walls

    Science.gov (United States)

    Hastings, Mardi C.; Godfrey, Richard; Babcock, G. Madison

    1996-05-01

    Damping properties of a viscoelastic material were determined using a standard resonant beam technique. The damping material was then applied to 1 by 2 foot gypsum panels in a constrained layer construction. Damping loss factors in panels with and without the constrained layer were determined based on reverberation times after excitation at third-octave band center frequencies. The constrained damping layer had been designed to increase damping by an order of magnitude above that of a single gypsum panel at 2000 Hz; however, relative to a gypsum panel of the same overall thickness as the panel with the constrained layer, loss factors increased only by a factor of three to five. Next modal damping loss factors in 9 by 14 foot gypsum single and double walls were calculated from the experimentally determined quality factor for each modal resonance. Results showed that below 2500 Hz, modes in 1 by 2 foot gypsum panels had nearly the same damping loss factors as modes in a 9 by 14 foot gypsum wall of the same thickness; however, loss factors for the wall were an order of magnitude lower than those of the 1 by 2 foot panels at frequencies above 2500 Hz, the coincidence frequency for 5/8-inch thick gypsum plates. Thus it was inconclusive whether or not damping loss factors measured using small panels could be used to estimate the effect of a constrained damping layer on transmission loss through a 9 by 14 foot wall unless boundary conditions and modal frequencies were the same for each size.

  12. Experimental investigation of nonlinear characteristics of a smart fluid damper

    Science.gov (United States)

    Rahman, Mahmudur; Ong, Zhi Chao; Chong, Wen Tong; Julai, Sabariah; Ahamed, Raju

    2018-05-01

    Smart fluids, known as smart material, are used to form controllable dampers in vibration control applications. Magnetorheological(MR) fluid damper is a well-known smart fluid damper which has a reputation to provide high damping force with low-power input. However, the force/velocity of the MR damper is significantly nonlinear and proper characteristic analysis are required to be studied for optimal implementation in structural vibration control. In this study, an experimental investigation is carried out to test the damping characteristics of MR damper. Dynamic testing is performed with a long-stroke MR damper model no RD-80410-1 from Lord corporation on a universal testing machine(UTM). The force responses of MR damper are measured under different stroke lengths, velocities and current inputs and their performances are analyzed. This study will play a key role to implement MR damper in many structural vibration control applications.

  13. A high-force controllable MR fluid damper–liquid spring suspension system

    International Nuclear Information System (INIS)

    Raja, Pramod; Wang, Xiaojie; Gordaninejad, Faramarz

    2014-01-01

    The goal of the present research is to investigate the feasibility of incorporating a liquid spring in a semi-active suspension system for use in heavy off-road vehicles. A compact compressible magneto-rheological (MR) fluid damper–liquid spring (CMRFD–LS) with high spring rate is designed, developed and tested. Compressible MR fluids with liquid spring and variable damping characteristics are used. These fluids can offer unique functions in reducing the volume/weight of vehicle struts and improving vehicle dynamic stability and safety. The proposed device consists of a cylinder and piston–rod arrangement with an internal annular MR fluid valve. The internal pressures in the chambers on either side of the piston develop the spring force, while the pressure difference across the MR valve produces the damping force, when the fluid flows through the MR valve. Harmonic characterization of the CMRFD–LS is performed and the force–displacement results are presented. A fluid-mechanics based model is also developed to predict the performance of the system at different operating conditions and compared to the experimental results. Good agreement between the experimental results and theoretical predictions has been achieved. (paper)

  14. Air Damping in a Fan-Shaped Rotational Resonator with Comb Electrodes

    Science.gov (United States)

    Uchida, Yuki; Sugano, Koji; Tsuchiya, Toshiyuki; Tabata, Osamu; Ikehara, Tsuyoshi

    We theoretically and experimentally evaluated the damping effect in a rotational resonator with a comb-drive actuator and sensor. The resonator was fabricated from an SOI wafer and has a fan-shaped mass. The underlying substrate was removed using back side deep reactive ion etching. One set of comb electrodes was attached to each side of the mass: one for electrostatic driving and the other for capacitive detection. In our theoretical analysis, the dynamics of the resonator were simplified so that they could be represented by a lumped system. In this lumped system, the damping coefficient was estimated by assuming the damping to be slide film damping and the air flow to be a Stokes flow. The phase shift due to the slide film damping of thick air layers was included in the lumped system. In the experimental evaluation, one side of the rotational combs was removed step-by-step and a half of the mass using a laser trimming tool so that the individual damping effects caused by the comb electrodes and mass could be determined quantitatively. We compared the experimental results with the results of the theoretical analysis and found that the difference in the damping coefficients between the experimental results and results of the theoretical analysis was less than 40%.

  15. Approximation of the modal damping coefficients equivalent to material damping by harmonic excitation with ASKA

    International Nuclear Information System (INIS)

    Edme, R.

    1983-01-01

    If a dynamic response analysis (harmonic excitation) is carried out with the modal method, the modal damping coefficients must be approximated to match the structural damping. The program ASKA-Damping, which also supplies an error assessment of the approximation, was developed for this purpose. The modal method and the direct method are applied to a test example and their results compared. It is suggested that the ASKA manufacturers extend the spectral earthquake response analysis to take these modal damping coefficients into account so that the results become less conservative. (orig.) [de

  16. Special class of nonlinear damping models in flexible space structures

    Science.gov (United States)

    Hu, Anren; Singh, Ramendra P.; Taylor, Lawrence W.

    1991-01-01

    A special class of nonlinear damping models is investigated in which the damping force is proportional to the product of positive integer or the fractional power of the absolute values of displacement and velocity. For a one-degree-of-freedom system, the classical Krylov-Bogoliubov 'averaging' method is used, whereas for a distributed system, both an ad hoc perturbation technique and the finite difference method are employed to study the effects of nonlinear damping. The results are compared with linear viscous damping models. The amplitude decrement of free vibration for a single mode system with nonlinear models depends not only on the damping ratio but also on the initial amplitude, the time to measure the response, the frequency of the system, and the powers of displacement and velocity. For the distributed system, the action of nonlinear damping is found to reduce the energy of the system and to pass energy to lower modes.

  17. Magnelok technology: a complement to magnetorheological fluids

    Science.gov (United States)

    Carlson, J. David

    2004-07-01

    Magnetorheological or MR fluids have been successfully used to enable highly effective semi-active control systems in automobile primary suspensions to control unwanted motions in civil engineering structures and to provide force-feedback in steer-by-wire systems. A key to the successful use of MR fluids is an appreciation and understanding of the balance and trade-off between the magnetically controlled on-state force and the ever-present off-state viscous force. In all MR fluid applications, one must deal with the fact that MR fluids never fully decouple or go to zero force in their off-state. Magnelok devices are a magnetically controlled compliment to traditional MR fluid devices that have been developed to enable a true force decoupling in the off-state. Magnelok devices may be embodied as linear or rotary dampers, brakes, lockable struts or position holding devices. They are particularly suitable for lock/un-lock applications. Unlike MR fluid devices they contain no fluid yet they do provide a variable level of friction damping that is controlled by the magnitude of the applied magnetic field. Magnelok devices are low cost as they easily accommodate relatively loose mechanical tolerances and require no seals or accumulator. A variety of controllable Magnelok devices and applications are described.

  18. Study of squeeze film damping in a micro-beam resonator based on micro-polar theory

    Directory of Open Access Journals (Sweden)

    Mina Ghanbari

    Full Text Available In this paper, squeeze film damping in a micro-beam resonator based on micro-polar theory has been investigated. The proposed model for this study consists of a clamped-clamped micro-beam bounded between two fixed layers. The gap between the micro-beam and layers is filled with air. As fluid behaves differently in micro scale than macro, the micro-scale fluid field in the gap has been modeled based on micro-polar theory. Equation of motion governing transverse deflection of the micro- beam based on modified couple stress theory and also non-linear Reynolds equation of the fluid field based on micropolar theory have been non-dimensionalized, linearized and solved simultaneously in order to calculate the quality factor of the resonator. The effect of micropolar parameters of air on the quality factor has been investigated. The quality factor of the of the micro-beam resonator for different values of non-dimensionalized length scale of the beam, squeeze number and also non-dimensionalized pressure has been calculated and compared to the obtained values of quality factor based on classical theory.

  19. Enhancing damping of gas bearings using linear parameter-varying control

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Galeazzi, Roberto

    2017-01-01

    systems to regulate the injection pressure of the fluid. Due to the strong dependencies of system performance on system parameters, the sought controller should be robust over a large range of operational conditions. This paper addresses the damping enhancement of controllable gas bearings through robust...... control approaches. Through an extensive experimental campaign the paper evaluates two robust controllers, a linear parametervarying (LPV) controller and ∞ controller, on their capability to guarantee stability and performance of a gas bearing across the large operational envelopes in rotational speed...

  20. Design of passive piezoelectric damping for space structures. Final Report Ph.D. Thesis

    Science.gov (United States)

    Hagood, Nesbitt W., IV; Aldrich, Jack B.; Vonflotow, Andreas H.

    1994-01-01

    Passive damping of structural dynamics using piezoceramic electromechanical energy conversion and passive electrical networks is a relatively recent concept with little implementation experience base. This report describes an implementation case study, starting from conceptual design and technique selection, through detailed component design and testing to simulation on the structure to be damped. About 0.5kg. of piezoelectric material was employed to damp the ASTREX testbed, a 500kg structure. Emphasis was placed upon designing the damping to enable high bandwidth robust feedback control. Resistive piezoelectric shunting provided the necessary broadband damping. The piezoelectric element was incorporated into a mechanically-tuned vibration absorber in order to concentrate damping into the 30 to 40 Hz frequency modes at the rolloff region of the proposed compensator. A prototype of a steel flex-tensional motion amplification device was built and tested. The effective stiffness and damping of the flex-tensional device was experimentally verified. When six of these effective springs are placed in an orthogonal configuration, strain energy is absorbed from all six degrees of freedom of a 90kg. mass. A NASTRAN finite element model of the testbed was modified to include the six-spring damping system. An analytical model was developed for the spring in order to see how the flex-tensional device and piezoelectric dimensions effect the critical stress and strain energy distribution throughout the component. Simulation of the testbed demonstrated the damping levels achievable in the completed system.

  1. Damped fiber optic low-frequency tiltmeter for real-time monitoring of structural displacements

    International Nuclear Information System (INIS)

    Meng, Dewei; Ansari, Farhad

    2013-01-01

    This study reports on the design, development and testing of a fiber optic Bragg grating (FBG)-based tiltmeter. The tiltmeter design is based on the correlation between the bending strains and rotations of a lumped mass ended cantilever beam. The design of the system includes incorporation of a damping fluid to control the dynamic response. Temperature compensation for the sensor was achieved by using two symmetrically placed FBGs for cancellation of thermal effects. The tiltmeter is designed to exhibit linearity over the range of measurements common in low-frequency vibrations in bridges and exhibits measurement resolution of 0.005°. The study reports on the static calibration tests, correlations with the theoretical relationships, and dynamic characterization and response. (paper)

  2. Vibration of fusion reactor components with magnetic damping

    Energy Technology Data Exchange (ETDEWEB)

    D’Amico, Gabriele; Portone, Alfredo [Fusion for Energy – Torres Diagonal Litoral B3 – c/Josep Plá n.2, Barcelona (Spain); Rubinacci, Guglielmo [Department of Electrical Eng. and Information Technologies, Università di Napoli Federico II, Via Claudio, 21, 80125 Napoli (Italy); Testoni, Pietro, E-mail: pietro.testoni@f4e.europa.eu [Fusion for Energy – Torres Diagonal Litoral B3 – c/Josep Plá n.2, Barcelona (Spain)

    2016-11-01

    The aim of this paper is to assess the importance of the magnetic damping in the dynamic response of the main plasma facing components of fusion machines, under the strong Lorentz forces due to Vertical Displacement Events. The additional eddy currents due to the vibration of the conducting structures give rise to volume loads acting as damping forces, a kind of viscous damping, being these additional loads proportional to the vibration speed. This effect could play an important role when assessing, for instance, the inertial loads associated to VV movements in case of VDEs. In this paper, we present the results of a novel numerical formulation, in which the field equations are solved by adopting a very effective fully 3D integral formulation, not limited to the analysis of thin shell structures, as already successfully done in several approaches previously published.

  3. Dampness in buildings and health

    DEFF Research Database (Denmark)

    Bornehag, Carl-Gustaf; Blomquist, G.; Gyntelberg, F.

    2001-01-01

    Several epidemiological investigations concerning indoor environments have indicated that "dampness" in buildings is associated to health effects such as respiratory symptoms, asthma and allergy The aim of the present interdisciplinary review is to evaluate this association as shown in the epidem...

  4. Damping-controlled fluidelastic instability forces in multi-span tubes with loose supports

    International Nuclear Information System (INIS)

    Hassan, Marwan A.; Rogers, Robert J.; Gerber, Andrew G.

    2011-01-01

    This paper presents simulations of a loosely supported multi-span tube subjected to turbulence and fluidelastic instability forces in order to compare several time-domain fluid force models simulating the damping-controlled fluidelastic instability mechanism in tube arrays. These models include the negative damping model based on the Connors equation, fluid force coefficient-based models (Chen; Tanaka and Takahara), and two semi-analytical models (Price and Paidoussis; and Lever and Weaver). Time domain modelling challenges for each of these theories are discussed. The implemented models are validated against available experimental data. The linear simulations (without tube/support clearance) show that the Connors-equation based model exhibits the most conservative prediction of the critical flow velocity when the recommended design values for the Connors equation are used. The models are then utilized to simulate the nonlinear response of a three-span cantilever tube in a lattice bar support subjected to air crossflow. The tube is subjected to a single-phase flow passing over the spans where the flow velocity and the support clearance are varied. Special attention is paid to the tube/support interaction parameters that affect wear, such as impact forces, contact ratio, and normal work rate. As was seen for the linear cases, the reduced flow velocity at the instability threshold differs for the fluid force models considered. The investigated models do, however, exhibit similar response characteristics for the impact force, tip lift response, and work rate, except for the Connors-based model that overestimates the response and the tube/support interaction parameters for the loose support case, especially at large clearances.

  5. Application of consistent fluid added mass matrix to core seismic

    International Nuclear Information System (INIS)

    Koo, K. H.; Lee, J. H.

    2003-01-01

    In this paper, the application algorithm of a consistent fluid added mass matrix including the coupling terms to the core seismic analysis is developed and installed at SAC-CORE3.0 code. As an example, we assumed the 7-hexagon system of the LMR core and carried out the vibration modal analysis and the nonlinear time history seismic response analysis using SAC-CORE3.0. Used consistent fluid added mass matrix is obtained by using the finite element program of the FAMD(Fluid Added Mass and Damping) code. From the results of the vibration modal analysis, the core duct assemblies reveal strongly coupled vibration modes, which are so different from the case of in-air condition. From the results of the time history seismic analysis, it was verified that the effects of the coupled terms of the consistent fluid added mass matrix are significant in impact responses and the dynamic responses

  6. Thiol-ene/methacrylate systems for mechanical damping

    Science.gov (United States)

    McNair, Olivia; Senyurt, Askim; Wei, Huanyu; Gould, Trent; Piland, Scott; Hoyle, Charles; Savin, Daniel

    2010-03-01

    Ternary thiol-ene-methacrylate (TEMA) networks as materials for mechanical energy damping are unique to the sports world. Using a photoinitiation process, TEMA systems are formed via an initial thiol-ene step-growth mechanism along with traditional radical polymerization of acrylate and ene monomers. Final networks have two-part morphologies: acrylate homopolymer sectors imbedded in a multi-component mesh. Several (TEMA) systems have been synthesized and analyzed via thermal and mechanical probing. Initial studies on these ternary systems have shown excellent properties compared to traditional ethylene vinyl alcohol (EVA) copolymers. For example, PEMA networks exhibit glass transition temperatures 33 K higher than EVA, resulting in improved damping at room temperature. This research will help develop relationships between tan delta, glass transition and their effects on mechanical energy damping for ternary (TEMA) systems.

  7. The effect of damping on a quantum system containing a Kerr-like medium

    Science.gov (United States)

    Mohamed, A.-B. A.; Sebawe Abdalla, M.; Obada, A.-S. F.

    2018-05-01

    An analytical description is given for a model which represents the interaction between Su(1,1) and Su(2) quantum systems taking into account Su(1,1)-cavity damping and Kerr medium properties. The analytic solution for the master equation of the density matrix is obtained. The examination of the effects of the damping parameter as well as the Kerr-like medium features is performed. The atomic inversion is discussed where the revivals and collapses phenomenon is realized at the considered period of time. Our study is extended to include the degree of entanglement where the system shows partial entanglement in all cases, however, disentanglement is also observed. The death and rebirth is seen in the system provided one selects the suitable values of the parameters. The correlation function of the system shows non-classical as well as classical behavior.

  8. Evaluation of magnetorheological fluid augmented fabric as a fragment barrier material

    International Nuclear Information System (INIS)

    Son, Kwon Joong; Fahrenthold, Eric P

    2012-01-01

    The augmentation of high strength fabrics with non-Newtonian fluids has been suggested as a means for improving the ballistic performance of fragment barrier materials widely used in fan blade containment, body armor, orbital debris shielding, and other applications. Magnetorheological (MR) fluids have attracted particular interest, in view of their controllability and proven effectiveness in a variety of damping applications. In a basic research investigation of the MR fluid augmented fabric barrier concept, the authors have fabricated MR fluid saturated Kevlar targets and measured the ballistic performance of these targets both with and without an applied magnetic field. The experimental results show that magnetization of the MR fluid does, when considered in isolation, improve the ability of the augmented fabric to absorb impact energy. However, the benefits of plastic and viscous energy dissipation in the magnetized semi-solid are more than offset by the detrimental effects of yarn lubrication associated with the fluid’s hydrocarbon carrier. An analytical model developed to assist in the interpretation of the experimental data suggests that frictional interaction of the yarns is significantly more effective than magnetorheological augmentation of the fabric in distributing projectile loads away from the point of impact. (paper)

  9. DAMPs, ageing, and cancer: The 'DAMP Hypothesis'.

    Science.gov (United States)

    Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J; Kang, Rui; Lotze, Michael T; Tang, Daolin

    2015-11-01

    Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. The effect of chromatic decoherence on transverse injection oscillation damping

    International Nuclear Information System (INIS)

    Jackson, G.P.

    1993-01-01

    In order to eliminate or reduce transverse emittance growth during transfers between accelerators, transverse damper systems are used to eliminate residual dipole oscillations before phase space dilution takes place. In transfers where the target accelerator has high chromaticity or the beam has a large momentum spread, phase space dilution due to chromatic decoherence can take place on a scale short compared to the damping time of the transverse injection oscillation damper. The effect of the damper on the beam phase space is not clear while the coherent oscillation is suppressed by this decoherence. The purpose of this paper is to quantify the effectiveness of dampers at eliminating emittance blowup at transfers in the presence of chromatic decoherence

  11. An application of eddy current damping effect on single point diamond turning of titanium alloys

    Science.gov (United States)

    Yip, W. S.; To, S.

    2017-11-01

    Titanium alloys Ti6Al4V (TC4) have been popularly applied in many industries. They have superior material properties including an excellent strength-to-weight ratio and corrosion resistance. However, they are regarded as difficult to cut materials; serious tool wear, a high level of cutting vibration and low surface integrity are always involved in machining processes especially in ultra-precision machining (UPM). In this paper, a novel hybrid machining technology using an eddy current damping effect is firstly introduced in UPM to suppress machining vibration and improve the machining performance of titanium alloys. A magnetic field was superimposed on samples during single point diamond turning (SPDT) by exposing the samples in between two permanent magnets. When the titanium alloys were rotated within a magnetic field in the SPDT, an eddy current was generated through a stationary magnetic field inside the titanium alloys. An eddy current generated its own magnetic field with the opposite direction of the external magnetic field leading a repulsive force, compensating for the machining vibration induced by the turning process. The experimental results showed a remarkable improvement in cutting force variation, a significant reduction in adhesive tool wear and an extreme long chip formation in comparison to normal SPDT of titanium alloys, suggesting the enhancement of the machinability of titanium alloys using an eddy current damping effect. An eddy current damping effect was firstly introduced in the area of UPM to deliver the results of outstanding machining performance.

  12. An application of eddy current damping effect on single point diamond turning of titanium alloys

    International Nuclear Information System (INIS)

    Yip, W S; To, S

    2017-01-01

    Titanium alloys Ti6Al4V (TC4) have been popularly applied in many industries. They have superior material properties including an excellent strength-to-weight ratio and corrosion resistance. However, they are regarded as difficult to cut materials; serious tool wear, a high level of cutting vibration and low surface integrity are always involved in machining processes especially in ultra-precision machining (UPM). In this paper, a novel hybrid machining technology using an eddy current damping effect is firstly introduced in UPM to suppress machining vibration and improve the machining performance of titanium alloys. A magnetic field was superimposed on samples during single point diamond turning (SPDT) by exposing the samples in between two permanent magnets. When the titanium alloys were rotated within a magnetic field in the SPDT, an eddy current was generated through a stationary magnetic field inside the titanium alloys. An eddy current generated its own magnetic field with the opposite direction of the external magnetic field leading a repulsive force, compensating for the machining vibration induced by the turning process. The experimental results showed a remarkable improvement in cutting force variation, a significant reduction in adhesive tool wear and an extreme long chip formation in comparison to normal SPDT of titanium alloys, suggesting the enhancement of the machinability of titanium alloys using an eddy current damping effect. An eddy current damping effect was firstly introduced in the area of UPM to deliver the results of outstanding machining performance. (paper)

  13. Travelling Solitons in the Damped Driven Nonlinear Schroedinger Equation

    CERN Document Server

    Barashenkov, I V

    2003-01-01

    The well-known effect of the linear damping on the moving nonlinear Schrodinger soliton (even when there is energy supply via the spatially homogeneous driving) is to quench its momentum to zero. Surprisingly, the zero momentum does not necessarily mean zero velocity. We show that two or more parametrically driven damped solitons can form a complex travelling with zero momentum at a nonzero constant speed. All travelling complexes we have found so far, turned out to be unstable. Thus, the parametric driving is capable of sustaining the uniform motion of damped solitons, but some additional agent is required to make this motion stable.

  14. Travelling solitons in the damped driven nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Barashenkov, I.V.; Zemlyanaya, E.V.

    2003-01-01

    The well known effect of the linear damping on the moving nonlinear Schroedinger soliton (even when there is energy supply via the spatially homogeneous driving) is to quench its momentum to zero. Surprisingly, the zero momentum does not necessarily mean zero velocity. We show that two or more parametrically driven damped solitons can form a complex travelling with zero momentum at a nonzero constant speed. All travelling complexes we have found so far, turned out to be unstable. Thus, the parametric driving is capable of sustaining the uniform motion of damped solitons, but some additional agent is required to make this motion stable

  15. The effect of inertia, viscous damping, temperature and normal ...

    Indian Academy of Sciences (India)

    Nitish Sinha

    2018-04-16

    Apr 16, 2018 ... physical parameters such as inertia, viscous damping, temperature and normal stress on the chaotic ... However, the present study has shown the appearance of chaos for the specific .... Although chaos is a general man-.

  16. Comparative study of popular objective functions for damping power system oscillations in multimachine system.

    Science.gov (United States)

    Islam, Naz Niamul; Hannan, M A; Shareef, Hussain; Mohamed, Azah; Salam, M A

    2014-01-01

    Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode's performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.

  17. Energy dependence of the emittance of damping ring beams

    International Nuclear Information System (INIS)

    Stiening, R.

    1985-01-01

    The energy at which the SLC damping rings are operated was chosen to be 1.21 GeV. At the time that that specification was made, the repetition rate of the SLC was expected to be 180 Hz. It is now anticipated that the repetition rate during the initial year of operation of the SLC will be 120 Hz. The following curves which show the output emittance of the damping rings as a function of input emittance and energy suggest that there is a range of energies over which the rings can be operated without changing the SLC luminosity. It should be noted that in the era of polarized beams, the damping ring energy will be fixed at the design value on account of the spin precession required in the LTR and RTL transport lines. The SLC design output emittance of the damping rings is 3 x 10 -5 radian-meters. Because of space charge disruption and quantum emission downstream of the damping rings, much lower values than the design value may not have a large beneficial effect on the luminosity. 3 figures

  18. Equivalent Representation Form of Oscillators with Elastic and Damping Nonlinear Terms

    Directory of Open Access Journals (Sweden)

    Alex Elías-Zúñiga

    2013-01-01

    Full Text Available In this work we consider the nonlinear equivalent representation form of oscillators that exhibit nonlinearities in both the elastic and the damping terms. The nonlinear damping effects are considered to be described by fractional power velocity terms which provide better predictions of the dissipative effects observed in some physical systems. It is shown that their effects on the system dynamics response are equivalent to a shift in the coefficient of the linear damping term of a Duffing oscillator. Then, its numerical integration predictions, based on its equivalent representation form given by the well-known forced, damped Duffing equation, are compared to the numerical integration values of its original equations of motion. The applicability of the proposed procedure is evaluated by studying the dynamics response of four nonlinear oscillators that arise in some engineering applications such as nanoresonators, microresonators, human wrist movements, structural engineering design, and chain dynamics of polymeric materials at high extensibility, among others.

  19. Quantitative analysis of the thermal damping of coherent axion oscillations

    International Nuclear Information System (INIS)

    Turner, M.S.

    1985-01-01

    Unruh and Wald have recently discussed a new mechanism for damping coherent axion oscillations, ''thermal damping,'' which occurs due to the temperature dependence of the axion mass and neutrino viscosity. We investigate the effect quantitatively and find that the present energy density in axions can be written as rho/sub a/ = rho/sub a0//(1+J/sub UW/), where rho/sub a/0 is what the axion energy density would be in the absence of the thermal-damping effect and J/sub UW/ is an integral whose integrand depends upon (dm/sub a//dT) 2 . As a function of f(equivalentPeccei-Quinn symmetry-breaking scale) J/sub UW/ achieves its maximum value for f/sub PQ/approx. =3 x 10 12 GeV; unless the axion mass turn-on is very sudden, Vertical Bar(T/m/sub a/)(dm/sub a//dT)Vertical Bar>>1, J/sub UW/ is <<1, implying that this damping mechanism is not significant

  20. An experimental study on damping characteristics of mechanical snubber for nuclear power plant piping systems

    International Nuclear Information System (INIS)

    Chiba, T.; Kobayashi, H.; Kitamura, K.; Ando, K.; Koyanagi, R.

    1983-01-01

    The objectives of this study are 1) to clarify the damping characteristics and the dynamic stiffness of mechanical snubber, 2) to take the damping characteristics of mechanical snubber into the damping evaluation method obtained in SDREP. Therefore, following vibration tests were conducted. 1) Component test: As a first step, mechanical snubbers were excited with sinusoidal wave, and damping ratio and dynamic stiffness were measured at several loading levels. 2) Piping model test: Second, a 8'' diameter x 16 m length 3-dimensional piping model simulating the supporting conditions of actual piping systems was tested. Damping ratio and made shapes of piping model with mechanical snubbers were measured at several supporting conditions and response levels. From the results of these tests, the damping characteristics and the dynamic stiffness of mechanical snubber can be summarized as follows: 1) The damping effect of mechanical snubber is as strong as that of oil snubber. 2) Mechanical snubber contributes effectively to the damping of piping system, and it is indicated that the damping characteristics of mechanical snubber is applicable to the damping evaluation method obtained in SDREP. (orig./HP)

  1. Modelling of Dampers and Damping in Structures

    DEFF Research Database (Denmark)

    Høgsberg, Jan Riess

    2006-01-01

    and the maximum attainable damping are found by maximizing the expression for the damping ratio. The theory is formulated for linear damper models, but may also be applied for non-linear dampers in terms of equivalent linear parameters for stiffness and damping, respectively. The format of the expressions......, and thereby the damping, of flexible structures are generally described in terms of the dominant vibration modes. A system reduction technique, where the damped vibration mode is constructed as a linear combination of the undamped mode shape and the mode shape obtained by locking the damper, is applied....... This two-component representation leads to a simple solution for the modal damping representing the natural frequency and the associated damping ratio. It appears from numerical examples that this system reduction technique provides very accurate results. % Analytical expressions for the optimal tuning...

  2. Requirements for longitudinal HOM damping in superconducting recirculating linacs

    International Nuclear Information System (INIS)

    Bisognano, J.J.; Fripp, M.L.

    1989-01-01

    Transverse beam breakup provides the primary current limitation in the operation of superconducting recirculating linacs and requires the significant damping of transverse-deflecting higher order modes. The need to damp the coexisting longitudinal HOMs in these nominally isochronous machines, however, is not as clear. Isochronicity implies that energy variations induced by excitation of longitudinal modes do not translate directly into position and current modulations. Such modulations, if present, could enhance the initial excitation, effectively closing a potentially unstable feedback loop. Design optimization of cavity structures may suggest that no longitudinal damping be provided. On the other hand, easing of the isochronicity requirement may provide desired flexibility in lattice design. In this note, limits are placed on the requirements for longitudinal HOM damping and on the tolerances for isochronicity which are driven by possible longitudinal multipass phenomena. 2 refs., 1 fig

  3. An approach for including the stiffness and damping of elastohydrodynamic point contacts in deep groove ball bearing equilibrium models

    Science.gov (United States)

    Nonato, Fábio; Cavalca, Katia L.

    2014-12-01

    This work presents a methodology for including the Elastohydrodynamic (EHD) film effects to a lateral vibration model of a deep groove ball bearing by using a novel approximation for the EHD contacts by a set of equivalent nonlinear spring and viscous damper. The fitting of the equivalent contact model used the results of a transient multi-level finite difference EHD algorithm to adjust the dynamic parameters. The comparison between the approximated model and the finite difference simulated results showed a suitable representation of the stationary and dynamic contact behaviors. The linear damping hypothesis could be shown as a rough representation of the actual hysteretic behavior of the EHD contact. Nevertheless, the overall accuracy of the model was not impaired by the use of such approximation. Further on, the inclusion of the equivalent EHD contact model is equated for both the restoring and the dissipative components of the bearing's lateral dynamics. The derived model was used to investigate the effects of the rolling element bearing lubrication on the vibration response of a rotor's lumped parameter model. The fluid film stiffening effect, previously only observable by experimentation, could be quantified using the proposed model, as well as the portion of the bearing damping provided by the EHD fluid film. Results from a laboratory rotor-bearing test rig were used to indirectly validate the proposed contact approximation. A finite element model of the rotor accounting for the lubricated bearing formulation adequately portrayed the frequency content of the bearing orbits observed on the test rig.

  4. Surge-damping vacuum valve

    International Nuclear Information System (INIS)

    Bullock, J.C.; Kelley, B.E.

    1977-01-01

    A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve

  5. Advances in the SLAC RDDS: Modeling Manifold Damping and its Effect on the Wakefield for the Next Linear Collider

    International Nuclear Information System (INIS)

    Jones, Roger M

    2000-01-01

    The RDDS (Rounded Damped Detuned Structure) accelerator damps the transverse wakefield excited by bunches of electrons traversing thousands of linear accelerator structures. Errors in the fabrication of the cells which constitute each structure can result in a wakefield which is resonantly driven by the bunches, leading to BBU (Beam Break Up) and to a substantial growth in the beam emittance. One means to avoid these deleterious effects is to provide additional damping of the manifold, via plating the walls of the manifold with an electrically lossy material such as canthol or by fabricating the wall with stainless steel rather than copper. Results are presented on the wakefield and emittance growth in structures with a moderately lossy manifold

  6. Toroidal effects on propagation, damping, and linear mode conversion of lower hybrid waves

    International Nuclear Information System (INIS)

    Ignat, D.W.

    1980-09-01

    A common simplifying assumption made in the consideration of radio-frequency heating of tokamaks near the lower hybrid frequency is that the wave-length imposed by the coupling device parallel to the magnetic field is not modified by gradients along the field. In the present calculation, the parallel wave-length is allowed to vary, and important effects are found on wave penetration and damping if the toroidal aspect ratio (R/sub major//r/sub minor/) is less than approx. 5. The calculation shows that heating at the center of a small aspect ratio torus is inhibited by a decrease of k/sub parallel/ if waves are launched at the outside, and that it may be possible to change the plasma current via electron Landau damping with a coupler of symmetric power spectrum by placing the coupler at the top (or bottom) of the torus

  7. Effective mass and damping of submerged structures

    International Nuclear Information System (INIS)

    Dong, R.G.

    1979-01-01

    A number of structures important for safety in nuclear power plants are submerged in water. These include spent fuel storage racks, main pressure relief valve lines, and internal structures in the reactor vessel. Dynamic analyses of such structures must include the force and damping effects of water. A wide variety of modeling assumptions are being used in design analyses, and currently there are no uniform positions by which to judge the adequacy of the assumptions . A study was caried out to establish a technical basis for evaluating the assymptions and to recommend suitable methods to describe the effects of the water. The results of the study were based on information published in the literature or conveyed by industrial firms. A survey of 32 firms and 49 technical references was carried out. Heavy emphasis was placed on validating the results with available experimental data. The information collected apply generally to idealized structures such as single isolated members, arrays of members and coaxial cylinders. The results of the study are categorized with respect to such idealized structures, and the applicability to actual reactor structures was discussed through observations and recommendations. (orig.)

  8. Dynamic response analysis of a 24-story damped steel structure

    Science.gov (United States)

    Feng, Demin; Miyama, Takafumi

    2017-10-01

    In Japanese and Chinese building codes, a two-stage design philosophy, damage limitation (small earthquake, Level 1) and life safety (extreme large earthquake, Level 2), is adopted. It is very interesting to compare the design method of a damped structure based on the two building codes. In the Chinese code, in order to be consistent with the conventional seismic design method, the damped structure is also designed at the small earthquake level. The effect of damper systems is considered by the additional damping ratio concept. The design force will be obtained from the damped design spectrum considering the reduction due to the additional damping ratio. The additional damping ratio by the damper system is usually calculated by a time history analysis method at the small earthquake level. The velocity dependent type dampers such as viscous dampers can function well even in the small earthquake level. But, if steel damper is used, which usually remains elastic in the small earthquake, there will be no additional damping ratio achieved. On the other hand, a time history analysis is used in Japan both for small earthquake and extreme large earthquake level. The characteristics of damper system and ductility of the structure can be modelled well. An existing 24-story steel frame is modified to demonstrate the design process of the damped structure based on the two building codes. Viscous wall type damper and low yield steel panel dampers are studied as the damper system.

  9. WAMS Based Damping Control of Inter-area Oscillations Employing Energy Storage System

    Directory of Open Access Journals (Sweden)

    MA, J.

    2012-05-01

    Full Text Available This paper presents a systematic design procedure for a wide-area damping controller (WADC employing Energy Storage Systems (ESSs. The WADC is aimed at enhancing the damping of multiple inter-area modes in a large scale power system. Firstly, geometric measures of controllability and obsevability are used to select the control locations for ESSs and most effective stabilizing signals, respectively. Then, the WADC coordinates these signals to achieve multiple-input-multiple-output (MIMO controllers with the least Frobenius norm feedback gain matrix. The simulation results of frequency and time domains verify the effectiveness of the wide-area damping controller for various operating conditions. Furthermore, the robustness of the wide-area damping controller is also tested with respect to time delay and uncertainty of models.

  10. Energy spread in SLC linac with Landau damping

    International Nuclear Information System (INIS)

    Seeman, J.

    1984-01-01

    The possibility of using Landau damping to reduce the growth of the beam size due to transverse wake fields has been known for some time. Recently K. Bane has calculated the effects of Landau damping for the SLC. The energy spread is then slowly removed so that at the end of the linac it has returned to the SLC specification of less than +0.5%. The purpose of the energy spread is to reduce the resonant driving of the tail of the bunch by the head. In this note the expected energy spreads within the beam are tabulated at various positions along the linac for use by those people designing momentum dependent equipment and for those interested in Landau damping

  11. Effect of substitutional defects on Kambersky damping in L1{sub 0} magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Qu, T. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Victora, R. H., E-mail: victora@umn.edu [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2015-02-16

    Kambersky damping, representing the loss of magnetic energy from the electrons to the lattice through the spin orbit interaction, is calculated for L1{sub 0} FePt, FePd, CoPt, and CoPd alloys versus chemical degree of order. When more substitutional defects exist in the alloys, damping is predicted to increase due to the increase of the spin-flip channels allowed by the broken symmetry. It is demonstrated that this corresponds to an enhanced density of states (DOS) at the Fermi level, owing to the rounding of the DOS with loss of long-range order. Both the damping and the DOS of the Co-based alloy are found to be less affected by the disorder. Pd-based alloys are predicted to have lower damping than Pt-based alloys, making them more suitable for high density spintronic applications.

  12. WAKEFIELD DAMPING FOR THE CLIC CRAB CAVITY

    CERN Document Server

    Ambattu, P; Dexter, A; Carter, R; Khan, V; Jones, R; Dolgashev, V

    2009-01-01

    A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively.

  13. Damping rates of the SRRC storage ring

    International Nuclear Information System (INIS)

    Hsu, K.T.; Kuo, C.C.; Lau, W.K.; Weng, W.T.

    1995-01-01

    The SRRC storage ring is a low emittance synchrotron radiation machine with nominal operation energy 1.3 GeV. The design damping time due to synchrotron radiation is 10.7, 14.4, 8.7 ms for the horizontal, vertical and longitudinal plane, respectively. The authors measured the real machine damping time as a function of bunch current, chromaticity, etc. To damp the transverse beam instability, especially in the vertical plane, they need to increase chromaticity to large positive value. The damping rates are much larger than the design values. Landau damping contribution in the longitudinal plane is quite large, especially in the multibunch mode. The estimated synchrotron tune spread from the Landau damping is in agreement with the measured coherent longitudinal coupled bunch oscillation amplitude

  14. Landau damping of dust acoustic solitary waves in nonthermal plasmas

    Science.gov (United States)

    Ghai, Yashika; Saini, N. S.; Eliasson, B.

    2018-01-01

    Dust acoustic (DA) solitary and shock structures have been investigated under the influence of Landau damping in a dusty plasma containing two temperature nonthermal ions. Motivated by the observations of Geotail spacecraft that reported two-temperature ion population in the Earth's magnetosphere, we have investigated the effect of resonant wave-particle interactions on DA nonlinear structures. The Korteweg-de Vries (KdV) equation with an additional Landau damping term is derived and its analytical solution is presented. The solution has the form of a soliton whose amplitude decreases with time. Further, we have illustrated the influence of Landau damping and nonthermality of the ions on DA shock structures by a numerical solution of the Landau damping modified KdV equation. The study of the time evolution of shock waves suggests that an initial shock-like pulse forms an oscillatory shock at later times due to the balance of nonlinearity, dispersion, and dissipation due to Landau damping. The findings of the present investigation may be useful in understanding the properties of nonlinear structures in the presence of Landau damping in dusty plasmas containing two temperature ions obeying nonthermal distribution such as in the Earth's magnetotail.

  15. Magnetically tuned mass dampers for optimal vibration damping of large structures

    International Nuclear Information System (INIS)

    Bourquin, Frederic; Siegert, Dominique; Caruso, Giovanni; Peigney, Michael

    2014-01-01

    This paper deals with the theoretical and experimental analysis of magnetically tuned mass dampers, applied to the vibration damping of large structures of civil engineering interest. Two devices are analysed, for which both the frequency tuning ratio and the damping coefficient can be easily and finely calibrated. They are applied for the damping of the vibrations along two natural modes of a mock-up of a bridge under construction. An original analysis, based on the Maxwell receding image method, is developed for estimating the drag force arising inside the damping devices. It also takes into account self-inductance effects, yielding a complex nonlinear dependence of the drag force on the velocity. The analysis highlights the range of velocities for which the drag force can be assumed of viscous type, and shows its dependence on the involved geometrical parameters of the dampers. The model outcomes are then compared to the corresponding experimental calibration curves. A dynamic model of the controlled structure equipped with the two damping devices is presented, and used for the development of original optimization expressions and for determining the corresponding maximum achievable damping. Finally, several experimental results are presented, concerning both the free and harmonically forced vibration damping of the bridge mock-up, and compared to the corresponding theoretical predictions. The experimental results reveal that the maximum theoretical damping performance can be achieved, when both the tuning frequencies and damping coefficients of each device are finely calibrated according to the optimization expressions. (paper)

  16. Effects of Added Mass and Structural Damping on Dynamic Responses of a 3D Wedge Impacting on Water

    Directory of Open Access Journals (Sweden)

    Pengyao Yu

    2018-05-01

    Full Text Available The impact between the wave and the bottom of a high-speed vessel is often simplified as water-entry problems of wedges. Most investigations focus on the water entry of two dimensional (2D wedges. The effects of added mass and structural damping are still not fully investigated. By combining the normal mode method, the hydrodynamic impact model of rigid wedges and the potential flow theory, a dynamic model for predicting the response of a three dimensional (3D wedge impacting on water with a constant velocity is established in this paper. The present model can selectively consider the effects of the added mass and the structural damping. The present method has been validated through comparisons with results of published literatures and commercial software. It is found that the added mass can increase the stress response before the flow separation, and reduce the vibration frequency after the flow separation. Due to the effect of the added mass, the stress response of some positions after the flow separation is even higher than that before the flow separation. The structural damping has a negligible effect on the stress before the flow separation, but it can reduce vibration stress after the flow separation.

  17. Bounce-harmonic Landau Damping of Plasma Waves

    Science.gov (United States)

    Anderegg, Francois

    2015-11-01

    We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v vph / 5 . The measurements are conducted in trapped pure ion plasmas contained in Penning-Malmberg trap, with wave-coherent LIF diagnostics of particle velocities. Our focus is on bounce harmonics damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

  18. Next generation HOM-damping

    Science.gov (United States)

    Marhauser, Frank

    2017-06-01

    Research and development for superconducting radio-frequency cavities has made enormous progress over the last decades from the understanding of theoretical limitations to the industrial mass fabrication of cavities for large-scale particle accelerators. Key technologies remain hot topics due to continuously growing demands on cavity performance, particularly when in pursuit of high quality beams at higher beam currents or higher luminosities than currently achievable. This relates to higher order mode (HOM) damping requirements. Meeting the desired beam properties implies avoiding coupled multi-bunch or beam break-up instabilities depending on the machine and beam parameters that will set the acceptable cavity impedance thresholds. The use of cavity HOM-dampers is crucial to absorb the wakefields, comprised by all beam-induced cavity Eigenmodes, to beam-dynamically safe levels and to reduce the heat load at cryogenic temperature. Cavity damping concepts may vary, but are principally based on coaxial and waveguide couplers as well as beam line absorbers or any combination. Next generation energy recovery linacs and circular colliders call for cavities with strong HOM-damping that can exceed the state-of-the-art, while the operating mode efficiency shall not be significantly compromised concurrently. This imposes major challenges given the rather limited damping concepts. A detailed survey of established cavities is provided scrutinizing the achieved damping performance, shortcomings, and potential improvements. The scaling of the highest passband mode impedances is numerically evaluated in dependence on the number of cells for a single-cell up to a nine-cell cavity, which reveals the increased probability of trapped modes. This is followed by simulations for single-cell and five-cell cavities, which incorporate multiple damping schemes to assess the most efficient concepts. The usage and viability of on-cell dampers is elucidated for the single-cell cavity since it

  19. Identification of Damping from Structural Vibrations

    DEFF Research Database (Denmark)

    Bajric, Anela

    Reliable predictions of the dynamic loads and the lifetime of structures are influenced by the limited accuracy concerning the level of structural damping. The mechanisms of damping cannot be derived analytically from first principles, and in the design of structures the damping is therefore based...... on experience or estimated from measurements. This thesis consists of an extended summary and three papers which focus on enhanced methods for identification of damping from random struc-tural vibrations. The developed methods are validated by stochastic simulations, experimental data and full-scale measurements...... which are representative of the vibrations in small and large-scale structures. The first part of the thesis presents an automated procedure which is suitable for estimation of the natural frequencies and the modal damping ratios from random response of structures. The method can be incorporated within...

  20. On Landau damping

    KAUST Repository

    Mouhot, Clément

    2011-09-01

    Going beyond the linearized study has been a longstanding problem in the theory of Landau damping. In this paper we establish exponential Landau damping in analytic regularity. The damping phenomenon is reinterpreted in terms of transfer of regularity between kinetic and spatial variables, rather than exchanges of energy; phase mixing is the driving mechanism. The analysis involves new families of analytic norms, measuring regularity by comparison with solutions of the free transport equation; new functional inequalities; a control of non-linear echoes; sharp "deflection" estimates; and a Newton approximation scheme. Our results hold for any potential no more singular than Coulomb or Newton interaction; the limit cases are included with specific technical effort. As a side result, the stability of homogeneous equilibria of the non-linear Vlasov equation is established under sharp assumptions. We point out the strong analogy with the KAM theory, and discuss physical implications. Finally, we extend these results to some Gevrey (non-analytic) distribution functions. © 2011 Institut Mittag-Leffler.

  1. Shape memory alloys as damping materials

    International Nuclear Information System (INIS)

    Humbeeck, J. van

    2000-01-01

    Shape memory alloys are gaining an increased interest as passive as well as active damping materials. This damping ability when applied in structural elements can lead to a better noise control, improved life time and even better performance of the envisaged tools. By passive damping, it is understood that the material converts a significant part of unwanted mechanical energy into heat. This mechanical energy can be a (resonance) vibration, impact loading or shock waves. This high damping capacity finds its origin in the thermoelastic martensitic phase due to the hysteretic mobility of martensite-variants or different phase interfaces. The damping capacity increases with increasing amplitude of the applied vibration or impact and is almost frequency independent. Special interest exists moreover for damping extreme large displacements by applying the mechanical hysteresis performed during pseudoelastic loading. This aspect is nowadays very strongly studied as a tool for protecting buildings against earthquakes in seismic active regions. Active damping can be obtained in hybrid composites by controlling the recovery stresses or strains of embedded shape memory alloy wires. This controls the internal energy fo a structure which allows controlled modal modification and tuning of the dynamical properties of structural elements. But also impact damage, acoustic radiation, dynamic shape control can be actively controlled. As a consequence improved fatigue-resistance, better performance and a longer lifetime of the structural elements can be obtained. (orig.)

  2. Modified multiple time scale method for solving strongly nonlinear damped forced vibration systems

    Science.gov (United States)

    Razzak, M. A.; Alam, M. Z.; Sharif, M. N.

    2018-03-01

    In this paper, modified multiple time scale (MTS) method is employed to solve strongly nonlinear forced vibration systems. The first-order approximation is only considered in order to avoid complexicity. The formulations and the determination of the solution procedure are very easy and straightforward. The classical multiple time scale (MS) and multiple scales Lindstedt-Poincare method (MSLP) do not give desire result for the strongly damped forced vibration systems with strong damping effects. The main aim of this paper is to remove these limitations. Two examples are considered to illustrate the effectiveness and convenience of the present procedure. The approximate external frequencies and the corresponding approximate solutions are determined by the present method. The results give good coincidence with corresponding numerical solution (considered to be exact) and also provide better result than other existing results. For weak nonlinearities with weak damping effect, the absolute relative error measures (first-order approximate external frequency) in this paper is only 0.07% when amplitude A = 1.5 , while the relative error gives MSLP method is surprisingly 28.81%. Furthermore, for strong nonlinearities with strong damping effect, the absolute relative error found in this article is only 0.02%, whereas the relative error obtained by MSLP method is 24.18%. Therefore, the present method is not only valid for weakly nonlinear damped forced systems, but also gives better result for strongly nonlinear systems with both small and strong damping effect.

  3. Nanoscale shape-memory alloys for ultrahigh mechanical damping.

    Science.gov (United States)

    San Juan, Jose; Nó, Maria L; Schuh, Christopher A

    2009-07-01

    Shape memory alloys undergo reversible transformations between two distinct phases in response to changes in temperature or applied stress. The creation and motion of the internal interfaces between these phases during such transformations dissipates energy, making these alloys effective mechanical damping materials. Although it has been shown that reversible phase transformations can occur in nanoscale volumes, it is not known whether these transformations have a sample size dependence. Here, we demonstrate that the two phases responsible for shape memory in Cu-Al-Ni alloys are more stable in nanoscale pillars than they are in the bulk. As a result, the pillars show a damping figure of merit that is substantially higher than any previously reported value for a bulk material, making them attractive for damping applications in nanoscale and microscale devices.

  4. Fluid friction and wall viscosity of the 1D blood flow model.

    Science.gov (United States)

    Wang, Xiao-Fei; Nishi, Shohei; Matsukawa, Mami; Ghigo, Arthur; Lagrée, Pierre-Yves; Fullana, Jose-Maria

    2016-02-29

    We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Evaluation of spreading and effectiveness of injection products against rising damp in mortar damp in mortar/brick combinations. Youth in conservation of cultural heritage, YOCOCU 2012

    NARCIS (Netherlands)

    Hacquebord, A.; Lubelli, B.A.; Hees, R.P.J. van; Nijland, T.G.

    2013-01-01

    Rising damp is one of the most recurrent and well-known hazards to existing buildings and monuments. Several types of intervention exist to tackle the problem. Among these, the creation of a damp-proof course against capillary rise by means of injection of chemical products is one of the most

  6. The Use of the Artificial Damped Outrigger Systems in Tall R.C Buildings Under Seismic Loading

    Directory of Open Access Journals (Sweden)

    Abbas Abd Elmajeed Allawi

    2016-04-01

    Full Text Available This paper studies the combination of fluid viscous dampers in the outrigger system to add supplementary damping into the structure, which purpose to remove the dependability of the structure to lower variable intrinsic damping. This optimizes the accuracy of the dynamic response and by providing higher level of damping, basically minimizes the wanted stiffness of the structure while at the same time optimizing the achievement. The modal considered is a 36 storey square high rise reinforced concrete building. By constructing a discrete lumped mass model and using frequency-based response function, two systems of dampers, parallel and series systems are studied. The maximum lateral load at the top of the building is calculated, and this load will be applied at every floor of the building, giving a conservative solution. For dynamic study Response Spectrum Analysis was conducted and the behavior of the building was determined considering response parameters. MATLAB software, has been used in the dynamic analysis for three modes. For all modes, it is observed that the parallel system of dampers result in lower amplitude of vibration and achieved more efficiently compared to the damper is in series, until the parallel system arrives 100% damping for mode three.

  7. An Adaptive Damping Network Designed for Strapdown Fiber Optic Gyrocompass System for Ships

    Directory of Open Access Journals (Sweden)

    Jin Sun

    2017-03-01

    Full Text Available The strapdown fiber optic gyrocompass (strapdown FOGC system for ships primarily works on external horizontal damping and undamping statuses. When there are large sea condition changes, the system will switch frequently between the external horizontal damping status and the undamping status. This means that the system is always in an adjustment status and influences the dynamic accuracy of the system. Aiming at the limitations of the conventional damping method, a new design idea is proposed, where the adaptive control method is used to design the horizontal damping network of the strapdown FOGC system. According to the size of acceleration, the parameters of the damping network are changed to make the system error caused by the ship’s maneuvering to a minimum. Furthermore, the jump in damping coefficient was transformed into gradual change to make a smooth system status switch. The adaptive damping network was applied for strapdown FOGC under the static and dynamic condition, and its performance was compared with the conventional damping, and undamping means. Experimental results showed that the adaptive damping network was effective in improving the dynamic performance of the strapdown FOGC.

  8. DAMPING OF SUBSYNCHRONOUS MODES OF OSCILLATIONS

    Directory of Open Access Journals (Sweden)

    JAGADEESH PASUPULETI

    2006-06-01

    Full Text Available The IEEE bench mark model 2 series compensated system is considered for analysis. It consists of single machine supplying power to infinite bus through two parallel lines one of which is series compensated. The mechanical system considered consists of six mass, viz, high pressure turbine, intermediate pressure turbine, two low pressure turbines, generator and an exciter. The excitation system considered is IEEE type 1 with saturation. The auxiliary controls considered to damp the unstable subsynchronous modes of oscillations are Power System Stabilizer (PSS and Static var Compensator (SVC. The different cases of power system stabilizer and reactive power controls are adapted to study the effectiveness of damping these unstable subsynchronous modes of oscillations.

  9. Optimal design of a vehicle magnetorheological damper considering the damping force and dynamic range

    International Nuclear Information System (INIS)

    Nguyen, Quoc-Hung; Choi, Seung-Bok

    2009-01-01

    This paper presents an optimal design of a passenger vehicle magnetorheological (MR) damper based on finite element analysis. The MR damper is constrained in a specific volume and the optimization problem identifies the geometric dimensions of the damper that minimize an objective function. The objective function consists of the damping force, the dynamic range, and the inductive time constant of the damper. After describing the configuration of the MR damper, the damping force and dynamic range are obtained on the basis of the Bingham model of an MR fluid. Then, the control energy (power consumption of the damper coil) and the inductive time constant are derived. The objective function for the optimization problem is determined based on the solution of the magnetic circuit of the initial damper. Subsequently, the optimization procedure, using a golden-section algorithm and a local quadratic fitting technique, is constructed via commercial finite element method parametric design language. Using the developed optimization tool, optimal solutions of the MR damper, which are constrained in a specific cylindrical volume defined by its radius and height, are determined and a comparative work on damping force and inductive time constant between the initial and optimal design is undertaken

  10. Controllable outrigger damping system for high rise building with MR dampers

    Science.gov (United States)

    Wang, Zhihao; Chang, Chia-Ming; Spencer, Billie F., Jr.; Chen, Zhengqing

    2010-04-01

    A novel energy dissipation system that can achieve the amplified damping ratio for a frame-core tube structures is explored, where vertical dampers are equipped between the outrigger and perimeter columns. The modal characteristics of the structural system with linear viscous dampers are theoretically analyzed from the simplified finite element model by parametric analysis. The result shows that modal damping ratios of the first several modes can increase a lot with this novel damping system. To improve the control performance of system, the semi-active control devices, magnetorheological (MR) dampers, are adopted to develop a controllable outrigger damping system. The clipped optimal control with the linear-quadratic Gaussian (LQG) acceleration feedback is adopted in this paper. The effectiveness of both passive and semi-active control outrigger damping systems is evaluated through the numerical simulation of a representative tall building subjected to two typical earthquake records.

  11. Numerical evaluation of acoustic characteristics and their damping of a thrust chamber using a constant-volume bomb model

    Directory of Open Access Journals (Sweden)

    Jianxiu QIN

    2018-03-01

    Full Text Available In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation (FFT, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal (1L acoustic mode can be excited easily and is hard to be damped. The axial position of the central constant-volume bomb has little influence on the amplitude and damping capacity of the First Radial (1R and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential (1T mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber. Keywords: Acoustic mode, Constant-volume bomb, Damping characteristics, Damping factor, Half-power bandwidth, Pressure oscillation

  12. Particle Damping with Granular Materials for Multi Degree of Freedom System

    Directory of Open Access Journals (Sweden)

    Masanobu Inoue

    2011-01-01

    Full Text Available A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range.

  13. Study on optimum aseismic design of complex structure system focusing on damping effect

    International Nuclear Information System (INIS)

    Takahashi, Yoshitaka; Suzuki, Kohei

    1995-01-01

    Optimum design technique for the purpose of aseismic design of complex plant structures such as piping and boiler structures is proposed. Particular attention is focused on the evaluation of the optimum damping and stiffness of the structures and components. Pseudo least square algorithm is introduced to determine the optimum design parameters. Under the requirement of certain allowable maximum response to a given earthquake excitation, optimum stiffness and damping values of the structure can be simultaneously calculated by this proposed method. The applicability of the method is demonstrated through three structural models; (1) linear multi-storied building model in which stiffness and damping constant of each floor are optimized; (2) nonlinear multi-storied building model having the isolated floor in which hysteretic energy absorber of the isolator is optimized; (3) combined boiler-supporting structure model connected by the inelastic seismic ties with each other is optimized. In this model, optimum values of damping characteristic of the seismic ties are evaluated. This work is particularly important for the aseismic design of complex plant structures like integrated boiler-supporting structure in thermal power plant and piping-containment vessel structure in nuclear power plant

  14. Thermoelastic Damping in FGM Nano-Electromechanical System in Axial Vibration Based on Eringen Nonlocal Theory

    Science.gov (United States)

    Rahimi, Z.; Rashahmadi, S.

    2017-11-01

    The thermo-elastic damping is a dominant source of internal damping in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS). The internal damping cannot neither be controlled nor minimized unless either mechanical or geometrical properties are changed. Therefore, a novel FGMNEM system with a controllable thermo-elastic damping of axial vibration based on Eringen nonlocal theory is considered. The effects of different parameter like the gradient index, nonlocal parameter, length of nanobeam and ambient temperature on the thermo-elastic damping quality factor are presented. It is shown that the thermo-elastic damping can be controlled by changing different parameter.

  15. Influence of wire EDM parameters on the damping behaviour of A356.2 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Dora Siva, E-mail: dorasivaprasad@gmail.com [Dept of Mechanical Engineering, GITAM University, Visakhapatnam, 530045 (India); Shoba, Chintada [Dept of Industrial Engineering, GITAM University, Visakhapatnam, 530045 (India); Varma, Kalidindi Rahul [Dept of Mechanical Engineering, RAGHU College of Engineering, Visakhapatnam (India); Khurshid, Abdul [M.Tech (CAD/CAM), Dept of Mechanical Engineering, GITAM University, Visakhapatnam, 530045 (India)

    2015-10-15

    The effect of different Wire electrical discharge machining (WEDM) process parameters on the damping behavior of A356.2 aluminum alloy is investigated. In the present investigation pulse on time (T{sub ON}), pulse off time (T{sub OFF}) and peak current (IP) which are considered to be the most significant process parameters from the previous studies are varied using one factor at a time approach, to study the effect on damping behavior of A356.2 aluminum alloy. Damping experiments are performed on a dynamic mechanical analyzer (DMA 8000) at constant strain under dual cantilever mode over a frequency range of 1–100 Hz at room temperature. The scanning electron microscope was used for characterization of the wire EDMed samples. Experimental results reveal that the damping behavior greatly depends on the wire EDM process parameters. The related mechanisms are presented. - Highlights: • Damping capacity increase with the increase in frequency. • Increasing pulse on time increases the damping capacity of aluminum alloy. • The damping capacity was found to decrease with the increase in pulse off time. • No significant change in damping capacity was noticed with varied peak current. • The formation of white layer plays an important role in the damping behavior.

  16. Stability analysis of internally damped rotating composite shafts using a finite element formulation

    Science.gov (United States)

    Ben Arab, Safa; Rodrigues, José Dias; Bouaziz, Slim; Haddar, Mohamed

    2018-04-01

    This paper deals with the stability analysis of internally damped rotating composite shafts. An Euler-Bernoulli shaft finite element formulation based on Equivalent Single Layer Theory (ESLT), including the hysteretic internal damping of composite material and transverse shear effects, is introduced and then used to evaluate the influence of various parameters: stacking sequences, fiber orientations and bearing properties on natural frequencies, critical speeds, and instability thresholds. The obtained results are compared with those available in the literature using different theories. The agreement in the obtained results show that the developed Euler-Bernoulli finite element based on ESLT including hysteretic internal damping and shear transverse effects can be effectively used for the stability analysis of internally damped rotating composite shafts. Furthermore, the results revealed that rotor stability is sensitive to the laminate parameters and to the properties of the bearings.

  17. Numerical study on aerodynamic damping of floating vertical axis wind turbines

    Science.gov (United States)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen; Moan, Torgeir

    2016-09-01

    Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover, the aerodynamic damping is almost independent of the rotor azimuth angle, and is to some extent sensitive to the blade number.

  18. Charged-particle incoherent-motion damping in storage rings by means of dissipative elements

    International Nuclear Information System (INIS)

    Derbenev, Ya.S.; Khejfets, S.A.

    1979-01-01

    In consecutive order a possibility of damping of beam incoherent oscillations in a storage ring was studied by means of an external dissipative system in a sufficient common case. It is shown, that a useful effect, as for the case of electron cooling, is one-particle effect of particle oscillations damping due to nonconservatism of its interaction with an external system. Each other mutual influence through the external system becomes significant with increasing beam density and results in the limitation to achievable damping decrements

  19. Choke-mode damped structure design for the Compact Linear Collider main linac

    CERN Document Server

    Zha, Hao; Grudiev, Alexej; Huang, Wenhui; Shi, Jiaru; Tang, Chuanxiang; Wuensch, Walter

    2012-01-01

    Choke-mode damped structures are being studied as an alternative design to waveguide damped structures for the main linac of the Compact Linear Collider (CLIC). Choke-mode structures have the potential for lower pulsed temperature rise and simpler and less expensive fabrication. An equivalent circuit model based on transmission line theory for higher-order-mode damping is presented. Using this model, a new choke geometry is proposed and the wakefield performance is verified using GDFIDL. This structure has a comparable wakefield damping effect to the baseline design which uses waveguide damping. A prototype structure with the same iris dimensions and accelerating gradient as the nominal CLIC design, but with the new choke geometry, has been designed for high-power tests. DOI: 10.1103/PhysRevSTAB.15.122003

  20. Nonlinear damping based semi-active building isolation system

    Science.gov (United States)

    Ho, Carmen; Zhu, Yunpeng; Lang, Zi-Qiang; Billings, Stephen A.; Kohiyama, Masayuki; Wakayama, Shizuka

    2018-06-01

    Many buildings in Japan currently have a base-isolation system with a low stiffness that is designed to shift the natural frequency of the building below the frequencies of the ground motion due to earthquakes. However, the ground motion observed during the 2011 Tohoku earthquake contained strong long-period waves that lasted for a record length of 3 min. To provide a novel and better solution against the long-period waves while maintaining the performance of the standard isolation range, the exploitation of the characteristics of nonlinear damping is proposed in this paper. This is motivated by previous studies of the authors, which have demonstrated that nonlinear damping can achieve desired performance over both low and high frequency regions and the optimal nonlinear damping force can be realized by closed loop controlled semi-active dampers. Simulation results have shown strong vibration isolation performance on a building model with identified parameters and have indicated that nonlinear damping can achieve low acceleration transmissibilities round the structural natural frequency as well as the higher ground motion frequencies that have been frequently observed during most earthquakes in Japan. In addition, physical building model based laboratory experiments are also conducted, The results demonstrate the advantages of the proposed nonlinear damping technologies over both traditional linear damping and more advanced Linear-Quadratic Gaussian (LQG) feedback control which have been used in practice to address building isolation system design and implementation problems. In comparison with the tuned-mass damper and other active control methods, the proposed solution offers a more pragmatic, low-cost, robust and effective alternative that can be readily installed into the base-isolation system of most buildings.

  1. Nonlinear damping of drift waves by strong flow curvature

    International Nuclear Information System (INIS)

    Sidikman, K.L.; Carreras, B.A.; Garcia, L.; Diamond, P.H.

    1993-01-01

    A single-equation model has been used to study the effect of a fixed poloidal flow (V 0 ) on turbulent drift waves. The electron dynamics come from a laminar kinetic equation in the dissipative trapped-electron regime. In the past, the authors have assumed that the mode frequency is close to the drift-wave frequency. Trapped-electron density fluctuations are then related to potential fluctuations by an open-quotes iδclose quotes term. Flow shear (V 0 ') and curvature (V 0 double-prime) both have a stabilizing effect on linear modes for this open-quotes iδclose quotes model. However, in the nonlinear regime, single-helicity effects inhibit the flow damping. Neither V 0 ' nor V 0 double-prime produces a nonlinear damping effect. The above assumption on the frequency can be relaxed by including the electron time-response in the linear part of the evolution. In this time-dependent model, instability drive due to trapped electrons is reduced when mode frequency is greater than drift-wave frequency. Since V 0 double-prime produces such a frequency shift, its linear effect is enhanced. There is also nonlinear damping, since single-helicity effects do not eliminate the shift. Renormalized theory for this model predicts nonlinear stability for sufficiently large curvature. Single-helicity calculations have already shown nonlinear damping, and this strong V 0 double-prime regime is being explored. In the theory, the Gaussian shape of the nonlinear diffusivity is expanded to obtain a quadratic potential. The implications of this assumption will be tested by solving the full renormalized equation using a shooting method

  2. The Duffing oscillator with damping

    DEFF Research Database (Denmark)

    Johannessen, Kim

    2015-01-01

    An analytical solution to the differential equation describing the Duffing oscillator with damping is presented. The damping term of the differential equation and the initial conditions satisfy an algebraic equation, and thus the solution is specific for this type of damping. The nonlinear term...... of the differential equation is allowed to be considerable compared to the linear term. The solution is expressed in terms of the Jacobi elliptic functions by including a parameter-dependent elliptic modulus. The analytical solution is compared to the numerical solution, and the agreement is found to be very good....... It is established that the period of oscillation is shorter compared to that of a linearized model but increasing with time and asymptotically approaching the period of oscillation of the linear damped model. An explicit expression for the period of oscillation has been derived, and it is found to be very accurate....

  3. Swing damped movement of suspended objects

    International Nuclear Information System (INIS)

    Jones, J.F.; Petterson, B.J.; Werner, J.C.

    1990-01-01

    Transportation of large objects such as nuclear waste shipping casks using overhead cranes can induce pendular motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop are obtainable. This report reviews the theory associated with formulating such oscillation damped trajectories for a simply suspended object (e.g., simple pendulum). In addition, the use of force servo damping to eliminate initial oscillation of simply suspended objects is discussed. This is often needed to provide a well defined initial state for the system prior to executing an oscillation damped move. Also included are descriptions of experiments using a CIMCORP XR6100 gantry robot and results from these experiments. Finally, sources of error resulting in small residual oscillations are identified and possible solutions presented

  4. Topology Optimization of Constrained Layer Damping on Plates Using Method of Moving Asymptote (MMA Approach

    Directory of Open Access Journals (Sweden)

    Zheng Ling

    2011-01-01

    Full Text Available Damping treatments have been extensively used as a powerful means to damp out structural resonant vibrations. Usually, damping materials are fully covered on the surface of plates. The drawbacks of this conventional treatment are also obvious due to an added mass and excess material consumption. Therefore, it is not always economical and effective from an optimization design view. In this paper, a topology optimization approach is presented to maximize the modal damping ratio of the plate with constrained layer damping treatment. The governing equation of motion of the plate is derived on the basis of energy approach. A finite element model to describe dynamic performances of the plate is developed and used along with an optimization algorithm in order to determine the optimal topologies of constrained layer damping layout on the plate. The damping of visco-elastic layer is modeled by the complex modulus formula. Considering the vibration and energy dissipation mode of the plate with constrained layer damping treatment, damping material density and volume factor are considered as design variable and constraint respectively. Meantime, the modal damping ratio of the plate is assigned as the objective function in the topology optimization approach. The sensitivity of modal damping ratio to design variable is further derived and Method of Moving Asymptote (MMA is adopted to search the optimized topologies of constrained layer damping layout on the plate. Numerical examples are used to demonstrate the effectiveness of the proposed topology optimization approach. The results show that vibration energy dissipation of the plates can be enhanced by the optimal constrained layer damping layout. This optimal technology can be further extended to vibration attenuation of sandwich cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles as an

  5. Biomolecular ligands screening using radiation damping difference WaterLOGSY spectroscopy

    International Nuclear Information System (INIS)

    Sun Peng; Jiang Xianwang; Jiang Bin; Zhang Xu; Liu Maili

    2013-01-01

    Water-ligand observed via gradient spectroscopy (WaterLOGSY) is a widely used nuclear magnetic resonance method for ligand screening. The crucial procedure for the effectiveness of WaterLOGSY is selective excitation of the water resonance. The selective excitation is conventionally achieved by using long selective pulse, which causes partial saturation of the water magnetization leading to reduction of sensitivity, in addition to time consuming and error prone. Therefore, many improvements have been made to enhance the sensitivity and robustness of the method. Here we propose an alternative selective excitation scheme for WaterLOGSY by utilizing radiation damping effect. The pulse scheme starts simply with a hard inversion pulse, instead of selective pulse or pulse train, followed by a pulse field gradient to control the radiation damping effect. The rest parts of the pulse scheme are similar to conventional WaterLOGSY. When the gradient pulse is applied immediately after the inversion pulse, the radiation damping effect is suppressed, and all of the magnetization is inversed. When the gradient pulse and the inversion pulse are about 10–20 ms apart, the radiation damping effect remains active and drives the water magnetization toward +z-axis, resulting in selective non-inversion of the water magnetization. By taking the differences of the spectra obtained under these two conditions, one should get the result of WaterLOGSY. The method is demonstrated to be simple, robust and sensitive for ligand screening

  6. Damping Estimation of Friction Systems in Random Vibrations

    DEFF Research Database (Denmark)

    Friis, Tobias; Katsanos, Evangelos; Amador, Sandro

    Friction is one of the most efficient and economical mechanisms to reduce vibrations in structural mechanics. However, the estimation of the equivalent linear damping of the friction damped systems in experimental modal analysis and operational modal analysis can be adversely affected by several...... assumptions regarding the definition of the linear damping and the identification methods or may be lacking a meaningful interpretation of the damping. Along these lines, this project focuses on assessing the potential to estimate efficiently the equivalent linear damping of friction systems in random...

  7. Emittance damping considerations for TESLA

    International Nuclear Information System (INIS)

    Floettmann, K.; Rossbach, J.

    1993-03-01

    Two schemes are considered to avoid very large damping rings for TESLA. The first (by K.F.) makes use of the linac tunnel to accomodate most of the damping 'ring' structure, which is, in fact, not a ring any more but a long linear structure with two small bends at each of its ends ('dog-bone'). The other scheme (by J.R.) is based on a positron (or electron, respectively) recycling scheme. It makes use of the specific TESLA property, that the full bunch train is much longer (240 km) than the linac length. The spent beams are recycled seven times after interaction, thus reducing the number of bunches to be stored in the damping ring by a factor of eight. Ultimately, this scheme can be used to operate TESLA in a storage ring mode ('storage linac'), with no damping ring at all. Finally, a combination of both schemes is considered. (orig.)

  8. Lagrangian finite element formulation for fluid-structure interaction and application

    International Nuclear Information System (INIS)

    Hautfenne, M.H.

    1983-01-01

    The aim of this communication is to present a new finite element software (FLUSTRU) for fluid-structure interaction in a lagrangian formulation. The stiffness and damping matrices of the fluid are computed from the governing laws of the medium: the fluid is supposed to be viscous and compressible (Stokes' equations). The main problem stated by the lagrangian formulation of the fluid is the presence of spurious free-vibration modes (zero energy modes) in the fluid. Those modes are generated by the particular form of the matrix. These spurious modes have been examined and two particular methods to eliminate them have been developed: industrial applications prove the efficiency of the proposed methods. (orig./GL)

  9. [Efficiency of benazepril combined with wind dispelling and dampness removing chinese herbs on stage 3 chronic kidney disease with wind-dampness syndrome: a prospective study].

    Science.gov (United States)

    Fang, Yi-Qing; Lu, Ying; Wang, Yong-Jun

    2012-03-01

    To observe the clinical efficiency and safety of Benazepril and wind dispelling and dampness removing Chinese herbs were singly or combined used in patients with stage 3 chronic kidney disease (CKD 3), and to provide effective integrative medicine methods for treatment of CKD 3. The CKD 3 was allocated to qi and yin deficiency syndrome, inner disturbance of wind and damp syndrome, stasis in Shen meridian syndrome, and inner accumulation of damp and heat syndrome. Recruited were patients of inner disturbance of wind and damp syndrome accompanied or unaccompanied with the other 3 syndrome types. In the prospective, randomized, double blind controlled study, 60 patients confirmed as primary chronic glomerulonephritis (CGN) were randomly assigned to 3 groups with a total course of treatment for 24 weeks. Patients in the Western medicine group (WM, 23 cases) took Benazepril (10 mg/d). Those in the Chinese medicine group (CM, 20 cases) received treatment by syndrome typing. Those in the combination group (17 cases) used the two methods. The therapeutic efficacy and the occurrence of adverse reactions were observed in the 3 groups. The inner disturbance of wind and damp syndrome accompanied qi and yin deficiency syndrome and stasis in Shen meridian syndrome was most often seen in these patients. It accounted for 75.0% in the CM group, 60.9% in the WM group, and 82.4% in the combination group. Totally 54 patients completed this trial. Of them, there were 19 in the CM group, 19 in the WM group, and 16 in the combination group. There was no significant difference in the total effective rate of Chinese medicine syndrome among the 3 groups (84.2%, 78.9%, and 87.5%, respectively) (P>0.05). As for the total effective rate of WM, it was obviously higher in the combination group than in the WM group and the CM group (100.0%, 94.7%, and 94.7%, respectively) (PBenazepril combined with wind dispelling and dampness removing Chinese herbs showed favorable renal protective effects. It

  10. Experimental vibration study of in-air and fluid coupled co-axial cylinders

    International Nuclear Information System (INIS)

    Chu, M.; Brown, S.; Lestingi, J.

    1979-01-01

    It was the objective of this study to develop and carry out an experimental program which would provide additional insight into the mechanics of fluid--solid interaction with respect to the response of a set of coaxial cylinders with water in the annulus. Such configurations are found in nuclear reactors in the vessel wall-thermal liner. The effects of cylinder thickness and the fluid filled annulus gap size on the resonant frequencies and mode shapes of the cylinders (either singly or coupled in air and a water environment) are presented in this paper; also included is an evaluation of damping for selected gaps and cylinder thicknesses. Details of the experimental setup and procedures are also outlined

  11. Evaluation of Damping Using Time Domain OMA Techniques

    DEFF Research Database (Denmark)

    Bajric, Anela; Brincker, Rune; Georgakis, Christos T.

    2014-01-01

    . In this paper a comparison is made of the effectiveness of three existing OMA techniques in providing accurate damping estimates for varying loadings, levels of noise, number of added measurement channels and structural damping. The evaluated techniques are derived in the time domain and are namely the Ibrahim...... Time Domain (ITD), Eigenvalue Realization Algorithm (ERA) and the Polyreference Time Domain (PTD). The response of a two degree-of-freedom (2DOF) system is numerically established from specified modal parameters with well separated and closely spaced modes. Two types of response are considered, free...

  12. Vibration isolation and damping in high precision equipment

    Science.gov (United States)

    Bukkems, B.; Ruijl, T.; Simons, J.

    2017-06-01

    All systems located in a laboratory environment or factory are subject to disturbances. These disturbances can either come from the surroundings, e.g. floor-induced vibrations, or from the system itself, e.g. stage-induced vibrations. In many cases it is needed to minimize the effect of these disturbances. This can either be done by isolating the system from its disturbance source or by applying damping to the system. In this paper we present various cases in which we have effectively reduced the impact of disturbances on the system's performance, either by improving its isolation system, by minimizing the impact of stage reaction forces, or by designing polymer damping into the system.

  13. Damped Oscillator with Delta-Kicked Frequency

    Science.gov (United States)

    Manko, O. V.

    1996-01-01

    Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

  14. Forced excitation and active control for the measurement of fluid-elastic forces

    International Nuclear Information System (INIS)

    Caillaud, Sebastien

    1999-01-01

    The action of a fluid flow on a tubes bundle is commonly decomposed into a random turbulent excitation and a fluid-elastic excitation. The fluid-elastic forces which are coupled to the tubes movement can be experimentally determined from an analysis of the vibratory response of the structure excited by turbulent forces. For low flow velocities, the turbulent excitation can be insufficient to make the tube significantly vibrate and to permit a correct vibratory analysis. On the opposite side, the structure can become unstable for high flow velocities: the fluid-elastic forces make the fluid-structure damping system fall towards zero. Two experimental methods are proposed in order to extend the considered flow rate. An additional excitation force allows to increase the tube vibration level for improving the signal-noise ratio at low velocities. When the tube is submitted to fluid-elastic instability, an artificial damping contribution by active control allows to stabilize it. Methods are implemented on a flexible tube inserted into rigid tubes bundle water and water-air transverse flows. Two actuator technologies are used: an electromagnetic exciter and piezoelectric actuators. The additional excitation method shows that the fluid-elastic forces remain insignificant at low velocity single phase flow. With the active control method, it is possible to carry out tests beyond the fluid-elastic instability. In two-phase flow, the stabilization of the structure is observed for low vacuum rates. The obtained new results are analyzed with the literature expected results in terms of fluid-elastic coupling and turbulent excitation. (author) [fr

  15. Development of magnetorheological elastomers based on Deproteinised natural rubber as smart damping materials

    Science.gov (United States)

    Ismail, Nik Intan Nik; Kamaruddin, Shamsul

    2017-12-01

    Magnetorheological elastomers (MREs) are composite materials consist of micron-sized magnetizable particles carbonyl iron particles [CIPs]) embedded in a soft elastomer matrix. MRE technology offers variable stiffness and damping properties under the influence of a magnetic field. Herein, the feasibility of incorporating a new generation specialty rubber, Pureprena as a matrix for MREs was investigated. Pureprena or Deproteinised Natural Rubber (DPNR) is a specialty natural rubber that has good dynamic properties, particularly with respect to damping parameters. DPNR was compounded with 60 wt% of CIPs to fabricate MREs. The performance of the DPNR-based MRE was measured in terms of tensile strength, dynamic properties, and magnetorheological (MR) effect and compared with polyisoprene (IR)-based MRE with the same amount of CIPs. Dynamic Mechanical Analyzer (DMA) showed that the loss factor in the glass transition region of the DPNR-based MRE was higher than that of the IR-based MRE, indicating better damping properties. Further investigation was undertaken using a servo-hydraulic testing machine to characterise the effect of strain amplitude and frequency on the dynamic properties (e.g. damping coefficient) of MREs at zero magnetic fields. The results demonstrate that DPNR-based MREs possess a comparable damping coefficient to that of IR-based MREs. In addition, MR effect, which relates to the ratio between elastic modulus with applied magnetic field (on-state) to the same modulus without applied fields (off-state), was measured using a parallel plate rheometer. As a result, DPNR-based MREs have improved MR effect than that of IR-based MREs. Moreover, variable stiffness is obtained when the magnetic field was increased to 0.8T. Loss factor or tan δ of MREs was found to vary against different magnetic fields. Finally, MREs with varied stiffness and damping were found to have potential as active control devices for smart damping materials.

  16. Magnon damping in two-dimensional Heisenberg ferromagnetic system

    International Nuclear Information System (INIS)

    Cheng, T.-M.; Li Lin; Ze Xianyu

    2006-01-01

    A magnon-phonon interaction model is set up for a two-dimensional insulating ferromagnetic system. By using Matsubara function theory we have studied the magnon damping -I m Σ* (1) (k->) and calculated the magnon damping -I m Σ* (1) (k->) curve on the main symmetric point and line in the Brillouin zone for various parameters in the system. It is concluded that at the boundary of Brillouin zone there is a strong magnon damping. However, the magnon damping is very weak on the zone of small wave vector and the magnon damping reaches maximal value at very low temperature. The contributions of longitudinal phonon and transverse phonon on the magnon damping are compared and the influences of various parameters are also discussed

  17. Damping effect of the inner band electrons on the optical absorption and bandwidth of metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ochoo, Lawrence, E-mail: lawijapuonj@yahoo.com; Migwi, Charles; Okumu, John [Kenyatta University, Physics Department (Kenya)

    2012-12-15

    Conflicts and discrepancies around nanoparticle (NP) size effect on the optical properties of metal NPs of sizes below the mean free path of electron can be traced to the internal damping effect of the hybrid resonance of the inner band (IB) and the conduction band (CB) electrons of the noble metals. We present a scheme to show how alternative mathematical formulation of the physics of interaction between the CB and the IB electrons of NP sizes <50 nm justifies this and resolves the conflicts. While a number of controversies exist between classical and quantum theories over the phenomenological factors to attribute to the NP size effect on the absorption bandwidth, this article shows that the bandwidth behavior can be well predicted from a different treatment of the IB damping effect, without invoking any of the controversial phenomenological factors. It finds that the IB damping effect is mainly frequency dependent and only partly size dependent and shows how its influence on the surface plasmon resonance can be modeled to show the influence of NP size on the absorption properties. Through the model, it is revealed that strong coupling of IB and CB electrons drastically alters the absorption spectra, splitting it into distinctive dipole and quadrupole modes and even introduce a behavioral switch. It finds a strong overlap between the IB and the CB absorptions for Au and Cu but not Ag, which is sensitive to the NP environment. The CB modes shift with the changing refractive index of the medium in a way that can allow their independent excitation, free of influence of the IB electrons. Through a hybrid of parameters, the model further finds that metal NP sizes can be established not only by their spectral absorption peak locations but also from a proper correlation of the peak location and the bandwidth (FWHM).

  18. Nuclear fluid dynamics with long-mean-free-path dissipation: Multipole vibrations and isoscalar giant resonance widths

    International Nuclear Information System (INIS)

    Hasse, R.W.; Ghosh, G.

    1982-01-01

    The long-mean-free-path nuclear fluid dynamics is extended to include damping. First the damping stress is derived from the solution of the Boltzmann equation for a breathing spherical container filled with a Fermi gas. Then the corresponding damping force is incorporated into Euler equations of motion and energies and widths of low lying collective resonances are computed as eigenfrequencies of a vibrating nucleus under surface tension and Coulomb potential as well as the high lying isoscalar giant resonances as eigenfrequencies of an elastic nucleus. Maximum damping is obtained if the particle frequency approximately resonates with the wall frequency. Theoretical results are compared with experimental data and future improvements are indicated

  19. Modeling and analysis of rotating plates by using self sensing active constrained layer damping

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Zheng Chao; Wong, Pak Kin; Chong, Ian Ian [Univ. of Macau, Macau (China)

    2012-10-15

    This paper proposes a new finite element model for active constrained layer damped (CLD) rotating plate with self sensing technique. Constrained layer damping can effectively reduce the vibration in rotating structures. Unfortunately, most existing research models the rotating structures as beams that are not the case many times. It is meaningful to model the rotating part as plates because of improvements on both the accuracy and the versatility. At the same time, existing research shows that the active constrained layer damping provides a more effective vibration control approach than the passive constrained layer damping. Thus, in this work, a single layer finite element is adopted to model a three layer active constrained layer damped rotating plate. Unlike previous ones, this finite element model treats all three layers as having the both shear and extension strains, so all types of damping are taken into account. Also, the constraining layer is made of piezoelectric material to work as both the self sensing sensor and actuator. Then, a proportional control strategy is implemented to effectively control the displacement of the tip end of the rotating plate. Additionally, a parametric study is conducted to explore the impact of some design parameters on structure's modal characteristics.

  20. Modeling and analysis of rotating plates by using self sensing active constrained layer damping

    International Nuclear Information System (INIS)

    Xie, Zheng Chao; Wong, Pak Kin; Chong, Ian Ian

    2012-01-01

    This paper proposes a new finite element model for active constrained layer damped (CLD) rotating plate with self sensing technique. Constrained layer damping can effectively reduce the vibration in rotating structures. Unfortunately, most existing research models the rotating structures as beams that are not the case many times. It is meaningful to model the rotating part as plates because of improvements on both the accuracy and the versatility. At the same time, existing research shows that the active constrained layer damping provides a more effective vibration control approach than the passive constrained layer damping. Thus, in this work, a single layer finite element is adopted to model a three layer active constrained layer damped rotating plate. Unlike previous ones, this finite element model treats all three layers as having the both shear and extension strains, so all types of damping are taken into account. Also, the constraining layer is made of piezoelectric material to work as both the self sensing sensor and actuator. Then, a proportional control strategy is implemented to effectively control the displacement of the tip end of the rotating plate. Additionally, a parametric study is conducted to explore the impact of some design parameters on structure's modal characteristics

  1. Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume, E-mail: david.martinez@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain)

    2017-03-01

    The presence of neutral species in a plasma has been shown to greatly affect the properties of magnetohydrodynamic waves. For instance, the interaction between ions and neutrals through momentum transfer collisions causes the damping of Alfvén waves and alters their oscillation frequency and phase speed. When the collision frequencies are larger than the frequency of the waves, single-fluid magnetohydrodynamic approximations can accurately describe the effects of partial ionization, since there is a strong coupling between the various species. However, at higher frequencies, the single-fluid models are not applicable and more complex approaches are required. Here, we use a five-fluid model with three ionized and two neutral components, which takes into consideration Hall’s current and Ohm’s diffusion in addition to the friction due to collisions between different species. We apply our model to plasmas composed of hydrogen and helium, and allow the ionization degree to be arbitrary. By analyzing the corresponding dispersion relation and numerical simulations, we study the properties of small-amplitude perturbations. We discuss the effect of momentum transfer collisions on the ion-cyclotron resonances and compare the importance of magnetic resistivity, and ion–neutral and ion–ion collisions on the wave damping at various frequency ranges. Applications to partially ionized plasmas of the solar atmosphere are performed.

  2. Power Oscillation Damping from VSC-HVDC Connected Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Zeni, Lorenzo; Eriksson, Robert; Goumalatsos, Spyridon

    2016-01-01

    The implementation of power oscillation damping service on offshore wind power plants connected to onshore grids by voltage-source-converter-based high voltage direct current transmission is discussed. Novel design guidelines for damping controllers on voltage-source converters and wind power plant...... regarding real wind power plants are discussed: 1) robustness against control/communication delays; 2) limitations due to mechanical resonances in wind turbine generators; 3) actual capability of wind power plants to provide damping without curtailing production; and 4) power-ramp rate limiters....... controllers are derived, using phasor diagrams and a test network model and are then verified on a generic power system model. The effect of voltage regulators is analyzed, which is important for selecting the most robust damping strategy. Furthermore, other often disregarded practical implementation aspects...

  3. Kraus representation of a damped harmonic oscillator and its application

    International Nuclear Information System (INIS)

    Liu Yuxi; Oezdemir, Sahin K.; Miranowicz, Adam; Imoto, Nobuyuki

    2004-01-01

    By definition, the Kraus representation of a harmonic oscillator suffering from the environment effect, modeled as the amplitude damping or the phase damping, is directly given by a simple operator algebra solution. As examples and applications, we first give a Kraus representation of a single qubit whose computational basis states are defined as bosonic vacuum and single particle number states. We further discuss the environment effect on qubits whose computational basis states are defined as the bosonic odd and even coherent states. The environment effects on entangled qubits defined by two different kinds of computational basis are compared with the use of fidelity

  4. Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

    Science.gov (United States)

    Parsons, David; Smith, Andrew; Knight, Brent; Hunt, Ron; LaVerde, Bruce; Craigmyle, Ben

    2012-01-01

    Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

  5. Effect of kappa distribution on the damping rate of the obliquely propagating magnetosonic mode

    Science.gov (United States)

    Imran, Ali KHAN; G, MURTAZA

    2018-03-01

    Data from spacecrafts suggest that space plasma has an abundance of suprathermal particles which are controlled by the spectral index κ when modeled on kappa particle velocity distribution. In this paper, considering homogeneous plasma, the effect of integer values of κ on the damping rate of an obliquely propagating magnetosonic (MS) wave is studied. The frequency of the MS wave is assumed to be less than ion cyclotron frequency, i.e., ω \\ll {ω }{{i}}. Under this assumption, the dispersion relation is investigated both numerically and analytically, and it is found that the real frequency of the wave is not a sensitive function of κ, but the imaginary part of the frequency is. It is also shown that for those values of κ where a large number of resonant particles participate in wave-particle interaction, the wave is heavily damped, as expected. The possible application of the results to the solar wind is discussed.

  6. Limitations of modal analysis of damped structures

    International Nuclear Information System (INIS)

    Krapf, K.G.; Woelfel, H.

    1983-01-01

    Quite recently discrete spring-damper elements are increasingly used for the low-tuned supports of nuclear power-plant buildings and equipment (reactor building, turbine-fundaments etc.) to reduce the vibration response due to the dynamic load cases earthquake and airplane crash. Because of this development, it is to be investigated whether the usual modal analysis method is applicable within the design process or should be changed respectively replaced in special cases. The paper contributes to this discussion by demonstrating and valuing the discrepancies in the different ways for the implementation of damping. Different methods for uncoupling (energy weighting, reduction to Rayleigh-damping) are compared with the solution of the coupled equations of motion. In particular vertical vibrations of a spring-damper-supported building on foundation (including ground springs) are examined using a two-degree-of-freedom-system. The results of coupled and (by force) uncoupled methods are interpreted concerning free vibration by comparison of the damping of natural vibrations, natural frequencies and natural mode shapes. The effect on the forced vibrations is shown by floor response spectra to an earthquake accelerogram. (orig./HP)

  7. Parametric Landau damping of space charge modes

    Energy Technology Data Exchange (ETDEWEB)

    Macridin, Alexandru [Fermilab; Burov, Alexey [Fermilab; Stern, Eric [Fermilab; Amundson, James [Fermilab; Spentzouris, Panagiotis [Fermilab

    2016-09-23

    Landau damping is the mechanism of plasma and beam stabilization; it arises through energy transfer from collective modes to the incoherent motion of resonant particles. Normally this resonance requires the resonant particle's frequency to match the collective mode frequency. We have identified an important new damping mechanism, parametric Landau damping, which is driven by the modulation of the mode-particle interaction. This opens new possibilities for stability control through manipulation of both particle and mode-particle coupling spectra. We demonstrate the existence of parametric Landau damping in a simulation of transverse coherent modes of bunched accelerator beams with space charge.

  8. Recommendation for the Feasibility of more Compact LC Damping Rings

    CERN Document Server

    Pivi, M.T.F.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Shibata, K.; Ohmi, K.; Dugan, G.; Palmer, M.; Crittenden, J.A.; Harkay, K.; Boon, L.; Furman, M.A.; Venturini, M.; Celata, C.; Malyshev, O.B.; Papaphilippou, I.

    2010-01-01

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of the shorter damping ring with respect to the electron cloud build-up and related beam instabilities. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 and would allow considerable reduction of the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigation techniques and the integration of the CesrTA results into the Damping Ring design

  9. Recommendation for the Feasibility of more Compact LC Damping Rings

    International Nuclear Information System (INIS)

    Pivi, M.T.F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Shibata, K.; Ohmi, K.; Dugan, G.; Palmer, M.; Crittenden, J.A.; Harkay, K.; Boon, L.; Furman, M.A.; Venturini, M.; Celata, C.; Malyshev, O.B.; Papaphilippou, I.

    2010-01-01

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of the shorter damping ring with respect to the electron cloud build-up and related beam instabilities. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 (1) and would allow considerable reduction of the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigation techniques and the integration of the CesrTA results into the Damping Ring design.

  10. The forced harmonic oscillator with damping and thermal effects

    International Nuclear Information System (INIS)

    Menezes Franca, H. de; Thomaz, M.T.

    1984-01-01

    Nonperturbative quantum mechanical solutions of the forced harmonic oscillator with radiation reaction damping are obtained from previous analysis based on Stochastic Electrodynamics. The transition to excited states is shown to be to coherent states which follow the classical trajectory. The quantum Wigner distribution in phase space is constructed. All the results are extended to finite temperatures. (Author) [pt

  11. Enhanced vortex damping by eddy currents in superconductor-semiconductor hybrids

    Science.gov (United States)

    Danckwerts; Goni; Thomsen; Eberl; Rojo

    2000-04-17

    An enhancement of vortex-motion damping in thin Pb/In superconducting films is obtained through coupling to an adjacent two-dimensional electron gas formed in a modulation-doped GaAs/AlGaAs heterostructure. This effect is observed by monitoring the power dissipation in the superconductor in the vortex state while increasing the density of the electron gas using a gate voltage. Quantitative agreement is found with calculations based on a viscous damping model which considers generation of eddy currents in the electron gas by moving flux lines. In the regime of filamentary vortex flow, eddy-current damping leads to a striking dissipation breakdown due to the stopping of entire vortex channels.

  12. Resonant Electromagnetic Shunt Damping of Flexible Structures

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker

    2016-01-01

    Electromagnetic transducers convert mechanical energy to electrical energy and vice versa. Effective passive vibration damping of flexible structures can therefore be introduced by shunting with an accurately calibrated resonant electrical network thatcontains a capacitor to create the desired...

  13. On the effect of damping on dispersion curves in plates

    DEFF Research Database (Denmark)

    Manconia, Elisabetta; Sorokin, Sergey

    2013-01-01

    This paper presents a study on quantitative prediction and understanding of time-harmonic wave characteristics in damped plates. Material dissipation is modelled by using complex-valued velocities of free dilatation and shear waves in an unbounded volume. As a numerical example, solution...

  14. A symmetric positive definite formulation for monolithic fluid structure interaction

    KAUST Repository

    Robinson-Mosher, Avi; Schroeder, Craig; Fedkiw, Ronald

    2011-01-01

    In this paper we consider a strongly coupled (monolithic) fluid structure interaction framework for incompressible flow, as opposed to a loosely coupled (partitioned) method. This requires solving a single linear system that combines the unknown velocities of the structure with the unknown pressures of the fluid. In our previous work, we were able to obtain a symmetric formulation of this coupled system; however, it was also indefinite, making it more difficult to solve. In fact in practice there have been cases where we have been unable to invert the system. In this paper we take a novel approach that consists of factoring the damping matrix of deformable structures and show that this can be used to obtain a symmetric positive definite system, at least to the extent that the uncoupled systems were symmetric positive definite. We use a traditional MAC grid discretization of the fluid and a fully Lagrangian discretization of the structures for the sake of exposition, noting that our procedure can be generalized to other scenarios. For the special case of rigid bodies, where there are no internal damping forces, we exactly recover the system of Batty et al. (2007) [4]. © 2010 Elsevier Inc.

  15. A symmetric positive definite formulation for monolithic fluid structure interaction

    KAUST Repository

    Robinson-Mosher, Avi

    2011-02-01

    In this paper we consider a strongly coupled (monolithic) fluid structure interaction framework for incompressible flow, as opposed to a loosely coupled (partitioned) method. This requires solving a single linear system that combines the unknown velocities of the structure with the unknown pressures of the fluid. In our previous work, we were able to obtain a symmetric formulation of this coupled system; however, it was also indefinite, making it more difficult to solve. In fact in practice there have been cases where we have been unable to invert the system. In this paper we take a novel approach that consists of factoring the damping matrix of deformable structures and show that this can be used to obtain a symmetric positive definite system, at least to the extent that the uncoupled systems were symmetric positive definite. We use a traditional MAC grid discretization of the fluid and a fully Lagrangian discretization of the structures for the sake of exposition, noting that our procedure can be generalized to other scenarios. For the special case of rigid bodies, where there are no internal damping forces, we exactly recover the system of Batty et al. (2007) [4]. © 2010 Elsevier Inc.

  16. Relativity damps OPEP in nuclear matter

    International Nuclear Information System (INIS)

    Banerjee, M.K.

    1998-06-01

    Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. The author finds that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. He shows that the damping of derivative-coupled OPEP is actually due to the decrease of M * /M with increasing density. He points out that if derivative-coupled OPEP is the preferred form of nuclear effective lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M * it cannot replicate the damping. He suggests an examination of the feasibility of using pseudoscalar coupled πN interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter

  17. Coherent Synchrotron Radiation effect in damping rings

    International Nuclear Information System (INIS)

    Raubenheimer, T

    2004-01-01

    Coherent Synchrotron Radiation (CSR) can play an important role by not only increasing the energy spread and emittance of a beam, but also leading to a potential instability. Previous studies of the CSR induced longitudinal instability were carried out for the CSR impedance due to dipole magnets. In this paper, the instability due to the CSR impedance from a wiggler is studied assuming a large wiggler parameter K. The primary consideration is a low frequency microwave-like instability in the damping rings of several linear collider projects. The threshold is determined by the instability with the longest possible wavelength

  18. Damping-off in forest nurseries

    Science.gov (United States)

    Carl Hartley

    1921-01-01

    Damping-off is the commonest English name for a symptomatic group of diseases affecting great numbers of plant species of widely separated phylogenetic groups. It is commonly used for any disease which results in the rapid decay of young succulent seedlings or soft cuttings. Young shoots from underground rootstocks may also be damped-off before they break through the...

  19. Landau damping dynamic aperture and octupole in LHC

    CERN Document Server

    Gareyte, Jacques; Ruggiero, F

    1997-01-01

    Maximization of the dynamic aperture and Landau damping of the collective instabilities are partly conflicting requirements. On the one hand, the non-linearities of the lattice must be minimized at large oscillation amplitude to guarantee the stability of the single particle motion. On the other hand, a spread of the betatron frequencies is necessary to guarantee the stability of the collective motion of bunches of particles; this requires the introduction of non-linearities effective at small amplitudes. We show in this note that the `natural' spread of betatron tunes due to the field imperfections is inadequate or Landau damping. An octupole scheme is required to provide collective stability at high energy. At low energy it may be used to find the optimum between the correction of the octupolar field imperfections and Landau damping. The solution of the stability problem taking into account the two degrees of freedom of the transverse motion allows a significant saving in octupole strength: 144 octupoles wi...

  20. Comparison calculation/experiment on the load case ``shutdown of TH high pressure pumps under consideration of fluid structure interaction``; Vergleich Rechnung/Messung zum Lastfall ``Abschaltung der TH-Hochdruckpumpen unter Beruecksichtigung der Fluid-Struktur-Wechselwirkung``

    Energy Technology Data Exchange (ETDEWEB)

    Erath, W.; Nowotny, B.; Maetz, J. [KED, Rodenbach (Germany)

    1998-11-01

    Measurements of an experiment in a pipe system with pump shutdown and valve closing have been performed in the nuclear power plant KRB II. Comparative calculations of fluid and structure including interaction show an excellent agreement with the measured results. Theory and implementation of the fluid/structure interaction and the results of the comparison are described. It turns out that the consideration of the fluid/structure interaction is mostly a significant increase of the effective structural damping. (orig.) [Deutsch] Es wurden Messungen am nuklearen Nachkuehlsystem des Kernkraftwerks Gundremmingen (KRB II) bei einem Versuche mit Pumpenabschalten und Ventilschliessen durchgefuehrt. Vergleichsrechnungen der Fluid-Strukturdynamik unter echter Beruecksichtigung der Wechselwirkung ergaben eine ausgezeichnete Uebereinstimmung der Rechnung mit den Messungen. Es werden Theorie und Implementierung der Koppelung der Fluid- und Struktur-Berechnungen sowie die Vergleiche von Messung und Rechnung beschrieben. Es ergibt sich, dass die Beruecksichtigung der Wechselwirkung notwendig ist zur genaueren Berechnung von `weichen` Rohrleitungsystemen. Eine wichtige Folge der Wechselwirkung ist meist eine deutliche Erhoehung der effektiven Strukturdaempfung. (orig.)

  1. Three-dimensional inverse modelling of damped elastic wave propagation in the Fourier domain

    Science.gov (United States)

    Petrov, Petr V.; Newman, Gregory A.

    2014-09-01

    3-D full waveform inversion (FWI) of seismic wavefields is routinely implemented with explicit time-stepping simulators. A clear advantage of explicit time stepping is the avoidance of solving large-scale implicit linear systems that arise with frequency domain formulations. However, FWI using explicit time stepping may require a very fine time step and (as a consequence) significant computational resources and run times. If the computational challenges of wavefield simulation can be effectively handled, an FWI scheme implemented within the frequency domain utilizing only a few frequencies, offers a cost effective alternative to FWI in the time domain. We have therefore implemented a 3-D FWI scheme for elastic wave propagation in the Fourier domain. To overcome the computational bottleneck in wavefield simulation, we have exploited an efficient Krylov iterative solver for the elastic wave equations approximated with second and fourth order finite differences. The solver does not exploit multilevel preconditioning for wavefield simulation, but is coupled efficiently to the inversion iteration workflow to reduce computational cost. The workflow is best described as a series of sequential inversion experiments, where in the case of seismic reflection acquisition geometries, the data has been laddered such that we first image highly damped data, followed by data where damping is systemically reduced. The key to our modelling approach is its ability to take advantage of solver efficiency when the elastic wavefields are damped. As the inversion experiment progresses, damping is significantly reduced, effectively simulating non-damped wavefields in the Fourier domain. While the cost of the forward simulation increases as damping is reduced, this is counterbalanced by the cost of the outer inversion iteration, which is reduced because of a better starting model obtained from the larger damped wavefield used in the previous inversion experiment. For cross-well data, it is

  2. Offline software for the DAMPE experiment

    Science.gov (United States)

    Wang, Chi; Liu, Dong; Wei, Yifeng; Zhang, Zhiyong; Zhang, Yunlong; Wang, Xiaolian; Xu, Zizong; Huang, Guangshun; Tykhonov, Andrii; Wu, Xin; Zang, Jingjing; Liu, Yang; Jiang, Wei; Wen, Sicheng; Wu, Jian; Chang, Jin

    2017-10-01

    A software system has been developed for the DArk Matter Particle Explorer (DAMPE) mission, a satellite-based experiment. The DAMPE software is mainly written in C++ and steered using a Python script. This article presents an overview of the DAMPE offline software, including the major architecture design and specific implementation for simulation, calibration and reconstruction. The whole system has been successfully applied to DAMPE data analysis. Some results obtained using the system, from simulation and beam test experiments, are presented. Supported by Chinese 973 Program (2010CB833002), the Strategic Priority Research Program on Space Science of the Chinese Academy of Science (CAS) (XDA04040202-4), the Joint Research Fund in Astronomy under cooperative agreement between the National Natural Science Foundation of China (NSFC) and CAS (U1531126) and 100 Talents Program of the Chinese Academy of Science

  3. Structural damping values as a function of dynamic response stress and deformation levels

    International Nuclear Information System (INIS)

    Stevenson, J.D.

    1980-01-01

    Damping as it is normally defined is the means by which the response motion of a structural system is reduced as the result of energy losses. However, as used in the context of nuclear plant design, the effects of changes in structural stiffness, geometry, support configuration, and modulus of elasticity are also usually lumped under the general heading of damping in current design methods. For convenience in structural design, damping in usually assumed as viscous in nature and in recognition of its use in modal response spectrum dynamic analysis is normally expressed as a percent of critical. In general, it should be understood that damping as used in design or analysis of nuclear plants is an experimentally determined factor which is used to make the results of linear elasticity analysis of dynamic systems agree reasonably well with observed experimental results. In this paper, damping data existing in the open literature applicable to nuclear power plant structures and equipment is summarized and statistically analyzed. Results of this analysis are used to develop damping trend curves which predict applicable damping values to be used in design at various levels of stress or deformation. (orig.)

  4. Calculations of the electron-damping force on moving-edge dislocations

    International Nuclear Information System (INIS)

    Mohri, T.

    1982-11-01

    Dynamic effect of a moving dislocation has been recognized as one of essential features of deformation behavior at very low temperatures. Damping mechanisms are the central problems in this field. Based on the free-electron-gas model, the electron-damping force (friction force) on a moving-edge dislocation in a normal state is estimated. By applying classical MacKenzie-Sondheimer's procedures, the electrical resistivity caused by a moving dislocation is first estimated, and the damping force is calculated as a Joule-heat-energy dissipation. The calculated values are 3.63x10 - 6 , 7.62x10 - 7 and 1.00x10 - 6 [dyn sec/cm - 2 ] for Al, Cu and Pb, respectively. These values show fairly good agreements as compared with experimental results. Also, numerical calculations are carried out to estimate magnetic effects caused by a moving dislocation. The results are negative and any magnetic effects are not expected. In order to treat deformation behavior at very low temperatures, a unification of three important deformation problems is attempted and a fundamental equation is derived

  5. Evaluation of Spreading and Effectiveness of Injection Products against Rising Damp in Mortar/Brick Combinations

    NARCIS (Netherlands)

    Hacquebord, A.; Lubelli, B.; Van Hees, R.P.J.; Nijland, T.

    2013-01-01

    Rising damp is one of the most recurrent and well-known hazards to existing buildings and monuments. Several types of intervention exist to tackle the problem. Among these, the creation of a damp-proof course against capillary rise by means of injection of chemical products is one of the most

  6. Satellite Dynamic Damping via Active Force Control Augmentation

    Science.gov (United States)

    Varatharajoo, Renuganth

    2012-07-01

    An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a satellite active dynamic damping towards a full attitude control. The AFC method has been established to facilitate a robust motion control of dynamical systems in the presence of disturbances, parametric uncertainties and changes that are commonly prevalent in the real-world environment. The usefulness of the method can be extended by introducing intelligent mechanisms to approximate the mass or inertia matrix of the dynamic system to trigger the compensation effect of the controller. AFC is a technique that relies on the appropriate estimation of the inertial or mass parameters of the dynamic system and the measurements of the acceleration and force signals induced by the system if practical implementation is ever considered. In AFC, it is shown that the system subjected to a number of disturbances remains stable and robust via the compensating action of the control strategy. We demonstrate that it is possible to design a spacecraft attitude feedback controller that will ensure the system dynamics set point remains unchanged even in the presence of the disturbances provided that the actual disturbances can be modeled effectively. In order to further facilitate this analysis, a combined energy and attitude control system (CEACS) is proposed as a model satellite attitude control actuator. All the governing equations are established and the proposed satellite attitude control architecture is made amenable to numerical treatments. The results show that the PD-AFC attitude damping performances are superiorly better than that of the solely PD type. It is also shown that the tunings of the AFC system gains are crucial to ensure a better attitude damping performance and this process is mandatory for AFC systems. Finally, the results demonstrate an important satellite dynamic damping enhancement capability using the AFC

  7. Wave dispersion of carbon nanotubes conveying fluid supported on linear viscoelastic two-parameter foundation including thermal and small-scale effects

    Science.gov (United States)

    Sina, Nima; Moosavi, Hassan; Aghaei, Hosein; Afrand, Masoud; Wongwises, Somchai

    2017-01-01

    In this paper, for the first time, a nonlocal Timoshenko beam model is employed for studying the wave dispersion of a fluid-conveying single-walled carbon nanotube on Viscoelastic Pasternak foundation under high and low temperature change. In addition, the phase and group velocity for the nanotube are discussed, respectively. The influences of Winkler and Pasternak modulus, homogenous temperature change, steady flow velocity and damping factor of viscoelastic foundation on wave dispersion of carbon nanotubes are investigated. It was observed that the characteristic of the wave for carbon nanotubes conveying fluid is the normal dispersion. Moreover, implying viscoelastic foundation leads to increasing the wave frequencies.

  8. Fluid-Elastic Instability of U-Tube Bundle in Air-Water Two-Phase Flow

    International Nuclear Information System (INIS)

    Chu, In Cheol; Lee, Chang Hee; Yun, Young Jung; Chung, Heung June

    2007-03-01

    Using steam generator U-tube flow-induced vibration test facility, the flow-induced vibration characteristics of U-tube in row 34-44 and line 71-77 were investigated. Air and water at room temperature and near atmospheric pressure were used as working fluids. In the present experiments, followings were evaluated under two-phase cross-flow condition: the fundamental vibration responses and the critical gap velocity for a fluid-elastic instability of U-tubes, the damping ratio and hydrodynamic mass of U-tubes. In addition, the fluid-elastic instability factor, K, was preliminary assessed using Connors' relation. In the case of the U-tubes which are not supported by partial egg-crate in OPR100 steam generator, it has been found that the vibration displacement of those U-tubes are highly possible to exceed the design limit even by a turbulent excitation mechanism. The damping ratio of U-tubes measured in the present experiments was significantly higher than the OPR1000 steam generator design value. The fluid-elastic instability factor of U-tube bundle obtained in the present experiments were preliminary evaluated to be mostly in the range of 6.5-10.5

  9. Damage/Danger Associated Molecular Patterns (DAMPs Modulate Chlamydia pecorum and C. trachomatis Serovar E Inclusion Development In Vitro.

    Directory of Open Access Journals (Sweden)

    Cory Ann Leonard

    Full Text Available Persistence, more recently termed the chlamydial stress response, is a viable but non-infectious state constituting a divergence from the characteristic chlamydial biphasic developmental cycle. Damage/danger associated molecular patterns (DAMPs are normal intracellular components or metabolites that, when released from cells, signal cellular damage/lysis. Purine metabolite DAMPs, including extracellular ATP and adenosine, inhibit chlamydial development in a species-specific manner. Viral co-infection has been shown to reversibly abrogate Chlamydia inclusion development, suggesting persistence/chlamydial stress. Because viral infection can cause host cell DAMP release, we hypothesized DAMPs may influence chlamydial development. Therefore, we examined the effect of extracellular ATP, adenosine, and cyclic AMP exposure, at 0 and 14 hours post infection, on C. pecorum and C. trachomatis serovar E development. In the absence of de novo host protein synthesis, exposure to DAMPs immediately post or at 14 hours post infection reduced inclusion size; however, the effect was less robust upon 14 hours post infection exposure. Additionally, upon exposure to DAMPs immediately post infection, bacteria per inclusion and subsequent infectivity were reduced in both Chlamydia species. These effects were reversible, and C. pecorum exhibited more pronounced recovery from DAMP exposure. Aberrant bodies, typical in virus-induced chlamydial persistence, were absent upon DAMP exposure. In the presence of de novo host protein synthesis, exposure to DAMPs immediately post infection reduced inclusion size, but only variably modulated chlamydial infectivity. Because chlamydial infection and other infections may increase local DAMP concentrations, DAMPs may influence Chlamydia infection in vivo, particularly in the context of poly-microbial infections.

  10. Effect of Seed Quality and Combination Fungicide-Trichoderma spp. Seed Treatments on Pre- and Postemergence Damping-Off in Cotton.

    Science.gov (United States)

    Howell, Charles R

    2007-01-01

    ABSTRACT Good quality seeds of cotton cultivars often escaped pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae, and they were resistant to postemergence damping-off incited by Rhizoctonia solani. Poor quality seeds, however, were highly susceptible to both phases of seedling disease and required seed treatment in order to survive. Pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae could be controlled by seed treatment with biocontrol preparations of a number of Trichoderma spp., but these treatments were much less effective in controlling postemergence disease incited by Rhizoctonia solani. Postemergence seedling disease can be controlled by fungicides, but they were much less effective in controlling the pre-emergence phase of the disease. Combination seed treatments of poor quality cotton seeds with fungicides and Trichoderma spp. preparations, followed by planting in pathogen-infested soil, indicated that this technique will control both phases of seedling disease. Seed treatment with either the fungicides or the biocontrol agents alone did not achieve this goal. The optimum combination treatment for disease control was that of chloroneb plus Trichoderma spp., followed by chloroneb plus metalaxyl (Deltacoat AD) plus T. virens strain G-6.

  11. Transverse wakefield of waveguide damped structures and beam dynamics

    International Nuclear Information System (INIS)

    Lin, X.

    1995-08-01

    In the design of new high energy particle colliders with higher luminosity one is naturally led to consider multi-bunch operation. However, the passage of a leading bunch through an accelerator cavity Generates a wakefield that may have a deleterious effect on the motion of the subsequent bunches. Therefore, the suppression of the wakefield is an essential requirement for beam stability. One solution to this problem, which has been studied extensively is to drain the wakefield energy out of the cavity by means of waveguides coupled with the cavity and fed into matched terminations. Waveguide dimensions are chosen to yield a cutoff frequency well above the frequency of the accelerating mode so that the latter is undamped. This paper presents a thorough investigation of the wakefield for this configuration. The effectiveness of waveguide damping has typically been assessed by evaluating the resultant Q ext of higher order cavity modes to determine their exponential damping rate. We have developed an efficient method to calculate Q ext of the damped modes from popular computer simulation codes such as MAFIA. This method has been successively applied to the B-factory RF cavity We have also found another type of wakefield, associated with waveguide cut-off, which decays as t -3/2 rather than in the well-known exponentially damped manner. Accordingly, we called it the persistent Wakefield. A similar phenomenon with essentially the same physical origin but occurring in the decay of unstable quantum states, has received extensive study. Then we have developed various methods of calculating this persistent wakefield, including mode matching and computer simulation. Based on a circuit model we estimate the limit that waveguide damping can reach to reduce the wakefield

  12. Single bunch beam breakup in linacs and BNS damping

    International Nuclear Information System (INIS)

    Toyomasu, Takanori

    1991-12-01

    We study a single-bunch beam breakup (BBU) problem by a macro-particle model. We consider both the BBU solution and the Landau damping solution which includes the Balakin-Novokhatsky-Smirnov (BNS) damping. In the BBU solution, we get an analytic solution which includes both the Chao-Richter-Yao solution and the two-particle model solution and which agrees well with simulation. The solution can also be used in a multi-bunch case. In the Landau damping solution, we can be see the mechanism of Landau damping formally and can get some insights into BNS damping. We confirm that a two-particle model criterion for BNS damping is a good one. We expect that the two-particle model criterion is represented by the first order interaction in Landau damping solution of a macro-particle model. (author)

  13. Acoustic Velocity and Attenuation in Magnetorhelogical fluids based on an effective density fluid model

    Directory of Open Access Journals (Sweden)

    Shen Min

    2016-01-01

    Full Text Available Magnetrohelogical fluids (MRFs represent a class of smart materials whose rheological properties change in response to the magnetic field, which resulting in the drastic change of the acoustic impedance. This paper presents an acoustic propagation model that approximates a fluid-saturated porous medium as a fluid with a bulk modulus and effective density (EDFM to study the acoustic propagation in the MRF materials under magnetic field. The effective density fluid model derived from the Biot’s theory. Some minor changes to the theory had to be applied, modeling both fluid-like and solid-like state of the MRF material. The attenuation and velocity variation of the MRF are numerical calculated. The calculated results show that for the MRF material the attenuation and velocity predicted with this effective density fluid model are close agreement with the previous predictions by Biot’s theory. We demonstrate that for the MRF material acoustic prediction the effective density fluid model is an accurate alternative to full Biot’s theory and is much simpler to implement.

  14. Study of damping characteristics of fibre reinforced composite aerospace structure

    International Nuclear Information System (INIS)

    Khan, M.Z.; Saleh, S.; Munir, A.

    2006-01-01

    Composite materials are used in a variety of high demanding structural applications. Apart from their other preferable properties, they have high-energy dissipation characteristics, which is important aspect when we repeatedly wiggle the system back and forth. It is important to have thorough understanding of material damping behavior; in general materials damping tends to be complex nonlinear function of vibration amplitude, frequency of loading and material formulation. There are number of mathematical models available in literature to obtain hysteresis curves. One approach for identifying damping characteristics used mechanical hysteresis curves. In present work, a phenomenon was observed during testing of fibre reinforced composite beam of an aerospace structure, that for increase load in structure, the path of Force vs. Displacement curve is different than the path of unloading. A plot is generated which indicate the hysteresis loop representing the steady state dynamic behavior of material. The area enclosed by such curves is proportional to energy dissipation per cycle. However, the specific shape of the curve also has important implications for characterizing the specific functional form of the damping. Therefore, it is important to develop methods for accurately accounting for such effects. The current work explores the damping characteristics both theoretically and experimentally. (author)

  15. Electrorheologic fluids; Fluidos electroreologicos

    Energy Technology Data Exchange (ETDEWEB)

    Rejon G, Leonardo; Lopez G, Francisco; Montoya T, Gerardo [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico); Manero B, Octavio [Instituto de Investigaciones en Materiales, UNAM.(Mexico)

    2003-07-01

    The present article has as an objective to offer a review of the research work made in the Instituto de Investigaciones Electricas (IIE) on the study of the electrorheologic fluids whose flow properties can abruptly change in the presence of an electric field when this is induced by a direct current. The electrorheologic fluids have their main application in the manufacture of self-controlling damping systems. [Spanish] El presente articulo tiene por objetivo ofrecer una resena de los trabajos de investigacion realizados en el Instituto de Investigaciones Electricas (IIE) sobre el estudio de los fluidos electroreologicos cuyas propiedades de flujo pueden cambiar abruptamente en presencia de un campo electrico cuando este es inducido por una corriente directa. Los fluidos electroreologicos tienen su principal aplicacion en la fabricacion de sistemas de amortiguamiento autocontrolables.

  16. The effect of convection and shear on the damping and propagation of pressure waves

    Science.gov (United States)

    Kiel, Barry Vincent

    Combustion instability is the positive feedback between heat release and pressure in a combustion system. Combustion instability occurs in the both air breathing and rocket propulsion devices, frequently resulting in high amplitude spinning waves. If unchecked, the resultant pressure fluctuations can cause significant damage. Models for the prediction of combustion instability typically include models for the heat release, the wave propagation and damping. Many wave propagation models for propulsion systems assume negligible flow, resulting in the wave equation. In this research the effect of flow on wave propagation was studied both numerically and experimentally. Two experiential rigs were constructed, one with axial flow to study the longitudinal waves, the other with swirling flow to study circumferential waves. The rigs were excited with speakers and the resultant pressure was measured simultaneously at many locations. Models of the rig were also developed. Equations for wave propagation were derived from the Euler Equations. The resultant resembled the wave equation with three additional terms, two for the effect of the convection and a one for the effect of shear of the mean flow on wave propagation. From the experimental and numerical data several conclusions were made. First, convection and shear both act as damping on the wave propagation, reducing the magnitude of the Frequency Response Function and the resonant frequency of the modes. Second, the energy extracted from the mean flow as a result of turbulent shear for a given condition is frequency dependent, decreasing with increasing frequency. The damping of the modes, measured for the same shear flow, also decreased with frequency. Finally, the two convective terms cause the anti-nodes of the modes to no longer be stationary. For both the longitudinal and circumferential waves, the anti-nodes move through the domain even for mean flow Mach numbers less than 0.10. It was concluded that convection

  17. Prognostic and predictive value of DAMPs and DAMP-associated processes in cancer

    Directory of Open Access Journals (Sweden)

    Jitka eFucikova

    2015-08-01

    Full Text Available It is now clear that human neoplasms form, progress and respond to therapy in the context of an intimate crosstalk with the host immune system. In particular, accumulating evidence demonstrates that the efficacy of most, if not all, chemo- and radiotherapeutic agents commonly employed in the clinic critically depends on the (reactivation of tumor-targeting immune response. One of the mechanisms whereby conventional chemotherapeutics, targeted anticancer agents and radiotherapy can provoke a therapeutically relevant, adaptive immune response against malignant cells is commonly known as „immunogenic cell death (ICD. Importantly, dying cancer cells are perceived as immunogenic only when they emit a set of immunostimulatory signals upon the activation of intracellular stress response pathways. The emission of these signals, which are generally referred to as „damage-associated molecular patterns (DAMPs, may therefore predict whether patients will respond to chemotherapy or not, at least in some settings. Here, we review clinical data indicating that DAMPs and DAMP-associated stress responses might have prognostic or predictive value for cancer patients.

  18. Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities

    International Nuclear Information System (INIS)

    Alicia Hofler; Jean Delayen

    2005-01-01

    Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations

  19. Structural damping results from vibration tests of straight piping sections

    International Nuclear Information System (INIS)

    Ware, A.G.; Thinnes, G.L.

    1984-01-01

    EG and G Idaho is assisting the USNRC and the Pressure Vessel Research Committee in supporting a final position on revised damping values for structural analyses of nuclear piping systems. As part of this program, a series of vibrational tests on 76-mm and 203-mm (3-in. amd 8-in.) Schedule 40 carbon steel piping was conducted to determine the changes in structural damping due to various parametric effects. The 10-m (33-ft) straight sections of piping were rigidly supported at the ends. Spring, rod, and constant force hangers, as well as a sway brace and snubbers were included as intermediate supports. Excitation was provided by low-force level hammer inpacts, a hydraulic shaker, and a 445-kN (50-ton) overhead crane. Data was recorded using acceleration, strain, and displacement time histories. This paper presents results from the testing showing the effect of stress level and type of supports on structural damping in piping

  20. MR damping system on Dongting Lake cable-stayed bridge

    Science.gov (United States)

    Chen, Z. Q.; Wang, X. Y.; Ko, J. M.; Ni, Y. Q.; Spencer, Billie F., Jr.; Yang, G.

    2003-08-01

    The Dongting Lake Bridge is a cable-stayed bridge crossing the Dongting Lake where it meets the Yangtze River in southern central China. After this bridge was completed in 1999, its cables were observed to be sensitive to rain-wind-induced vibration, especially under adverse weather conditions of both rain and wind. To investigate the possibility of using MR damping systems to reduce cable vibration, a joint project between the Central South University of China and the Hong Kong Polytechnic University was conducted. Based on the promising research results, the bridge authority decided to install MR damping systems on the longest 156 stay cables. The installation started in July 2001 and finished in June 2002, making it the world's first application of MR dampers on cable-stayed bridge to suppress the rain-wind-induced cable vibration. As a visible and permanent aspect of bridge, the MR damping system must be aesthetically pleasing, reliable, durable, easy to maintain, as well as effective in vibration mitigation. Substantial work was done to meet these requirements. This paper describes the implementation of MR damping systems for cable vibration reduction.

  1. Comment on “Effects of damping solitary wave in a viscosity bounded plasma” [Phys. Plasmas 21, 022118 (2014)

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Uday Narayan, E-mail: unghosh1@rediffmail.com; Chatterjee, Prasanta; Roychoudhury, Rajkumar [Department of Mathematics, Siksha Bhavana, Visva Bharati, Santiniketan 731235 (India)

    2015-07-15

    Recently Gun Li et al. discussed “Effects of damping solitary wave in a viscosity bounded plasma” [Phys. Plasmas 21, 022118 (2014)]. The paper contains some serious errors which have been pointed out in this Comment.

  2. Chatter reduction in boring process by using piezoelectric shunt damping with experimental verification

    Science.gov (United States)

    Yigit, Ufuk; Cigeroglu, Ender; Budak, Erhan

    2017-09-01

    Chatter is a self-excited type of vibration that develops during machining due to process-structure dynamic interactions resulting in modulated chip thickness. Chatter is an important problem as it results in poor surface quality, reduced productivity and tool life. The stability of a cutting process is strongly influenced by the frequency response function (FRF) at the cutting point. In this study, the effect of piezoelectric shunt damping on chatter vibrations in a boring process is studied. In piezoelectric shunt damping method, an electrical impedance is connected to a piezoelectric transducer which is bonded on cutting tool. Electrical impedance of the circuit consisting of piezoceramic transducer and passive shunt is tuned to the desired natural frequency of the cutting tool in order to maximize damping. The optimum damping is achieved in analytical and finite element models (FEM) by using a genetic algorithm focusing on the real part of the tool point FRF rather than the amplitude. Later, a practical boring bar is considered where the optimum circuit parameters are obtained by the FEM. Afterwards, the effect of the optimized piezoelectric shunt damping on the dynamic rigidity and absolute stability limit of the cutting process are investigated experimentally by modal analysis and cutting tests. It is both theoretically and experimentally shown that application of piezoelectric shunt damping results in a significant increase in the absolute stability limit in boring operations.

  3. The improved damping of superconductor bearings for 35 kWh superconductor flywheel energy storage system

    International Nuclear Information System (INIS)

    Han, Y.H.; Park, B.J.; Jung, S.Y.; Han, S.C.; Lee, W.R.; Bae, Y.C.

    2013-01-01

    Highlights: ► We made a 35 kWh superconductor flywheel energy storage system. ► The damping coefficient of the superconductor bearing was increased over 3000 N s/m. ► The source of damping was discussed. -- Abstract: A 35 kWh Superconductor Flywheel Energy Storage system (SFES) using hybrid bearing sets, which is composed of a high temperature superconductor (HTS) bearing and an active magnet damper (AMD), has been developed at KEPCO Research Institute (KEPRI). Damping is a source of energy loss but necessary for the stability of the flywheel system. We found that the damping of HTS bearings can be improved by thermal insulating bolts, which play a role of passive type external damper. To investigate the source of the increased damping, damping coefficients were measured with HTS bearings using insulating bolts made of three kinds of polymer materials. The damping coefficient was raised over 3000 N s/m in the case of PEEK bolts. The value was almost a quarter of the AMD. In this study, thermoelastic and Coulomb friction damping mechanisms are discussed. The main damping mechanism was the thermoelastic damping of the bolts themselves. And interfacial gap between the insulating bolt and metal chamber, which increased during the cooling process, was considered to be the cause of the anisotropic damping coefficients. Finally, the effects of the HTS bearings on the first critical speed are shown

  4. Small horizontal emittance in the TESLA damping ring

    International Nuclear Information System (INIS)

    Decking, W.

    2001-01-01

    The present TESLA damping ring is designed for a normalized horizontal emittance of 8x10 -6 m. γ-γ collisions at the TESLA linear collider will benefit from a further decrease of the horizontal emittance. This paper reviews the processes which limit the horizontal emittance in the damping ring. Preliminary estimates on the smallest horizontal emittance for the present TESLA damping ring design as well as an ultimate limit of the emittance reachable with the TESLA damping ring concept will be given

  5. Damping of elastic waves in crystals with impurities

    International Nuclear Information System (INIS)

    Lemanov, V.V.; Petrov, A.V.; Akhmedzhanov, F.R.; Nasyrov, A.N.

    1979-01-01

    Elastic wave damping and thermal conductivity of NaCl-NaBr and Y 3 AL 5 O 12 crystals with Er impurity has been examined. The experimental results on a decrease in elastic wave damping in such crystals are analyzed in the framework of the Ahiezer damping theory. The measurements were made in the frequency range of 300-1500 MHz in propagation of longitudinal and transverse elastic waves along the [100] and [110] directions. At 10 % concentration of erbium impurity the transverse wave damping decreases by a factor of three, and for longitudinal waves by a factor of two in NaBr:Cl crystals, and by approximately 10 and 30 % for NaBr:Cl and Y 3 Al 5 O 12 :Er crystals, respectively. In Y 3 Al 5 O 12 crystals, unlike NaCl-NaBr crystals, no noticeable anisotropy of damping is observed. The transVerse wave damping in impurity crystals has been shown to increase significantly with decreasing temperature and increasing the impurity concentration

  6. The DAMPE silicon–tungsten tracker

    Energy Technology Data Exchange (ETDEWEB)

    Azzarello, P., E-mail: philipp.azzarello@unige.ch [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Ambrosi, G. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Asfandiyarov, R. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Bernardini, P. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Bertucci, B.; Bolognini, A. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Cadoux, F. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Caprai, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); De Mitri, I. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Domenjoz, M. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Dong, Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); Duranti, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Fan, R. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); and others

    2016-09-21

    The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV–10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon–tungsten tracker–converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m{sup 2}. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.

  7. Experimental Investigation of Stiffness Characteristics and Damping Properties of a Metallic Rubber Material

    Science.gov (United States)

    Lu, Ch. Zh.; Li, Jingyuan; Zhou, Bangyang; Li, Shuang

    2017-09-01

    The static stiffness and dynamic damping properties of a metallic rubber material (MR) were investigated, which exhibited a nonlinear deformation behavior. Its static stiffness is analyzed and discussed. The effects of structural parameters of MR and experimental conditions on its shock absorption capacity were examined by dynamic tests. Results revealed excellent elastic and damping properties of the material. Its stiffness increased with density, but decreased with thickness. The damping property of MR varied with its density, thickness, loading frequency, and amplitude.

  8. Contribution to the damping identification: experimental and numerical approaches

    International Nuclear Information System (INIS)

    Crambuer, R.

    2013-01-01

    Since earthquakes are a natural threat in France, it seems reasonable to construct buildings capable of resisting them. Since 1955, A.S. 55 recommendations regulations have taken into account this risk in all new constructions. The rules were created following an earthquake in Orleansville (Algeria) on 9. September 1954 and since then they have been modified in the aftermath of several significant earthquakes. As it stands now, the law requires that measurements of energy dissipation be carried out during the earthquakes in an effective manner. However, at present it is a great challenge to determine this, especially where reinforced concrete structures are concerned. The reason for this is the many different causes of energy dissipation which can be material, such as steel yielding, cracking of the concrete or deterioration of the interface between the Steel/concrete interface or environmental, such as the interactions with neighbouring structures or radiative damping. These dissipations typically creep into the essential pattern of the structures as a uniform, slight damping, and which is heavily quantify such as modal or Rayleigh damping. The challenge is therefore to ascertain how to carry out damping in a way that relies more on the laws of physics themselves. This study aims at bringing some clarifications to this problem. In order to achieve this, two objectives were targeted during the case study: the first consisted in experimentally qualifying and quantifying the sources of damping in concrete, the second aims at developing a method which model both the overall behaviour and the damping in a realistic way with low computational costs. A series of reverse 3-point bending tests were carried out to determine and quantify the mechanisms responsible for damping. This approach was innovative in that the tests were carried out on not only sound beams, but also on pre-damaged beams. When processing the results of these experiments, we focused on the overall

  9. A review of selected pumping systems in nature and engineering--potential biomimetic concepts for improving displacement pumps and pulsation damping.

    Science.gov (United States)

    Bach, D; Schmich, F; Masselter, T; Speck, T

    2015-09-03

    The active transport of fluids by pumps plays an essential role in engineering and biology. Due to increasing energy costs and environmental issues, topics like noise reduction, increase of efficiency and enhanced robustness are of high importance in the development of pumps in engineering. The study compares pumps in biology and engineering and assesses biomimetic potentials for improving man-made pumping systems. To this aim, examples of common challenges, applications and current biomimetic research for state-of-the art pumps are presented. The biomimetic research is helped by the similar configuration of many positive displacement pumping systems in biology and engineering. In contrast, the configuration and underlying pumping principles for fluid dynamic pumps (FDPs) differ to a greater extent in biology and engineering. However, progress has been made for positive displacement as well as for FDPs by developing biomimetic devices with artificial muscles and cilia that improve energetic efficiency and fail-safe operation or reduce noise. The circulatory system of vertebrates holds a high biomimetic potential for the damping of pressure pulsations, a common challenge in engineering. Damping of blood pressure pulsation results from a nonlinear viscoelastic behavior of the artery walls which represent a complex composite material. The transfer of the underlying functional principle could lead to an improvement of existing technical solutions and be used to develop novel biomimetic damping solutions. To enhance efficiency or thrust of man-made fluid transportation systems, research on jet propulsion in biology has shown that a pulsed jet can be tuned to either maximize thrust or efficiency. The underlying principle has already been transferred into biomimetic applications in open channel water systems. Overall there is a high potential to learn from nature in order to improve pumping systems for challenges like the reduction of pressure pulsations, increase of jet

  10. Tuned mass absorbers on damped structures under random load

    DEFF Research Database (Denmark)

    Krenk, Steen; Høgsberg, Jan Becker

    2008-01-01

    the mass ratio alone, and the damping can be determined subsequently. Only approximate results are available for the influence of damping in the original structure, typically in the form of series expansions. In the present paper it is demonstrated that for typical mass ratios in the order of a few percent......A substantial literature exists on the optimal choice of parameters of a tuned mass absorber on a structure excited by a force or by ground acceleration with random characteristics in the form of white noise. In the absence of structural damping the optimal frequency tuning is determined from...... for the response variance of a structure with initial damping in terms of the mass ratio and both damping ratios. Within this format the optimal tuning of the absorber turns out to be independent of the structural damping, and a simple explicit expression is obtained for the equivalent total damping....

  11. Higher Order Mode (HOM) Impedance and Damping Study for the LHC Capture Cavity

    CERN Document Server

    Linnecar, Trevor Paul R; Tückmantel, Joachim; CERN. Geneva. SPS and LHC Division

    2001-01-01

    To investigate the higher order mode, HOM, damping in the LHC 200MHz ACN cavity when using four HOM couplers, simulations have been done by both 3-D frequency domain and time domain methods. These simulations have previously been used in other studies of HOM damped cavities and shown to be effective by comparing measurement and simulation results[1] [2]. Using these methods the impedance spectrum of the HOM modes in the cavity before and after damping has been obtained. From this, detailed information about the HOM coupler's contribution to HOM damping can be obtained. The distribution and magnitude of some potentially dangerous HOM modes in the ACN cavity have been found.

  12. CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

    Science.gov (United States)

    Sances, Dillon J.; Gangadharan, Sathya N.; Sudermann, James E.; Marsell, Brandon

    2010-01-01

    Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response.

  13. Tuning of damping controller for UPFC using quantum particle swarm optimizer

    Energy Technology Data Exchange (ETDEWEB)

    Shayeghi, H., E-mail: hshayeghi@gmail.co [Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Shayanfar, H.A. [Center of Excellence for Power System Automation and Operation, Electrical Engineering Department, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jalilzadeh, S.; Safari, A. [Technical Engineering Department, Zanjan University, Zanjan (Iran, Islamic Republic of)

    2010-11-15

    On the basis of the linearized Phillips-Herffron model of a single machine power system, we design optimally the unified power flow controller (UPFC) based damping controller in order to enhance power system low frequency oscillations. The problem of robustly UPFC based damping controller is formulated as an optimization problem according to the time domain-based objective function which is solved using quantum-behaved particle swarm optimization (QPSO) technique that has fewer parameters and stronger search capability than the particle swarm optimization (PSO), as well as is easy to implement. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller is demonstrated through non-linear time-domain simulation and some performance indices studies under various disturbance conditions of over a wide range of loading conditions. The results analysis reveals that the designed QPSO based UPFC controller has an excellent capability in damping power system low frequency oscillations in comparison with the designed classical PSO (CPSO) based UPFC controller and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the {delta}{sub E} based damping controller is superior to the m{sub B} based damping controller.

  14. Vibration isolation analysis of new design OEM damper for malaysia vehicle suspension system featuring MR fluid

    Science.gov (United States)

    Unuh, M. H.; Muhamad, P.; Norfazrina, H. M. Y.; Ismail, M. A.; Tanasta, Z.

    2018-01-01

    The applications of semi-active damper employing magnetorheological (MR) fluids keep increasing in fulfilling the demand to control undesired vibration effect. The aim of this study is to introduce the new design of damper for Malaysian vehicle model as well to evaluate its effectiveness in promoting comfort. The vibration isolation performance of the OEM damper featuring MR fluid was analysed physically under real road profile excitation experimentally. An experiment using quarter car rig suspension and LMS SCADAS Mobile was conducted to demonstrate the influence of current in controlling the characteristics of MR fluid in alter the damping behaviour under 5 cm bump impact. Subsequently, the displacement values were measured with respect to time. The new design OEM damper featuring MR fluid was validated by comparing the data with original equipment manufacturer (OEM) passive damper results under the same approach of testing. Comparison of numerical data of the new design OEM damper shown that it can reduce the excitation amplitude up to 40% compared to those obtained by OEM passive damper. Finally, the new design OEM damper featuring MR fluid has effectively isolated the disturbance from the road profile and control the output force.

  15. An Optimal Reactive Power Control Strategy for a DFIG-Based Wind Farm to Damp the Sub-Synchronous Oscillation of a Power System

    Directory of Open Access Journals (Sweden)

    Bin Zhao

    2014-05-01

    Full Text Available This study presents the auxiliary damping control with the reactive power loop on the rotor-side converter of doubly-fed induction generator (DFIG-based wind farms to depress the sub-synchronous resonance oscillations in nearby turbogenerators. These generators are connected to a series capacitive compensation transmission system. First, the damping effect of the reactive power control of the DFIG-based wind farms was theoretically analyzed, and a transfer function between turbogenerator speed and the output reactive power of the wind farms was introduced to derive the analytical expression of the damping coefficient. The phase range to obtain positive damping was determined. Second, the PID phase compensation parameters of the auxiliary damping controller were optimized by a genetic algorithm to obtain the optimum damping in the entire subsynchronous frequency band. Finally, the validity and effectiveness of the proposed auxiliary damping control were demonstrated on a modified version of the IEEE first benchmark model by time domain simulation analysis with the use of DigSILENT/PowerFactory. Theoretical analysis and simulation results show that this derived damping factor expression and the condition of the positive damping can effectively analyze their impact on the system sub-synchronous oscillations, the proposed wind farms reactive power additional damping control strategy can provide the optimal damping effect over the whole sub-synchronous frequency band, and the control effect is better than the active power additional damping control strategy based on the power system stabilizator.

  16. Resummation and the gluon damping rate in hot QCD

    International Nuclear Information System (INIS)

    Pisarski, R.D.

    1990-08-01

    At high temperature a consistent perturbative expansion requires the resummation of an infinite subset of loop corrections into an effective expansion. This effective exansion is used to compute the gluon damping rate at leading order. 25 refs

  17. Vibration damping method and apparatus

    Science.gov (United States)

    Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.

    1999-01-01

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.

  18. Two methods for damping torsional vibrations in DFIG-based wind generators using power converters

    Science.gov (United States)

    Zhao, Zuyi; Lu, Yupu; Xie, Da; Yu, Songtao; Wu, Wangping

    2017-01-01

    This paper proposes novel damping control algorithms by using static synchronous compensator (STATCOM) and energy storage system (ESS) to damp torsional vibrations in doubly fed induction generator (DFIG) based wind turbine systems. It first analyses the operating characteristics of STATCOM and ESS for regulating power variations to increase grid voltage stability. Then, new control strategies for STATCOM and ESS are introduced to damp the vibrations. It is followed by illustration of their effectiveness to damp the drive train torsional vibrations of wind turbines, which can be caused by grid disturbances, such as voltage sags and frequency fluctuations. Results suggest that STATCOM is a promising technology to mitigate the torsional vibrations caused by grid voltage sags. By contrast, the ESS connected to the point of common coupling (PCC) of wind turbine systems shows even obvious advantages because of its capability of absorbing/releasing both active and reactive power. It can thus be concluded that STATCOM is useful for stabilizing power system voltage fluctuations, and ESS is more effective both in regulating PCC voltage fluctuations and damping torsional vibrations caused by grid voltage frequency fluctuations.

  19. Application of damping mechanism model and stacking fault probability in Fe-Mn alloy

    International Nuclear Information System (INIS)

    Huang, S.K.; Wen, Y.H.; Li, N.; Teng, J.; Ding, S.; Xu, Y.G.

    2008-01-01

    In this paper, the damping mechanism model of Fe-Mn alloy was analyzed using dislocation theory. Moreover, as an important parameter in Fe-Mn based alloy, the effect of stacking fault probability on the damping capacity of Fe-19.35Mn alloy after deep-cooling or tensile deformation was also studied. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability of γ-austenite and ε-martensite was determined by means of X-ray diffraction (XRD) profile analysis. The microstructure was observed using scanning electronic microscope (SEM). The results indicated that with the strain amplitude increasing above a critical value, the damping capacity of Fe-19.35Mn alloy increased rapidly which could be explained using the breakaway model of Shockley partial dislocations. Deep-cooling and suitable tensile deformation could improve the damping capacity owning to the increasing of stacking fault probability of Fe-19.35Mn alloy

  20. Dynamic analysis of electro- and magneto-rheological fluid dampers using duct flow models

    International Nuclear Information System (INIS)

    Esteki, Kambiz; Bagchi, Ashutosh; Sedaghati, Ramin

    2014-01-01

    Magneto-rheological (MR) and electro-rheological (ER) fluid dampers provide a semi-active control mechanism for suppressing vibration responses of a structure. MR and ER fluids change their viscosity under the influence of magnetic and electrical fields, respectively, which facilitates automatic control when these fluids are used in damping devices. The existing models, namely the phenomenological models for simulating the behavior of MR and ER dampers, rely on various parameters determined experimentally by the manufacturers for each damper configuration. It is of interest to develop mechanistic models of these dampers which can be applied to various configurations so that their fundamental characteristics can be studied to develop flexible design solutions for smart structures. This paper presents a formulation for dynamic analysis of electro-rheological (ER) and magneto-rheological (MR) fluid dampers in flow and mix mode configurations under harmonic and random excitations. The procedure employs the vorticity transport equation and the regularization function to deal with the unsteady flow and nonlinear behavior of ER/MR fluid in general motion. The finite difference method has been used to solve the governing differential equations. Using the developed approach, the damping force of ER/MR dampers can be calculated under any type of excitation. (paper)

  1. Feasibility of Influencing the Dynamic Fluid Film Coefficients of a Multirecess Journal Bearing by means of Active Hybrid Lubrication

    DEFF Research Database (Denmark)

    Santos, Ilmar; Watanabe, F. Y.

    2003-01-01

    and control techniques. The feasibility of influencing the dynamic fluid film coefficients (stiffness and damping) by means of a controllable fluid injection into opposed bearing recesses is investigated. By controlling the pressure and flow injection using servo control systems, it is possible to obtain...

  2. High damping Fe-Mn martensitic alloys for engineering applications

    International Nuclear Information System (INIS)

    Baik, S.-H.

    2000-01-01

    Conventional methods for reducing vibration in engineering designs (i.e. by stiffening or detuning) may be undesirable or inadequate in conditions where size or weight must be minimized or where complex vibration spectra exist. Alloys which combine high damping capacity with good mechanical properties can provide attractive technical and economic solutions to problems involving seismic, shock and vibration isolation. To meet these trends, we have developed a new high damping Fe-17%Mn alloy. Also, the alloy has advantages of good mechanical properties and is more economical than any other known damping alloys (a quarter the cost of non-ferrous damping alloy). Thus, the high damping Fe-17%Mn alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components with its excellent damping capacity (SDC, 30%) and mechanical property (T.S. 700 MPa). It is the purpose of this paper to introduce the characterization of the high damping Fe-17%Mn alloy and the results of retrofit of several such applications. (orig.)

  3. Structural dynamic analysis with generalized damping models analysis

    CERN Document Server

    Adhikari , Sondipon

    2013-01-01

    Since Lord Rayleigh introduced the idea of viscous damping in his classic work ""The Theory of Sound"" in 1877, it has become standard practice to use this approach in dynamics, covering a wide range of applications from aerospace to civil engineering. However, in the majority of practical cases this approach is adopted more for mathematical convenience than for modeling the physics of vibration damping. Over the past decade, extensive research has been undertaken on more general ""non-viscous"" damping models and vibration of non-viscously damped systems. This book, along with a related book

  4. Damping of multispan heat exchanger tubes. Pt. 1: in gases

    International Nuclear Information System (INIS)

    Pettigrew, M.J.; Goyder, H.G.D.; Qiao, Z.L.; Axisa, F.

    1986-07-01

    Flow-induced vibration analyses of heat exchanger tubes require the knowledge of damping. This paper treats the question of damping on multispan heat exchanger tubes in air and gases. The different energy dissipation mechanisms that contribute to tube damping are discussed. The available experimental data are reviewed and analysed. We find that the main damping mechanism in gases is friction between tube and tube-supports. Damping is strongly related to tube-support thickness. Damping values are recommended for design purposes. This study is interesting in the nuclear industry for it often uses heat exchangers

  5. Perceptual studies of violin body damping and vibrato.

    Science.gov (United States)

    Fritz, Claudia; Woodhouse, Jim; Cheng, Felicia P-H; Cross, Ian; Blackwell, Alan F; Moore, Brian C J

    2010-01-01

    This work explored how the perception of violin notes is influenced by the magnitude of the applied vibrato and by the level of damping of the violin resonance modes. Damping influences the "peakiness" of the frequency response, and vibrato interacts with this peakiness by producing fluctuations in spectral content as well as in frequency and amplitude. Initially, it was shown that thresholds for detecting a change in vibrato amplitude were independent of body damping, and thresholds for detecting a change in body damping were independent of vibrato amplitude. A study of perceptual similarity using triadic comparison showed that vibrato amplitude and damping were largely perceived as independent dimensions. A series of listening tests was conducted employing synthesized, recorded, or live performance to probe perceptual responses in terms of "liveliness" and preference. The results do not support the conclusion that liveliness results from the combination of the use of vibrato and a "peaky" violin response. Judgments based on listening to single notes showed inconsistent patterns for liveliness, while preferences were highest for damping that was slightly less than for a reference (real) violin. In contrast, judgments by players based on many notes showed preference for damping close to the reference value.

  6. Effects of counterion valency on the damping of phonons propagating along the axial direction of liquid-crystalline DNA

    Science.gov (United States)

    Liu, Yun; Chen, Sow-Hsin; Berti, Debora; Baglioni, Piero; Alatas, Ahmet; Sinn, Harald; Alp, Ercan; Said, Ayman

    2005-12-01

    The phonon propagation and damping along the axial direction of films of aligned 40wt% calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S (Q,E) as a function of transferred energy E =ℏω, and the magnitude of the transferred wave vector Q. S (Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30nm-1. A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q =4nm-1. The high-frequency sound speed obtained in this Q range is 3100m /s, which is about twice faster than the ultrasound speed of 1800m/s, measured by Brillouin light scattering at Q ˜0.01nm-1 at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between ˜12.5 and ˜22.5nm-1 are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4ps.

  7. Ultra-low magnetic damping in metallic and half-metallic systems

    Science.gov (United States)

    Shaw, Justin

    The phenomenology of magnetic damping is of critical importance to devices which seek to exploit the electronic spin degree of freedom since damping strongly affects the energy required and speed at which a device can operate. However, theory has struggled to quantitatively predict the damping, even in common ferromagnetic materials. This presents a challenge for a broad range of applications in magnonics, spintronics and spin-orbitronics that depend on the ability to precisely control the damping of a material. I will discuss our recent work to precisely measure the intrinsic damping in several metallic and half-metallic material systems and compare experiment with several theoretical models. This investigation uncovered a metallic material composed of Co and Fe that exhibit ultra-low values of damping that approach values found in thin film YIG. Such ultra-low damping is unexpected in a metal since magnon-electron scattering dominates the damping in conductors. However, this system possesses a distinctive feature in the bandstructure that minimizes the density of states at the Fermi energy n(EF). These findings provide the theoretical framework by which such ultra-low damping can be achieved in metallic ferromagnets and may enable a new class of experiments where ultra-low damping can be combined with a charge current. Half-metallic Heusler compounds by definition have a bandgap in one of the spin channels at the Fermi energy. This feature can also lead to exceptionally low values of the damping parameter. Our results show a strong correlation of the damping with the order parameter in Co2MnGe. Finally, I will provide an overview of the recent advances in achieving low damping in thin film Heusler compounds.

  8. The Microstructural Basis of Damping in High Damping Alloys

    Science.gov (United States)

    1989-09-01

    This transformation is diffusionless and is characterized by the cooperative movement of atoms in a given section of crystal. Removal of the stress...martensites. The cooperative movement of atoms causes large internal friction and high damping. The temperature range in which this transformation can

  9. Finite Element Analysis of Fluid-Structure Interaction in a Blast-Resistant Window System (PREPRINT)

    National Research Council Canada - National Science Library

    Chung, Jae H; Consolazio, Gary R; Dinan, Robert J; Rinehart, Stephen A

    2008-01-01

    .... The influences of shock wave propagation and fluid venting inside the damping chamber of the flex-window system are quantified and the influences of such phenomena on panel deflections, deformations, and internal forces are presented.

  10. TDHF and fluid dynamics of nuclear collective motions

    International Nuclear Information System (INIS)

    Di Nardo, M.; Di Toro, M.; Giansiracusa, G.; Lombardo, U.; Russo, G.

    1983-01-01

    The nuclear fluid dynamical equations are derived from a mean field description of the nuclear dynamics. Simple approximate solutions, corresponding to generalized scaling modes, are worked out for rotations and vibrations, with the evaluation of inertial parameters and flow patterns. Giant resonances are shown to be quite well described within an irrotational ansatz, which is equivalent to a lowest multipoles (up to lsub(max)=2) distortion of the momentum distribution. The physical meaning of a higher order truncation of the TDHF-Fluid-Dynamics chain is finally discussed with its implication on low lying states and on some description of the Landau damping. (author)

  11. On the origin of nonlocal damping in plasmonic monomers and dimers

    Science.gov (United States)

    Tserkezis, Christos; Yan, Wei; Hsieh, Wenting; Sun, Greg; Khurgin, Jacob B.; Wubs, Martijn; Mortensen, N. Asger

    2017-09-01

    The origin and importance of nonlocal damping is discussed through simulations with the generalized nonlocal optical response (GNOR) theory, in conjunction with time-dependent density functional theory (TDDFT) calculations and equivalent circuit modeling, for some of the most typical plasmonic architectures: metal-dielectric interfaces, metal-dielectric-metal gaps, spherical nanoparticles and nanoparticle dimers. It is shown that diffusive damping, as introduced by the convective-diffusive GNOR theory, describes well the enhanced losses and plasmon broadening predicted by ab initio calculations in few-nm particles or few-to-sub-nm gaps. Through the evaluation of a local effective dielectric function, it is shown that absorptive losses appear dominantly close to the metal surface, in agreement with TDDFT and the mechanism of Landau damping due to generation of electron-hole pairs near the interface. Diffusive nonlocal theories provide therefore an efficient means to tackle plasmon damping when electron tunneling can be safely disregarded, without the need to resort to more accurate, but time-consuming fully quantum-mechanical studies.

  12. Damping capacity and dynamic mechanical characteristics of the plasma-sprayed coatings

    International Nuclear Information System (INIS)

    Yu Liming; Ma Yue; Zhou Chungen; Xu Huibin

    2005-01-01

    The damping properties and dynamic mechanical performance of NiCrAlY coating, FeCrMo ferromagnetic coating, AlCuFeCr quasicrystalline coating and nanostructured ZrO 2 ceramic coating, which were prepared by plasma-spray method, were investigated. The measuring results of the dynamic mechanical thermal analyzer (DMTA) and the flexural resonance testing method show that the damping capacity (Q -1 ) of the coated sample has a notable improvement compared to the substrate, while the dynamic modulus has a dramatic decrease. The resonance frequency of the coated cantilever beam structure shifted to high-frequency, and the resonance amplitude, especially high mode resonance, was dramatically attenuated. The internal friction peaks were observed in the Q -1 -temperature spectrogram and a normal amplitude effects were shown in the coated samples damping characteristics. The damping mechanism based on the interaction between substrate and coating layer, and the microstructure of the coated sample were also discussed in this paper

  13. Nonstandard conserved Hamiltonian structures in dissipative/damped systems: Nonlinear generalizations of damped harmonic oscillator

    International Nuclear Information System (INIS)

    Pradeep, R. Gladwin; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.

    2009-01-01

    In this paper we point out the existence of a remarkable nonlocal transformation between the damped harmonic oscillator and a modified Emden-type nonlinear oscillator equation with linear forcing, xe+αxx+βx 3 +γx=0, which preserves the form of the time independent integral, conservative Hamiltonian, and the equation of motion. Generalizing this transformation we prove the existence of nonstandard conservative Hamiltonian structure for a general class of damped nonlinear oscillators including Lienard-type systems. Further, using the above Hamiltonian structure for a specific example, namely, the generalized modified Emden equation xe+αx q x+βx 2q+1 =0, where α, β, and q are arbitrary parameters, the general solution is obtained through appropriate canonical transformations. We also present the conservative Hamiltonian structure of the damped Mathews-Lakshmanan oscillator equation. The associated Lagrangian description for all the above systems is also briefly discussed.

  14. Experimental determination of damping factors for walls of masonry and reinforced concrete

    International Nuclear Information System (INIS)

    Buttman, P.

    1983-01-01

    'Damping' is a fundamental parameter for the determination of the internal force with a given acceleration response spectrum when designing and dimensioning masonry and reinforced concrete walls for the loading case earthquake. The actual dampings of masonry and reinforced concrete walls are determined on a scale of 1:1 by means of a horizontal excitation at a chosen test setup. The test specimen have the dimensions b/h/d=100/200/11,5 cm and 24 cm. The horizontal and sinusoidal excitation of the test specimen is effected by a dynamic oscillating excitation with a maximum power of 20 kN. The evaluation of the measurements shows that the assumed damping values of 4% for the operating basis earthquake are realistic. In case of amplitudes corresponding to the loadings of the safe shutdown earthquake, however, dampings of 11% for reinforced concrete walls and of 24% for masonry walls were determined. This real damping behavior of reinforced concrete and masonry walls was documented by means of measurements, films and pictures. (orig.)

  15. Experimental validation of solid rocket motor damping models

    Science.gov (United States)

    Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio

    2017-12-01

    In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe

  16. Experimental validation of solid rocket motor damping models

    Science.gov (United States)

    Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio

    2018-06-01

    In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe

  17. DAMPE

    CERN Multimedia

    Chen, D

    The $\\textbf{DA}$rk $\\textbf{M}$atter $\\textbf{P}$article $\\textbf{E}$xplorer (DAMPE) experiment is a high-energy astroparticle physics satellite mission to search for Dark Matter signatures in space, study the cosmic ray spectrum and composition up to 100 TeV, and perform high-energy gamma astronomy. The launch is planned for end 2015, initially for 3 years, to compliment existing space missions FERMI, AMS and CALET.

  18. Collisional damping of Langmuir waves in the collisionless limit

    International Nuclear Information System (INIS)

    Auerbach, S.P.

    1977-01-01

    Linear Langmuir wave damping by collisions is studied in the limit of collision frequency ν approaching zero. In this limit, collisions are negligible, except in a region in velocity space, the boundary layer, centered about the phase velocity. If kappa, the ratio of the collisional equilibration time in the boundary layer to the Landau damping time, is small, the boundary layer width scales as ν/sup 1/3/, and the perturbed distribution function scales as ν/sup -1/3/. The damping rate is thus independent of ν, although essentially all the damping occurs in the collision-dominated boundary layer. Solution of the Fokker--Planck equation shows that the damping rate is precisely the Landau (collisionless) rate. The damping rate is independent of kappa, although the boundary layer thickness is not

  19. Local invariants in non-ideal flows of neutral fluids and two-fluid plasmas

    Science.gov (United States)

    Zhu, Jian-Zhou

    2018-03-01

    The main objective is the locally invariant geometric object of any (magneto-)fluid dynamics with forcing and damping (nonideal), while more attention is paid to the untouched dynamical properties of two-fluid fashion. Specifically, local structures, beyond the well-known "frozen-in" to the barotropic flows of the generalized vorticities, of the two-fluid model of plasma flows are presented. More general non-barotropic situations are also considered. A modified Euler equation [T. Tao, "Finite time blowup for Lagrangian modifications of the three-dimensional Euler equation," Ann. PDE 2, 9 (2016)] is also accordingly analyzed and remarked from the angle of view of the two-fluid model, with emphasis on the local structures. The local constraints of high-order differential forms such as helicity, among others, find simple formulation for possible practices in modeling the dynamics. Thus, the Cauchy invariants equation [N. Besse and U. Frisch, "Geometric formulation of the Cauchy invariants for incompressible Euler flow in flat and curved spaces," J. Fluid Mech. 825, 412 (2017)] may be enabled to find applications in non-ideal flows. Some formal examples are offered to demonstrate the calculations, and particularly interestingly the two-dimensional-three-component (2D3C) or the 2D passive scalar problem presents that a locally invariant Θ = 2θζ, with θ and ζ being, respectively, the scalar value of the "vertical velocity" (or the passive scalar) and the "vertical vorticity," may be used as if it were the spatial density of the globally invariant helicity, providing a Lagrangian prescription to control the latter in some situations of studying its physical effects in rapidly rotating flows (ubiquitous in atmosphere of astrophysical objects) with marked 2D3C vortical modes or in purely 2D passive scalars.

  20. An experimental study of damping characteristics with emphasis on insulation for nuclear power plant piping system (Seismic Damping Ratio Evaluation Program)

    International Nuclear Information System (INIS)

    Shibata, H.; Ito, M.; Hayashi, T.; Chiba, T.; Kobayashi, H.; Kitamura, K.; Ando, K.; Koyanagi, R.

    1981-01-01

    To clarify the damping characteristics and mechanism in nuclear power plant piping systems, the study group was established and conducted to study SDREP (Seismic Damping Ratio Evaluation Program). As the Phase II of this study, vibration tests were conducted to investigate factors which might contribute to damping characteristics of piping systems. These tests are composed of the next three model tests: 1) The component damping characteristics test of thermal insulator 2) The simplified piping model test 3) The scale model test. In these tests, we studied damping characteristics with emphasis on thermal insulator (mainly calcium silicate insulator). The acceleartion level of pipings is the same as that of the actual seismic response. The excitation was by sinusoidal sweep method using the shaking table and by free vibration method using snapback. (orig./RW)

  1. Optics design of Intrabeam Scattering dominated damping rings

    CERN Document Server

    Antoniou, Fanouria; Papaphilippou, Ioannis

    A e+/e- linear collider, the Compact Linear Collider (CLIC) is under design at CERN, aiming to explore the terascale particle physics regime. The collider has been optimized at 3 TeV center of mass energy and targets a luminosity of 1034 cm-2 s-1. In order to achieve this high luminosity, high intensity bunches with ultra low emittances, in all three planes, are required. The generation of ultra low emittance is achieved in the Damping Rings (DR) complex of the collider. The large input beam emittances, especially the ones coming from the positron source, and the requirement of ultra low emittance production in a fast repetition time of 20 ms, imply that the beam damping is done in two stages. Thus, a main-damping ring (DR) and a predamping ring (PDR) are needed, for each particle species. The high bunch brightness gives rise to several collective effects, with Intra-beam scattering (IBS) being the main limitation to the ultra-low emittance. This thesis elaborates the lattice design and non-linear optimizatio...

  2. Enhancing the damping of wind turbine rotor blades, the DAMPBLADE project

    DEFF Research Database (Denmark)

    Chaviaropoulos, P.K.; Politis, E.S.; Lekou, D.J.

    2006-01-01

    A research programme enabling the development of damped wind turbine blades, having the acronym DAMPBLADE, has been supported by the EC under its 5th Framework Programme. In DAMPBLADE the following unique composite damping mechanisms were exploited aiming to increase the structural damping......: tailoring of laminate damping anisotropy, damping layers and damped polymer matrices. Additional objectives of the project were the development of the missing critical analytical technologies enabling the explicit modelling of composite structural damping and a novel ‘composite blade design capacity......’ enabling the direct prediction of aeroelastic stability and fatigue life; the development and characterization of damped composite materials; and the evaluation of new technology via the design and fabrication of damped prototype blades and their full-scale laboratory testing. After 4 years of work a 19 m...

  3. Calculated dependence of FePt damping on external field magnitude and direction

    Directory of Open Access Journals (Sweden)

    N. A. Natekar

    2017-05-01

    Full Text Available Near the Curie temperature (Tc, magnetic parameters including magnetization, anisotropy, and damping depend strongly on both temperature and length scale. This manifestation of renormalization theory is most readily seen in the case of magnetization where the magnitude of the atomic spin is largely unaffected by temperature, but the bulk magnetization vanishes at Tc. It has been previously argued that the Landau-Lifshitz-Gilbert damping parameter alpha exhibits a similar effect owing to its dependence on both atomic effects and magnon-magnon scattering, the latter having a strong length dependence. Here, we calculate, using an anisotropic exchange description of L10 FePt (Tc = 705 K, the damping (and other magnetic properties dependence on temperature for FePt at length scales around 1.0 nm as appropriate for high temperature micromagnetic simulation. While the damping reduces as the applied field along the easy direction increases, it tends to increase as the field direction is changed to in-plane. The renormalized parameters are also calculated for higher and lower Tc (770K and 630K by invoking the linear relationship between the exchange stiffness parameter and Curie temperature. This corresponds to doped and/or non-stoichiometric FePt and allows better understanding of the effects of varying anisotropy to exchange ratio.

  4. Capacitor current feedback for output filter damping in switched-mode magnet power supplies

    International Nuclear Information System (INIS)

    Paven Kumar, M.R.; Kim, J.M.S.

    1994-01-01

    In magnet power supplies for a particle accelerator system, a second-order low-pass filter is used to reduce the output current ripple content within specifications. The output filter must be properly damped in order to avoid any large amplification at the resonant frequency and large transient responses of voltages and currents at the step change of the line voltage. Conventionally, a series combination of resistance and capacitance is added in parallel with the filter capacitor to provide the required damping. This approach, however, requires a large dc-blocking capacitor which has to be several times larger than the filter capacitor. In this paper, a filter damping technique using capacitor current feedback is presented. The basic concept of the capacitor current feedback is established using a linear model of the converter involved, and then a sampled-data model of the converter is used to analyze the filter damping technique. The filter damping effect of the capacitor current feedback is verified experimentally

  5. Dynamic apeerture in damping rings with realistic wigglers

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yunhai; /SLAC

    2005-05-04

    The International Linear Collider based on superconducting RF cavities requires the damping rings to have extremely small equilibrium emittance, huge circumference, fast damping time, and large acceptance. To achieve all of these requirements is a very challenging task. In this paper, we will present a systematic approach to designing the damping rings using simple cells and non-interlaced sextupoles. The designs of the damping rings with various circumferences and shapes, including dogbone, are presented. To model realistic wigglers, we have developed a new hybrid symplectic integrator for faster and accurate evaluation of dynamic aperture of the lattices.

  6. Analytical predictions for vibration phase shifts along fluid-conveying pipes due to Coriolis forces and imperfections

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Dahl, Jonas

    2010-01-01

    -shift measuring devices such as Coriolis mass flowmeters in particular. Small imperfections related to elastic and dissipative support conditions are specifically addressed, but the suggested approach is readily applicable to other kinds of imperfection, e.g. non-uniform stiffness or mass, non......-proportional damping, weak nonlinearity, and flow pulsation. A multiple time scaling perturbation analysis is employed for a simple model of an imperfect fluid-conveying pipe. This leads to simple analytical expressions for the approximate prediction of phase shift, providing direct insight into which imperfections...... the symmetric part of damping as well as non-uniformity in mass or stiffness do not affect phase shift. The validity of such hypotheses can be tested using detailed fluid-structure interaction computer models or laboratory experiments....

  7. Collisionless damping of dust-acoustic waves in a charge varying dusty plasma with nonextensive ions

    Energy Technology Data Exchange (ETDEWEB)

    Amour, Rabia; Tribeche, Mouloud [Faculty of Physics, Theoretical Physics Laboratory (TPL), Plasma Physics Group (PPG), University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria)

    2014-12-15

    The charge variation induced nonlinear dust-acoustic wave damping in a charge varying dusty plasma with nonextensive ions is considered. It is shown that the collisionless damping due to dust charge fluctuation causes the nonlinear dust acoustic wave propagation to be described by a damped Korteweg-de Vries (dK-dV) equation the coefficients of which depend sensitively on the nonextensive parameter q. The damping term, solely due to the dust charge variation, is affected by the ion nonextensivity. For the sake of completeness, the possible effects of nonextensivity and collisionless damping on weakly nonlinear wave packets described by the dK-dV equation are succinctly outlined by deriving a nonlinear Schrödinger-like equation with a complex nonlinear coefficient.

  8. Collisionless damping of dust-acoustic waves in a charge varying dusty plasma with nonextensive ions

    International Nuclear Information System (INIS)

    Amour, Rabia; Tribeche, Mouloud

    2014-01-01

    The charge variation induced nonlinear dust-acoustic wave damping in a charge varying dusty plasma with nonextensive ions is considered. It is shown that the collisionless damping due to dust charge fluctuation causes the nonlinear dust acoustic wave propagation to be described by a damped Korteweg-de Vries (dK-dV) equation the coefficients of which depend sensitively on the nonextensive parameter q. The damping term, solely due to the dust charge variation, is affected by the ion nonextensivity. For the sake of completeness, the possible effects of nonextensivity and collisionless damping on weakly nonlinear wave packets described by the dK-dV equation are succinctly outlined by deriving a nonlinear Schrödinger-like equation with a complex nonlinear coefficient

  9. Techniques for the design of highly damped structures

    International Nuclear Information System (INIS)

    Nelson, F.C.

    1975-01-01

    This paper discusses several techniques for the design of highly damped structures, techniques which have proven successful for large scale, low frequency steel and concrete structures which are typical of nuclear power reactors and their components. The ability to augment structural damping can be useful in increasing the seismic withstandability of structures. Seismic excitation is broadband in its frequency content and will excite many strutural resonances. Broadband damping will limit these resonant responses and thereby reduce the seismic load on structures and their components. This paper discusses three techniques: the design of structural joints and interfaces to promote damping; the use of layers of viscoelastic material; and the employment of damping links. The emphasis is on explaining the ways in which these techniques work and in describing the ways in which they have been used. (Auth.)

  10. Digital notch filter based active damping for LCL filters

    DEFF Research Database (Denmark)

    Yao, Wenli; Yang, Yongheng; Zhang, Xiaobin

    2015-01-01

    . In contrast, the active damping does not require any dissipation elements, and thus has become of increasing interest. As a result, a vast of active damping solutions have been reported, among which multi-loop control systems and additional sensors are necessary, leading to increased cost and complexity....... In this paper, a notch filter based active damping without the requirement of additional sensors is proposed, where the inverter current is employed as the feedback variable. Firstly, a design method of the notch filter for active damping is presented. The entire system stability has then been investigated...... in the z-domain. Simulations and experiments are carried out to verify the proposed active damping method. Both results have confirmed that the notch filter based active damping can ensure the entire system stability in the case of resonances with a good system performance....

  11. Research on Fluid Viscous Damper Parameters of Cable-Stayed Bridge in Northwest China

    Directory of Open Access Journals (Sweden)

    Xiongjun He

    2017-01-01

    Full Text Available To optimize the aseismic performance of nonlinear fluid viscous dampers (FVD of cable-stayed bridge in the highly seismic zone, Xigu Yellow River Bridge in northwest China is taken as an example. Nonlinear time-history analysis method is used to research on the relation among the internal forces, displacements, and damping parameters of the 650 tonnage FVD. The method of getting the minimum of binary functions is used to obtain the optimal parameters of FVD. Also, the 1 : 1 full-scale FVD model is made and used in the constitutive relation test. Then the test result of the damping parameters can be got by normal equation method. The optimized method to obtain the damping parameters is further verified. The results indicate that seismic response in key positions of the cable-stayed bridge can be reduced by installing longitudinal nonlinear FVD between the towers and girders if choosing reasonable damping parameters C and ξ. The optimal damping parameters can be calculated accurately by the proposed method of optimizing damping parameters of nonlinear FVD, and the constitutive relation test verifies the correctness of the optimization analysis method. Conclusions concerned can be applied to the design of nonlinear FVD for cable-stayed bridges.

  12. INEL/USNRC pipe damping experiments and studies

    International Nuclear Information System (INIS)

    Ware, A.G.

    1987-08-01

    Since the previous paper on this subject presented at the 8th SMiRT Conference, the Idaho National Engineering Laboratory (INEL) has conducted further research on piping system damping for the United States Nuclear Regulatory Commission (USNRC). These efforts have included vibration tests on two laboratory piping systems at response frequencies up to 100 Hz, and damping data calculations from both of these two systems and from a third laboratory piping system test series. In addition, a statistical analysis was performed on piping system damping data from tests representative of seismic and hydrodynamic events of greater than minimal excitation. The results of this program will be used to assist regulators in establishing suitable damping values for use in dynamic analyses of nuclear piping systems, and in revising USNRC Regulatory Guide (RG) 1.61

  13. Superelastic behavior and damping capacity of CuAlBe alloys

    International Nuclear Information System (INIS)

    Montecinos, Susana; Moroni, Maria Ofelia; Sepulveda, Aquiles

    2006-01-01

    Shape memory alloys (SMAs) showing the superelastic effect, dissipate energy through hysteretic cycles up to large strain amplitudes, without remnant strains after unloading. This effect is associated with a reversible stress-induced martensitic transformation. In this paper, the behavior of copper-based SMAs is examined, with the perspective of potential applications in seismic-energy dissipative devices. In particular, two different compositions of CuAlBe are characterized using chemical analysis, differential scanning calorimetry (DSC), light and scanning electron microscopy and X-rays diffraction. Mechanical and hysteretic damping properties are determined from cyclic tensile and tension-compression tests, for different strain amplitudes and frequencies. Both alloys show superelastic behavior, although hysteresis loops differ, due to differences in the composition and transformation phase temperatures. Equivalent damping up to 5% was obtained for the largest strain imposed. Frequency, in the range of interest for seismic applications, had a small influence on the damping values. It is concluded that alloy Cu-11.8 wt.% Al-0.5 wt.% Be best exhibited properties for the application intended

  14. Variation of structural damping with response amplitude in piping systems

    International Nuclear Information System (INIS)

    Ware, A.G.

    1986-01-01

    From tests conducted over the last several years, it has become apparent that structural damping is not a single number applicable to all piping systems, but is highly dependent on piping system parameters such as supports, response amplitude, and insulation. As a result, there is considerable scatter in the available data. Furthermore, the relationships between the parameters and damping are often highly complex, interrelated, and difficult to predict. From tests of piping supported by various typical methods, two basic types of energy dissipation in the supports can be observed. The first is friction such as between spring hangers and their housings or in the internal mechanisms of constant force hangers. The second is impacting such as occurs in snubbers, rigid struts, and rod hangers. Overall, these effects lead to a wide variety of possibilities that can occur at low vibration levels and can change with only a slight perturbation of vibration amplitude. This can account for much of the scatter in the data at low strain levels. Thus damping is almost impossible to predict at low amplitudes, and extrapolation of this type data to higher amplitudes is cautioned. However, once strain levels rise above 100 to 200 micro in/in, the damping trend becomes easier to characterize. From the 100 to 200 micro in/in to 800 to 1000 micro in/in range the damping is fairly constant and is induced primarily by the supports. At the upper end of this range a threshold is reached in which damping increases with increasing strain amplitude. Data in the high strain (plastic range) is sparse since the test usually renders the pipe unsuitable for further use. 15 refs

  15. Frequency and temperature dependence of high damping elastomers

    International Nuclear Information System (INIS)

    Kulak, R.F.; Hughes, T.H.

    1993-01-01

    High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between -20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer's response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between -20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping

  16. Vortex-Induced Vibrations of a Square Cylinder with Damped Free-End Conditions

    Directory of Open Access Journals (Sweden)

    S. Manzoor

    2013-01-01

    Full Text Available The authors report the results of vortex-induced vibrations of a square cylinder in a wind tunnel. This constitutes a high mass ratio environment. The square cylinder is mounted in the wind tunnel in such a fashion that it only performs rigid body oscillations perpendicular to the flow direction with damped free-end conditions. This physical situation allows a direct evaluation for analytical models relying on simplified 2D assumptions. The results are also compared with two-dimensional fluid-structure (CFD-CSD numerical simulations. The comparison shows that despite having one-dimensional motion, the analytical model does not predict the VIV region with correctness. Results show that the numerical simulations and experimental results differ from the analytical model for the prediction of reduced velocity corresponding to peak amplitude. Also the analytical reduced velocity envelope is underpredicted compared to both numerical simulations and experimental data despite the structure being lightly damped. The findings are significant as the experimental results for freely oscillating high mass ratio body show differences from the low mass ratio especially in the transition between VIV and galloping regions. However the numerical simulations show comparatively close agreement.

  17. Considering dynamic friction and proper structural response in hydraulic load cases for realistic piping design

    International Nuclear Information System (INIS)

    Diesselhorst, T.; Diatschuk, P.; Schnellhammer, W.

    2005-01-01

    Concerning the design for hydraulic load cases there is always a sequence of fluid- and structural dynamic calculations, where the structural vibrations are induced by the time depending fluid forces. Therefore, in order to prevent excessive structural reactions, it is most important to avoid conservative fluid dynamic results. That refers to the maximum value of the pressure surge as well as to the damping of pressure oscillations. This is especially relevant in case of fluid-structure resonance. To meet these requirements the effect of dynamic wall friction was implemented in our fluid dynamic code. Thus, a more realistic damping behavior of the fluid forces was achieved. In the structural analysis code the damping of the pipe structure could be more accurate adapted to the real conditions. Additionally the local damping by viscous damper was included in the model. At supports now non-linear behavior like clearances can be simulated. The possibility of coupled calculation was installed to consider the effect of fluid structure interaction. The programmed effects are validated against measurement results from power plant systems. The favorable effects of the program improvements are demonstrated by typical examples. These included the realistic damping of pressure oscillations as well as a case of fluid-structure resonance. Additionally the effectiveness of the improved models of piping supports is demonstrated. (authors)

  18. Public health and economic impact of dampness and mold

    Energy Technology Data Exchange (ETDEWEB)

    Mudarri, David; Fisk, William J.

    2007-06-01

    The public health risk and economic impact of dampness and mold exposures was assessed using current asthma as a health endpoint. Individual risk of current asthma from exposure to dampness and mold in homes from Fisk et al. (2007), and asthma risks calculated from additional studies that reported the prevalence of dampness and mold in homes were used to estimate the proportion of U.S. current asthma cases that are attributable to dampness and mold exposure at 21% (95% confidence internal 12-29%). An examination of the literature covering dampness and mold in schools, offices, and institutional buildings, which is summarized in the appendix, suggests that risks from exposure in these buildings are similar to risks from exposures in homes. Of the 21.8 million people reported to have asthma in the U.S., approximately 4.6 (2.7-6.3) million cases are estimated to be attributable to dampness and mold exposure in the home. Estimates of the national cost of asthma from two prior studies were updated to 2004 and used to estimate the economic impact of dampness and mold exposures. By applying the attributable fraction to the updated national annual cost of asthma, the national annual cost of asthma that is attributable to dampness and mold exposure in the home is estimated to be $3.5 billion ($2.1-4.8 billion). Analysis indicates that exposure to dampness and mold in buildings poses significant public health and economic risks in the U.S. These findings are compatible with public policies and programs that help control moisture and mold in buildings.

  19. Controlled damping of a physical pendulum: experiments near critical conditions

    International Nuclear Information System (INIS)

    Gonzalez, Manuel I; Bol, Alfredo

    2006-01-01

    This paper presents an experimental device for the study of damped oscillatory motion along with three associated experiments. Special emphasis is given on both didactic aspects and the interactivity of the experimental set-up, in order to assist students in understanding fundamental aspects of damped oscillatory motion and allow them to directly compare their experimental results with the well-known theory they can find in textbooks. With this in mind, a physical pendulum was selected with an eddy-current damping system that allows the damping conditions to be controlled with great precision. The three experiments examine accurate control of damping, frequency shift near critical damping and the transition from underdamped to overdamped conditions

  20. Seismic damage diagnosis of a masonry building using short-term damping measurements

    Science.gov (United States)

    Kouris, Leonidas Alexandros S.; Penna, Andrea; Magenes, Guido

    2017-04-01

    It is of considerable importance to perform dynamic identification and detect damage in existing structures. This paper describes a new and practical method for damage diagnosis of masonry buildings requiring minimum computational effort. The method is based on the relative variation of modal damping and validated against experimental data from a full scale two storey shake table test. The experiment involves a building subjected to uniaxial vibrations of progressively increasing intensity at the facilities of EUCENTRE laboratory (Pavia, Italy) up to a near collapse damage state. Five time-histories are applied scaling the Montenegro (1979) accelerogram. These strong motion tests are preceded by random vibration tests (RVT's) which are used to perform modal analysis. Two deterministic methods are applied: the single degree of freedom (SDOF) assumption together with the peak-picking method in the discrete frequency domain and the Eigen realisation algorithm with data correlations (ERA-DC) in the discrete time domain. Regarding the former procedure, some improvements are incorporated to locate rigorously the natural frequencies and estimate the modal damping. The progressive evolution of the modal damping is used as a key indicator to characterise damage on the building. Modal damping is connected to the structural mass and stiffness. A square integrated but only with two components expression for proportional (classical) damping is proposed to fit better with the experimental measurements of modal damping ratios. Using this Rayleigh order formulation the contribution of each of the damping components is evaluated. The stiffness component coefficient is proposed as an effective index to detect damage and quantify its intensity.

  1. Analysis of enhanced modal damping ratio in porous materials using an acoustic-structure interaction model

    DEFF Research Database (Denmark)

    Kook, Junghwan; Jensen, Jakob Søndergaard

    2014-01-01

    The aim of this paper is to investigate the enhancement of the damping ratio of a structure with embedded microbeam resonators in air-filled internal cavities. In this context, we discuss theoretical aspects in the framework of the effective modal damping ratio (MDR) and derive an approximate...... relation expressing how an increased damping due to the acoustic medium surrounding the microbeam affect the MDR of the macrobeam. We further analyze the effect of including dissipation of the acoustic medium by using finite element (FE) analysis with acoustic-structure interaction (ASI) using a simple...... phenomenological acoustic loss model. An eigenvalue analysis is carried out to demonstrate the improvement of the damping characteristic of the macrobeam with the resonating microbeam in the lossy air and the results are compared to a forced vibration analysis for a macrobeam with one or multiple embedded...

  2. SOGI-based capacitor voltage feedback active damping in LCL-filtered grid converters

    DEFF Research Database (Denmark)

    Xin, Zhen; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    The capacitor voltage feedback active damping control is an attractive way to suppress LCL-filter resonance especially for the systems where the capacitor voltage is used for grid synchronization, since no extra sensors are added. The derivative is the core of the capacitor voltage feedback active...... derivative is more suited for capacitor voltage feedback active damping control. Experimental results validate the effectiveness of the proposed method....

  3. Onset of chaos in Josephson junctions with intermediate damping

    International Nuclear Information System (INIS)

    Yao, X.; Wu, J.Z.; Ting, C.S.

    1990-01-01

    By use of the analytical solution of the Stewart-McCumber equation including quadratic damping and dc bias, the Melnikov method has been extended to the parameter regions of intermediate damping and dc bias for the Josephson junctions with quadratic damping and with linear damping and cosφ term. The comparison between the thresholds predicted by the Melnikov method and that derived from numerical simulation has been studied. In addition, the validity conditions for the Melnikov threshold are also discussed

  4. The growth temperature and measurement temperature dependences of soft magnetic properties and effective damping parameter of (FeCo-Al alloy thin films

    Directory of Open Access Journals (Sweden)

    Yusuke Ariake

    2018-05-01

    Full Text Available The soft magnetic properties and effective damping parameters of Fe73Co25Al2 alloy thin films are discussed. The effective damping parameter αeff measured by ferromagnetic resonance for the 10 nm-thick sample is nearly constant (≈0.004 ± 0.0008 for a growth temperature Ts from ambient to 200 °C, and then tends to decrease for higher temperatures and αeff is 0.002 ± 0.0004 at Ts = 300 °C. For the 80 nm-thick sample, the αeff seems to increase with Ts from αeff = 0.001 ± 0.0002 at Ts = ambient to αeff = 0.002 ± 0.0004. The αeff is found nearly constant (αeff = 0.004 ± 0.0008 over a temperature range from 10 to 300 K for the 10 nm films with the different Ts (ambient, 100 and 200 °C. Together with an increasing non-linearity of the frequency dependence of the linewidth at low Ts, extrinsic contributions such as two-magnon scattering dominate the observed temperature dependence of effective damping and linewidth.

  5. Temperature dependent elasticity and damping in dehydrated sandstone

    Science.gov (United States)

    Darling, T. W.; Struble, W.

    2013-12-01

    Work reported previously at this conference, outlining our observation of anomalously large elastic softening and damping in dehydrated Berea sandstone at elevated temperatures, has been analysed to study shear and compressional effects separately. Modeling of the sample using COMSOL software was necessary to identify modes, as the vibration spectrum of the sample is poorly approximated by a uniform isotropic solid. The first torsional mode of our evacuated, dry, core softens at nearly twice the rate of Young's modulus modes (bending and compressional) and is also damped nearly twice as strongly as temperature increases. We consider two possible models for explaining this behavior, based on the assumption that the mechanical properties of the sandstone are dominated by the framework of quartz grains and polycrystalline cementation, neglecting initially the effects of clay and feldspar inclusions. The 20cm x 2.54cm diameter core is dry such that the pressure of water vapor in the experiment chamber is below 1e-6 Torr at 70C, suggesting that surface water beyond a small number of monolayers is negligible. Our models consider (1) enhanced sliding of grain boundaries in the cementation at elevated temperature and reduced internal water content, and (2) strain microcracking of the cementatioin at low water content due to anisotropic expansion in the quartz grains. In model (1) interfaces parallel to polyhedral grain surfaces were placed in the cement bonds and assigned frictional properties. Model (2) has not yet been implemented. The overall elasticity of a 3-D several-grain model network was determined by modeling quasistatic loading and measuring displacements. Initial results with a small number of grains/bonds suggests that only the first model provides softening and damping for all the modes, however the details of the effects of defect motioin at individual interfaces as the source for the frictional properties is still being evaluated. Nonlinear effects are

  6. Fluid Effects in Polymers and Polymeric Composites

    CERN Document Server

    Weitsman, Y Jack

    2012-01-01

    Fluid Effects in Polymers and Polymeric Composites, written by the late Dr. Y. Jack Weitsman, addresses the wide range of parameters that affect the interaction of fluids with polymers and polymeric composites. The book aims at broadening the scope of available data, mostly limited up to this time to weight-gain recordings of fluid ingress into polymers and composites, to the practical circumstances of fluctuating exposure. Various forms of experimental data are given, in conjunction with theoretical models derived from basic scientific principles, and correlated with severity of exposure conditions and interpreted by means of rationally based theoretical models. The practical implications of the effects of fluids are discussed. The issue of fluid effects on polymers and polymeric composites is of concern to engineers and scientists active in aerospace and naval structures, as an increasing portion of these structures are made of polymeric composites and employ polymeric adhesives as a joining device. While...

  7. Research on the Multilayer Free Damping Structure Design

    Directory of Open Access Journals (Sweden)

    Jie Meng

    2018-01-01

    Full Text Available The aim of this paper is to put forward a design model for multilayer free damping structures. It sets up a mathematical model and deduces the formula for its structural loss factor η and analyzes the change rules of η along with the change rate of the elastic modulus ratio q1, the change rate of the loss factors of damping materials q2, and the change rate of the layer thickness ratio q3 under the condition with the layer thickness ratio h2=1,3,5,10 by software MATLAB. Based on three specific damping structures, the mathematical model is verified through ABAQUS. With the given structural loss factor (η≥2 and the layer number (n=3,4,5,6, 34 kinds of multilayer free damping structures are then presented. The study is meant to provide a more flexible and more diverse design solution for multilayer free damping structures.

  8. Robinson's radiation damping sum rule: Reaffirmation and extension

    International Nuclear Information System (INIS)

    Mane, S.R.

    2011-01-01

    Robinson's radiation damping sum rule is one of the classic theorems of accelerator physics. Recently Orlov has claimed to find serious flaws in Robinson's proof of his sum rule. In view of the importance of the subject, I have independently examined the derivation of the Robinson radiation damping sum rule. Orlov's criticisms are without merit: I work through Robinson's derivation and demonstrate that Orlov's criticisms violate well-established mathematical theorems and are hence not valid. I also show that Robinson's derivation, and his damping sum rule, is valid in a larger domain than that treated by Robinson himself: Robinson derived his sum rule under the approximation of a small damping rate, but I show that Robinson's sum rule applies to arbitrary damping rates. I also display more concise derivations of the sum rule using matrix differential equations. I also show that Robinson's sum rule is valid in the vicinity of a parametric resonance.

  9. Electron Cloud Build Up and Instability in the CLIC Damping Rings

    CERN Document Server

    Rumolo, G; Papaphilippou, Y

    2008-01-01

    Electron cloud can be formed in the CLIC positron damping ring and cause intolerable tune shift and beam instability. Build up simulations with the Faktor2 code, developed at CERN, have been done to predict the cloud formation in the arcs and wigglers of the damping rings. HEADTAIL simulations have been used to study the effect of this electron cloud on the beam and assess the thresholds above which the electron cloud instability would set in.

  10. Evaluation of damping property of long-span prestressed concrete cable-stayed bridges; Chodai PC shachokyo no gensui tokusei ni kansuru kosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yamanobe, S.; Niihara, Y.; Minami, H.; Kono, T. [Kajima Corp., Tokyo (Japan)

    1999-09-30

    As to the dynamic design in the antiseismic design of PC cable-stayed bridges, evaluation of damping is important. Since it is difficult to evaluate damping property theoretically and analytically, a lot of studies have not been made about how to set up damping coefficients. In this study, using analytical models of existing long-span PC cable-stayed bridges, to clarify causes of damping of long-span PC cable-stayed bridge, the rate of strain energy in each member was examined. Equivalent damping coefficients of each member, effects of friction in movable bearing, and effects of basically radiational damping were studied. The correspondence with the results of the vibration experiments conventionally made were studied. (translated by NEDO)

  11. On the Empirical Estimation of Utility Distribution Damping Parameters Using Power Quality Waveform Data

    Directory of Open Access Journals (Sweden)

    Irene Y. H. Gu

    2007-01-01

    Full Text Available This paper describes an efficient yet accurate methodology for estimating system damping. The proposed technique is based on linear dynamic system theory and the Hilbert damping analysis. The proposed technique requires capacitor switching waveforms only. The detected envelope of the intrinsic transient portion of the voltage waveform after capacitor bank energizing and its decay rate along with the damped resonant frequency are used to quantify effective X/R ratio of a system. Thus, the proposed method provides complete knowledge of system impedance characteristics. The estimated system damping can also be used to evaluate the system vulnerability to various PQ disturbances, particularly resonance phenomena, so that a utility may take preventive measures and improve PQ of the system.

  12. Dispersion relation and Landau damping of waves in high-energy density plasmas

    International Nuclear Information System (INIS)

    Zhu Jun; Ji Peiyong

    2012-01-01

    We present a theoretical investigation on the propagation of electromagnetic waves and electron plasma waves in high energy density plasmas using the covariant Wigner function approach. Based on the covariant Wigner function and Dirac equation, a relativistic quantum kinetic model is established to describe the physical processes in high-energy density plasmas. With the zero-temperature Fermi–Dirac distribution, the dispersion relation and Landau damping of waves containing the relativistic quantum corrected terms are derived. The relativistic quantum corrections to the dispersion relation and Landau damping are analyzed by comparing our results with those obtained in classical and non-relativistic quantum plasmas. We provide a detailed discussion on the Landau damping obtained in classical plasmas, non-relativistic Fermi plasmas and relativistic Fermi plasmas. The contributions of the Bohm potential, the Fermi statistics pressure and relativistic effects to the dispersion relation and Landau damping of waves are quantitatively calculated with real plasma parameters. (paper)

  13. Coupled oscillators in identification of nonlinear damping of a real parametric pendulum

    Science.gov (United States)

    Olejnik, Paweł; Awrejcewicz, Jan

    2018-01-01

    A damped parametric pendulum with friction is identified twice by means of its precise and imprecise mathematical model. A laboratory test stand designed for experimental investigations of nonlinear effects determined by a viscous resistance and the stick-slip phenomenon serves as the model mechanical system. An influence of accurateness of mathematical modeling on the time variability of the nonlinear damping coefficient of the oscillator is proved. A free decay response of a precisely and imprecisely modeled physical pendulum is dependent on two different time-varying coefficients of damping. The coefficients of the analyzed parametric oscillator are identified with the use of a new semi-empirical method based on a coupled oscillators approach, utilizing the fractional order derivative of the discrete measurement series treated as an input to the numerical model. Results of application of the proposed method of identification of the nonlinear coefficients of the damped parametric oscillator have been illustrated and extensively discussed.

  14. Modelling and Vibration Control of Beams with Partially Debonded Active Constrained Layer Damping Patch

    Science.gov (United States)

    SUN, D.; TONG, L.

    2002-05-01

    A detailed model for the beams with partially debonded active constraining damping (ACLD) treatment is presented. In this model, the transverse displacement of the constraining layer is considered to be non-identical to that of the host structure. In the perfect bonding region, the viscoelastic core is modelled to carry both peel and shear stresses, while in the debonding area, it is assumed that no peel and shear stresses be transferred between the host beam and the constraining layer. The adhesive layer between the piezoelectric sensor and the host beam is also considered in this model. In active control, the positive position feedback control is employed to control the first mode of the beam. Based on this model, the incompatibility of the transverse displacements of the active constraining layer and the host beam is investigated. The passive and active damping behaviors of the ACLD patch with different thicknesses, locations and lengths are examined. Moreover, the effects of debonding of the damping layer on both passive and active control are examined via a simulation example. The results show that the incompatibility of the transverse displacements is remarkable in the regions near the ends of the ACLD patch especially for the high order vibration modes. It is found that a thinner damping layer may lead to larger shear strain and consequently results in a larger passive and active damping. In addition to the thickness of the damping layer, its length and location are also key factors to the hybrid control. The numerical results unveil that edge debonding can lead to a reduction of both passive and active damping, and the hybrid damping may be more sensitive to the debonding of the damping layer than the passive damping.

  15. Active-Reactive Additional Damping Control of a Doubly-Fed Induction Generator Based on Active Disturbance Rejection Control

    Directory of Open Access Journals (Sweden)

    Yanfeng Ma

    2018-05-01

    Full Text Available Large-scale wind power interfacing to the power grid has an impact on the stability of the power system. However, with an additional damping controller of the wind generator, new ways for improving system damping and suppressing the low frequency oscillation (LFO of power systems can be put forward. In this paper, an active-reactive power additional damping controller based on active disturbance rejection control (ADRC is proposed. In order to improve the precision of the controller, the theory of data driven control is adopted, using the numerical algorithms for subspace state space system identification (N4SID to obtain the two order model of the ADRC controlled object. Based on the identification model, the ADRC additional damping controller is designed. Taking a 2-area 4-machine system containing the doubly fed induction generator (DFIG wind farm as an example, it is verified that the active-reactive additional damping controller designed in this paper performs well in suppressing negative-damping LFO and forced power oscillation. When the operation state of the power system changes, it can still restrain the LFO effectively, showing stronger robustness and better effectiveness compared to the traditional proportional–integral–derivative (PID additional damping controller.

  16. A Damping Grid Strapdown Inertial Navigation System Based on a Kalman Filter for Ships in Polar Regions.

    Science.gov (United States)

    Huang, Weiquan; Fang, Tao; Luo, Li; Zhao, Lin; Che, Fengzhu

    2017-07-03

    The grid strapdown inertial navigation system (SINS) used in polar navigation also includes three kinds of periodic oscillation errors as common SINS are based on a geographic coordinate system. Aiming ships which have the external information to conduct a system reset regularly, suppressing the Schuler periodic oscillation is an effective way to enhance navigation accuracy. The Kalman filter based on the grid SINS error model which applies to the ship is established in this paper. The errors of grid-level attitude angles can be accurately estimated when the external velocity contains constant error, and then correcting the errors of the grid-level attitude angles through feedback correction can effectively dampen the Schuler periodic oscillation. The simulation results show that with the aid of external reference velocity, the proposed external level damping algorithm based on the Kalman filter can suppress the Schuler periodic oscillation effectively. Compared with the traditional external level damping algorithm based on the damping network, the algorithm proposed in this paper can reduce the overshoot errors when the state of grid SINS is switched from the non-damping state to the damping state, and this effectively improves the navigation accuracy of the system.

  17. Design, Fabrication, and Properties of High Damping Metal Matrix Composites—A Review

    Directory of Open Access Journals (Sweden)

    Qianfeng Fang

    2009-08-01

    Full Text Available Nowadays it is commonly considered that high damping materials which have both the good mechanical properties as structural materials and the high damping capacity for vibration damping are the most direct vibration damping solution. In metals and alloys however, exhibiting simultaneously high damping capacity and good mechanical properties has been noted to be normally incompatible because the microscopic mechanisms responsible for internal friction (namely damping capacity are dependent upon the parameters that control mechanical strength. To achieve a compromise, one of the most important methods is to develop two-phase composites, in which each phase plays a specific role: damping or mechanical strength. In this review, we have summarized the development of the design concept of high damping composite materials and the investigation of their fabrication and properties, including mechanical and damping properties, and suggested a new design concept of high damping composite materials where the hard ceramic additives exhibit high damping capacity at room temperature owing to the stress-induced reorientation of high density point defects in the ceramic phases and the high damping capacity of the composite comes mainly from the ceramic phases.

  18. A Monte Carlo Simulation approach for the modeling of free-molecule squeeze-film damping of flexible microresonators

    KAUST Repository

    Leung, Roger

    2010-03-31

    Squeeze-film damping on microresonators is a significant damping source even when the surrounding gas is highly rarefied. This article presents a general modeling approach based on Monte Carlo (MC) simulations for the prediction of squeeze-film damping on resonators in the freemolecule regime. The generality of the approach is demonstrated in its capability of simulating resonators of any shape and with any accommodation coefficient. The approach is validated using both the analytical results of the free-space damping and the experimental data of the squeeze-film damping on a clamped-clamped plate resonator oscillating at its first flexure mode. The effect of oscillation modes on the quality factor of the resonator has also been studied and semi-analytical approximate models for the squeeze-film damping with diffuse collisions have been developed.

  19. Predicting phase shift of elastic waves in pipes due to fluid flow and imperfections

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Dahl, Jonas; Fuglede, Niels

    2009-01-01

    . This is relevant for understanding wave propagation in elastic media in general, and for the design and trouble-shooting of phase-shift measuring devices such as Coriolis mass flowmeters in particular. A multiple time scaling perturbation analysis is employed for a simple model of a fluid-conveying pipe......Flexural vibrations of a fluid-conveying pipe is investigated, with special consideration to the spatial shift in phase caused by fluid flow and various imperfections, e.g., non-ideal supports, non-uniform stiffness or mass, non-proportional damping, weak nonlinearity, and flow pulsation...

  20. Damping element for reducing the vibration of an airfoil

    Science.gov (United States)

    Campbell, Christian X; Marra, John J

    2013-11-12

    An airfoil (10) is provided with a tip (12) having an opening (14) to a center channel (24). A damping element (16) is inserted within the opening of the center channel, to reduce an induced vibration of the airfoil. The mass of the damping element, a spring constant of the damping element within the center channel, and/or a mounting location (58) of the damping element within the center channel may be adjustably varied, to shift a resonance frequency of the airfoil outside a natural operating frequency of the airfoil.

  1. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    Directory of Open Access Journals (Sweden)

    H. K. Lee

    2016-05-01

    Full Text Available We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO and Pt capped LSMO thin films on SrTiO3 (001 substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1 × 10−3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

  2. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H. K., E-mail: hankl@uci.edu; Barsukov, I.; Yang, L.; Krivorotov, I. N. [Physics and Astronomy, University of California, Irvine, California 92697 (United States); Swartz, A. G.; Kim, B. [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Hwang, H. Y. [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-05-15

    We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and Pt capped LSMO thin films on SrTiO{sub 3} (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10{sup −3}, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

  3. Magnetization damping in two-component metal oxide micropowder and nanopowder compacts by broadband ferromagnetic resonance measurements

    Science.gov (United States)

    Youssef, Jamal Ben; Brosseau, Christian

    2006-12-01

    The microwave damping mechanisms in magnetic inhomogeneous systems have displayed a richness of phenomenology that has attracted widespread interest over the years. Motivated by recent experiments, we report an extensive experimental study of the Gilbert damping parameter of multicomponent metal oxides micro- and nanophases. We label the former by M samples, and the latter by N samples. The main thrust of this examination is the magnetization dynamics in systems composed of mixtures of magnetic (γ-Fe2O3) and nonmagnetic (ZnO and epoxy resin) materials fabricated via powder processing. Detailed ferromagnetic resonance (FMR) measurements on N and M samples are described so to determine changes in the microwave absorption over the 6-18GHz frequency range as a function of composition and static magnetic field. The FMR linewidth and the field dependent resonance were measured for the M and N samples, at a given volume fraction of the magnetic phase. The asymmetry in the form and change in the linewidth for the M samples are caused by the orientation distribution of the local anisotropy fields, whereas the results for the N samples suggest that the linewidth is very sensitive to details of the spatial magnetic inhomogeneities. For N samples, the peak-to-peak linewidth increases continuously with the volume content of magnetic material. The influence of the volume fraction of the magnetic phase on the static internal field was also investigated. Furthermore, important insights are gleaned through analysis of the interrelationship between effective permeability and Gilbert damping constant. Different mechanisms have been considered to explain the FMR linewidth: the intrinsic Gilbert damping, the broadening induced by the magnetic inhomogeneities, and the extrinsic magnetic relaxation. We observed that the effective Gilbert damping constant of the series of N samples are found to be substantially smaller in comparison to M samples. This effect is attributed to the surface

  4. A Resonant Damping Study Using Piezoelectric Materials

    Science.gov (United States)

    Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

    2008-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

  5. Cellular Magnesium Matrix Foam Composites for Mechanical Damping Applications

    Science.gov (United States)

    Shunmugasamy, Vasanth Chakravarthy; Mansoor, Bilal; Gupta, Nikhil

    2016-01-01

    The damping characteristics of metal alloys and metal matrix composites are relevant to the automotive, aerospace, and marine structures. Use of lightweight materials can help in increasing payload capacity and in decreasing fuel consumption. Lightweight composite materials possessing high damping capabilities that can be designed as structural members can greatly benefit in addressing these needs. In this context, the damping properties of lightweight metals such as aluminum and magnesium and their respective composites have been studied in the existing literature. This review focuses on analyzing the damping properties of aluminum and magnesium alloys and their cellular composites. The damping properties of various lightweight alloys and composites are compared on the basis of their density to understand the potential for weight saving in structural applications. Magnesium alloys are observed to possess better damping properties in comparison to aluminum. However, aluminum matrix syntactic foams reinforced with silicon carbide hollow particles possess a damping capacity and density comparable to magnesium alloy. By using the data presented in the study, composites with specific compositions and properties can be selected for a given application. In addition, the comparison of the results helps in identifying the areas where attention needs to be focused to address the future needs.

  6. The rheology of shear thickening fluid (STF) and the dynamic performance of an STF-filled damper

    International Nuclear Information System (INIS)

    Zhang, X Z; Li, W H; Gong, X L

    2008-01-01

    This paper presents a study of the rheological properties of shear thickening fluid (STF) and its application as a damper. The STF samples, with different weight fractions, were prepared by dispersing nanosized silica particles in a solvent. By using a parallel-plate rheometer, both steady-state and dynamic experiments were carried out to investigate the rheological properties of STFs. Experimental results indicated that these suspensions show an abrupt increase in complex viscosity beyond a critical dynamic shear rate, as well as this increase being reversible. Working with the fabricated STF materials, a prototype damper was fabricated and its dynamic performances were experimentally evaluated. An equivalent linear model through effective elastic stiffness and viscous damping was developed to address both the damping and the stiffness capabilities of the damper. Also, a mathematical model was developed to investigate working mechanisms of STF-based devices

  7. Enhanced damping for bridge cables using a self-sensing MR damper

    Science.gov (United States)

    Chen, Z. H.; Lam, K. H.; Ni, Y. Q.

    2016-08-01

    This paper investigates enhanced damping for protecting bridge stay cables from excessive vibration using a newly developed self-sensing magnetorheological (MR) damper. The semi-active control strategy for effectively operating the self-sensing MR damper is formulated based on the linear-quadratic-Gaussian (LQG) control by further considering a collocated control configuration, limited measurements and nonlinear damper dynamics. Due to its attractive feature of sensing-while-damping, the self-sensing MR damper facilitates the collocated control. On the other hand, only the sensor measurements from the self-sensing device are employed in the feedback control. The nonlinear dynamics of the self-sensing MR damper, represented by a validated Bayesian NARX network technique, are further accommodated in the control formulation to compensate for its nonlinearities. Numerical and experimental investigations are conducted on stay cables equipped with the self-sensing MR damper operated in passive and semi-active control modes. The results verify that the collocated self-sensing MR damper facilitates smart damping for inclined cables employing energy-dissipative LQG control with only force and displacement measurements at the damper. It is also demonstrated that the synthesis of nonlinear damper dynamics in the LQG control enhances damping force tracking efficiently, explores the features of the self-sensing MR damper, and achieves better control performance over the passive MR damping control and the Heaviside step function-based LQG control that ignores the damper dynamics.

  8. Dynamic Optimization of Constrained Layer Damping Structure for the Headstock of Machine Tools with Modal Strain Energy Method

    Directory of Open Access Journals (Sweden)

    Yakai Xu

    2017-01-01

    Full Text Available Dynamic stiffness and damping of the headstock, which is a critical component of precision horizontal machining center, are two main factors that influence machining accuracy and surface finish quality. Constrained Layer Damping (CLD structure is proved to be effective in raising damping capacity for the thin plate and shell structures. In this paper, one kind of high damping material is utilized on the headstock to improve damping capacity. The dynamic characteristic of the hybrid headstock is investigated analytically and experimentally. The results demonstrate that the resonant response amplitudes of the headstock with damping material can decrease significantly compared to original cast structure. To obtain the optimal configuration of damping material, a topology optimization method based on the Evolutionary Structural Optimization (ESO is implemented. Modal Strain Energy (MSE method is employed to analyze the damping and to derive the sensitivity of the modal loss factor. The optimization results indicate that the added weight of damping material decreases by 50%; meanwhile the first two orders of modal loss factor decrease by less than 23.5% compared to the original structure.

  9. Design and Analysis of Robust Active Damping for LCL Filters using Digital Notch Filters

    DEFF Research Database (Denmark)

    Yao, Wenli; Yang, Yongheng; Zhang, Xiaobin

    2017-01-01

    Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp the reso......Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp...... the resonance, where the notch frequency should be aligned exactly to the resonant frequency of the LCL filter. However, parameter variations of the LCL filter as well as the time delay appearing in digital control systems will induce resonance drifting, and thus break this alignment, possibly deteriorating...... the original damping. In this paper, the effectiveness of the notch filter based active damping is firstly explored, considering the drifts of the resonant frequency. It is revealed that, when the resonant frequency drifts away from its nominal value, the phase lead or lag introduced by the notch filter may...

  10. Experimental evaluation of a self-powered smart damping system in reducing vibrations of a full-scale stay cable

    International Nuclear Information System (INIS)

    Kim, In-Ho; Jung, Hyung-Jo; Koo, Jeong-Hoi

    2010-01-01

    This paper investigates the effectiveness of a self-powered smart damping system consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) device in reducing cable vibrations. The proposed smart damping system incorporates an EMI device, which is capable of converting vibration energy into useful electrical energy. Thus, the incorporated EMI device can be used as an alternative power source for the MR damper, making it a self-powering system. The primary goal of this experimental study is to evaluate the performance of the proposed smart damping system using a full-scale, 44.7 m long, high-tension cable. To this end, an EMI part and an MR damper were designed and manufactured. Using a cable test setup in a laboratory setting, a series of tests were performed to evaluate the effectiveness of the self-powered smart damping system in reducing free vibration responses of the cable. The performances of the proposed smart damping system are compared with those of an equivalent passive system. Moreover, the damping characteristics of the smart damping system and the passive system are compared. The experimental results show that the self-powered smart damping system outperforms the passive control cases in reducing the vibrations of the cable. The results also show that the EMI can operate the smart damping system as a sole power source, demonstrating the feasibility of the self-powering capability of the system

  11. Design method for fluid viscous dampers

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Jiuhong; Hua, Hongxing [Shanghai Jiaotong University, State Key Laboratory of Mechanical System and Vibration, Shanghai (China); Du, Jianye; Wang, Yu [Naval Arming Academy, Institute of Naval Vessels, Beijing (China)

    2008-09-15

    A basic design method of doubly acting fluid viscous dampers with double guide bars is presented. The flow of the viscoelastic fluid between two parallel plates, one of which is started suddenly and the other of which is still, is analyzed. According to this solution, the velocity and the shear stress of the fluid at the fringe of the piston are solved approximately. A mathematical model of viscous dampers is derived, and the shock test is carried out. From experimental results, the parameters of the mathematical model are determined. Consequently, a semi-empirical design equation is obtained. Applying this equation to a certain practical damper, the damping material is chosen and the physical dimensions of the damper are determined. Shock tests using this damper are performed. Theoretical results are in good agreement with experimental results, which validates the reliability of the calculated physical dimensions of the specimen damper and the validity of the basic design equation. (orig.)

  12. Complex modes and frequencies in damped structural vibrations

    DEFF Research Database (Denmark)

    Krenk, Steen

    2004-01-01

    It is demonstrated that the state space formulation of the equation of motion of damped structural elements like cables and beams leads to a symmetric eigenvalue problem if the stiffness and damping operators are self-adjoint, and that this is typically the case in the absence of gyroscopic forces....... The corresponding theory of complex modal analysis of continuous systems is developed and illustrated in relation to optimal damping and impulse response of cables and beams with discrete dampers....

  13. Structural damage identification using damping: a compendium of uses and features

    Science.gov (United States)

    Cao, M. S.; Sha, G. G.; Gao, Y. F.; Ostachowicz, W.

    2017-04-01

    The vibration responses of structures under controlled or ambient excitation can be used to detect structural damage by correlating changes in structural dynamic properties extracted from responses with damage. Typical dynamic properties refer to modal parameters: natural frequencies, mode shapes, and damping. Among these parameters, natural frequencies and mode shapes have been investigated extensively for their use in damage characterization by associating damage with reduction in local stiffness of structures. In contrast, the use of damping as a dynamic property to represent structural damage has not been comprehensively elucidated, primarily due to the complexities of damping measurement and analysis. With advances in measurement technologies and analysis tools, the use of damping to identify damage is becoming a focus of increasing attention in the damage detection community. Recently, a number of studies have demonstrated that damping has greater sensitivity for characterizing damage than natural frequencies and mode shapes in various applications, but damping-based damage identification is still a research direction ‘in progress’ and is not yet well resolved. This situation calls for an overall survey of the state-of-the-art and the state-of-the-practice of using damping to detect structural damage. To this end, this study aims to provide a comprehensive survey of uses and features of applying damping in structural damage detection. First, we present various methods for damping estimation in different domains including the time domain, the frequency domain, and the time-frequency domain. Second, we investigate the features and applications of damping-based damage detection methods on the basis of two predominant infrastructure elements, reinforced concrete structures and fiber-reinforced composites. Third, we clarify the influential factors that can impair the capability of damping to characterize damage. Finally, we recommend future research directions

  14. Chaotic transport and damping from θ-ruffled separatrices.

    Science.gov (United States)

    Kabantsev, A A; Dubin, Daniel H E; Driscoll, C F; Tsidulko, Yu A

    2010-11-12

    Variations in magnetic or electrostatic confinement fields give rise to trapping separatrices, and neoclassical transport theory analyzes effects from collision-induced separatrix crossings. Experiments on pure electron plasmas now quantitatively characterize a broad range of transport and wave damping effects due to "chaotic" separatrix crossings, which occur due to equilibrium plasma rotation across θ-ruffled separatrices, and due to wave-induced separatrix fluctuations.

  15. Foucault pendulum with eddy-current damping of the elliptical motion

    Science.gov (United States)

    Mastner, G.; Vokurka, V.; Maschek, M.; Vogt, E.; Kaufmann, H. P.

    1984-10-01

    A newly designed Foucault pendulum is described in which the mechanical Charron ring, used throughout in previous designs for damping of the elliptical motion of the pendulum, is replaced by an electromagnetic eddy-current brake, consisting of a permanent magnet attached to the bottom of the bob and a metallic ring. This damping device is very efficient, as it is self-aligning, symmetrical in the damping effect, and never wears out. The permanent magnet is also used, together with a coil assembly and an electronic circuitry, for the dipole-torque drive of the pendulum as well as for accurate stabilization of the amplitude of the swing. A latched time display, controlled by Hall probes activated by the magnet, is used to visualize the Foucault rotation. The pendulum system and its associated electronic circuitry are described in detail. The optimizing of the drive mode is discussed. Measurements of deviations from theoretical value of the Foucault rotation velocity made automatically in a continuous run show a reproducible accuracy of ±1% or better in individual 360° rotations during the summer months. The quality factor of the pendulum as mechanical resonator was measured as a function of the amplitude in the presence of the eddy-current damping ring.

  16. Asymptotical Behavior of the Solution of a SDOF Linear Fractionally Damped Vibration System

    Directory of Open Access Journals (Sweden)

    Z.H. Wang

    2011-01-01

    Full Text Available Fractional-order derivative has been shown an adequate tool to the study of so-called "anomalous" social and physical behaviors, in reflecting their non-local, frequency- and history-dependent properties, and it has been used to model practical systems in engineering successfully, including the famous Bagley-Torvik equation modeling forced motion of a rigid plate immersed in Newtonian fluid. The solutions of the initial value problems of linear fractional differential equations are usually expressed in terms of Mittag-Leffler functions or some other kind of power series. Such forms of solutions are not good for engineers not only in understanding the solutions but also in investigation. This paper proves that for the linear SDOF oscillator with a damping described by fractional-order derivative whose order is between 1 and 2, the solution of its initial value problem free of external excitation consists of two parts, the first one is the 'eigenfunction expansion' that is similar to the case without fractional-order derivative, and the second one is a definite integral that is independent of the eigenvalues (or characteristic roots. The integral disappears in the classical linear oscillator and it can be neglected from the solution when stationary solution is addressed. Moreover, the response of the fractionally damped oscillator under harmonic excitation is calculated in a similar way, and it is found that the fractional damping with order between 1 and 2 can be used to produce oscillation with large amplitude as well as to suppress oscillation, depending on the ratio of the excitation frequency and the natural frequency.

  17. TCSC Nonlinear Adaptive Damping Controller Design Based on RBF Neural Network to Enhance Power System Stability

    DEFF Research Database (Denmark)

    Yao, Wei; Fang, Jiakun; Zhao, Ping

    2013-01-01

    the characteristics of the conventional PID, but adjust the parameters of PID controller online using identified Jacobian information from RBFNN. Hence, it has strong adaptability to the variation of the system operating condition. The effectiveness of the proposed controller is tested on a two-machine five-bus power...... system and a four-machine two-area power system under different operating conditions in comparison with the lead-lag damping controller tuned by evolutionary algorithm (EA). Simulation results show that the proposed damping controller achieves good robust performance for damping the low frequency......In this paper, a nonlinear adaptive damping controller based on radial basis function neural network (RBFNN), which can infinitely approximate to nonlinear system, is proposed for thyristor controlled series capacitor (TCSC). The proposed TCSC adaptive damping controller can not only have...

  18. The electron damping ring for the SLAC Linear Collider

    International Nuclear Information System (INIS)

    Davies-White, W.; Hutton, A.; Harvey, A.

    1987-10-01

    A second damping ring to store and damp two electron bunches for the SLC project was constructed in 1985 and brought into operation early in 1986. Although generally similar to the damping ring (now used for positrons) constructed earlier, there are a number of design improvements and changes. The dipole magnetic field was raised to 2.1 T to improve damping. Sextupole fields were provided by separate permanent magnets, rather than being incorporated in the dipoles. The vacuum chambers, including the beam position monitors, were re-designed for lower longitudinal impedance. A new kicker was developed by Fermilab to handle the two electron bunches. Improvements were made to the dc septum magnet design. Several of the features are described in detail elsewhere. Where possible, the improvements were incorporated in an upgrade of the earlier damping ring

  19. Nonadiabatic effects on surfaces: Kohn anomaly, electronic damping of adsorbate vibrations, and local heating of single molecules

    International Nuclear Information System (INIS)

    Kroeger, J

    2008-01-01

    Three aspects of electron-phonon coupling at metal surfaces are reviewed. One aspect is the Kohn effect, which describes an anomalous dispersion relation of surface phonons due to quasi-one-dimensional nesting of Fermi surface contours. The combination of electron energy loss spectroscopy and angle-resolved photoelectron spectroscopy allows us to unambiguously characterize Kohn anomaly systems. A second aspect is the nonadiabatic damping of adsorbate vibrations. Characteristic spectroscopic line shapes of vibrational modes allow us to estimate the amount of energy transfer between the vibrational mode and electron-hole pairs. Case studies of a Kohn anomaly and nonadiabatic damping are provided by the hydrogen- and deuterium-covered Mo(110) surface. As a third aspect of interaction between electrons and phonons, local heating of a C 60 molecule adsorbed on Cu(100) and in contact with the tip of a scanning tunnelling microscope is covered

  20. Structural Damping with Friction Beams

    Directory of Open Access Journals (Sweden)

    L. Gaul

    2008-01-01

    Full Text Available In the last several years, there has been increasing interest in the use of friction joints for enhancing damping in structures. The joints themselves are responsible for the major part of the energy dissipation in assembled structures. The dissipated work in a joint depends on both the applied normal force and the excitation force. For the case of a constant amplitude excitation force, there is an optimal normal force which maximizes the damping. A ‘passive’ approach would be employed in this instance. In most cases however, the excitation force, as well as the interface parameters such as the friction coefficient, normal pressure distribution, etc., are not constant. In these cases, a ‘semi-active’ approach, which implements an active varying normal force, is necessary. For the ‘passive’ and ‘semi-active’ approaches, the normal force has to be measured. Interestingly, since the normal force in a friction joint influences the local stiffness, the natural frequencies of the assembled structure can be tuned by adjusting the normal force. Experiments and simulations are performed for a simple laboratory structure consisting of two superposed beams with friction in the interface. Numerical simulation of the friction interface requires non-linear models. The response of the double beam system is simulated using a numerical algorithm programmed in MATLAB which models point-to-point friction with the Masing friction model. Numerical predictions and measurements of the double beam free vibration response are compared. A practical application is then described, in which a friction beam is used to damp the vibrations of the work piece table on a milling machine. The increased damping of the table reduces vibration amplitudes, which in turn results in enhanced surface quality of the machined parts, reduction in machine tool wear, and potentially higher feed rates. Optimal positioning of the friction beams is based on knowledge of the mode

  1. Three-dimensional fluid-structure interaction case study on cubical fluid cavity with flexible bottom

    Science.gov (United States)

    Ghelardi, Stefano; Rizzo, Cesare; Villa, Diego

    2017-12-01

    In this paper, we report our study on a numerical fluid-structure interaction problem originally presented by Mok et al. (2001) in two dimensions and later studied in three dimensions by Valdés Vazquez (2007), Lombardi (2012), and Trimarchi (2012). We focus on a 3D test case in which we evaluated the sensitivity of several input parameters on the fluid and structural results. In particular, this analysis provides a starting point from which we can look deeper into specific aspects of these simulations and analyze more realistic cases, e.g., in sails design. In this study, using the commercial software ADINA™, we addressed a well-known unsteadiness problem comprising a square box representing the fluid domain with a flexible bottom modeled with structural shell elements. We compared data from previously published work whose authors used the same numerical approach, i.e., a partitioned approach coupling a finite volume solver (for the fluid domain) and a finite element solver (for the solid domain). Specifically, we established several benchmarks and made comparisons with respect to fluid and solid meshes, structural element types, and structural damping, as well as solution algorithms. Moreover, we compared our method with a monolithic finite element solution method. Our comparisons of new and old results provide an outline of best practices for such simulations.

  2. Active and passive damping based on piezoelectric elements -controllability issues-

    NARCIS (Netherlands)

    Holterman, J.; de Vries, Theodorus J.A.; van Amerongen, J.; Jonker, Jan B.; Jonker, J.B.

    2001-01-01

    Piezoelectric elements are widely used for damping micro-vibrations in mechanical structures. Active damping can be realised robustly by means of collocated actuator-sensor-pairs, controlled so as to extract vibration energy. Excellent damping performance is possible as long as sufficient

  3. High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

    International Nuclear Information System (INIS)

    Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

    2000-01-01

    The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10 -3 ). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10 -2 , however, their densities are usually great than 5 x 10 3 kg m -3 , or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process

  4. Damped Lyman-alpha absorption by disk galaxies with large redshifts. III. Intermediate-resolution spectroscopy

    International Nuclear Information System (INIS)

    Turnshek, D.A.; Wolfe, A.M.; Lanzetta, K.M.; Briggs, F.H.; Cohen, R.D.

    1989-01-01

    New intermediate-resolution spectroscopy for six members of a sample of 68 moderate- to high-redshift QSOs is presented. Evidence is reported which indicates that seven strong absorption features in the QSO spectra are due to damped Ly-alpha absorption. A standard curve-of-growth analysis on five of the damped systems is performed, and relevant properties are tabulated and discussed. Six of the seven damped Ly-alpha systems have H I column densities of 2 x 10 to the 20th/sq cm or larger, while the remaining system has an H I column density of about 10 to the 20th/sq cm. It is suggested that damped Ly-alpha systems arise when a sight line intercepts a high-redshift protogalaxy disk containing a quiescent cloud component characterized by high column density and low effective velocity dispersion. At the same time, the sight line usually intercepts a broader turbulent component, which is identified as the halo, characterized by much lower column density and higher effective velocity dispersion. 42 refs

  5. Beam dynamic issues in TESLA damping ring

    International Nuclear Information System (INIS)

    Shiltsev, V.

    1996-05-01

    In this paper we study general requirements on impedances of the linear collider TESLA damping ring design. Quantitative consideration is performed for 17-km long ''dog-bone'' ring. Beam dynamics in alternative options of 6.3 and 2.3-km long damping rings is briefly discussed. 5 refs., 2 tabs

  6. Nonlinear evolution of magnetic islands in a two fluid torus

    International Nuclear Information System (INIS)

    Sugiyama, L.E.; Park, W.

    1996-01-01

    A numerical model MH3D-T for the two fluid description of macroscopic evolution in a full three dimensional torus has been developed. Based on the perturbative drift ordering, generalized to arbitrary perturbation size, the model follows the full temperature evolution, including the thermal equilibration along the magnetic field. It contains the diamagnetic drifts, ion gyroviscous stress tensor, and the Hall term in Ohm's law. Electron inertia is neglected. The numerical model solves the same equations in a torus and in several simplified configurations. It has been benchmarked against the diamagnetic ω* i stabilization of the resistive m = 1, n = 1 reconnecting mode in a cylinder. The nonlinear evolution of resistive magnetic islands with m,n ≠ 1,1 in a cylinder is found to agree with previous analytic and reduced-torus results, which show that the diamagnetic rotation vanishes early in the island evolution and the saturated island size is determined by the same external driving factor Δ' as in MHD. The two fluid evolution in a full torus, however, differs from that in a cylinder and from the resistive MHD evolution. The poloidal rotation velocity undergoes a degree of poloidal momentum damping in the torus, even without neoclassical effects. The two fluid magnetic island grows faster, nonlinearly, than the resistive MHD island, and also couples different toroidal harmonics more effectively. Plasma compressibility and processes operating along the magnetic field play a much more important role than in MHD or in simple geometry. The two fluid model contains all the important neoclassical fluid effects except for the b circ ∇ circ Π parallelj viscous force terms. The addition of these terms is in progress

  7. A PSO based unified power flow controller for damping of power system oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Shayeghi, H. [Technical Engineering Dept., Univ. of Mohaghegh Ardabili, Daneshgah Street, P.O. Box 179, Ardabil (Iran); Shayanfar, H.A. [Center of Excellence for Power Automation and Operation, Electrical Engineering Dept., Iran Univ. of Science and Technology, Tehran (Iran); Jalilzadeh, S.; Safari, A. [Technical Engineering Dept., Zanjan Univ., Zanjan (Iran)

    2009-10-15

    On the basis of the linearized Phillips-Herffron model of a single-machine power system, we approach the problem of select the best input control signal of the unified power flow controller (UPFC) and design optimal UPFC based damping controller in order to enhance the damping of the power system low frequency oscillations. The potential of the UPFC supplementary controllers to enhance the dynamic stability is evaluated. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robustly UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multiobjective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using particle swarm optimization technique (PSO) that has a strong ability to find the most optimistic results. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller is demonstrated through eigenvalue analysis, nonlinear time-domain simulation and some performance indices studies. The results analysis reveals that the tuned PSO based UPFC controller using the proposed multiobjective function has an excellent capability in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the {delta}{sub E} based controller is superior to the m{sub B} based controller. (author)

  8. The Frequency and Damping of Soil-Structure Systems with Embedded Foundation

    International Nuclear Information System (INIS)

    Ghannad, M. Ali; Rahmani, Mohammad T.; Jahankhah, Hossein

    2008-01-01

    The effect of foundation embedment on fundamental period and damping of buildings has been the title of several researches in three past decades. A review of the literature reveals some discrepancies between proposed formulations for dynamic characteristics of soil-embedded foundation-structure systems that raise the necessity of more investigation on this issue. Here, first a set of approximate polynomial equations for soil impedances, based on numerical data calculated from well known cone models, are presented. Then a simplified approach is suggested to calculate period and damping of the whole system considering soil medium as a viscoelastic half space. The procedure includes both material and radiation damping while frequency dependency of soil impedance functions is not ignored. Results show that soil-structure interaction can highly affect dynamic properties of system. Finally the results are compared with one of the commonly referred researches

  9. Unwrapped phase inversion with an exponential damping

    KAUST Repository

    Choi, Yun Seok

    2015-07-28

    Full-waveform inversion (FWI) suffers from the phase wrapping (cycle skipping) problem when the frequency of data is not low enough. Unless we obtain a good initial velocity model, the phase wrapping problem in FWI causes a result corresponding to a local minimum, usually far away from the true solution, especially at depth. Thus, we have developed an inversion algorithm based on a space-domain unwrapped phase, and we also used exponential damping to mitigate the nonlinearity associated with the reflections. We construct the 2D phase residual map, which usually contains the wrapping discontinuities, especially if the model is complex and the frequency is high. We then unwrap the phase map and remove these cycle-based jumps. However, if the phase map has several residues, the unwrapping process becomes very complicated. We apply a strong exponential damping to the wavefield to eliminate much of the residues in the phase map, thus making the unwrapping process simple. We finally invert the unwrapped phases using the back-propagation algorithm to calculate the gradient. We progressively reduce the damping factor to obtain a high-resolution image. Numerical examples determined that the unwrapped phase inversion with a strong exponential damping generated convergent long-wavelength updates without low-frequency information. This model can be used as a good starting model for a subsequent inversion with a reduced damping, eventually leading to conventional waveform inversion.

  10. Linear control strategies for damping of flexible structures

    DEFF Research Database (Denmark)

    Høgsberg, Jan Riess; Krenk, Steen

    2006-01-01

    increases with the phase angle of the damper, and that improved damping efficiency thus follows from the ability of an active device to produce a force acting ahead of velocity. Phase lead is equivalent to negative stiffness, and the effect of negative stiffness is illustrated by a radiation condition...

  11. System Reduction and Damping of Flexible Structures

    DEFF Research Database (Denmark)

    Høgsberg, Jan Riess; Krenk, Steen

    2007-01-01

    An increasing number of flexible structures such as cable-stayed bridges, pedestrian bridges and high-rise buildings are fitted with local dampers to mitigate vibration problems. In principle the effect of local dampers can be analyzed by use of complex modes, e.g. in conjunction with an averaging...... technique for local linearization of the damper characteristics. However, the complex mode shapes and frequencies depend on the magnitude of the damper and therefore are less suitable for design of the damper system. An efficient alternative consists in the use of a two-component representation...... of the damped modes of the structure. The idea is to represent the damped mode as a linear combination of the modes that occur in two distinctly different situations representing extreme conditions: the mode shape of the structure without the damper(s), and the mode shape of the structure, when the damper...

  12. Damping parameter study of a perforated plate with bias flow

    Science.gov (United States)

    Mazdeh, Alireza

    One of the main impediments to successful operation of combustion systems in industrial and aerospace applications including gas turbines, ramjets, rocket motors, afterburners (augmenters) and even large heaters/boilers is the dynamic instability also known as thermo-acoustic instability. Concerns with this ongoing problem have grown with the introduction of Lean Premixed Combustion (LPC) systems developed to address the environmental concerns associated with the conventional combustion systems. The most common way to mitigate thermo-acoustic instability is adding acoustic damping to the combustor using acoustic liners. Recently damping properties of bias flow initially introduced to liners only for cooling purposes have been recognized and proven to be an asset in enhancing the damping effectiveness of liners. Acoustic liners are currently being designed using empirical design rules followed by build-test-improve steps; basically by trial and error. There is growing concerns on the lack of reliability associated with the experimental evaluation of the acoustic liners with small size apertures. The development of physics-based tools in assisting the design of such liners has become of great interest to practitioners recently. This dissertation focuses primarily on how Large-Eddy Simulations (LES) or similar techniques such as Scaled Adaptive Simulation (SAS) can be used to characterize damping properties of bias flow. The dissertation also reviews assumptions made in the existing analytical, semi-empirical, and numerical models, provides a criteria to rank order the existing models, and identifies the best existing theoretical model. Flow field calculations by LES provide good insight into the mechanisms that led to acoustic damping. Comparison of simulation results with empirical and analytical studies shows that LES simulation is a viable alternative to the empirical and analytical methods and can accurately predict the damping behavior of liners. Currently the

  13. The DAMPE silicon tungsten tracker

    CERN Document Server

    Gallo, Valentina; Asfandiyarov, R; Azzarello, P; Bernardini, P; Bertucci, B; Bolognini, A; Cadoux, F; Caprai, M; Domenjoz, M; Dong, Y; Duranti, M; Fan, R; Franco, M; Fusco, P; Gargano, F; Gong, K; Guo, D; Husi, C; Ionica, M; Lacalamita, N; Loparco, F; Marsella, G; Mazziotta, M N; Mongelli, M; Nardinocchi, A; Nicola, L; Pelleriti, G; Peng, W; Pohl, M; Postolache, V; Qiao, R; Surdo, A; Tykhonov, A; Vitillo, S; Wang, H; Weber, M; Wu, D; Wu, X; Zhang, F; De Mitri, I; La Marra, D

    2017-01-01

    The DArk Matter Particle Explorer (DAMPE) satellite has been successfully launched on the 17th December 2015. It is a powerful space detector designed for the identification of possible Dark Matter signatures thanks to its capability to detect electrons and photons with an unprecedented energy resolution in an energy range going from few GeV up to 10 TeV. Moreover, the DAMPE satellite will contribute to a better understanding of the propagation mechanisms of high energy cosmic rays measuring the nuclei flux up to 100 TeV. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is made of twelve layers of single-sided AC-coupled silicon micro-strip detectors for a total silicon area of about 7 $m^2$ . To promote the conversion of incident photons into electron-positron pairs, tungsten foils are inserted into the supporting structure. In this document, a detailed description of the STK constructi...

  14. Radiation damping in focusing-dominated systems

    International Nuclear Information System (INIS)

    Huang, Zhirong; Chen, Pisin; Ruth, R.D.

    1995-01-01

    A quasi-classical method is developed to calculate the radiation damping of a relativistic particle in a straight, continuous focusing system. In one limiting case where the pitch angle of the particle θ p is much larger than the radiation opening angle 1/γ, the radiation power spectrum is similar to synchrotron radiation and the relative damping rate of the transverse action is proportional to the relative energy loss rate. In the other limiting case where θ p much-lt 1/γ, the radiation is dipole in nature and the relative damping rate of the transverse action is energy-independent and is much faster than the relative energy rate. Quantum excitation to the transverse action is absent in this focusing channel. These results can be extended to bent systems provided that the focusing field dominates over the bending field

  15. Damping of wind turbine tower vibrations

    DEFF Research Database (Denmark)

    Brodersen, Mark Laier; Pedersen, Mikkel Melters

    Damping of wind turbine vibrations by supplemental dampers is a key ingredient for the continuous use of monopiles as support for offshore wind turbines. The present thesis consists of an extended summary with four parts and appended papers [P1-P4] concerning novel strategies for damping of tower...... dominated vibrations.The first part of the thesis presents the theoretical framework for implementation of supplemental dampers in wind turbines. It is demonstrated that the feasibility of installing dampers at the bottom of the tower is significantly increased when placing passive or semiactive dampers...... in a stroke amplifying brace, which amplifies the displacement across the damper and thus reduces the desired level of damper force. For optimal damping of the two lowest tower modes, a novel toggle-brace concept for amplifying the bending deformation of the tower is presented. Numerical examples illustrate...

  16. The short circumference damping ring design for the ILC

    CERN Document Server

    Korostelev, Maxim S; Kuriki, Masao; Kuroda, Shigeru; Naito, Takashi; Ross, Marc; Urakawa, Junji; Zimmermann, Frank

    2005-01-01

    The ILC damping ring tentative design is driven by the operational scenario of the main linac, the beam-dynamics demand of producing a stable and high-quality beam, the injection/extraction scheme and the kicker performance. In this paper, a short circumference damping ring design based on TME cells is described. The ring accommodates injection kickers which provide a flat top of 280 nsec and a 60 nsec rise and fall time and very fast strip-line kickers for beam extraction with a 2 nsec rise and fall time for 3-MHz operation. The potential impact of collective effects and the possible degradation of the dynamic aperture by nonlinear-wiggler fields are estimated.

  17. On small vibrations of a damped Stieltjes string

    Directory of Open Access Journals (Sweden)

    Olga Boyko

    2015-01-01

    Full Text Available Inverse problem of recovering masses, coefficients of damping and lengths of the intervals between the masses using two spectra of boundary value problems and the total length of the Stieltjes string (an elastic thread bearing point masses is considered. For the case of point-wise damping at the first counting from the right end mass the problem of recovering the masses, the damping coefficient and the lengths of the subintervals by one spectrum and the total length of the string is solved.

  18. Impact of Damping Uncertainty on SEA Model Response Variance

    Science.gov (United States)

    Schiller, Noah; Cabell, Randolph; Grosveld, Ferdinand

    2010-01-01

    Statistical Energy Analysis (SEA) is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently, techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainties in the system properties. In the present paper uncertainty in the damping loss factor is propagated through SEA to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a floor-equipped cylindrical test article that resembles an aircraft fuselage. Realistic bounds on the damping loss factor are determined from measurements acquired on the sidewall of the test article. The analysis demonstrates that uncertainties in damping have the potential to significantly impact the mean and variance of the predicted response.

  19. Damping of Coherent oscillations

    CERN Document Server

    Vos, L

    1996-01-01

    Damping of coherent oscillations by feedback is straightforward in principle. It has been a vital ingredient for the safe operation of accelerators since a long time. The increasing dimensions and beam intensities of the new generation of hadron colliders impose unprecedented demands on the performance of future systems. The arguments leading to the specification of a transverse feedback system for the CERN SPS in its role as LHC injector and the LHC collider itself are developped to illustrate this. The preservation of the transverse emittance is the guiding principle during this exercise keeping in mind the hostile environment which comprises: transverse impedance bent on developping coupled bunch instabilities, injection errors, unwanted transverse excitation, unavoidable tune spreads and noise in the damping loop.

  20. Unimodal optimal passive electromechanical damping of elastic structures

    International Nuclear Information System (INIS)

    Ben Mekki, O; Bourquin, F; Merliot, E; Maceri, F

    2013-01-01

    In this paper, a new electromechanical damper is presented and used, made of a pendulum oscillating around an alternator axis and connected by a gear to the vibrating structure. In this way, the mechanical energy of the oscillating mass can be transformed into electrical energy to be dissipated when the alternator is branched on a resistor. This damping device is intrinsically non-linear, and the problem of the optimal parameters and of the best placement of this damper on the structure is studied. The optimality criterion chosen here is the maximum exponential time decay rate (ETDR) of the structural response. This criterion leads to new design formulas. The case of a bridge under construction is considered and the analytical results are compared with experimental ones, obtained on a mock-up made of a vertical tower connected to a free-end horizontal beam, to simulate the behavior of a cable-stayed bridge during the erection phase. Up to three electromechanical dampers are placed in order to study the multi-modal damping. The satisfactory agreement between the theoretical model and the experiments suggests that a multi-modal passive damping of electromagnetic type could be effective on lightweight flexible structures, when dampers are suitably placed. (paper)