publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
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2018-03-01 | An active mass damper for vibration control of an oscillator with two translational degrees of freedom is presented along with the corresponding closed-loop control algorithm. The damper consists of two eccentrically rotating masses. In a preferred mode of operation, the masses rotate in opposite directions with a mostly constant angular velocity about a single axis. The resulting force is a harmonic control force. Its direction is determined by the relative angular position of the masses. In previous research, a similar control algorithm for vibration control of a single degree of freedom oscillator has been proven to be effective. In this paper, the control algorithm is augmented such that it can be applied to an oscillator with two translational degrees of freedom. Various state variables are introduced and a feedback control algorithm is developed. The presented algorithm ensures that the rotational motion of the masses is smooth and that the control force has the required orientation. The algorithm is verified experimentally with a test setup for the damping of free vibrations and numerically for stochastically forced vibrations. Finally, the device is compared with a conventional active mass damper. It is shown that the power demand and the energy consumption of the presented device are smaller than those of the conventional active mass damper. | Active vibration control of an oscillator with two translational degrees of freedom using centrifugal forces created by two eccentrically rotating masses | 10.1007/s40435-016-0280-8 |
2018-03-01 | The disk-shaft system is a power transmission system with several industrial applications. The shafts, depending on the mechanism application, can be connected by U-joints through different rotating axes. In spite of the many advantages, these joints transform a constant rotating speed into a variable output one. Therefore, the multi-body system is self-excited that lead to dynamic instability. Here, a driveline system including three elastic shafts, which carry three disks, is considered. The oscillating behavior and resonance phenomenon of this fluctuating mechanism are investigated qualitatively and quantitatively. The angle of joints, damping and stiffness effects are the major topics of the present contribution. Eventually, dynamic stability diagrams are obtained by using a reliable and exact method based on the Floquet theory. It can be found that variations of the first U-joint angle and the intermediate shaft characteristics have greater impact on the machine instability. It is revealed how the stability of the system can be achieved by changing the geometry, shaft damping and stiffness, which should be considered in design and practical applications. | Stability of a multi-body driveshaft system excited through U-joints | 10.1007/s11012-017-0784-0 |
2018-03-01 | The damping capacity of a VT6 titanium alloy sample is shown to depend on the thickness of a new designed Al–Ni–Y alloy coating during vibrodynamic tests at the first flexural mode resonance frequency. The coating 20–100 μm thick is found to decrease the vibrostresses in the weakest section of the sample by 9–31% at a temperature of 20°C and by 40.6% at a temperature of 400°C and a coating thickness of 60 μm. The dependences of the damping capacity of the alloy–coating composition on high-temperature holding of coated samples in an atmospheric furnace ( t = 400°C, τ = 500 h), the salt fog chamber conditions ( t = 35°C, τ = 3 months), and the action of an abrasive flux (quartz sand, average particle fraction of 400 μm, particle velocity of 100 m/s) are studied. | Damping Capacity of Coated Plane VT6 Titanium Alloy Samples | 10.1134/S0036029518030096 |
2018-03-01 | In this paper, we consider a porous thermoelastic system with a micro-heat dissipation and a nonlinear frictional damping. We establish an explicit and general decay rate result, using some properties of the convex functions and the multiplier method. Our result is obtained without imposing any restrictive growth assumption on the damping term. | On the long-time behavior of a nonlinear damped porous thermoelastic system with second sound | 10.1007/s13370-017-0536-2 |
2018-03-01 | In this paper, we are concerned with the asymptotic behavior of solutions to Euler-Korteweg equations with damping. We prove that the solutions time-asymptotically behave like the nonlinear diffusion wave, as in Hsiao and Liu (Commun Math Phys 143:599–605, 1992 ) and Nishihara (J Differ Equ 131:171–188, 1996 ). Moreover, it is also shown that the Euler-Korteweg equations with damping could be a approximation of the Euler equations with damping. | Convergence to nonlinear diffusion waves for solutions of Euler-Korteweg equations with damping | 10.1007/s00028-017-0389-z |
2018-03-01 | Due to increasing power demand, incorporation of prosumers, continuous expansion, competitive market and inherent limitations of alternating current, the management and operation of power system has become very complex. For economical, reliable and secure operation, the use of emerging technologies is unavoidable. Flexible AC transmission system (FACTS) is one of the emerging technologies which does not only solve the problems but also gives new directions in existing high voltage AC (HVAC) and high voltage DC (HVDC) power systems. However, allocation of FACTS controllers i.e., determination of optimal location, size, number and type of these devices with minimized cost is a difficult problem. This paper, in broader sense, discusses FACTS allocation for the solution of issues of power system. The benefits and objectives of optimal allocation of FACTS have been reviewed from view point of objective functions, decision variables, constraints and recent optimization algorithms. | Optimal Allocation of Flexible AC Transmission System Controllers in Electric Power Networks | 10.1007/s41403-018-0035-2 |
2018-03-01 | To suppress the vibration of propeller blades and vibration transmission from the blades to bearings under broadband propeller force, a damping ring placed under the propeller hub is proposed. The configuration of the damping ring is introduced first. Then the analytical dynamic model of the damping ring is established. The dynamic model of the propeller-shaft-multiple bearings system with and without the damping ring is developed based on the modal properties of the propeller-shaft-multiple bearings system, the damping ring and friction interface characteristics between them. Node-to-node contact elements are introduced with both normal and tangential relative displacements. The dynamic model is solved by the Duhamel integration of single-degree-of-freedom system and then by employing the superposition method. It is shown that the damping ring can suppress the responses of the propeller blades and the force transmitted to the foundation at the in-phase blade modes of an integrated forming propeller and the longitudinal mode of the propeller-shaft-bearings system. The suppression mechanism is energy dissipation due to the friction phenomena on the interface. The time histories of the contact variables (tangential relative forces) of given contact points on the hub/ring interface are given to illustrate the local behavior of the contact interface. Parametric analysis is carried out to investigate the influence of the inherent damping of the coupled system, rotation speed, tangential stiffness and friction coefficient on the interface. It is shown that the tangential stiffness and friction coefficient on the interface are two key parameters. The theoretical study will provide some references on designing the damping ring for propellers. | Vibration transmission suppression for propeller-shaft system by hub-embedded damping ring under broadband propeller force | 10.1007/s11071-017-4037-5 |
2018-03-01 | Nonlinear behavior of a rotating bladed disk system is investigated at the critical speed, where the rotor internal damping starts to destabilize the rotor vibrations. A simple bladed Jeffcott model is suggested to study the Hopf bifurcation around the critical speed. The Euler–Bernoulli theory is employed to model the flexible blades, which bend in the plane of the motion. Duffing’s type nonlinearity is considered for the bearing stiffness. The equations of motion are derived using the Lagrange equations, and the bifurcation equation is obtained by the multiple scales method. The characteristics of the limit cycle are studied through the bifurcation equation near the critical speed. The nonlinear analysis results are validated by a numerical simulation. The results show that the blade dynamic can deteriorate the asynchronous vibrations and even widen the instability region. | The stability and nonlinear analysis of a rotating bladed disk at the critical speed | 10.1007/s00419-017-1316-z |
2018-03-01 | Sand is rarely found clean in natural deposits and it’s usually in composition of gravel, clay and silt. The purpose of this paper is to examine the effect of stress induced anisotropy ( $$kc = \sigma^{\prime}_{1} /\sigma^{\prime}_{3} \ne 1$$ k c = σ 1 ′ / σ 3 ′ ≠ 1 ) as one of the most important factors affecting the dynamic properties of natural mixed (with sand and silt) sandy soils. For this purpose, 77 dynamic triaxial tests is carried out on 10 cylindrical samples prepared from two mixed sandy materials, using large triaxial apparatus in isotropic and anisotropic conditions under different confining pressures and loading frequencies. The results showed that, for the studied materials, increase in anisotropy to $$kc = 2$$ k c = 2 cause considerable increase in shear modulus, but shear modulus decreased for greater ratios. Also, shear modulus and damping ratio were dependent to confining pressure and loading frequency so that increase in loading frequency cause increase in shear modulus and damping ratio. Moreover, increase in confining pressure increased shear modulus but decreased damping ratio. The results were remarkably different from the available literature (performed studies on standard sands) at high frequencies. | The Effect of Stress Induced Anisotropy on Shear Modulus and Damping Ratio of Mixed Sandy Soils | 10.1007/s40098-017-0236-8 |
2018-03-01 | In the present study, response-only system identification is explored towards estimating modal dynamic properties of buildings under earthquake excitation. Seismic structural response signals are adopted with two different implemented Operational Modal Analysis (OMA) techniques, namely a refined Frequency Domain Decomposition algorithm and an improved data-driven Stochastic Subspace Identification ( SSI-DATA ) procedure, working in the Frequency Domain and in the Time Domain, respectively. These algorithms are specifically conceived to operate with seismic structural responses and at simultaneous heavy damping (in terms of identification challenge), towards achieving consistent estimations of natural frequencies, mode shapes and modal damping ratios. Classical OMA assumptions shall not contemplate short-duration, non-stationary earthquake-induced response signals. Nevertheless, the present enhanced output-only algorithms allow for estimating all strong ground motion modal parameters. First, a linear three-storey frame structure under ten selected earthquake base-excitations is considered, in order to assess the two OMA techniques at synthetic seismic response input. Comprehensive results are presented, by comparing the two developed methods, between achieved modal estimates and sought target values. Second, an existing instrumented building (CESMD database) is analyzed, by adopting real seismic response signals, reaching again effective modal estimates and corroborating the previous necessary condition analysis. According to this investigation, best up-to-date, re-interpreted, output-only techniques may effectively be used for potential Structural Health Monitoring purposes in the Earthquake Engineering range. | Assessment of Frequency versus Time Domain enhanced technique for response-only modal dynamic identification under seismic excitation | 10.1007/s10518-017-0259-7 |
2018-03-01 | A theory of dynamic bending of beams made of functionally graded materials is presented. The refined theoretical model takes into account the shear and normal strains and stresses. The distribution of stresses in the beams in cylindrical bending at different vibration frequencies is considered. Their damping properties in the frequency range are estimated. | Dynamic properties of symmetric and asymmetric Beams made of Functionally Graded materials in bending | 10.1007/s11029-018-9723-y |
2018-03-01 | In this paper, a design method is proposed for a robust stabilizing fractional order proportional integral derivative (FOPID) controller for One Non-Integer Order Plus Time Delay plant (NIOPTD-I). The NIOPTD-I model is obtained after reducing the higher order continuous time process model. The FOPID controller is designed by using stability boundary locus method, which satisfies user defined frequency domain specifications phase margin and the gain crossover frequency. A robust control system is designed against gain variations by achieving flat phase condition which is due to zero slope at the gain crossover frequency of the phase plot. Thus robust stabilizing FOPID controller for NIOPTD-I fractional order plant is designed. The applicability of the proposed method is illustrated with simulation example and experimental validation with the liquid level control system. | Design of FOPID controller for fractional-order plants with experimental verification | 10.1007/s40435-017-0305-y |
2018-03-01 | The chaotic characteristic of a system with vibro-impact nonlinear energy sink is studied here. An analytical method is developed to calculate Lyapunov exponent. The mechanism by which impact results in chaos is further clarified rather than only by the calculation of Lyapunov exponent. In addition, an approach to identifying Lyapunov exponents from experimental data is proposed, and the estimated results are consistent with numerical results. | Chaotic characteristic of a linear oscillator coupled with vibro-impact nonlinear energy sink | 10.1007/s11071-017-4015-y |
2018-03-01 | The effect of borax, sewage sludge ash, silicon carbide, and perlite microparticles on the tensile, damping, and vibration characteristics of S-glass/epoxy composite laminates was examined Their damping and vibration properties were evaluated experimentally by using the dynamic modal analysis, identifying the response of the fundamental natural frequency to the type and weight content of the particulates. The results obtained showed that the introduction of specific amounts of such particulates into the matrix of S-glass/epoxy composite noticeably improved its mechanical properties. | Toughening Effect of Microscale Particles on the Tensile and Vibration Properties of S-Glass-Fiber-Reinforced Epoxy Composites | 10.1007/s11029-018-9724-x |
2018-03-01 | The last stages of powerful power gas turbines play an important role in the development of power and efficiency of the whole unit as well as in the distribution of the flow parameters behind the last stage, which determines the efficient operation of the exhaust diffusers. Therefore, much attention is paid to improving the efficiency of the last stages of gas turbines as well as the distribution of flow parameters. Since the long blades of the last stages of multistage high-power gas turbines could fall into the resonance frequency range in the course of operation, which results in the destruction of the blades, damping wires or damping bolts are used for turning out of resonance frequencies. However, these damping elements cause additional energy losses leading to a reduction in the efficiency of the stage. To minimize these losses, dampening shrouds are used instead of wires and bolts at the periphery of the working blades. However, because of the strength problems, designers have to use, instead of the most efficient full shrouds, partial shrouds that do not provide for significantly reducing the losses in the tip clearance between the blade and the turbine housing. In this paper, a computational study is performed concerning an effect that the design of the shroud of the turbine-working blade exerted on the flow structure in the vicinity of the shroud and on the efficiency of the stage as a whole. The analysis of the flow structure has shown that a significant part of the losses under using the shrouds is associated with the formation of vortex zones in the cavities on the turbine housing before the shrouds, between the ribs of the shrouds, and in the cavities at the outlet behind the shrouds. All the investigated variants of a partial shrouding are inferior in efficiency to the stages with shrouds that completely cover the tip section of the working blade. The stage with a unshrouded working blade was most efficient at the values of the relative tip clearance less than 0.9%. | Computational Study on the Effect of Shroud Shape on the Efficiency of the Gas Turbine Stage | 10.1134/S0040601518030011 |
2018-02-15 | The most promising technology in the field of semi-active suspension systems is the use of magnetorheological property of MR fluid, whose material behavior can be controlled through external magnetic field. Devices developed based on this principle are adaptive and controllable as desired for a specific application. It is important to understand the damping characteristics of these devices before employing them, using experimental or computational approaches. In the present work, both experimental and computational methods have been adopted for characterizing a twin-tube MR damper with an intention to develop a computational approach as an alternative to experimental test in the preliminary design stage. Initially, experimental characterization of MR damper was carried out at 1.5 and 2 Hz frequencies for damper stroke length of ± 5 mm under different DC currents ranging from 0.1 to 0.4 A. Later, coupled finite-element and computational fluid dynamic analysis has been carried out to estimate the damping force under same conditions as used in the experiment. The results of computation are in good agreement with experimental ones. Furthermore, using this computational approach, the damping force at different frequencies of 1.5, 2, 3, and 4 Hz has been estimated and its time histories are also plotted. The influence of fluid flow gap on the damping force has been determined and results revealed that damping force behaves inversely with fluid flow gap. | An approach for characterizing twin-tube shear-mode magnetorheological damper through coupled FE and CFD analysis | 10.1007/s40430-018-1066-z |
2018-02-01 | Diesel engine is inherently an unstable machine and requires a reliable control system to regulate its speed for safe and efficient operation. Also, the diesel engine may operate at fixed or variable speeds depending upon user’s needs and accordingly the speed control system should have essential features to fulfil these requirements. This paper proposes a mathematical model of a marine diesel engine speed control system with droop governing function. The mathematical model includes static and dynamic characteristics of the control loop components. Model of static characteristic of the rotating fly weights speed sensing element provides an insight into the speed droop features of the speed controller. Because of big size and large time delay, the turbo charged diesel engine is represented as a first order system or sometimes even simplified to a pure integrator with constant gain which is considered acceptable in control literature. The proposed model is mathematically less complex and quick to use for preliminary analysis of the diesel engine speed controller performance. | A Mathematical Model of Marine Diesel Engine Speed Control System | 10.1007/s40032-017-0420-8 |
2018-02-01 | We consider time discretizations of the Vlasov–HMF (Hamiltonian mean-field) equation based on splitting methods between the linear and nonlinear parts. We consider solutions starting in a small Sobolev neighborhood of a spatially homogeneous state satisfying a linearized stability criterion (Penrose criterion). We prove that the numerical solutions exhibit a scattering behavior to a modified state, which implies a nonlinear Landau damping effect with polynomial rate of damping. Moreover, we prove that the modified state is close to the continuous one and provide error estimates with respect to the time step size. | On Numerical Landau Damping for Splitting Methods Applied to the Vlasov–HMF Model | 10.1007/s10208-016-9333-9 |
2018-02-01 | The results of a theoretical and experimental investigation of the influence of damping and pitch plays on the dynamics of electromechanical systems in the zones of main, harmonic, and subharmonic resonances under parametrical disturbances are presented. Design models of electromechanical systems taking into account spring linkages, pitch plays, mechanical damping, and inconstancy of a gear ratio and reduction radius are proposed. The equations and structural schematics describing the movement of electromechanical systems under consideration in the initial values and adopted system of generalized parameters and relative units are presented. The electric drive is described by a linear mechanical characteristic taking into account the electromagnetic inertia of power circuits. The problems of linearization of electromechanical systems under parametric disturbances are considered, and the zone parameters are revealed under which it is possible. The analytical relationships for determining the optimum parameters of electric drive and the estimation of resonant amplitudes of oscillations of the elastic torque are obtained. Results of analysis of the influence of pitch-play formation on the oscillations in the zones of main and subharmonic resonances are presented. Features of these oscillations related to the magnitude of average load of transmissions and the direction of change in the frequency of parametric disturbances are considered. The reliability of theoretical regulations and conclusions of the article are confirmed by the results of industrial experience in the use of various circuits of a reduction-gear electric drive of rotation of an excavator under parametric disturbances caused by a gear wheel meshing with the gear ring. | Dynamic Modes of Electromechanical Systems under Parametrical Disturbances | 10.3103/S106837121802013X |
2018-02-01 | To reveal some dynamic properties of the deploying process for the solar power satellite via an arbitrarily large phased array (SPS-ALPHA) solar receiver, the symplectic Runge-Kuttamethod is used to simulate the simplified model with the consideration of the Rayleigh damping effect. The system containing the Rayleigh damping can be separated and transformed into the equivalent nondamping system formally to insure the application condition of the symplectic Runge-Kutta method©First, the Lagrange equation with the Rayleigh damping governing the motion of the system is derived via the variational principle. Then, with some reasonable assumptions on the relations among the damping, mass, and stiffness matrices, the Rayleigh damping system is equivalently converted into the nondamping system formally, so that the symplectic Runge-Kutta method can be used to simulate the deploying process for the solar receiver. Finally, some numerical results of the symplectic Runge-Kutta method for the dynamic properties of the solar receiver are reported. The numerical results show that the proposed simplified model is valid for the deploying process for the SPS-ALPHA solar receiver, and the symplectic Runge-Kutta method can preserve the displacement constraints of the system well with excellent long-time numerical stability. | Dynamic modeling and simulation of deploying process for space solar power satellite receiver | 10.1007/s10483-018-2293-6 |
2018-02-01 | This study presents an extended unit load method in which the displacement of a chosen degree of freedom (DOF) in a nonlinear structure under arbitrary dynamic loading is expressed as an integration of mutual strain energy density over a continuum domain. This new integral formulation for the displacement of a chosen DOF is developed by using the virtual work principle and can be used for linear or nonlinear structural behaviours. The integral form of the displacement is then used to develop new formulations for structural topology optimization involving arbitrary dynamic loading using the moving iso-surface threshold (MIST) method. Presented are two specific topology optimization problems with two objective functions: (a) to minimize the peak of a chosen displacement; or (b) to minimize the average power spectral density (PSD) of the chosen displacement over a finite time interval. New MIST formulations and algorithms are developed for solving two damping topology optimization problems of a structure under arbitrary dynamic loading, with or without large displacements, and having cellular damping materials with multi-volume fractions. Several numerical examples are presented to demonstrate the validity and efficiency of the presented unit load method and the MIST formulations and algorithms. | Topology optimization of nonlinear structures with damping under arbitrary dynamic loading | 10.1007/s00158-017-1765-6 |
2018-02-01 | The effects of damping on the bending and twisting modes of flax fibre-reinforced polypropylene composites are investigated. The laminate was manufactured by a vacuum bagging process; its dynamic behaviour was then found from the vibration measurements of a beam test specimen using an impulse hammer technique to frequencies of 1 kHz. The frequency response of a sample was measured, and the bending and twisting responses at resonance were used to estimate the natural frequency and loss factor. The single-degree-of-freedom circle-fit method and Newton’s divided differences formula were used to estimate the natural frequencies as well as the loss factors. The damping estimates were also investigated using a “carpet” plot. The results show significant variations in loss factors depending on the type of mode. The loss factor generally lies in the range of 1.7-2.2 % for the bending modes, while 4.8 % on average for the twisting modes. Numerical estimates of the response, and in particular the natural frequencies, were made using a Mechanical APDL (ANSYS parametric design language) finite element model, with the beam being discretised into a number of shell elements. The natural frequencies from the finite element analysis show reasonably good agreement (errors < 5 %) with the measured natural frequencies. | Influence of Damping on the Bending and Twisting Modes of Flax Fibre-reinforced Polypropylene Composite | 10.1007/s12221-018-7588-7 |
2018-02-01 | For seismic assessment of wind turbines in seismically-active areas, International Standards and Guidelines allow the combination of two uncoupled analyses under environmental and earthquake loads, respectively. The separate earthquake response is generally computed including an additional aerodynamic damping in the structural model. Although some work has been done to estimate the effectiveness of uncoupled analyses for land-based wind turbines, and determine appropriate levels of aerodynamic damping, to date no similar studies have been carried out for offshore wind turbines. This paper assesses the accuracy of different time-domain implementations of uncoupled analyses for offshore wind turbines, and investigates pertinent levels of aerodynamic damping. The case study is a 5-MW wind turbine, resting on a tripod in intermediate waters. | On time-domain uncoupled analyses for offshore wind turbines under seismic loads | 10.1007/s10518-017-0191-x |
2018-02-01 | Temporal variations of the main hydrological variables over 16 years were systematically investigated based on the results from an integrated hydrological modeling at the Sagehen Creek watershed in northern Sierra Nevada. Temporal scaling of these variables and damping effects of the hydrological system as well as its subsystems, i.e., the land surface, unsaturated zone, and saturated zone, were analyzed with spectral analyses. It was found that the hydrological system may act as a cascade of hierarchical fractal filters which sequentially transfer a non-fractal or less correlated fractal hydrological signal to a more correlated fractal signal. The temporal scaling of simulated infiltration (SI), simulated actual evapotranspiration (SET), simulated recharge (SR), measured baseflow (MBF), measured streamflow (MSF) exist and the temporal autocorrelation of these variables increase as water moves through the system. The degree of the damping effect of the subsystems is different and is strongest in the unsaturated zone compared with that of the land surface and saturated zone. The temporal scaling of the simulated groundwater levels (S h ) also exists and is strongly affected by the river: the temporal autocorrelation of S h near the river is similar to that of the river stage fluctuations and increases away from the river. There is a break in the temporal scaling of S h near the river at low frequencies due to the effect of the river. Temporal variations of the simulated soil moisture (S θ ) is more complicated: the value of the scaling exponent ( β ) for S θ increases with depth as water moves downwards and its high-frequency fluctuations are damped by the unsaturated zone. The temporal fluctuations of measured precipitation and SI are fractional Gaussian noise, those of SET, SR, MBF, and MSF are fractional Brownian motion (fBm), and those of S h away from the river are 2nd-order fBm based on the values of β obtained in this study. | Analysis of temporal variation and scaling of hydrological variables based on a numerical model of the Sagehen Creek watershed | 10.1007/s00477-017-1421-0 |
2018-02-01 | Objective The present work adopted damped vibration absorbers (DVAs) to attenuate multi-mode longitudinal vibration of the hollow shaft. The dynamic behavior of a shaft is analyzed for the guidance to the initial parameter design of DVAs and the parameters of DVAs are optimized. Subsequently, specific structures of DVAs are designed taking into account the hollow characteristic of the shaft. Furthermore, finite element stimulation of solid modeling has been performed. Methods In this work, with the aid of the transfer matrix method (TMM) in conjunction with the substructure synthesis method (SSM), a dynamic model of the shaft incorporating multiple DVAs is established. The proposed method is developed for the calculation of dynamics character of the coupled system and estimation of absorption effectiveness of DVAs. Simulation To demonstrate the validity of theoretical result obtained from the TMM proposed in this paper, a simulation of the shaft vibration by means of the finite element method (FEM) is also carried out. Conclusion Theoretical and stimulation results both demonstrate that the resonance peaks of the shaft longitudinal vibration are suppressed obviously with the application of those DVAs, which verify the effectiveness of the absorption performance of DVAs. | Damped Vibration Absorbers for Multi-mode Longitudinal Vibration Control of a Hollow Shaft | 10.1007/s42417-018-0002-y |
2018-02-01 | We present an iterative procedure based on a damped inexact Newton iteration for solving linear complementarity problems. We introduce the method in the framework of a popular problem arising in mechanical engineering: the analysis of cavitation in lubricated contacts. In this context, we show how the perturbation and the damping parameter are chosen in our method and we prove the global convergence of the entire procedure. A Fortran implementation of the method is finally analyzed. First, we validate the procedure and analyze all its components, performing also a comparison with a recently proposed technique based on the Fischer–Burmeister–Newton iteration. Then, we solve a 2D problem and provide some insights on an efficient implementation of the method exploiting routines of the Lapack and of the PETSc packages for the solution of inner linear systems. | An inexact Newton method for solving complementarity problems in hydrodynamic lubrication | 10.1007/s10092-018-0244-9 |
2018-01-23 | The excitation and damping of the transversal coronal loop oscillations and quantitative relation between damping time, damping property (damping time per period), oscillation amplitude, dissipation mechanism and the wake phenomena are investigated. The observed time series data with the Atmospheric Imaging Assembly (AIA) telescope on NASA’s Solar Dynamics Observatory (SDO) satellite on 2015 March 2, consisting of 400 consecutive images with 12 s cadence in the 171 Å $\mathring{\mathrm{A}}$ pass band is analyzed for evidence of transversal oscillations along the coronal loops by the Lomb–Scargle periodgram. In this analysis signatures of transversal coronal loop oscillations that are damped rapidly were found with dominant oscillation periods in the range of P = 12.25 – 15.80 $\mathrm{P}=12.25\,\text{--}\,15.80$ min. Also, damping times and damping properties of the transversal coronal loop oscillations at dominant oscillation periods are estimated in the range of τ d = 11.76 – 21.46 ${\tau_{\mathrm{d}}=11.76}\,\text{--}\,{21.46}$ min and τ d / P = 0.86 – 1.49 ${\tau_{\mathrm{d}}/\mathrm{P}=0.86}\,\text{--}\,{1.49}$ , respectively. The observational results of this analysis show that damping properties decrease slowly with increasing amplitude of the oscillation, but the periods of the oscillations are not sensitive functions of the amplitude of the oscillations. The order of magnitude of the damping properties and damping times are in good agreement with previous findings and the theoretical prediction for damping of kink mode oscillations by the dissipation mechanism. Furthermore, oscillations of the loop segments attenuate with time roughly as t − α $t^{-\alpha}$ and the magnitude values of α $\alpha$ for 30 different segments change from 0.51 to 0.75. | Observations of Excitation and Damping of Transversal Oscillations in Coronal Loops by AIA/SDO | 10.1007/s11207-018-1240-6 |
2018-01-02 | Transparent soil, manufactured with transparent granular particles and pore fluid with matching refractive index, used to mimic the behavior of natural saturated soil, is widely used in visualization model tests. The properties of transparent soils are not only affected by granular particles’ characteristics, but also influenced by pore fluids’ characteristics. However, the researches focused on the dynamic properties of transparent soil influenced by pore fluids are relatively rare in the literature. In this paper, the dynamic shear modulus and damping ratios of transparent soils manufactured by fused quartz and three different pore fluids (mixed oil, calcium bromide $$(\hbox {CaBr}_{2})$$ ( CaBr 2 ) solution, and sucrose solution) were measured through a series of resonant column tests and dynamic torsional shear tests. The laboratory tests on dry fused quartz specimens were also carried out for comparative analysis. It is found that the transparent soils have a certain similar dynamic behaviors as those of natural soil, and the values of dynamic shear modulus and damping ratios are influenced by pore fluids. With the test results, transparent soil manufactured by fused quartz and mixed oil shows a great potential as a substitute for natural sand and is expected to be widely used in dynamic model tests. | Investigation on shear modulus and damping ratio of transparent soils with different pore fluids | 10.1007/s10035-017-0779-5 |
2018-01-01 | This chapter deals with the methods of estimating damping in offshore structures. Different types of damping models, their comparison, and suitability to offshore structures are discussed in detail. Example problems are solved, and estimation of damping using different models is explained. | Damping in Offshore Structures | 10.1007/978-981-10-6089-2_4 |
2018-01-01 | This chapter deals with introduction to structural dynamics and its application to offshore structures. Basics of single-degree of freedom are discussed to highlight the conventional mathematical model of single-degree of freedom. Free vibration analysis and forced vibration analysis are discussed with focus on few important dynamic characteristics of the single and multi-degrees of freedom models. Solved numerical examples of determining natural frequencies and mode shapes of different mathematical model of single and multi-degrees of freedom systems are included. | Introduction to Structural Dynamics | 10.1007/978-981-10-6089-2_3 |
2018-01-01 | This chapter analyzes the basic principle of passive damping with shunted piezoelectric transducers. Resistive shunting and inductive shunting are examined successively. The various ways of tuning the inductor (maximum stability and equal peak design) are carefully reviewed, and the robustness with respect to the shunt parameters is discussed. Next, the switch shunt is analyzed, leading to the technique known as synchronized switch damping on inductor (SSDI); the performances of the various shunting modes are compared. The chapter concludes with a short list of references and a set of problems. | Passive Damping with Piezoelectric Transducers | 10.1007/978-3-319-72296-2_5 |
2018-01-01 | Rock dynamic characteristics are important factors influencing the long-term stability of rock masses. In addition, they are important parameters for seismic response analysis and safety evaluation. In this study, a solution was discussed for the evaluation of the damping coefficient of rock masses under cyclic loading. Then, low cyclic loading tests with a frequency of 3 Hz were carried out on sandstone samples. Through these tests, the influences of the amplitude stress and cycle number on the dynamic elastic modulus and Poisson’s ratio, damping ratio and coefficient, and their relationships were evaluated. Under the cyclic loading condition, the dynamic elastic modulus and Poisson’s ratio increased parabolically and linearly with the increase in the amplitude stress, respectively; however, the damping ratio and coefficient decreased in accord with a power function. The damping ratio and coefficient increased linearly with the increase in the cycle number, and their increments for low-amplitude stresses were larger than those at high stresses. The results suggest that the damping parameters of rock masses could be obtained from the hysteresis loop measured from the intermediate cycle during a 31-cycle cyclic loading test. | Experimental Investigations of Rock Dynamical Characteristics Under Cyclic Loading | 10.1007/978-981-13-0113-1_19 |
2018-01-01 | Present works deal with the insight into the friction-induced stick-slip vibration which takes place by virtue of the difference in the values of static and kinetic friction between the rubbing surfaces, which causes decrease in friction force with velocity. The produced intermittent motion is objectionable as it is the cause of serious nuisance, power loss, quadrant glitch, limit cycle, inaccuracy in control, etc. A comprehensive description of this phenomenon by capturing the effect of influencing parameter has become challenging research task for system dynamics especially for control. In present work, the motion of mass on rough surface, being dragged at constant velocity, is studied by stiction model. In this research work, it has been tried to capture the effect of influencing parameters to define the acceptable and optimum criteria of selecting them to ensure motion without stick slip. The study is performed by varying relevant parameters like coefficient of friction, viscous damping, driving velocity, ratio of static friction to kinetic friction. The outcome of this study is the range of these parameters and their combinations, for which friction-induced disturbances are the minimum. The results obtained in this work may be used as a generalized guide line for reducing and avoiding these disturbances. | Circumvention of Friction-Induced Stick-Slip Vibration by Modeling and Simulation | 10.1007/978-981-10-5903-2_174 |
2018-01-01 | An active mass damper utilizing rotating masses to damp the vibrations of an oscillator with two translational degrees of freedom in a horizontal plane and one rotational degree of freedom about a vertical axis is presented along with a corresponding closed-loop control algorithm. The damper consists of two masses rotating about a single vertical axis, powered by two actuators. In a preferred mode of operation, these masses rotate with a nearly constant and equal angular velocity in opposite directions, thus producing a harmonic control force in a single horizontal direction. By varying the relative angular position of the rotating masses, this control force can be directed in an arbitrary direction and used to damp the translational motion. In previous research, a control algorithm was derived for this purpose. The rotational degree of freedom can additionally be controlled by producing a moment by imposing angular accelerations on the rotating masses. In this paper, the previous control algorithm is augmented such that the rotational degree of freedom is additionally controlled. The augmented control algorithm is verified with help of numerical simulations. | Active Vibration Control of a Three Degree of Freedom Oscillator Using Two Eccentrically Rotating Masses | 10.1007/978-3-319-67443-8_52 |
2018-01-01 | It is noted that the most important parameters of an earthquake ground motions are its maximum motion, predominant period, and Effective duration effective durations [524]. | Representation of Seismic Ground Motions | 10.1007/978-3-319-40358-8_10 |
2018-01-01 | This chapter analyzes linear single-degree-of-freedom systems and their response to harmonic, impulsive and periodic excitations. The response to such excitations is important because it provides insight into how the system will respond to other types of forces. Finally also the response to earthquake records is considered. The chapter ends with some considerations about the nonlinear response. | SDOF Systems | 10.1007/978-3-319-72541-3_2 |
2018-01-01 | The aim of this work is to consider the internal stabilization of a nonlinear coupled system of two Korteweg–de Vries equations in a finite interval under the effect of a very weak localized damping. The system was introduced by Gear and Grimshaw to model the interactions of two-dimensional, long, internal gravity waves propagation in a stratified fluid. Considering feedback controls laws and using “Compactness–Uniqueness Argument ,” which reduce the problem to use a unique continuation property, we establish the exponential stability of the weak solutions when the exponent in the nonlinear term ranges over the interval [1, 4). | Stabilization of the Gear–Grimshaw System with Weak Damping | 10.1007/s10883-017-9363-x |
2018-01-01 | The main issue of this chapter is the notion of energy of solutions, a very effective tool for the treatment of nonstationary or evolution models. We introduce energies for different models and explain conservation of energies, if possible. Sometimes, the choice of a suitable energy seems to be a miracle, sometimes one has different choices. Do we have energy conservation? Do we have blow up of the energy for t → ∞ ? Do we have a decay of the energy for t → ∞ ? These and related questions will be answered in this chapter. Moreover, it is shown how lower order terms may influence the choice and the long-time behavior of a suitable energy. Here we restrict ourselves to mass and different damping terms. Finally, we explain for several models the long-time behavior of local energies for solutions of mixed problems with Dirichlet condition in exterior domains. | The Notion of Energy of Solutions: One of the Most Important Quantities | 10.1007/978-3-319-66456-9_11 |
2018-01-01 | The control challenges of LCL -type grid-connected inverter arise from the resonance problem. At the resonance frequency, the LCL filter resonance causes a sharp phase step down of −180° with a high resonance peak. This resonance peak would easily lead to system instability and should be damped. In this chapter, the resonance hazard resulted by the LCL filter is reviewed first, and then, the existing passive- and active-damping solutions are described systematically to reveal the relationship among them. Among the six basic passive-damping solutions, adding a resistor in parallel with capacitor shows the best damping performance, but it results in a high power loss. In order to avoid the power loss in the damping resistor, the active-damping solutions equivalent to a resistor in parallel with capacitor are derived, and the capacitor-current-feedback active damping is superior for its simple implementation and effectiveness. This chapter provides the basis for the study of the control techniques of LCL -type grid-connected inverter in the following chapters. | Resonance Damping Methods of LCL Filter | 10.1007/978-981-10-4277-5_4 |
2018-01-01 | This chapter focuses on collocated systems. The property of alternating poles and zeros is used to develop single-input single-output active damping schemes with guaranteed stability for various actuator and sensor types. The following controller are examined: Lead controller, Direct Velocity Feedback (DVF), Positive Position Feedback (PPF), Integral Force Feedback (IFF). The duality between the Lead and the IFF controller is discussed and the formula for the maximum achievable damping is demonstrated. The results are later generalized to the decentralized control of multi-input multi-output structures with collocated pairs. The chapter concludes with a short list of references and a set of problems. | Active Damping with Collocated System | 10.1007/978-3-319-72296-2_7 |
2018-01-01 | It is well known that the friction between interfaces at bolted joints plays a major role in the characterization of damping. Friction can be either induced by macroslip or microslip. The aim of this chapter is to model and quantify the dissipated energy by microslip in the joints in order to compute the damping ratio. It is assumed that the coefficient of friction between the nominally flat surfaces is constant and that friction is the only source of energy dissipation. An experimental study is reported to measure static normal load and dynamic tangential load without any coupling between these two main directions. A rheological contact model, Extended Greenwood Model (EGM), based on microcontacts and statistical distributions is developed and studied. Experimental results and simulations are compared in order to assess and discuss the model. | Microslip Induced Damping in the Contact of Nominally Flat Surfaces with Geometric Defects | 10.1007/978-3-319-56818-8_19 |
2018-01-01 | A novel active mass damper, the twin rotor damper (TRD), was presented in previous research, including control algorithms for monofrequent vibrations. In this paper, the steady-state damping performance is evaluated by applying a harmonic excitation force to a single degree of freedom (SDOF) oscillator with and without the action of the damping device. Using the velocity of the SDOF oscillator as feedback, adequate steady-state damping performance can be achieved with the TRD by setting the control force of the TRD in antiphase to the velocity of the SDOF oscillator. An analytic solution describing the steady-state damping performance is derived. The analytic solution allows for the comparison with a dynamic vibration absorber (DVA) of comparable size (stroke) and control mass. The analytic comparison shows that the TRD achieves greatly better damping performance than the DVA. | An Analytic Comparison Regarding Steady-State Damping Performance Between the Twin Rotor Damper and a Dynamic Vibration Absorber | 10.1007/978-3-319-67443-8_48 |
2018-01-01 | In this paper, we derive the global existence of smooth solutions of the 3D incompressible Euler equations with damping for a class of large initial data, whose Sobolev norms H ^ s can be arbitrarily large for any s ≥ 0. The approach is through studying the quantity representing the difference between the vorticity and velocity. And also, we construct a family of large solutions for MHD equations with damping. | A class of large solutions to the 3D incompressible MHD and Euler equations with damping | 10.1007/s10114-016-6271-z |
2018-01-01 | Control strategy of unified power flow controller (UPFC) utilizing dq decoupling control is deduced in this paper, which can closely follow the control orders of the active and reactive power. The subsynchronous resonance (SSR) characteristics of a series compensated system equipped with UPFC are studied, and the results reveal that SSR characteristics of the system may vary significantly with UPFC in service or not. Consequently, supplementary subsynchronous damping controller (SSDC) for UPFC is proposed and investigated, and the effectiveness of the proposed SSDC is verified by damping torque analysis and time domain simulations. | Subsynchronous resonance and its mitigation for power system with unified power flow controller | 10.1007/s40565-017-0283-2 |
2018-01-01 | Is it simpler? In most cases, it is. Remember the difficulty you faced by working solely in the time domain, in the previous chapter (Chap. 2 ), in solving a differential equation with impulsive excitation? Except for these odd cases, time domain analysis is usually simpler. In this chapter, we discuss how linear circuits can be completely analysed without using Laplace or Fourier transforms. Is this analysis simpler than that using transform techniques? You should judge for yourself to realize. | Circuit Analysis Without Transforms | 10.1007/978-981-10-6919-2_7 |
2018-01-01 | The grids for transmission and distribution of electric energy have an ever-increasing share of static power converters. They include the source-side converters, the bus converters, and the load-side converters. Typical source-side converters are the inverters that collect the electric energy from the wind power plants or solar power plants, convert the energy into a set of three-phase voltages and currents, and inject the active and reactive power into the three-phase ac grid. The bus power converters are used for connections between the grids of different voltage levels, and they can be either ac/ac, dc/dc, or ac/dc. In a way, the bus converters tend to replace the traditional line-frequency power transformers. The load-side power converters are used as the power interface between the grid and the load. They convert the grid voltages and adjust the load voltages to suit the needs of the electric power application. With the advent of local accumulation and considering the regeneration needs of electrical drives, most load-side converters have to be bidirectional, capable of supplying electric energy into the grid during brief intervals of time. Therefore, the basic functionality of all the grid-side converters is similar. When interfacing the ac grids, the grid-side power converter has to provide the voltages and inject the currents that are in synchronism with the grid voltages. Therefore, it is necessary to provide the means for detecting the frequency and the phase of the grid ac voltages. Most common device in use is the phase-locked loop (PLL), often used in radio circuits. | Synchronization and Control | 10.1007/978-3-319-73278-7_8 |
2018-01-01 | The universal dispersion model is a collection of dispersion models (contributions to the dielectric response) describing individual elementary excitation in solids. All contributions presented in this chapter satisfy the basic conditions that follow from the theory of dispersion (time reversal symmetry, Kramers–Kronig consistency and finite sum rule integral). The individual contributions are presented in an unified formalism. In this formalism the spectral distributions of the contributions are parameterized using dispersion functions normalized with respect to the sum rule. These normalized dispersion functions must be multiplied by the transition strengths parameters which can be related to the density of charged particles. The separation of contributions into the transitions strengths and normalized spectral distributions is beneficial since it allows us to elegantly introduce the temperature dependencies into these models. | Universal Dispersion Model for Characterization of Thin Films Over Wide Spectral Range | 10.1007/978-3-319-75325-6_3 |
2018-01-01 | This chapter presents briefly an analytical example of implementing the dual function EH/TVA theory developed in Chaps. 5 and 6 on Vibration control a more realistic application. The response of an electronic box, vibrating at its resonance frequency, is optimally attenuated with the help of the proposed EH/TVA. The work demonstrates that the proposed energy harvesting Energy harvesting TVA combines the merits of classical mechanical and electrical TVAs and reduces their relative shortcomings and, hence, resulting in a new type of more adaptable, compact and agile electromechanical TVAs Electromechanical TVA . In vibration energy harvesting Energy harvesting process, transfer of mechanical vibration energy into electrical energy introduces additional damping Damping (i.e. electrical damping) in the system which can be used to tune the electromechanical TVA at its optimum condition. In the example presented, it is shown that optimum degree of vibration suppression of an electronic box is attained by using this dual function TVA through appropriate tuning of the connected electrical circuitry Electrical circuit which mimics efficiently the tuning of parameters of the mechanical TVA. MatLab code generating the simulations presented in this chapter is attached in Appendix-A at the end of the book. | Example of Vibration Suppression of Electronic Box Using Dual Function EH/TVA | 10.1007/978-3-319-69442-9_7 |
2018-01-01 | The forced resonant vibrations and vibrational heating of viscoelastic plates with actuators are modeled considering geometrical nonlinearity and transverse shear. An approximate analytical solution of the problem is obtained for a hinged rectangular plate by the Bubnov–Galerkin method. The effect of geometrical nonlinearity and shear deformations on the efficiency of active damping of vibrations with piezoelectric actuators is analyzed. | Forced Vibrations and Dissipative Heating of Hinged Flexible Viscoelastic Rectangular Plates with Actuators Under Shear Deformation | 10.1007/s10778-018-0862-6 |
2018-01-01 | For ordinary people, mechanical damping is the attenuation of a motion over time under possible eventual external actions. The phenomenon is produced by the loss or dissipation of energy during motion and thus time. The concept of real time is therefore at the center of the phenomenon of damping and given the recent scientific contributions (of gravitational waves in 2016), the notion of space-time calls for reflections and comments. The systemic approach of the phenomenon taking into account the mechanical system, its input and output variables (generalized forces or displacements) allows a very convenient analysis of the phenomenon. We insist on the differences between a phenomenon and a system: the causality, the linearity, the hysteresis are for example properties of phenomena and not properties of system; on the other hand we can consider dissipative or non-dissipative systems. We describe some macroscopic dissipation mechanisms in structures and some microscopic dissipation at the molecular level in materials or mesoscopic dissipation in composites materials. After specifying the notion of internal forces of a system we present some classical dissipative mechanisms currently used: viscous dissipation, friction dissipation, micro-frictions. The purpose of this presentation is not to list new dissipative systems but to point out a number of errors, both scientific and technical, which are frequently committed. | Damping in Materials and Structures: An Overview | 10.1007/978-3-319-77504-3_1 |
2018-01-01 | Active methods for damping the oscillations and limiting the dynamic loads of spring machine elements that are implemented owing to the additional force effects created by an electric drive providing the reduction of maximum work in spring gears of operated machinery were studied. The main parameters and energy characteristics of electromechanical systems that affect the efficiency of using of active means of dynamic load limitation by an electric drive in spring elements of mechanical gears were determined. It was shown that the maximum value of electric-engine current and its rate of change can decrease the efficiency of the active dynamic load limitation in machines by an electric drive and impede its practical implementation. Analytic equations for calculating the minimax torque (current) values of an engine and EMF of its supplying converter required for an effective decrease of the dynamic loads in spring machine elements were derived. The effects of the hardware and electric-drive parameters on the efficiency of decreasing dynamic loads in spring mechanical gears was specified. Research was performed to determine the efficiency and range of application of the active methods of dynamic load limitation in spring gears of machines using the existing electric drives. The results of the research were used in the implementation of active means of dynamic load limitation by an electric drive in spring gears of the thrust mechanism of an EKG-4.6B mine excavator and the digging mechanisms of EKG-20 excavators, as well as for decreasing the speed and force oscillations of the operating parts of balanced MP-100 manipulators and the weightless environment of zero-gravity simulators for training astronauts. | On the Use of Electromechanical Systems for Limiting Dynamic Loads in Spring Mechanisms | 10.3103/S1068371218010121 |
2018-01-01 | The assumptions made to derive the equations of motion in a FE environment are similar to those of the minimal model. | Optimization of Finite Element Models of Disc Brakes | 10.1007/978-3-319-62713-7_4 |
2018-01-01 | This chapter presents an experimentally validated distributed parameter model Distributed parameter model , of a base-excited cantilever bimorph, without any tip mass Tip mass . Euler–Bernoulli beam theory Euler-Bernoulli beam theory and the well-known constitutive piezoelectric equation are used to derive the model. The main features of this chapter relative to [ 1 , 2 ] are illustrated as below: As no tip mass Tip mass is used in the present study, this is known to be a more stringent validation of the distributed parameter piezoelectric beam model since the presence of a tip mass reduces the influence of the distributed inertia of the beam and restricts effective operation to low frequencies (e.g. 45–50 Hz resonance in) [ 4 ]. This study covers the relatively higher resonance frequency range, 120–130 Hz, for which most harvesters are designed for. The graphs showing variation in resonance frequency, resonant voltage amplitude, resonant power and resonant deflection amplitude with respect to change in electrical load are presented. These graphs give a deeper insight into the electromechanical interaction and also provide useful insight into theory and experimental results. Nyquist plots Nyquist plots of the FRFs are presented. The Nyquist plots are more descriptive than the usual magnitude graphs. Nyquist plots are used for two purposes here: To determine the mechanical damping. To observe the evolution of the FRFs as the electrical load is changed. The measured FRFs are obtained through the application of random excitation, also known as band-limited white noise, rather than a sine sweep [ 4 ]. The MatLab code, modelling and simulating the complex equations, of the mathematical model presented in this chapter is attached in Appendix-A of the book. | Distributed Parameter Modelling and Experimental Validation | 10.1007/978-3-319-69442-9_3 |
2018-01-01 | The problem of synthesizing the control of the intellectual suspension of a vehicle is regarded as a problem of synthesizing optimal law of the Lagrangian system parametric control. There has been developed a method for synthesizing optimal law parametric control in conditions of uncontrollable external exposures, what allows to speak of the possibility to build a “smart” damping system. The obtained laws of control are technically feasible being characterized by low amount of computational effort. | Combined Maximum Principle as the Basis of Intellectualization of Control Systems for a Suspension of Vehicles | 10.1007/978-3-319-68321-8_16 |
2018-01-01 | In a nonlinear dynamic analysis, the most popular way of representing the inherent damping exhibited by the structure is by adopting the classical Rayleigh damping model. Although a large number of studies have identified issues with this model, it remains the most popular choice in the currently available non-linear time-history analysis software. A new paradigm for modelling damping was proposed by the authors in Puthanpurayil AM, Lavan O, Carr AJ, Dhakal RP (Bull Earthq Eng 14:2405–2434, 2016) and is summarised in this chapter. This new model provides for the damping effects at an elemental level. The chapter outlines the performance of the elemental damping models in comparison to the classical global damping models by conducting Incremental Dynamic Analyses (IDA) on a four-storey RC frame designed to Eurocodes. The IDA study presented in the chapter illustrates the fact that the elemental damping models give a more reliable estimate for the structural responses in comparison to all other models. | Inherent Damping in Nonlinear Time-History Analyses: A Recommended Modelling Approach | 10.1007/978-3-319-62099-2_4 |
2018-01-01 | The effect of extension ratio on the structure and property of expanded polytetrafluoroethylene (ePTFE) has been decisively studied. ePTFE is unique with its porous fibrillar network structure connected by nodes and also with its degree of orientation which increases with increases in extension ratio. It is found that the Poisson’s ratio of ePTFE is negative, and it is reduced dramatically with increased extension ratio. At the extension ratio of 30, the Poisson’s ratio reaches − 10.00. By changes of extension ratio from 1 to 10, the segmental mobility of polymer chains becomes harder, and the dynamic glass transition temperature ( T _g) is increased. Broad glass transition regions are revealed in tan δ versus temperature curves in polytetrafluoroethylene specimens stretched 20- (S20) and 30-fold (S30). As the extension ratio is increased, the thermal conductivity of the specimens is decreased. The thermal conductivity coefficient is dropped to 0.051 W m^−1 K owing to the appearance of more pores and low degree of crystallinity at higher extension ratio. The properties of ePTFE modified by carbonyl iron powder (CIP) have been investigated. CIP has affected the structure and properties of modified ePTFE. CIP-modified ePTFE also exhibits a negative Poisson’s ratio which is larger than ePTFE at the same extension ratio. The modified ePTFE reveals higher thermal conductivity coefficient than ePTFE itself. | Expanded polytetrafluoroethylene as an auxetic material: effect of extension ratio on its structure and properties | 10.1007/s13726-017-0581-6 |
2018-01-01 | The paper is focused on study of new type of vibration control damper which has been designed, machined, assembled, and calibrated by authors. In typical oil dampers, attenuation force is generated by fixed orifices, where oil passes from one chamber to another. More advanced designs include variable orifices, where it is possible to regulate precisely flow area, e.g., by proportional valve. Thus, these solutions are so-called valve mode, also very popular in whole group of magnetorheological dampers. Another known in engineering type of dampers is based on viscous friction. Steel rood passed through cylinder head, where interference fit creates movement resistance. This paper proposes novel design of damper, where in order to control damping force, simple direct current motor and special mechanism, similar to wedge, has been proposed. To perform basic research on damper’s characteristics, special test stand was designed. Crankshaft mechanism was used to generate reciprocating movement. During tests, one end fixed damper was connected to slider by force transducer. To describe phenomenon of variable damping force, force–displacement and force–velocity characteristics have been registered and described. | Study on Mechanical Characteristics in Electromechanical Disengaging Damper | 10.1007/978-3-319-68619-6_35 |
2018-01-01 | We developed a passive haptic technique, using the brake of a DC motor, to create a greater perception of impulse force. We found that when using the brake of a DC motor, delivering two short pulses immediately prior to the main brake significantly increases the operator’s perception of impulse force. This finding was verified during our empirical assessment. In the experiment, all five participants reported that a damping brake with pulsive resistances delivered a larger resistance than that caused by a brake without pulsive changes. Our technique is applicable to passive haptic interfaces, which are inherently safe and energy-efficient. | Passive Haptics: Pulsive Damping Brake for Greater Impulse Perception | 10.1007/978-981-10-4157-0_37 |
2018-01-01 | This paper presents simulation of two level voltage source inverter based on SVPWM (space vector pulse width modulation) technique. The concept of two level inverter is used to reduce the harmonic distortion in output voltage waveform without decreasing the inverter output power. Simulation results are presented to realize the validity of SVPWM technique. | Simulation of Three Phase Voltage Source Inverter Based on SVPWM Technique | 10.1007/978-3-319-63085-4_19 |
2018-01-01 | This chapter summarizes a few projects which have been conducted in the early days of the Active Structures Laboratory of ULB (mostly before 2002) in various fields including active damping, precision positioning, and vibroacoustics; all of them include numerical and experimental results. After a few words about digital control, the chapter begins with the active damping of a truss structure, followed by a six-axis piezoelectric Stewart platform that is proposed as generic damping interface (it can also be used for precision positioning). Next, the active damping of a piezoelectric plate is considered, with an experiment flown in 1995. It is followed by the active damping of a stiff beam using acceleration feedback and a proof-mass actuator. The next section, on HAC/LAC control, shows how embedding a collocated active damping loop in a non-collocated precision control may be effective in increasing the control bandwidth. The next section is devoted to the development of a sound radiation sensor for active structural acoustic control; the starting point is a discrete array of piezoelectric sensors; finally, a distributed sensor forming a porous electrode is developed successfully, all computations being confirmed by experiments. The chapter concludes with a short list of references and a set of problems. | Applications | 10.1007/978-3-319-72296-2_14 |
2018-01-01 | Machine tools in actual construction, being related to the trend towards to machine tools of high productivity and increased precision and having in view the context of transition to Industry 4.0, have to be studied deeply in the stage of conception and also in that of exploiting. For both situations, the modeling and simulation of the machine tool regarded as a mechatronic system represent methods of analysis, assessment, and optimization for its improvement. This work proposes the approaching the subject from the point of view of modeling and simulation of one assembly of the machine tool that proves one of the most sensitive kinematic structure responsible for the machine tool precision. The modeling, either Rigid Body Simulation, Digital Block Simulation, Finite Element Modeling or combinations types, implies a concrete and accurate definition of the dynamic parameters stiffness, damping, and friction. Some mathematical approaches for determining these parameters are presented. Also, some product catalog values and relations coming from the engineering and research experience applied to feed drive components and also to the whole kinematic chain are given. Furthermore, some practical testing and calculation methods are presented. | Dynamic Definition of Machine Tool Feed Drive Models in Advanced Machine Tools | 10.1007/978-3-319-89563-5_9 |
2018-01-01 | An equivalent lumped-parameter model of a beam-like piezoelectric TMD TMD (tune mass damper) under short-circuited conditions is analyzed. This enabled the calculation of the optimal viscous damping required by a TMD according to the classical theory for a given application. This hypothetical optimally damped, electrically uncoupled system, is then used as a benchmark to calculate the optimal R-L-C parameters in the actual (electrically coupled) TMD TMD using optimisation tools in MATLAB. Four different R-L-C circuit R-L-C circuit configurations are investigated. The frequency response functions ( receptances Receptance ) of the host structure with the attached electromechanical TMD TMD are compared with those from the benchmark system which is designed using classical mechanical vibration theory. The analysis is performed by the analytical modal analysis method (AMAM) and verified by the dynamic stiffness method. The results show that, for all four circuit configurations, correct tuning of the R-L-C parameters is capable of producing a response that very closely replicates the benchmark response. Of the four circuit configurations considered, the most convenient and economical is the one where the bimorphs were connected in parallel with each other across a capacitor that was in turn connected in parallel with a resistor-inductor series combination. MATLAB optimisation Optimization program MatLab optimization program developed for the simulations is presented as Annex-A of the book. | A Theoretical Analysis of an ‘Electromechanical’ Beam Tuned Mass Damper | 10.1007/978-3-319-69442-9_5 |
2018-01-01 | The purpose of this chapter is to present a computational tool for the analysis of the vibration behavior of jointed structures whose dynamics are considered nonlinear under the operating conditions of interest. The method is based on the concept of nonlinear modes. The definition of nonlinear modes is here adjusted in such a way that the modes reflect periodic vibration behavior in the presence of isolated resonances. From a given model of the structure and the nonlinear constitutive law describing the joint interactions, the method extracts amplitude-dependent vibrational features such as natural frequencies, damping ratios, and vibrational deflection shapes. Based on these modal characteristics, a reduced order model is then constructed that facilitates the efficient vibration prediction in a wide range of operating conditions and parameters. Special attention is paid to the aspect of computational efficiency, as well as the compatibility with conventional analysis procedures involving finite element codes. Hence, the methodology is considered particularly useful for the state-of-the-art design process of jointed structures, possibly involving reliability analysis to account for uncertainty. | Nonlinear Modal Analysis and Modal Reduction of Jointed Structures | 10.1007/978-3-319-56818-8_29 |
2018-01-01 | The topology optimization algorithm of viscoelastic material microstructure based on bi-directional evolutionary structural optimization (BESO) method is proposed for macroscopic damping characteristics of the structures. The optimization aims to obtain the optimal topologies of the material microstructures within given volume fraction so that the resulting structure has optimal damping characteristics. The design concept of this scheme is essentially a two-scale design which considers the effective properties of material microstructures and macroscopic performance. Viscoelastic material is used for the damping of the macrostructure and the frequency constraint is also applied so that the resulting macrostructure has the best damping performance with prescribed natural frequencies. The microstructures of the material are represented by periodic unit cells (PUCs) and the effective properties of the material microstructures are homogenized and integrated into the finite element analysis of the macroscopic structures. The sensitivity analysis is conducted for iteratively updating the topologies of material microstructures. Numerical examples are presented to demonstrate the effectiveness of the proposed optimization algorithm. | Topology Optimization of Viscoelastic Materials for Maximizing Damping and Natural Frequency of Macrostructures | 10.1007/978-3-319-67988-4_131 |
2018-01-01 | Recently, Direct Current (DC) magnetic field processing of materials has found widespread applications in metallurgy, especially in metals and semiconductor industries. The main goal is to control the behavior of melts during solidification so as to improve process performance and achieve better quality products. DC magnetic fields are effective in introducing some special magnetohydrodynamic effects, e.g., flow damping, which are commonly used in continuous casting of steels or crystal growth control. In parallel, the development of super conducting technology, which is able to produce high magnetic fields in a large space, has open many new possibilities in control of the processing of materials in solid and liquid state. The novelty comes from the creation of magnetization forces on non-magnetic or feeble magnetic materials due to high magnetic fields. Morerover, it has been realized quite recently that the thermo-electric phenomena under high DC magnetic field can produce strong electromagnetic forces in solid and liquid metals, leading to a phenomenon called Thermo-Electric-Magnetic Convection (TEMC). The forces are able to generate significant liquid motion especially when temperature gradients are present, and therefore strongly influence the solidification of metallic alloys. This chapter reviews the major progresses and applications related to the uses of strong/intense DC magnetic fields in processing of materials (mainly metallic alloys) in solidification processes. In the first section, we review the underlying principles in magnetohydrodynamics and magnetic effects. In the second section, we discuss the phenomena induced by DC magnetic fields in materials processing. We deal in particular with flow damping effects on liquid metals, and control of structure of materials during solidification, including texturing, phase separation and thermoelectric effect. Finally we give two examples of successful industrial applications. | High Magnetic Field Processing of Metal Alloys | 10.1007/978-3-319-94842-3_6 |
2018-01-01 | The chapter analyzes the structural seismic analysis methods. The four common analysis method are illustrated (Linear static, linear dynamic, nonlinear static, and nonlinear dynamic analyses). Additionally, the direct displacement-based seismic design procedure is discussed in detail. | Methods of Analysis | 10.1007/978-3-319-72541-3_14 |
2018-01-01 | Cooperation between surgeon and robot is one of the key technologies that limit the robot to be widely used in orthopedic clinics. In this study, the evolution of human-robot cooperation methods and the control strategies for typical human-robot cooperation in robot-assisted orthopedics surgery were reviewed at first. Then an intelligent admittance control method, which combines the fuzzy model reference learning control with the virtual constraint control, is proposed to solve the requirements of intuitive human-robot interaction during orthopedics surgery. That is, a variable damping parameter model of the admittance control based on fuzzy model learning control algorithm is introduced to make the robot move freely by using the reference model of surgeon’s motion equation with the minimum jerk trajectory. And the virtual constraint control method based on the principle of virtual fixture is adopted to make the robot move within the pre-defined area so as to perform more safe surgery. The basic principle and its realization of this intelligent control method are described in details. At last, a test platform is built based on our designed 6 DOF articulated robot. Experiments of safety and precision on acrylic model with this method show that the robot has the ability of better intuitive interaction and the high precision. And the pilot experiment of bone tumor resection on sawbone model shows the effectiveness of this method. | Intelligent Control for Human-Robot Cooperation in Orthopedics Surgery | 10.1007/978-981-13-1396-7_19 |
2018-01-01 | Broadband impact excitation in structural dynamics is a common technique used to detect and characterize nonlinearities in mechanical systems since it excites many frequencies of a structure at once. Nonstationary time signals from transient ring-down measurements require time-frequency analysis tools to observe variations in frequency and energy dissipation as the response evolves. This chapter uses the Short-Time Fourier Transform (STFT) to estimate the instantaneous parameters from measured or simulated data. By combining the discrete Fourier transform with an expanding or contracting window function that moves along the time axis, the resulting spectra are used to estimate the instantaneous frequencies, damping ratios, and complex Fourier coefficients. Other methods such as Hilbert transforms in conjunction with the Zeroed Early Fast Fourier Transform (ZEFFT) or wavelet based approaches are also able to be applied in similar manners as the STFT. From any of these methods, the amplitude-frequency dependence in the damped response is able to be extracted in order to determine the parameters for a joint model. | Parameter Estimation via Instantaneous Frequency and Damping from Transient Ring-Down Data | 10.1007/978-3-319-56818-8_21 |
2018-01-01 | In this chapter, an analytical model is developed for the motion response and wave attenuation of a raft-type wave-powered desalination device. The desalination module of the device is simplified as a Power Take-Off (PTO) system. The analytical solution of diffraction and radiation problem of multiple two-dimensional rectangular bodies floating on a layer of water of finite depth is obtained using a linearized potential flow theory. Wave excitation forces, added masses and wave damping coefficients for these bodies are calculated from incident, diffracted and radiated potentials. Upon solving the motion equation, response, power absorption and wave attenuation of a raft-type wave power device are obtained. The model is validated by comparison of the present results with the existing ones, and energy conservation is checked. The validated model is then utilized to examine the effect of PTO damping coefficient, raft draft, spacing between two rafts, water depth, and raft numbers on power absorption and wave transmission coefficient of raft-type wave power device. The influence of structure length ratio is also discussed. It is found that the same wave transmission coefficient can be obtained by any certain raft-type wave power device, regardless of wave propagation direction. | Analytical Study on Hydrodynamic Characteristics | 10.1007/978-981-10-5517-1_2 |
2018-01-01 | During the last decades, biomimetics has attracted increasing attention as well from basic and applied research as from various fields of industry. Biomimetics has a high innovation potential and offers the possibility for the development of sustainable technical products and production chains. Novel sophisticated methods for quantitatively analyzing and simulating the form–structure–function relationship on various hierarchical levels allow new fascinating insights into multi-scale mechanics and other functional parameter spaces of biological materials systems. On the other hand, new production methods enable for the first time the transfer of many outstanding properties of the biological role models into innovative biomimetic products at reasonable costs. Presented examples of biomimetic developments and products inspired by plants include branched and unbranched fiber-reinforced lightweight composite materials, structural materials with a high energy dissipation capacity as fiber-reinforced graded foams and compound materials, solutions for elastic architecture as the biomimetic façade-shading systems Flectofin^® and Flectofold inspired by the bird of paradise flower and the waterwheel plant, respectively. Finally, a short overview of bioinspired self-repairing materials is given and a short discussion of the potential of biomimetic products to contribute to sustainable material development is presented. | Biomechanics and Functional Morphology of Plants—Inspiration for Biomimetic Materials and Structures | 10.1007/978-3-319-79099-2_18 |
2018-01-01 | Stated choice (SC) experiments are the most popular method to estimate the value of travel time changes (VTTC) of a population. In the simplest VTTC experiment, the SC design variables are time changes and cost changes. The levels of these variables create a particular setting from which preferences are inferred. This paper tries to answer the question “do preferences vary with SC settings?”. For this, we investigate the role of the variables used in the SC experiment on the estimation of the set of VTTC (i.e. mean and covariates). Ideally, one would like to observe the same individuals completing different SC experiments. Since that option is not available, an alternative approach is to use a large dataset of responses, and split it according to different levels of the variable of interest. We refer to this as partial data analysis. The estimation of the same model on each sub-sample provides insights into potential effects of the variable of interest. This approach is applied in relation to three design variables on the data for the last national VTTC study in the UK, using state-of-the-art model specifications. The results show several ways in which the estimated set of VTTC can be affected by the levels of SC design variables. We conclude that model estimates (including the VTTC and covariates) are different in different settings. Hence by focussing the survey on specific settings, sample level results will be affected accordingly. Our findings have implications for appraisal and can inform the construction of future SC experiments. | Understanding valuation of travel time changes: are preferences different under different stated choice design settings? | 10.1007/s11116-016-9716-4 |
2018-01-01 | The chapter introduces the energy balance equation of a generic system. Attention is given to damping energy and plastic energy (Vakakis et al., Nonlinear targeted energy transfer in mechanical and structural systems, vol 156. Springer, Dordrecht, 2008). Two methods are introduced to estimate the damping on the structural systems through experimental techniques: the Logarithmic Decrement Analysis (LDA) and the Half-Power Method (HPM). The ductility factor and the equal displacement criteria is also introduced. | Energy Dissipation | 10.1007/978-3-319-72541-3_5 |
2018-01-01 | Carbon nanotube (CNT) reinforced acrylonitrile-butadiene-styrene (ABS) composites fabricated using a fused deposition modeling approach were characterized for mechanical strain energy storage and dissipation capabilities. Dynamic mechanical analysis (DMA) was performed to quantify loss factor as a function of applied dynamic strain. In addition, DMA was performed at varying temperatures to give insight into the molecular interactions present in these composites. Insight into the microstructure was provided by atomic force microscopy (AFM). The results are compared to neat ABS and ABS/CNT systems processed through an injection molding technique. Results show large energy dissipation, accompanied by permanent damage, in both injection molded and additively manufactured neat ABS samples. In contrast, the additively manufactured ABS/CNT nanocomposites exhibited strain energy dissipation but reduced the effect of cavitation and crazing by possible reinforcement. This result suggests CNT fillers have the potential to alter the dissipation mechanisms present in additively manufactured structures to control structural damping. This research provides insight into the design and additive manufacturing of materials where energy dissipation is essential to maintain structural stability and functionality under dynamic loading. | Strain Energy Dissipation Mechanisms in Carbon Nanotube Composites Fabricated by Additive Manufacturing | 10.1007/978-3-319-62834-9_5 |
2018-01-01 | We consider a parameter-dependent family of damped hyperbolic equations with interesting limit behavior: the system approaches steady states exponentially fast and for parameter to zero, the solutions converge to that of a parabolic limit problem. We establish sharp estimates and elaborate their dependence on the model parameters. For the numerical approximation, we then consider a mixed finite element method in space together with a Runge–Kutta method in time. Due to the variational and dissipative nature of this approximation, the limit behavior of the infinite-dimensional level is inherited almost automatically by the discrete problems. The resulting numerical method thus is asymptotic preserving in the parabolic limit and uniformly exponentially stable. These results are further shown to be independent of the discretization parameters. Numerical tests are presented for a simple model problem which illustrate that the derived estimates are sharp in general. | An Asymptotic Preserving Mixed Finite Element Method for Wave Propagation in Pipelines | 10.1007/978-3-319-91545-6_39 |
2018-01-01 | This chapter describes the modified Costas loop for BPSK. While the conventional Costas loop operated with real signals, the modified circuit works with the so-called pre-envelope signal. This is a complex signal, also referred to as “analytical signal.” The real input signal of this Costas loop is converted to the pre-envelope signal using a Hilbert transformer. The local oscillator also generates a complex output signal. It is shown that the phase transfer function of this type of Costas loop is modified as well: The number of poles is reduced by one. This has a very advantageous effect on dynamic behavior of the loop. When the loop filter is realized by a PI filter (proportional + integral), the pull-in range can be made arbitrarily large (theoretically infinite). Following the mathematical analysis of the circuit, a case study for the design of a digital modified Costas loop for BPSK is presented. This guides the designer of a loop step by step through the entire circuit design. Two Simulink models can be used to simulate a modified Costas loop with user-specified parameters such as carrier frequency, symbol rate, frequency error. All relevant signals of the loop can be visualized on scopes. | Modified Costas Loop for BPSK | 10.1007/978-3-319-72008-1_5 |
2018-01-01 | This chapter addresses the problem of vibration isolation; the excitation may be harmonic or wide band. The chapter begins with the single-axis passive isolation: linear viscous isolator and relaxation isolator; an electromagnetic realization of the relaxation isolator is discussed. Next, the active isolation is considered: the celebrated single-axis sky-hook damper and its Integral Force Feedback (IFF) implementation. The difference between the two implementations when applied to flexible structures is highlighted, and the superiority (due to built-in stability properties) of the IFF is pointed out. Next, after a brief discussion of the payload isolation in spacecraft, the six-axis isolation is considered with a Gough–Stewart platform; the passive isolation when the legs consist of relaxation isolators and the active isolation when the legs are controlled according to the IFF are discussed and compared. The influence of the modal spread on performance is analyzed, as well as the parasitic stiffness of the spherical joints of the Stewart platform. Finally, a quarter-car model of a vehicle suspension is briefly analyzed. The chapter concludes with a short list of references and a set of problems. | Vibration Isolation | 10.1007/978-3-319-72296-2_8 |
2018-01-01 | The purpose of this chapter is to present a comprehensive overview of the previous research published relevant to the book’s aims and objectives introduced in Chap. 1. Due to the interdisciplinary nature of the field, the chapter begins with a short background highlighting the necessity of energy harvesting Energy harvesting with brief surveys of power generation capabilities of some potential ambient sources and power requirements by some modern electronic devices. This is then followed by a critical review of PVEH techniques and its application to vibration control Vibration control . In this chapter, it is endeavoured to build the fundamental understanding of the readers in order to comprehend the more complex modelling concepts of piezoelectric electromechanical energy harvesting systems developed in the later chapters of the book. | Overview of Vibration Energy Harvesting | 10.1007/978-3-319-69442-9_2 |
2018-01-01 | Particle damping is a passive vibration damping technology, with good energy consumption, simple structure, low cost, easy operation and is suitable for use in harsh environment. In this paper, the particle collision is taken as the object of study. The Hertz theory of contact mechanics is used to analyze the process of particle collision. Afterwards, the energy dissipation of the particles with different volumes under constant mass was simulated by using LS-DYNA finite element software. Finally, the cantilever beam verification experiment of the particle damper is carried out for the simulation results. Experimental showed that the energy loss is the largest among the particles with the same total mass, and the energy loss decreases with the increase of the gap between the two particles. | Energy Dissipation Analysis of Two Particles with Different Volume Under Fixed Mass | 10.1007/978-981-10-6553-8_92 |
2018-01-01 | The paper considers random fluctuation in damping coefficient of an electrostatically driven micro/nanoelectromechanical (M/NEMS) resonator and analyzes occurrence of stochastic resonance. The resonator device has been modeled as a damped harmonic oscillator with additive Gaussian damping noise characterized by exponential autocorrelation and zero mean. The condition for stochastic resonance has been analyzed with for variations in noise strength (variance), correlation rate, and drive frequency. It is found that both the amplitude and phase exhibit stochastic resonance at moderate noise strengths. As the amplitude stochastic resonance has been widely explored in literature, we focus particularly on analyzing the phase stochastic resonance from the perspective of exploiting this for enhancing sensitivity and quality factor of M/NEMS resonator chemical and biological sensors. | Damping Noise Induced Stochastic Resonance Improves Q-Factor of M/NEMS Resonators | 10.1007/978-981-10-8240-5_58 |
2018-01-01 | The flexibility of the powertrain leads to the driveline oscillating, which will deteriorate the drivability and comfort of the vehicle, in transient condition such as pedal tip in/out maneuver and regenerative braking. This problem has received increasing interest due to the higher drivability demand of drivers with the development of car industry. This paper aims at active damping of the powertrain oscillation with a shaft torque compensator. In this paper, a simplified powertrain model is established and the frequency response characteristics of the powertrain is analysed. In order to damp out the oscillation, the torque of the drive shaft is compensated with a feedforward and PID feedback controller which is designed based on the simplified powertrain model. For there usually is no torque sensor in the vehicle powertrain, a minimal order observer is established to observe the state variables that cannot be measured. The simulation results are proposed and compared with those with no oscillation controller, it shows the proposed controller can damp out the oscillation effectively. | Shaft Torque Compensation for Electric Vehicle Driveline Oscillation Active Damping with Feedforward and PID Feedback Controller | 10.1007/978-981-10-6553-8_52 |
2018-01-01 | With the increase of running speed and axel load of trains, the structure-borne noise emanating from the railway bridges is more and more serious. The constrained layer damping can achieve an obvious reduction of vibration and noise of the treated structure in a wide frequency range by means of dissipating the vibration energy owing to damping layer’s shear deformation. Based on the train-track-bridge coupled vibration, modal strain energy method and statistical energy analysis, a theoretical model for calculating the vehicle-induced vibration and noise of the railway bridge with constrained layer damping is presented. The vibration and noise of the (32 + 40 + 32) m steel-concrete composite bridge before and after constrained layer damping installation is simulated. The structure-borne noise radiated by the bridge in the whole analysis frequency range is reduced significantly. The sound pressure level at the field point which is 30 m to the track centerline in horizontal direction and 1.5 m to the ground in vertical direction is reduced by 4.3 dB(A). | Computation Model for Structure-Borne Noise from Railway Bridge with CLD | 10.1007/978-981-10-4508-0_41 |
2018-01-01 | The paper presents results of researches conducted on test bed of rotor system. The aim of research was to show how resonant frequency and amplitude might be changed by damping washers. Article presents an example of approach to the problem conducted in laboratory conditions, the results of which can be easily transferred on board of a ship or vessel. | The Impact Estimation of Damping Foundations in Dynamics of the Rotor System in Non-stationary States | 10.1007/978-3-319-61927-9_7 |
2018-01-01 | The physical mass and damping of a haptic device contribute features that can be considered parasitic in that they potentially mask the virtual environment the user is intended to feel. On the other hand, users are generally able to adapt to the mechanical properties of physical tools and concentrate on the dynamics of task objects in the environment. It would be unsurprising, then, if humans were also able to ignore parasitic effects and focus on the mechanical properties of interest within a rendered environment. In this work, we explore a particular parasitic effect (damping) and its impact on the perception of stiffness. We examine the various perceptual impacts of predictable or unpredictable levels of damping. We find that, overall, humans are quite capable of ignoring damping to focus on stiffness, but that this ability may be hampered in the presence of unpredictable damping. | Haptic Scene Analysis: Mechanical Property Separation Despite Parasitic Dynamics | 10.1007/978-3-319-93445-7_21 |
2018-01-01 | The overall aims of the chapter are twofold: (i) to present two alternatives modelling techniques for the uniform-section beam systems in Fig. 4.1 and (ii) to use these techniques in a theoretical study of a bimorph. The chapter presents the use of DSM for the solution of such a problem and illustrates its applicability to more complex problems. The DSM formulae derived are compared with the AMAM originally developed by Erturk and Inman [1] and used in the previous chapter. It is important to note that none of the works in [1] and Chap. 3 , of this book, verify their modelling against an alternative method. As in [1] and Chap. 3 , the Euler-Bernoulli model with piezoelectric coupling is used. However, the electrical load is a generic linear impedance, rather than just a resistor used in [1] and Chap. 3 . Moreover, certain damping Damping -related details that are unexplained or neglected in [1] and Chap. 3 are considered. In order to enable a direct comparison with the DSM, the AMAM of Erturk and Inman [1] (and Chap. 3 ) is reformulated to allow for a unified modelling of all three systems in Fig. 4.1 . This reformulation of AMAM is a contribution in itself since the modelling in [1] is fragmented to the extent that different ad hoc formulae, notation and variable definitions are used for the three systems in Fig. 4.1 . Each reformulated AMAM formula presented here covers all cases in [1]. The specialised DSM formulae similarly encompass all three systems in Fig. 4.1 . Moreover, the dynamic stiffness matrix of the beam itself could be used in the modelling of beams with different boundary conditions or an assembly of uniform-section beams [2]. This is a major advantage over the AMAM approach, which is restricted to the systems in Fig. 4.1 . Additionally, since DSM is based on an exact solution, less elements are required than the finite element method for an assembly of uniform-section beams, making it more accurate than finite element techniques for high-frequency applications [4]. The analysis performed in this research yields findings relating to the following issues: (i) tuning range of the energy harvester (with approximate formulae derived for the open-circuit resonances); (ii) the effect of the type of the external electrical impedance (resistive or capacitive), as well as the effect of series and parallel connection of the piezoelectric layers; (iii) the effect of damping Damping -related assumptions; (iv) the neutralising effect of a tuned harvester on the vibration at its base; and (v) the application of boundary constraints and segmented electrodes Segmented electrodes for increased power generation [3]. The modelling procedure is described from first principles in Sect. 4.2 . This is followed by a theoretical study of a cantilevered bimorph in Sect. 4.3 . Section 4.4 illustrates the extension of DSM to more complex systems through an example and discusses the limitations of DSM. | Modelling of Energy Harvesting Beams Using Dynamic Stiffness Method (DSM) | 10.1007/978-3-319-69442-9_4 |
2018-01-01 | Nonlinear energy sink (NES) refers to a lightweight nonlinear device that is attached to a primary linear or weakly nonlinear system for passive energy localization into itself. In this paper, the dynamics of 1-dof and 2-dof NES with geometrically nonlinear damping is investigated. For 1-dof NES, an analytical treatment for the bifurcations is developed by presenting a slow/fast decomposition leading to slow flows, where a truncation damping and failure frequency are reported. Existence of strongly modulated response (SMR) is also determined. The procedures are then partly paralleled to the investigation of 2-dof NES for the bifurcation analysis, with particular attention paid to the effect of mass distribution between the NES. To study the frequency response for 2-dof NES, the periodic solutions and their stability are obtained by incremental harmonic balance method and Floquet theory, respectively. Poincare map and energy spectrum are specially introduced for numerical analysis of the systems in the neighborhood of resonance frequency, which in turn are used to compare the efficiency of the NESs to the application of vibration suppression. It is demonstrated that a 2-dof NES can generate extra SMR by adjusting its mass distribution and hence to a great extent reduces the undesired periodic responses and provides with a more effective vibration absorber. | Dynamics of 1-dof and 2-dof energy sink with geometrically nonlinear damping: application to vibration suppression | 10.1007/s11071-017-3906-2 |
2018-01-01 | The paper presents an analysis of Bagley-Torvik system under the influence of frequency noise. The Bagley-Torvik system is characterised by a fractional order damping. Our analysis shows that the system exhibits a new type of stochastic resonance for noises with low correlation rates. This is in addition to the usual stochastic resonance observed in nonlinear systems with added noise power. | Stochastic Resonance in Bagley-Torvik Equation | 10.1007/978-981-10-8240-5_56 |
2018-01-01 | The capacitor-current-feedback active-damping is an effective approach for damping the resonance peak of the LCL filter. When the LCL -type grid-connected inverter is digitally controlled, the control delay will be generated. This will result in different behavior of the capacitor-current-feedback active-damping from that with analog control. In this chapter, the mechanism of the control delay in the digital control system is introduced first. Then, a series of equivalent transformations of the control block diagram considering the control delay are performed, and it reveals that the capacitor-current-feedback active-damping is no longer equivalent to a virtual resistor in parallel with the filter capacitor, but a virtual frequency-dependent impedance. A forbidden region for choosing the LCL filter resonance frequency is presented in order to guarantee the system stability. Then, the controller design for digitally controlled LCL -type grid-connected inverter with capacitor-current-feedback active-damping is studied. Since the control delay leads to a phase lag and consequently changes the location of −180°-crossing in the phase curve of the loop gain, the system stability might be guaranteed even without damping the resonance of LCL filter. For this case, the necessary condition for system stability is studied, and the controller design method is presented. Finally, the controller parameters design examples for the grid current regulator with and without the capacitor-current-feedback active-damping are given, and the effectiveness of the theoretical analysis is verified by the experimental results. | Design Considerations of Digitally Controlled LCL-Type Grid-Connected Inverter with Capacitor-Current-Feedback Active-Damping | 10.1007/978-981-10-4277-5_8 |
2018-01-01 | Damping in structures is an important aspect from the vibration control and dynamic stability point of views. These days, significant emphasis is placed on the damping in composite structures due to involvement of different mechanisms for controlling damping at micro (fibre-matrix interface, fibre orientation etc.) and macro levels (fibre orientation, stacking sequence etc.) under dynamic loading. This study scrutinizes the specimen cross-sectional effect on the damping capacity of hollow tubes. For this purpose, carbon fibre reinforced tubes of square and hexagonal cross-sections were investigated. To improve the damping capacity further, circular holes were drilled at different positions along the tube. Free vibration and base excitation tests were performed to induce vibration in tubes and responses at different locations (i.e., along the tube length) were recorded using accelerometers and strain gauges. It is observed from the experimental results that the damping ratio increases in presence of holes in tube specimens. Further, damping enhancement is found to be more for tubes containing smaller holes (owing to more localized stresses) in comparison to the tubes containing larger holes. Typically, damping of hexagonal tubes is found to be slightly less in comparison to the square tube. | Effect of Cross-Section and Discontinuities on Damping Enhancement in Composites: An Experimental Study | 10.1007/978-3-319-67443-8_62 |
2018-01-01 | In order to achieve more realistic structural parameter identification, it is inevitable to account for uncertainties. The present paper proposes a stochastic identification process to identify propagation parameters such as the wavenumber, the damping loss factor, and the wave attenuation, in presence of uncertainties. The proposed stochastic identification process combines, in a wave propagation framework, the Inhomogeneous Wave Correlation method with the Latin Hypercube Sampling method. It is compared to the identification process combining the Mc Daniel method and the Latin Hypercube Sampling method which are considered as reference for structural identification and uncertainty propagation, respectively. An isotropic beam example is considered and identification is done from Frequency Response Functions computed at several measurement points which coordinates are supposed to be the uncertain parameters. The effects of uncertainties on parameter identification are evaluated through statistical quantifications of the variability of the identified parameters. Obtained results show that all identified parameters are affected by uncertainties, except damping. | Inhomogeneous Wave Correlation for Propagation Parameters Identification in Presence of Uncertainties | 10.1007/978-3-319-66697-6_80 |
2018-01-01 | Chapter 3 describes the development of the research area which can be called “chemical periodical processes”. It emphasizes the phenomenon of four books: German 1913 book, English 1926 book, French 1934 book, and Russian (Soviet) 1938 book “Physico-chemical periodical processes”. This list can be enriched by including one more book, namely, “Liesegang rings and other periodical structures” (London, 1932). Kremann 1913 book states that the periodical reactions can be divided into two main groups: homogeneous and heterogeneous. However in the succeeding books this classification has been overshadowed by the other problems. Besides Liesegang rings and other periodical structures and processes these books are concerned with mathematical modeling of chemical periodicity. This is a specific subarea of the area of chemical periodicity. Lotka’s 1910 paper showed that by taking into consideration the phenomenon of autocatalysis one can propose the system of equations describing the slowly damped chemical oscillations, Lotka’s 1920 paper showed that by modifying his 1910 model one can produce the system of equations described (in particular) undamped oscillations. Besides Lotka, Hirniak (Lvov) contributed to the early mathematical studies of chemical periodical processes (1908, 1911). | A Research Area | 10.1007/978-3-319-95108-9_3 |
2018-01-01 | Acoustic cavitation is the formation and subsequent violent collapse of bubbles in liquid irradiated with intense ultrasound. Ultrasound is radiated by a vibrating plate connected to ultrasonic transducers made of piezoelectric materials driven by electrical power. Microscopic mechanism for vibration of piezoelectric materials is briefly described. There are two types of ultrasonic experimental equipment used to generate acoustic cavitation: ultrasonic horn (or probe) and ultrasonic bath. Ultrasonic standing waves and traveling waves are discussed by means of mathematical equations. Acoustic impedance is discussed, and transmission and reflection coefficients are described. Various types of acoustic cavitations are discussed: transient and stable cavitations, vaporous and gaseous cavitations. Fluctuations in degassing and re-gassing cause repeated change between vaporous and gaseous cavitation. Light emission associated with violent bubble collapse as well as chemical reactions inside and outside a bubble is discussed in the sections entitled “sonoluminescence” and “sonochemistry,” respectively. Unsolved problems in sonoluminescence are briefly discussed. Reasons for lesser amount of produced H radicals (H·) than that of OH radicals (OH·) in sonochemical reactions are discussed based on results generated from numerical simulations. In the last section, ultrasonic cleaning, especially for the application to silicon wafers, is discussed. | Acoustic Cavitation | 10.1007/978-3-319-68237-2_1 |
2018-01-01 | As compared to the conventional approach of trial solutions for solving the differential equation governing the transient response of RLC networks, we present here a different approach which is totally analytical. We also show that the three cases of damping, viz. overdamping, critical damping and underdamping, can be dealt with in a unified manner from the general solution. Won’t you appreciate my innovations? Please do and encourage me. | Transient Response of RLC Networks Revisited | 10.1007/978-981-10-6919-2_8 |
2018-01-01 | We propose an analytical algorithm to study harmonic oscillation Harmonic oscillation of a rectangular elastic plate in an incompressible fluid Incompressible fluid , with varying pressure conditions. Application of the two-dimensional Fourier transform leads to a two-dimensional integral equation with a two-dimensional integral as a kernel. The solution of the basic integral equation is represented as a series by the Chebyshev orthogonal polynomials. The problem is reduced to an infinite system of one-dimensional integral equations. The asymptotic approach allows us to solve each equation of the system independently. The solution of the integral equation leads to an ordinary differential equation of the fourth order for the function of the plate vibrations. The obtained solution determines the form of the oscillation. The results are given on example of the aluminum plate oscillations for a number of frequencies by varying air pressure density. The results are compared with experimental data. | Dynamic Properties of Thin-Walled Structures Under Changing Pressure Conditions in the Contact Fluid | 10.1007/978-3-319-56579-8_8 |
2018-01-01 | Conventionally, fixed-structure feedback controllers are designed by model-based approaches. However, such controllers are not necessarily ideal and optimal when connecting with the actual plant because of the existence of modeling uncertainty. In this paper, a paralleled damping controller as well as a novel hybrid reference model matching (RMM) and virtual reference feedback tuning (VRFT) approach for parameters’ tuning of the controller is presented. The composite damping controller for piezo-actuated nanopositioners is fixed-structure and low-order that uses a high-gain notch filter and a high-pass resonant controller to damp the first resonant peak. The proposed hybrid tuning approach combines an identified system model and a set of experimental input/output data into the parameters’ optimization of the proposed composite damping controller. The proposed hybrid approach simplifies the tuning process by decreasing the number of the parameters in the initial values’ choosing stage from the whole nine to four. Besides, the application of experimental data improves rejection of model uncertainty. A set of optimal parameters in the controller is obtained using the proposed hybrid design approach. Experimental results with comparisons to built-in PID controller are presented to show the effectiveness of the composite damping controller optimized via the hybrid approach. | Damping controller design for nanopositioners: A hybrid reference model matching and virtual reference feedback tuning approach | 10.1007/s12541-018-0002-6 |
2018-01-01 | The operating principle of the conventional Costas loop for BPSK is explained (other types of Costas loops for BPSK are discussed in chapters 5 and 8 ). Dynamic behavior of the loop is described using a novel mathematical model developed by the author. This new model allows the designer of a Costas loop to explicitly compute important key parameters (lock range, lock time, pull-in range, pull-in time) as a function of block parameters such as corner frequencies (of filters), gain parameters like phase detector gain and VCO gain. Using these equations, the designer of a Costas loop can taylor his system in order to meet desired key parameters, e.g., pull-in range. Two case studies are presented thereafter: (1) designing an analog Costas loop for BPSK, (2) designing a digital Costas loop for BPSK. These case studies guide a designer step by step through the entire design process. Finally a Simulink model is presented. This model allows the designer to simulate a given Costas loop design with user-specified parameters such as carrier frequency, symbol rate, frequency error. All relevant signals within the loop can be viewed on scopes. | Conventional Costas Loop for BPSK, Dynamic Analysis, Design Procedure, and Simulation | 10.1007/978-3-319-72008-1_3 |
2018-01-01 | This chapter presents a recently proposed nonlinear system identification methodology that has the promise of broad applicability based on a global–local approach. In the proposed nonlinear system identification methodology, measured time series are decomposed in terms of approximately monochromatic dominant intrinsic mode functions, which are either depicted in frequency-energy plots (the global aspect of nonlinear system identification), or are used to construct local models in terms of sets of intrinsic modal oscillators (the local aspect of nonlinear system identification). The proposed nonlinear system identification methodology is applied to the analysis and modeling of the nonlinear damping effects induced by a frictional interface on the dynamics of a beam with a bolted joint connection. In particular, we show that by studying the temporal decays of the logarithms of the moduli of the complex amplitudes of the forcing functions of the intrinsic modal oscillators, we can deduce the nonlinear damping effects in the dynamics. The nonlinear system identification methodology can be employed to study nonlinear damping effects in structural assemblies with more complex mechanical joints, and nonlinear stiffness effects in structural components with local or distributed nonlinearities of a different source. Moreover, it is possible to study the effects of nonproportional (linear or nonlinear) damping distribution on the modal responses, and conceive methods for modeling such effects and for examining how these effects perturb the result of classical modal analysis. | Elements of a Nonlinear System Identification Methodology of Broad Applicability with Application to Bolted Joints | 10.1007/978-3-319-56818-8_20 |
2018-01-01 | In this paper simplified expressions for assessing fundamental frequency and modal damping of high-rise buildings taking into account the soil-structure interaction (SSI) are proposed. To this end, several steps have been followed. First, a 3DoF model is formulated making use of dimensionless parameters. Second, the 3DoF model is simplified into an equivalent 1DoF system. Finally, cancelling high-order and cross-terms and making some mathematical manipulations a simplified expression for fundamental frequency and modal damping is obtained. Results of the equivalent 1DoF are compared with those of the 3DoF to check the accuracy. Furthermore, the influence of the foundation in the overall system is studied making use of several pile configurations and foundation layout. | Effects of Soil-Structure in High-Rise Buildings by Means of Dimensionless Analysis and a Simplified Model | 10.1007/978-3-319-59471-2_158 |
2018-01-01 | In this research, a low damping force shear-mode magneto-rheological (MR) damper that can replace conventional passive damper of a front-loading washing machine is designed and experimentally evaluated. In the design of the MR damper, required damping force, off-state friction force, size, and low cost of the MR damper are taken into account. Firstly, a suppression system for washing machines featuring MR dampers is proposed considering required damping force, available space, and cost of the system. Optimization of the proposed MR suspension system is then performed considering required damping force, off-state friction force, size, power consumption, and low cost of the MR damper. From the optimal results, simulated performance of the optimized MR damper is obtained and presented with discussions. A detailed design of the MR damper is then conducted, and a prototype MR damper is manufactured. In addition, experimental results on the prototype MR damper are obtained and compared with simulated ones. Finally, discussions on performance and application of the MR suspension system for front-loading washing machines are given. | Design and Evaluation of a Shear-Mode MR Damper for Suspension System of Front-Loading Washing Machines | 10.1007/978-981-10-7149-2_74 |
2018-01-01 | In this chapter we use analytic differential equations to solve for currents and voltages in various circuits. For simpler circuits we end up with differential equations of first order, where only initial conditions are needed; and for more complicated circuits we end up with differential equations of second order where both initial conditions and derivatives thereof are needed. We decompose the solution in terms of a homogeneous one and a particular one. Equivalently we decompose the solution into a transient one and a steady state one. The applied stimuli included sine, unit step, and a pulse. We study the 2nd order RLC problem and examine the three damping conditions: critically damped, over damped, and under damped cases. We compare to SPICE and observe excellent match. | Differential Equation Solution to Circuit Problems | 10.1007/978-3-319-71437-0_3 |
2018-01-01 | From our detailed consideration of induction in moving conductors, we became aware of the existence of the Lorentz force $$\displaystyle\boldsymbol{{F}}=Q(\boldsymbol{{u}}\times\boldsymbol{{B}}) $$ ( F for example in newton (=1 N), B in V s/m^2 (=1 T), u in m/s, Q in A s). This force acts on a charge Q which is moving at the velocity u in a magnetic field of flux density B . As can be seen from the vector product, the force is perpendicular both to the magnetic field and to the velocity of the charge (Fig. 8.1). | Forces in Magnetic Fields | 10.1007/978-3-319-50269-4_8 |
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