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2021-01-01 | The feature of the special topics is that the design diagram of the structure differs from the corresponding design diagram used in the classical course of structural mechanics. Introduction of additional assumptions that do not contradict the assumptions of the classical theory of structures leads to a new mathematical model of the structure, and allows to not only clarify the results obtained in the framework of the classical theory, but also discover new effects and properties of the structure. The following topics are considered in this chapter: Timoshenko-Ehrenfest theory takes into account the rotary inertia and the shear deformation and allows investigating the vibration of short beams for which the classical assumption (the rods are long and thin) is not fulfilled. The theory of flexural vibration of compressed beam allows refining the idealized Bernoulli-Euler model. Galef’s formula, which establishes a simplest relationship between the frequency of transverse vibration of a beam, static compressive force, and critical buckling force, is presented. The theory of traveling load takes into account velocity of moving load, and inertial properties of the beam and the load. The feature of this problem is the loss of stability of the structure in case of critical velocity of a load. The parametric vibration of the rod occurs in case of its loading by the axial harmonic force. The feature of this problem: the initial linear dynamical structure (the uniform rod) turns out to have time-varying stiffness. As the result, on the plane of the “system–load” parameters, alternating zones of stable and unstable vibration appear. Vibration protection methods . Decreasing the level of mechanical vibration is one of the most important problems of modern engineering. The set of methods and means of reducing vibrations are reviewed. The theory of a dynamic absorber is considered in detail. | Special Topics of Structural Dynamics | 10.1007/978-3-030-44394-8_18 |
2021-01-01 | Squeeze film dampers (SFDs) have become very essential for high-speed turbomachinery as means of vibration energy dissipating mechanism. However, SFDs are not very common for inter-shaft bearing applications and are still in the R&D phase. It is observed that the application of SFDs for inter-shaft bearing systems is not being pursued in a real practical sense, as it becomes extremely difficult to realize a compatible component facilitating the radial squeezing mechanism—where squeeze film oil could be introduced—thus resulting in squeeze film damping. The gap that could be made available between the inner spool and inner race or the outer spool and the outer race of the inter-shaft bearing also being very little further complicates the application of a conventional squeeze film damper in the inter-shaft bearing plane. In this research work, newly conceptualized inter-shaft squeeze film damper (ISSFD) rings are fabricated and tested for evaluating their damping potential characteristics in dedicated instrumented test rig/s fabricated for the purpose. Parametric experimentations are conducted in a single-spool test rig as a proof of concept in attempting to quantitatively evaluate the damping potential of ISSFD rings and hence the suitability of their applications in inter-shaft bearing plane of two-spool system. This research study very clearly indicated the damping contribution of the ISSFD rings, and the performance of the system improved in terms of substantial reduction in shaft vibration amplitudes. The study also clearly indicated that the ISSFD rings contribute toward the stiffness in the bearing plane also, and as a result, the rigid body critical speed gets shifted. Parametric experimental studies brought out the effect of different geometric parameters on the stiffness and damping contribution of ISSFD rings. | Feasibility Studies on Newly Conceptualized Inter-shaft Squeeze Film Damper (ISSFD) Rings for Vibration Attenuation | 10.1007/978-981-15-5701-9_22 |
2021-01-01 | Although chronobiologists have postulated self-sustainability in circadian clocks, we report here two examples of damped oscillation in the cyanobacterial circadian system. First, low temperature transformed the self-sustained KaiC phosphorylation rhythm into damped oscillations. Second, deletion of the kaiA gene showed damped oscillation in the bioluminescent rhythm. These damped rhythms resonated with periodical environmental changes and then recovered their oscillation amplitudes. Numerical experiments confirmed that biochemical networks with the characteristic of self-sustained oscillation are rare. Evolutionary searches revealed that photoperiodism might contribute to evolving the self-sustainability of circadian rhythms. Although damped oscillators have not received substantial chronobiological analyses, our findings suggest that the circadian clock can easily transform into a damped oscillator by environmental or genetic perturbation and might function as a semi-clock system. | Damped Oscillation in the Cyanobacterial Clock System | 10.1007/978-3-030-72158-9_12 |
2021-01-01 | High-speed turbomachinery designs rely on adequate damping at the bearing supports to provide smooth operation throughout the sub-idle and normal operating speed ranges. Squeeze film damper (SFD) designs employ a thin oil film between bearing and housing that softens the bearing support and provides increase damping. During operation, the dynamic motion of the damper squeezes the thin lubricant film, thus generating hydrodynamic pressures and film forces to dissipate mechanical energy. This paper discusses test results from two different sealed SFD designs: The first design uses butt-end piston rings to seal the damper film where the oil exits the damper through a small circumferential gap in the piston rings. The second design uses on overlap piston ring design which more completely seals the oil in the damper. For this design, an alternate set of exit holes is provided to allow the oil to exit the damper. Testing was done over a range of frequencies from 20 to 300 Hz, with oil supply pressures from 14 to 140 psi, with oil temperatures from 75 to 225F and with SFD eccentricity ratios from 0.05 to 0.5, encompassing both cavitated and non-cavitated regimes of operation. The damping and added mass terms for the SFD were identified through standard data reduction algorithms. Test results indicate that for the same basic damper geometry, a significant difference in measured damping coefficient was obtained between the two different damper designs. Variation in damping using the overlap piston ring damper design was much less than with the butt-end damper design due to the alternate set of exit holes at all operating conditions. No significant drop in damping observed at the cavitation regions for both the damper designs. Piston rings were observed to rotate. A discussion about the observed results is included. | Characterization of a Squeeze Film Damper for Aircraft Engine Applications | 10.1007/978-981-15-5701-9_23 |
2021-01-01 | We developed a seat suspension for use on earth-moving machines. The suspension’s mechanism consists of a torsion bar that produces non-linear spring characteristics, a magneto-spring, and a free play damper, which acts as a damping element despite having no actual damping force. We installed a structure that absorbs front-rear vibration of the suspension mechanism with a 40 mm stroke. The vibration control performance in the low- and high-frequency bands was improved by the dead zone of the two-layer suspension mechanism, as well as the free play damper. The phase control using seat suspension and magneto-suspension was able to satisfy ISO 7096:2000 EM7 guidelines. | Development of a Suspension Seat Using a Magneto-Spring and Free Play Damper | 10.1007/978-3-030-47618-2_19 |
2021-01-01 | The progress in active constrained-layer damping (ACLD) that has been made over the past years is presented in this paper. These systems are also called hybrid systems. ACLD treatments combine the best features of passive and active control of structural vibrations. Well-established techniques for passive control of structural vibrations and noise are described. A concise discussion of the development of so-called ‘smart’ actuators and sensors and the emergence of suitable control algorithms show how passive techniques were extended to produce ACLD. It is shown how the passive and active components of ACLD complement each other to enable control of both high and low frequency modes of vibration. The active elements allow structures to adapt to suit a changing environment while the passive elements provide a fail-safe mechanism. Because of the available technology, these benefits are available without significant penalties in terms of cost, weight and complexity. | Hybrid Vibration Control Systems | 10.1007/978-3-030-75275-0_12 |
2021-01-01 | The article deals with the mathematical model of wheel axle displacement after the end of the vehicle braking process on the uphill in the absence of moving the pneumatic tire contact patch relative to the road surface. The proposed dependencies for determining the coordinate of the wheel axis position and the speed of its movement on the basis of the general dynamics equation allow to determine the time during which the wheel axis deviates by the maximum distance from the axis of symmetry of the contact patch of the pneumatic tire, which is stationary relative to the surface of the pavement. The obtained simulation results made it possible to establish a relationship between the position of the wheel axis, the mass of the vehicle and the value of the longitudinal uphill of the pavement surface, and made it possible to evaluate the possibility of using the energy of the elastic deformation of the pneumatic tire at the moment when the vehicle started to moving on the uphill. The proposed mathematical model of rectilinear motion of the axle of the locked wheel, the contact patch of which does not move relative to the surface of the pavement, may be a theoretical basis for the analysis and synthesis of the algorithm for controlling the system of motion of the vehicle on the uphill. | Theoretical Studies of the Rectilinear Motion of the Axis of the Locked Wheel After Braking the Vehicle on the Uphill | 10.1007/978-3-030-58124-4_7 |
2021-01-01 | The unsaturated shear behaviour of soil is governed by the presence of negative pore water pressure or matric suction ( u _ a - u _ w ). Based on the distribution of solid, water and air phases, the soil–water characteristics curve (SWCC) is divided into three zones such as (1) boundary effect zone, (2) transition zone and (3) residual suction zone. The dynamic shear behaviour of soil in these three zones is entirely different due to their particular suction characteristics. However, this aspect of expansive soil has not been explored yet. Expansive soil has a very wide range of suction variation from 0 to 10,00,000 kPa. Hence, the aim of the current study is to evaluate the dynamic response of Nagpur expansive soil subjected to variation of matric suction and cyclic stress ratio (CSR). A series of stress-controlled cyclic simple shear (CSS) tests were carried out on the compacted specimens of Nagpur expansive soil at varying CSR (0.1, 0.3, and 0.5) and degree of saturation (30, 50, 70, and 95%). SWCC of Nagpur soil was determined through the filter paper method, and the saturation values for CSS tests were chosen to cover all the three zones of SWCC. Shear modulus was found to increase with the increase in matric suction until residual suction zone arrived. However, it decreased with further increase in matric suction. Rate and magnitude of stiffness degradation were observed to reduce with the decrease in CSR for complete matric suction range of Nagpur expansive soil. Dissipated cumulative strain energy and cumulative cyclic shear strain were maximum for lowest matric suction specimens for all CSRs. | Effect of Matric Suction and CSR on Dynamic Response of Expansive Soil | 10.1007/978-981-33-4001-5_10 |
2021-01-01 | This article concerns the oscillatory behavior of solutions to damped second-order linear functional differential equations with a mixed neutral term. The authors present new oscillation criteria that improve and extend some existing ones in the literature. Examples to illustrate the main results are included. | Oscillation of damped second-order linear mixed neutral differential equations | 10.1007/s00605-020-01469-6 |
2021-01-01 | Mechanical flexibility in robot manipulators is due to compliance at the joints and/or distributed deflection of the links. Dynamic models of the two classes of robots with flexible joints or flexible links are presented, together with control laws addressing the motion tasks of regulation to constant equilibrium states and of asymptotic tracking of output trajectories. Control design for robots with flexible joints takes advantage of the passivity and feedback linearization properties. In robots with flexible links, basic differences arise when controlling the motion at the joint level or at the tip level. | Flexible Robots | 10.1007/978-3-030-44184-5_176 |
2021-01-01 | As for the dual active bridge (DAB) converter and three-phase inverter based cascaded system, the stability is affected by the interaction between output and input impedance of the two sub-converters. The small-signal models of both DAB and three-phase inverter are firstly derived for stability analysis. Based on the improved Middlebrook criterion, this paper analyzes the difference in impedance characteristics between forward and reverse power flows, and the parameters that affect the stability of system. Then an optimized coordinated control strategy with active damping is proposed to improve the stability under forward power flow. The theoretical analysis results show that the optimized coordinated control can reduce the voltage fluctuation of the DC-link and achieve smooth transitions during sudden power changes and reversals, thereby improving the dynamic response of the system. Furthermore, robustness of the system is enhanced without changing proportional integral (PI) parameters and the circuit hardware. Finally, the optimized coordinated control is compared with conventional control by simulation results. | Optimized Coordinated Control of DAB and Three-Phase Inverter Based Cascaded System with Active Damping | 10.1007/978-981-15-9746-6_41 |
2021-01-01 | Engineers have always faced the challenge of solving conflicting objectives such as high stiffness combined with high damping. Structurally optimised components are used, especially by pushing lightweight construction. This design adaptation of component mass and stiffness generally has a negative effect on the dynamic component properties, as both the natural frequencies are shifted and component damping is reduced. In the majority of applications, the resulting vibrations are undesirable and must be reduced by suitable mechanisms. For example, vibrations in the vehicle can lead to a reduction in driving comfort or to a reduced service life. One approach to solving conflicting objectives is the targeted integration of effects into components through additive manufacturing. In this paper, the effect-engineering on a laser beam melted motorcycle triple clamp is illustrated. The triple clamp is a highly dynamically loaded structural component where unwanted vibrations occur due to road unevenness, leading to critical hand-arm vibrations. This paper focuses on the simulative design of the triple clamp. The triple clamp is topology-optimised and extended by the effect of particle damping, so that the component is optimised in terms of stiffness, damping and mass. The optimisation also makes it possible to achieve a high degree of functional integration by saving 20 components. The effect of particle damping is experimentally evaluated by preliminary studies, which show that component damping can be increased by up to a factor of 20. The laser powder bed fusion (LPBF) makes it possible to store unmelted powder in the interior of the component in a targeted manner and thus produce particle-damped structures inside the triple clamp. | Design of a Motorcycle Triple Clamp Optimised for Stiffness and Damping | 10.1007/978-3-662-63143-0_1 |
2021-01-01 | In this study, a dynamic analysis of a circular rigid foundation resting on the soil surface is carried out. An elastic half-space theory is used to compute the response of a circular foundation subjected to a vertical oscillation. The work deals essentially with the effect of Poisson’s ratio μ. Besides, the work aims to study the effect of the dimension of rigid circular foundation (foundation radius r_o) and dimensionless frequency a_0 on the maximum vertical displacement of the foundation under vertical dynamic load. Two relationships have been conducted, one for dynamic stiffness versus dimensionless frequency a_0 and the other between damping coefficients versus dimensionless frequency a_0 for various new values of Poisson’s ratio which have not been studied earlier. The dynamic stiffness (K_dyn) and dynamic damping (C_dyn) were used to estimate the maximum vertical displacement of the foundation. Results showed that the vertical dynamic stiffness coefficient is more affected by a variation of Poisson’s ratio values than the vertical damping coefficient. Consequently, the dynamic stiffness plays the main role of estimating the maximum displacement of the circular foundation for low values of dimensionless frequency a_0. In conclusion, the effect of Poisson’s ratio μ appears and increases gradually with increasing of dimensionless frequency a_0. | Mathematical Analysis of Vertical Vibration for Circular Rigid Foundation Resting on Soil Surface | 10.1007/978-981-15-9399-4_27 |
2021-01-01 | The proper modeling of noise control treatments is a key factor for the robustness of the numerical prediction of the sound transmission. Typical acoustic treatments applied in the industry include one or more layers of poroelastic materials. These are particularly challenging to model since they exhibit a complex, high dissipative behavior that is not only dependent on the material properties, but also on the interactions to other components. In this contribution, three different material formulations derived from the poroelasticity theory are employed to describe the poroelastic layers. In addition to these material models, a simplified approach based on a homogenized viscoelastic material behavior is tested. For this approach, the frequency-dependent stiffness and damping behavior of the damping material is determined in advance with the help of a vibrational test bench. Three different concepts for the noise reduction based on poroelastic materials are tested, namely, the insulation through a spring-mass component and the absorption of a porous layer as well as a combination of both. Moreover, three different test setups are investigated. At first, the sound transmission through a plate with an applied damping material is studied. Further, a simplified model of a vehicle’ front end is investigated. The calculated results of both setups are contrasted with measured data. The measurements are executed in a window test bench. Thirdly, a structurally excited plate with an attached damping layer is investigated in an anechoic room in terms of its radiated sound power. Finally, all mentioned approaches are compared and recommendations on the modeling approaches as well as an outlook are presented. | On the Numerical Modeling of Poroelastic Materials in Acoustic Analysis | 10.1007/978-981-15-8049-9_10 |
2021-01-01 | Control processes are responsible for maintenance of the organism’s internal environment (homeostasis) and, therefore, inextricable from the very definition of living matter. Optimal homeostasis involves adaptation and relies on processing of signals from the environment. Signaling and control processes are considered that exhibit nonlinear effects such as an all-of-nothing response, switches, modulation of oscillations, and hysteresis. Examples are drawn from intracellular molecular systems, as well as multicellular and inter-organ control networks: protein kinase cascades with feedback, dynamics of the transmembrane electrochemical potential, regulation of gene expression by metabolism, and control of breathing. | Signaling and Control | 10.1007/978-3-030-79146-9_4 |
2021-01-01 | Abstract Vertical axisymmetric vibrations of a vessel with a liquid, separated by a porous partition, are considered. The damping of vibrations caused by the presence of a porous partition is studied experimentally. The integral value of the reduced damping coefficient of the system is obtained. | Experimental Study of Axisymmetric Vibrations of a Liquid in a Cylindrical Vessel with a Porous Partition | 10.3103/S1068799821010098 |
2021-01-01 | This work presents a characterization of dynamic mechanical properties of composite beams that were 3D-printed using fused filament fabrication. Two materials were used in the manufacturing process: a flexible material was used as filler of the hollow section (FilaFlex—Polyether-Polyurethane elastomer) while polylactic acid (PLA) polymer was used for the external wall of the beam. The main objective for such material integration is to enhance damping properties without compromising the overall stiffness. Dynamic mechanical analysis (DMA) was used to determine the inherent beam stiffness (storage modulus) and damping (tanδ), to assess the influence of void-filling volume fraction in the dynamic properties and therefore optimize the beam static and dynamic performance. At room temperature, it was shown that the introduction of low contents of flexible filling actually generated an increased in stiffness due to the changes the filament orientation to accommodate the filling material. Regarding the damping performance, it was proved that the introduction of filling enhanced internal friction. It was possible to optimize both stiffness and damping of the beam design by finding the most beneficial combination of these properties. | Stiffness and Damping Properties of a Composite Beam Design | 10.1007/978-3-030-68277-4_8 |
2021-01-01 | This study aims at developing a systematic approach for designing the control input for an overhead crane. In a previous report, numerical simulations showed that residual vibrations can be suppressed in nonlinear damped systems by eliminating the natural frequency component from the apparent external force, which includes the influence of the system nonlinearity and damping. One problem is that the proposed method requires knowledge of the natural frequency of the system, which is generally difficult to estimate on-site with high accuracy. This paper employs two methods to improve the robustness to the estimation error for the natural frequency. One is to increase the number of eliminated frequency components, and the other is to make the frequency derivatives of the frequency component zero at the estimated natural frequency. Numerical simulations demonstrated the effectiveness of these approaches for reducing residual vibration in overhead crane operation, showing that they exhibit similar robustness. However, the latter is easier to use because it does not need additional parameters to be determined. | Robust Vibration Control of an Overhead Crane by Elimination of the Natural Frequency Component | 10.1007/978-3-030-47618-2_33 |
2021-01-01 | Dynamic properties of sandy soils, viz. shear modulus (G) and damping ratio (D), are the most important properties for designing geotechnical structures that involve dynamic loading of soils and soil–structure interaction. Liquefaction phenomenon is the most common cause of ground failure during earthquake which has produced severe damage to the structures all over the world. In this paper, a case study has been considered for Shahpurkandi Dam Project which is located on the Ravi River in Pathankot district of Punjab, India. The project also consists of 55.5 m high concrete gravity dam. The main purpose of the project is to generate electricity up to 206 MW and provide irrigation to Punjab and Jammu and Kashmir. The dam foundation consists of different strata of sand lenses at different depths. Efforts are made to study the effect of earthquake on liquefaction potential for these sand lenses at different depths. Undisturbed samples were collected from the sandy soil deposited below the foundation and carried out grain size analysis, proctor density, relative density, resonant column and cyclic simple shear tests in the laboratory for determining the material properties and liquefaction study. The liquid limit, plastic limit and plasticity index were also determined. The dry density and the moisture content of the material vary from 1.5 to 1.68 gm/cc and 8.7 to 14.2%, respectively. The relative density of the material varies from 50 to 73%. Resonant column tests were conducted for 70% relative density with the varying confining pressure from 1 to 4 kg/cm^2 and determined shear modulus and damping ratio. Effect of confining pressure was studied on dynamic properties of sandy soil. The study shows that the shear modulus increases and damping ratio decreases with increase in confining pressure. Also, it is observed that the damping ratio varies from 1.18 to 2.8% and shear modulus varies from 770 to 2000 kg/cm^2 for the confining pressure ranging from 1 to 4 kg/cm^2. The high value of shear modulus indicates that the sand is dense. It is also observed that the damping ratio increases and shear modulus decreases with increase in shear strain amplitude. Undrained cyclic simple shear tests were conducted on saturated soil specimens and determined cyclic strength which is required for evaluating the liquefaction potential of sandy soil. Seed’s simplified procedure has been used to evaluate liquefaction potential for the studied material. The study shows that the cyclic strength of the soil at different depths is more than the cyclic shear stresses induced due to earthquakes of two magnitudes (6.5 and 8.0). Liquefaction potential study shows that the sandy soil deposits are sufficiently dense and are not susceptible to liquefaction for the considered earthquake magnitudes. | Evaluation of Dynamic Properties and Liquefaction Studies for Sandy Soil—A Case Study | 10.1007/978-981-33-6969-6_10 |
2021-01-01 | The technique of improving damping characteristics by complexing fine particles in a viscoelastic material is well-known; however, the relevant underlying mechanism is not yet established. It was found damping characteristics were improved by compounding the particles from dynamic viscoelasticity test result. Furthermore, the strain amplitude dependency becomes stronger in the damping material which the fiber orientation and the tensile direction coincide, and a large damping characteristic is shown. The focus of this study is on the interface state and strain distribution in the composite material with fiber-shaped particles and the investigation of factors affecting the change of damping characteristics. The X-ray computed tomography image of a test piece was obtained, both before and after the application of a tensile load, and all the aforementioned factors were investigated through image processing. The strain was calculated by tracking the feature points on the image to create a three-dimensional (3D) strain distribution. It was confirmed that a local strain occurred from this distribution and was suggested to be a possible factor promoting more energy dissipation. | Three-Dimensional Strain Calculation of Rubber Composite with Fiber-Shaped Particles by Feature Point Tracking Using X-Ray Computed Tomography | 10.1007/978-3-030-48153-7_14 |
2021-01-01 | Structural vibration control as a cutting-edge technology comprises of energy dissipation devices to control excessive structural vibration, increases human solace and forestalls catastrophic structural failure due to strong winds and quakes. Bridge subjected to earthquake forces structural elements will be subjected to high levels of stress. And it is essential to study the dynamic behavior of bridge during earthquake. This study presents dynamic behavior of HOWE bridge truss, when subjected to strong ground motions. The prominent seismic-resistant technique—superstructure isolation of bridge by using high damping rubber bearing—is considered. And comparative study done on isolated and isolated HOWE truss bridge and also restoring capacity of high damping rubber bearing will be calculated. Response spectrum analysis is used to study the dynamic behavior. | Dynamic Behavior of Base Isolated Howe Bridges-Seismic Resistant | 10.1007/978-981-33-6969-6_27 |
2021-01-01 | Viscoelastic materials are used extensively for vibration isolation of aerospace systems. These materials’ time/frequency dependence leads to isolators with complex stiffness—and while the frequency dependence is tractable in a frequency-domain analysis, many critical simulations must be done in the time domain, where the material’s time dependence is difficult to represent. The simplest approach is to assign constant isolator properties based on a single key frequency, but doing so diminishes the accuracy of the predictions over a broad frequency range. It is possible to create a phenomenological model of the viscoelastic behavior by fitting a Maxwell model (Prony series) to test data from either a “complex stiffness” in the frequency domain or a relaxation response in the time domain. This paper shows how a generalized Maxwell model can be tuned to match complex stiffness test data for a viscoelastic isolator using a small number of parameters and then used to reproduce the frequency-dependent stiffness of the original data. In principle, constants for a Maxwell model determined in the frequency domain will also represent the relaxation behavior in the time domain. Representing general time-dependent stiffness requires one massless degree of freedom (DOF) per term in the Prony series, which requires careful treatment in a modal solution. This paper shows how to implement this technique in Nastran using residual vectors to represent the behavior of the massless DOFs and also investigates the implications of numerical integration algorithms on the accuracy of the representation in the time domain. | Modeling Viscoelastic Behavior in Transient Analyses | 10.1007/978-3-030-47709-7_8 |
2021-01-01 | In this contribution, a bladed wheel with dry friction couplings in tie bosses between neighbouring blades is studied. Bladed wheel is excited by stator nozzle excitation in addition to aeroelastic self-excitation modelled by Van der Pol model. Two types of self-excitation are studied, the first is dependent on absolute motion of each blade, the second on relative motions between neighbouring blade pairs. Results of simulations are shown for both cases for various number of stator blades and friction forces in tie-boss contacts. Damping ability of those contacts are compared. | Self-excited Vibrations of Bladed Wheel Analytical Model with Nozzle Excitation and Dry Friction Damping | 10.1007/978-981-15-8049-9_21 |
2021-01-01 | In Chaps. 1 – 5 , we assumed a model and then used that model to determine the system response in the time or frequency domain (or both). More often, however, we have an actual dynamic system and would like to build a model that we can use to represent its vibratory behavior in response to some external excitation. For example, in milling operations, the flexibility of the cutting tool-holder-spindle-machine structure (and sometimes the workpiece) determines the limiting axial depth of cut to avoid chatter, a self-excited vibration [1]. In this case, the dynamic response at the free end of the tool (and/or at the cutting location on the workpiece) is measured. Using this measured response, a model in the form of modal parameters can be developed for use in a time-domain simulation of the milling process. How can we work this “backward problem” of starting with a measurement and developing a model? To begin, we need to determine the modal mass, stiffness, and damping values from the measured frequency response function (FRF). | Model Development by Modal Analysis | 10.1007/978-3-030-52344-2_6 |
2021-01-01 | The three-dimensional magnetohydrodynamics equation with damping is considered in this paper. Global attractor of the 3D magnetohydrodynamics equations with damping is proved for $$4\le \beta <5$$ 4 ≤ β < 5 with any $$\alpha >0$$ α > 0 . | Attractors of the 3D Magnetohydrodynamics Equations with Damping | 10.1007/s40840-020-00949-0 |
2021-01-01 | The acoustic and vibratory analysis represent an essential research axis in the automotive industry because these phenomena directly affect the appreciation of the customer when using a vehicle. Indeed, the combustion engine represents the main source of mechanical energy but it generates an acyclic torque because of the explosions. This acyclism is responsible for noise and vibration fatigue. To reduce NVH issues, a possible mean is to use a Multiple Tuned Mass Damper (MTMD) adapted to rotating machine. The purpose of this paper is to propose a framework for the design of this type of MTMD. To achieve this goal, an optimization strategy is implemented in the non-rotating and rotating case to determine the optimal distribution of the MTMD frequencies. It is based on the minimization of the elastic strain energy of the transmission chain near the torsion mode. In addition, a dedicated reduced order method is proposed to reduce the calculation costs link to the modeling of the system by the finite element method and the optimization process. However, conventional reduction order methods are not suitable for this type of problem where the shape of the modes of the main structure and the MTMD are varying according to the rotation speed. To overcome this problem, a multi-model approach is employed. Finally, the influence of the number of absorbers composing the MTMD as well as the structural damping of the absorbers and their mass on the performance of the optimal solution is presented in the non-rotating and rotating case. | A Framework for the Design of Rotating Multiple Tuned Mass Damper | 10.1007/978-3-030-47717-2_40 |
2021-01-01 | This article intends a hybrid energy-harvesting shock absorber design which comprehends energy harvesting of automobile suspension vibration dissipation. A mathematical model of the energy harvesting prototype is established, and simulation results show that the dissipation energy can be recovered by varying the feed module, thereby got the damping forces (DF) ratio at different compression and extension stroke. The energy conversion from hydraulic energy to mechanical energy mainly then mechanical energy converted into electrical energy furthermore, we can recharge our battery from this recovered energy. This advanced mathematical model and prototype proposed maximum ride comfort meanwhile recovered the maximum suspension energy and fuel saving. This article shows the simulation results verifying it with prototype test results. The DF of expansion stroke is higher than the DF of compression stroke. The damping characteristics curves and speed characteristics curves verify the validity by simulation and prototyping damper at different amplitudes of off-road vehicles. The Hydraulic Electromagnetic Regenerative Shock Absorber (HERSA) prototype characteristic is tested in which 65 watts recovered energy at 1.67 Hz excitation frequency. So, 14.65% maximum energy recovery efficiency got at 20 mm rod diameter and 8 cc/rev motor displacement. The damping characteristics of the HERSA prototype examined and it has ideal performance as the standard requirements of the National Standard QC/T 491-1999. | A High-Efficiency Energy Harvesting by Using Hydraulic Electromagnetic Regenerative Shock Absorber | 10.1007/978-3-030-75793-9_28 |
2021-01-01 | The increasing interest in wide-area damping control poses significant challenges for the consistent operation, control and stability of the complete power system. This study investigates various techniques for mitigation of the effect of imperfect communication medium in a wide-area damping control system. The Modelling of an imperfect communication network is done by considering the signal latency, packet drop-out, and random noises in the remote wide-area signal. The signal latency is modelled using the third order of the Pade approximation method, and the random white noise is Gaussian in nature. Different control strategies are applied in a wide-area power system for mitigating the effects of signal latency and noise along with overall stability enhancement of the complete grid. The performance of various controllers as a wide-area damping controller (WADC) is evaluated upon a standard test power system through suitable time-domain simulations using the nonlinear model on MATLAB/Simulink platform. | A Comparative Analysis on Wide-Area Power System Control with Mitigation the Effects of an Imperfect Medium | 10.1007/978-981-33-6981-8_13 |
2021-01-01 | Internally, damped shaft–disk system when driven by a non-ideal power source, i.e., limited power source often exhibits complex dynamics. Upon exceeding a critical power input near resonance, the system may contribute to increasing the transverse vibration severely rather than increasing the spin speed. This phenomenon is referred to as the Sommerfeld effect. This effect can cause instability in high speed rotor system and needs to be addressed carefully for safe and smooth operations. In the present study, a semi-active control scheme based on switched-stiffness method is employed to attenuate the Sommerfeld effect of a eccentric shaft–disk system driven by a brushed DC motor. Following, the equations of motion are solved numerically to obtain time response and amplitude frequency response with a specified supply voltage. It has been shown that as the value of switched-stiffness increases, the Sommerfeld effect is found to be attenuated. However, the rotor response is corrupted with spikes as a fallout of switching stiffness technique, which may destabilize the system and becomes critical when the switching time is very fast. The attenuation of Sommerfeld effect can be further verified through the time varying potential energy plot which is seen to be diminished after crossing the critical speed owing to the dissipative characteristics of non-potential switching stiffness force. | Sommerfeld Effect Attenuation Using Switched-Stiffness Method of a Non-ideal Internally Damped Shaft–Disk System with Constant Eccentricity | 10.1007/978-981-15-5701-9_14 |
2021-01-01 | The article is devoted to rejection of unwanted dynamic reactions of flexible structures. The problem of vibrationless movement of an elastic object when natural oscillations are absent and the reaction of the system does not exceed the static reaction is considered. To analyze the oscillations of the system, the maximum response spectrum and the residual spectrum are used. The vibrationless movement property is defined as restrictions on these spectra specified by the control signal. The problem of vibrationless movement is solved by input shaping methods. The shaping filter built on fixed values of the eigenfrequencies of the system is unstable when the frequencies deviate from the set values. To solve this problem, robust modifications of the method are proposed. The high complexity of the considered problem requires computer modeling. In particular, using computer modeling, the problem of the choice of a shaping filter with the property of maximum robustness is solved. | Computer Modeling of Robust Control of Vibrationless Movement of Multi-mode Flexible Structures | 10.1007/978-981-33-6632-9_13 |
2021-01-01 | Damping capacity is a measure of a material's ability which absorb vibration energy by converting into heat energy. Materials which have high damping ability can suppress excessive vibrations to a reasonable limit. Therefore, this paper investigates the damping characteristics of five indigenous wood species ( Cordia Africana, Juniperus Procera, Afrocarpus Gracilior, Syzygium Guineense and Acacia Decurrens ) found in Ethiopia through analytical, numerical and experimental approaches. The experimental testing was performed using piezoelectric accelerometer in association with LabVIEW for a perfectly clamped-free cantilever beam based on the impact hammer excitation. The damping ratio was computed using logarithmic decrement method from the decay curve measured. Based on the investigation, the damping factor for all species of woods was almost equal to 0.020 at room condition, and it is definitely greater than most other crystalline materials. Thus, wooden materials are better suitable for engineering applications in terms of vibrations if the other strength properties are satisfactory. | Investigation on Damping Capability of Indigenous Wood Species in Ethiopia | 10.1007/978-3-030-80618-7_22 |
2021-01-01 | This contribution continues ongoing own research on uncertainty quantification in structural vibration isolation in early design stage by various deterministic and non-deterministic approaches. It takes into account one simple structural dynamic system example throughout the investigation: a one mass oscillator subject to passive and active vibration isolation. In this context, passive means that the vibration isolation only depends on preset inertia, damping, and stiffness properties. Active means that additional controlled forces enhance vibration isolation. The simple system allows a holistic, consistent and transparent look into mathematical modeling, numerical simulation, experimental test and uncertainty quantification for verification and validation. The oscillator represents fundamental structural dynamic behavior of machines, trusses, suspension legs etc. under variable mechanical loading. This contribution assesses basic experimental data and mathematical model form uncertainty in predicting the passive and enhanced vibration isolation after model calibration as the basis for further deterministic and non-deterministic uncertainty quantification measures. The prediction covers six different damping cases, three for passive and three for active configuration. A least squares minimization (LSM) enables calibrating multiple model parameters using different outcomes in time and in frequency domain from experimental observations. Its adequacy strongly depends on varied damping properties, especially in passive configuration. | Approach to Assess Basic Deterministic Data and Model Form Uncertaint in Passive and Active Vibration Isolation | 10.1007/978-3-030-77256-7_17 |
2021-01-01 | This work introduces a method for the identification of linear stiffness and viscous damping parameters from a one-degree-of-freedom force-displacement cycle. Using an original approach, the stiffness parameter is derived by a least-square formula from the discrete input force-displacement point coordinates of the loop. The damping ratio is obtained in a classic manner from the quotient of absorbed and elastic energy. The obtained stiffness and damping parameters are proposed to be used, with the known mass, as an equivalent linear mass-spring-damper that should predict the response to a known load for the original nonlinear system associated to the input force-displacement cycle. As an example study, the effectiveness of such prediction is qualitatively shown in the case of the steady-state response to a harmonic load for a particular hysteretic numerical model, by using a range of values for some dimensionless parameters. This kind of study is susceptible to be extended to other kinds of loading and/or numerical and experimental hysteretic models, as well as to other identification procedures available in the literature. | Least-Square Effective Stiffness to be Used for Equivalent Linear Model | 10.1007/978-3-030-73932-4_10 |
2021-01-01 | Self-oscillations under delays in elasticity and damping in a system with an energy source of limited power are considered. The dynamics of the system is described by nonlinear differential equations. The method of direct linearization of non-linearity is used for their solution. It has a number of advantages over the known methods of analysis of nonlinear systems: labor and time costs are reduced by several orders of magnitude; regardless of the specific type and degree of nonlinearity, you can get the final calculated ratios; there are no labor-intensive and complex approximations of various orders inherent in known methods. On the basis of this method, the equations of non-stationary and stationary movements are obtained, and the conditions for stability of stationary oscillations are derived. An analysis was performed to obtain information about the influence of delays on the parameters of stationary oscillations. The influence of delays on the amplitude of oscillations and the load on the energy source is shown. It turned out that depending on the delay value, the amplitude and load curves shift in the speed range of the energy source. | Influence of Delays on Self-oscillations in System with Limited Power-Supply | 10.1007/978-3-030-67133-4_12 |
2021-01-01 | Squeeze film dampers play a vital role in absorbing vibration energy in a rotor bearing system. The damper under study has an elastic ring with pedestals between bearing and stator dividing oil cavity into small oil pockets. This arrangement is different from conventional squeeze film damper where a single annular oil film is formed. This provides the required support stiffness as well as damping to the rotor. These types of dampers are called elastic ring squeeze film dampers (ERSFD) which are mainly used in high-speed small gas turbine engines by virtue of its compact design. There are very few literatures available to evaluate the damping offered by these SFDs. The main objective of this work is to determine the damping offered by ERSFD experimentally. For this study the rotor is designed to simulate the dynamics of a typical gas turbine engine. The rotor has to cross two rigid critical speeds within 18,000 rpm. The rotor response is measured under undamped (UND-without oil supply) and damped (D-with oil supply) conditions to evaluate the damper performance. The performance data is generated at three different oil temperatures (40, 70 and 100 ℃) under unbalanced load ranging from 2 to 8 g at 58.5 mm radius (UBR). This experimentation and performance analysis shows enhanced damping at critical speeds leading to the reduction in rotor vibrations after introducing ERSFD. The experimental data is further processed to calculate the amount of damping offered by ERSFD using rotor dynamic relations. | Experimental Evaluation of Elastic Ring Squeeze Film Dampers for Small Gas Turbine Engine | 10.1007/978-981-15-5039-3_31 |
2021-01-01 | The paper presents the free oscillation analysis of the reduced torsional system in the crankshaft of a six-cylinder piston internal combustion engine with a liquid or rubber (internal friction) damper mounted on the toe. Installing a torsional vibration damper on the sock of the crankshaft changes the frequency of free oscillations, and in addition, when installing a rubber damper, another mass of the torsional system is added with the coefficient of rigidity of the rubber layer and the moment of inertia of the damper flywheel. At the same time, for liquid torsional vibration damper, the flywheel which has no direct connection with the toe of the crankshaft, for the calculation of free oscillations to the moment of inertia of the sock it is necessary to add a half the moment of inertia of the flywheel. The order of selection of optimal damping coefficients, namely the moments of inertia of the damper flywheel and damping coefficients of silicone fluid, is considered. For the rubber (internal friction) damper, the necessary parameters include the moment of inertia of the flywheel, the stiffness coefficient of the rubber layer and the damping coefficient. The free oscillations are considered in a complex form, which allows obtaining a function after the transition to real values that can be taken as a function of optimizing the parameters of the liquid or rubber damper. In this case, at the optimum damping or maximum energy dissipated in the damper, the amplitude of torsional oscillations of the crankshaft toe is reduced as much as possible. Using this approach allows for a significant reduction in the number of calculations with different damping coefficients and chooses the most optimal results. | Selection of the Optimum Damping Coefficient for Torsional Vibration Dampers for Crankshafts of Reciprocating Internal Combustion Engine | 10.1007/978-3-030-54814-8_25 |
2021-01-01 | This paper presents the reduction phenomenon of the added damping in a stay cable caused by static wind loads acting on a cable with an external damper. First, an equation of motion of a sagging cable is derived that takes the consideration of dead loads including cable self-weight and static wind loads into account. Second, a finite difference formulation (FDF) for cable vibration is introduced to address the equation of motion and to determine the added cable damping. Third, the impacts of cable bending stiffness, damper support stiffness and various types of boundary conditions at cable ends consisting of hinged, fixed and rotational restraint ends on cable vibration characteristics are investigated. The results showed that in the presence of static wind loads acting on a cable, the global stiffness of a cable increases, leading to an increase in vibration frequency and a decrease in the added cable damping. | Effect of Static Wind Loads on Reduction of Damping in a Stay Cable with a Damper | 10.1007/978-981-16-0945-9_7 |
2021-01-01 | In the boring process, tool vibration is an important parameter due to its overhanging length and also leads to high cutting force, poor surface finish and increase in tool wear. To suppress tool vibration and increase the cutting performance, a novel idea has been developed in rheological fluid. In present work, a boring tool holder with magnetorheological damper was analysed. Magnetorheological damper received massive responsive due to their capability to reversely change from a linear, free-flowing viscous fluid to semis solid within seconds when a magnetic field is applied. In this paper, a boring tool holder was analysed using ANSYS software with damping force applied in various direction and without MR effect. The results prove that the use of Magnetorheological damper reduces tool vibration significantly. | Computational Analysis of Boring Tool Holder with Damping Force | 10.1007/978-981-15-4488-0_78 |
2021-01-01 | A review on dynamic properties of soil using cyclic triaxial test has been proposed in the present study. Several researchers have studied the dynamic properties of soil at large strain level using cyclic triaxial test and proposed either analytical solution or charts for shear modulus degradation curve and damping curve of soil. The dynamic behaviors of soil depend on various factors such as soil type, loading condition, relative density, confining pressure, void ratio, over-consolidation ratio, etc., as reported by researchers. The dynamic properties, especially the shear modulus degradation curve, and damping curve are important for designing of any geotechnical structures. In research purpose, it helps to simulate numerically to any geotechnical problems. A summarized review has been presented with their methodology and used parameters from the past literature. The locally available Solani river sand is collected from Roorkee region, tested in laboratory. The obtained test results from cyclic triaxial test have been validated with past literature. | Cyclic Triaxial Test to Measure Strain-Dependent Dynamic Properties—A Comprehensive Study | 10.1007/978-981-33-6564-3_59 |
2021-01-01 | The hysteretic damping approach is a satisfactory model for granular soils, although some mathematical inconsistencies may be pointed in its formulation. When cohesive saturated soils or soils saturated with high viscosity fluids are subject to dynamic loads, then a second mechanism of energy dissipation may occur with frequency dependence. The aim of this study is to investigate an alternative method to analyze the phenomenon of damping in soils by looking at the vibration problem as a coupled poromechanical system where the relative displacements and velocities between the fluid and solid phases generate interaction forces that can play an important role in the energy loss. The results predicted by the analytical equation are compared to those obtained from laboratory tests, as well as from other damping models available in the literature, in order to check the validity of the present proposition. | Formulation of a Dynamic Damping Equation for Soils in the Light of Poromechanics | 10.1007/978-3-030-64518-2_70 |
2021-01-01 | This paper presents results from experimental testing of a railway bridge. Forced vibration tests was performed using a hydraulic actuator with variable load amplitude. The estimated modal properties show that the increased load amplitude results in lower natural frequency and higher damping, especially for the first mode of vibration. Despite this, even at relatively large amplitude of vibration the estimated damping is lower than proposed by Eurocode EN 1991–2. A simple 2D model is presented that shows good agreement with the experimental results, both regarding natural frequencies, mode shapes and the response from passing trains. | Full-Scale Forced Vibration Tests of a Railway Bridge | 10.1007/978-3-030-64690-5_21 |
2021-01-01 | In Chaps. 1 – 5 we discussed the solution of discrete, lumped parameter models. For multiple degree of freedom systems, we employed modal analysis to enable us to transform the coupled equations of motion in local (model) coordinates into modal coordinates. In this coordinate frame, the equations of motion were uncoupled and we could apply single degree of freedom solution techniques. In Chap. 6 we shifted our attention to the “backwards problem”, which is representative of a common task for vibration engineers. In this problem, we begin with measurements of an existing structure and use this information to develop a model. We again used discrete models to describe the system behavior. | Continuous Beam Modeling | 10.1007/978-3-030-52344-2_8 |
2021-01-01 | An application of own algorithm for reduction optimization calculation time is presented in the paper. The algorithm is called Distributed Multi-Population Evolutionary Algorithm and uses a genetic algorithm with real-coded genes in the chromosome. The client-server architecture was used for processing lots of populations with a simultaneous data exchange between the populations. Each generation consists of standard genetic operators: a natural selection, one-point crossing, uniform mutation and a data exchange within the computational units. This method was used for selecting values of damping coefficients of a driver’s seat sub-assembly to improve driving comfort. Numerical results of a vehicle driving with different variants of velocity and obstacles are presented in the paper. | Increase Driver’s Comfort Using Multi-population Evolutionary Algorithm | 10.1007/978-981-16-1685-3_29 |
2021-01-01 | Base isolators have not been extensively used in Indonesia because they have to be primarily imported from abroad and thus, they need high costs. One of the efforts to reduce the costs of base isolators is the use of local rubber that is totally processed within the country, from harvesting the rubber latex until manufacturing elastomeric seismic bearing. Before using local rubber as base isolators, the prediction of vertical and horizontal stiffness of the base isolator is required through a grade 40 uniaxial test; 50; and 60 shore A in IRHD standard. The uniaxial test indicates that grade 50 samples have the best modulus so that the base isolator test only uses grade 50 rubber. From the test results, the damping value for energy dissipation is 12%. This value gives hope for the future development of low-cost base isolator technology in Indonesia. | Experimental Study of Two Stages on the Use of Local Rubber as Base Isolator for Dwelling Houses | 10.1007/978-981-33-6311-3_62 |
2021-01-01 | This chapter describes how to begin the task of designing a MEMS device from scratch, an effort that will proceed in parallel with design of other key pieces of the MEMS product system, such as the package and electronics. We describe how to use analytical models to efficiently estimate the design space of a novel device and thereby assess feasibility in the context of practical manufacturing and operational limits. We also describe when and how to effectively deploy computational modeling, accounting for uncertainty in input values, in order to save time and cost during product development. | Starting a New MEMS Device Design | 10.1007/978-3-030-61709-7_10 |
2021-01-01 | Purpose The purpose of this paper is to study detection, microstretch function, temperature distribution function and thermoelastic damping analysis due to thermal variations and stretch forces in homogeneous, isotropic microstretch, generalized thermoelastic thin circular plate. Method This theory is based on the Kirchho-Love plate theory assumptions. The governing equations for the transverse vibrations of microstretch thermoelastic thin circular plate have been derived. The analytical expressions for detection, microstretch function, temperature distribution function and thermoelastic damping have been numerically analyzed for clamped and simply supported boundary conditions in case of both non-Fourier and Fourier microstretch thermoelastic circular plate with the help of MATLAB programming software. Results Finally the analytical development for thermoelastic damping have been illustrated numerically for Silicon-like material. The computer simulated results have been presented graphically under different boundary conditions. Conclusion It leads to the conclusion that thermal relaxation time and microstretch parameters contribute to an increase in the magnitude of the critical value of damping. | Study of Thermoelastic Damping in Microstretch Thermoelastic Thin Circular Plate | 10.1007/s42417-020-00213-6 |
2021-01-01 | Ships operating in waves are continuously subjected to varying loads from waves. As a result of these loads the ship undergoes rigid body motions and deformations. The latter can be subdivided into two types, a quasi-static and a dynamic response. Two dynamic responses that are of interest for ships are springing and whipping. Springing is the steady-state resonant vibration of a flexural mode due to continuous wave loading. Whipping is the transient elastic vibration of the ship hull girder caused for example by slamming. Springing has an important contribution to increased lifetime consumption, whereas for assessment of ultimate stresses whipping is more important. One of the major uncertainties when examining global flexural response is the amount of damping to be incorporated. Because springing is a resonance phenomenon, damping is especially important. In this paper Operational Modal Analysis is used to retrieve damping from in-service measurements and is tested for a heavily instrumented frigate type vessel. The aim of this paper is both to explain and discuss the methodology and to provide typical damping parameters which are needed in the assessment of whipping and springing. The paper also shows sensitivity of frequency and damping of the flexural modes to selected operational parameters. The research in this paper is restricted to the two node vertical bending mode. Acceleration data is most commonly used to derive mode shapes. For the present application, however, accelerations and strains were combined. In order to obtain useful results stringent filtering on mode shape, frequency, damping and stationarity of operating conditions should be applied. Operating in confined waters also has a noticeable effect. Variations in the observed natural frequency can be as large as 10%. These variations must be related to mass variations. At average operating speeds in moderate environmental conditions, the damping of the two node bending mode is around 0.6 to 1%. However, analysis presented in this paper have indicated that damping is related to speed and wave height. Specifically, the damping in 26 knots increases to 2.5% from the 1% at 15 knots. In beam sea conditions, an increase in damping from 0.7% to 1.2% was found in wave heights ranging from 1 to 2 m. This indicates that when studying extreme conditions different damping ratios are applicable compared to intermediate conditions. | Calculation of Structural Damping of the Global Hull Structure from In-Service Measurements | 10.1007/978-981-15-4672-3_22 |
2021-01-01 | Pertaining to randomness in solar energy, its integration with synchronous generation needs robust controller design for improving small signal stability. Industrial proportional integral and lead-lag controllers are very much popular. But, due to complexity in power system the robustness of controller can be much enhanced with fractional-order controllers. Here, UPFC-PI with fractional lead-lag (PI-FLL) controller is proposed for enhancing small signal stability of variable solar-integrated power system. The controller parameters are tuned by whale optimization technique. It is observed that the stability is hampered with variable solar penetration without effective controller. Time and frequency domain simulations are being carried out to justify the effectiveness of PI-FLL controller. The response predicts that UPFC PI-FLL damps oscillations heavily in contrast to PI and lead-lag controllers optimized by particle swarm, grey wolf, and whale optimizations. | Dynamic Stability Enhancement of a Variable Solar Penetrated Power System by Fractional UPFC-Based Controller | 10.1007/978-981-15-4692-1_10 |
2021-01-01 | We study the Cauchy problem of the semilinear damped wave equation in one space dimension. We show the existence of global solutions in the critical case with small initial data in weighted L ^2-spaces. This problem in multidimensional cases was dealt with in Sobajima (Differ Integr Equ 32:615–638, 2019) via the weighted Hardy inequality which is false in one-dimension. The crucial idea of the proof is the use of an incomplete version of Hardy inequality. | Remark on One Dimensional Semilinear Damped Wave Equation in a Critical Weighted L
^2-space | 10.1007/978-3-030-73363-6_14 |
2021-01-01 | Optimized damping ratio of power system can effectively suppress the system low frequency oscillation. An improved gravity search algorithm is proposed for coordination and optimization the parameters of the power system stabilizer based on the standard gravity search algorithm. This algorithm introduces the black hole concept and devour operation to increase the search speed and convergence accuracy of the algorithm, balance the global search ability and local exploitation ability of the optimization algorithm, and improve its overall optimization performance. In addition, the eigenvalue and mechanical and electrical oscillating mode characteristics working on various operating conditions of the system are optimized as objective functions to ensure the adaptability and robustness of the coordinated optimization strategy. Finally, the suggested method is executed on the classical WSCC three-generator nine-bus system for confirming its efficacy. The results show that the damping characteristics of the power system have been optimized and power system low frequency oscillation has been effectively suppressed. | Coordinated Optimization of Multi-Machine PSS Based on Improved Gravitational Search Algorithm | 10.1007/978-981-33-6606-0_3 |
2021-01-01 | This chapter describes various methods for the seismic design of new steel building structures equipped with supplemental dampers and the seismic retrofitting of existing structures by supplemental dampers. The most widely used dampers are the fluid viscous ones (linear or nonlinear), which enhance the seismic energy of dissipation of the structures and thus reduce the seismic forces on them. The result is lighter new structures or effective retrofitting of existing structures against stronger earthquakes. The most widely used design methods are the force-based simplified linear ones, including the equivalent lateral force method and the response spectrum one. The ASCE code provisions are based on such force-based simplified methods. Displacement-based simplified design methods are also presented. The arrangement of dampers for an optimum structural performance is also discussed briefly here by mentioning appropriate optimization procedures for that purpose. The limitations of the simplified methods are pointed out and the method using nonlinear time-history analysis is suggested as the appropriate method for final design of a structure with dampers. Four numerical examples are presented in some detail in order to illustrate methods based on force or displacement as well as methods characterized by new concepts. | Design Using Supplemental Dampers | 10.1007/978-3-030-80687-3_13 |
2021-01-01 | Immune system provides the mechanisms for attacking foreign invaders, eliminating autologous toxic substances and offering self-tolerance. A reductionist approach of the immune system components and their interactions as provided in this chapter will offer knowledge important to better understand the core mechanisms of autoimmune diseases and design therapies targeting their pathogenic mechanisms. Immunity is divided into (a) innate (or natural), implemented by macrophages, dendritic cells, granulocytes (neutrophils, basophils, and eosinophils), natural killer cells, the complement system, and the acute-phase proteins, and (b) adaptive, implemented by B and T cells. Immune cells express sensors on cytoplasmic or endosomal membranes or in the cytoplasm, called “pathogen-associated molecular pattern receptors” (PAMPRs), also called pattern recognition receptors (PRRs), and damage-associated molecular pattern receptors (DAMPRs) to sense foreign invaders or damaged tissues and provide defense against them. Natural immunity cells provide the first line of defense, usually successful in eliminating pathogens, but also they limber up the adaptive immune system to take action in case of any failure of defense. The sensors of B and T cells are their antigen receptors (membrane immunoglobulins and T-cell receptors, respectively) which are dissimilar to each other in terms of specificity; each receptor recognizes very specifically one antigen and especially a few peptide residues on it (epitope). However, by taking as a whole the pool of lymphocytes, their receptors offer a vast array of specificities exceeding 10^11 that is more than the genes of the human body. This implies that not particular genes but rather gene fragments are spontaneously rearranged to make an immunoglobulin or a T-cell receptor gene. One such rearrangement for each peptide chain of the receptor is allowed, so the cells will retain their antigenic specificity as long as they live. Immune cells communicate with each other and approach their targets, either by cell-to-cell contact using adhesion molecules or by soluble mediators known as cytokines or chemokines, respectively. Mechanisms like central (taking place in bone marrow and thymus) and peripheral (taking place in the lymph nodes) tolerance ensure that the immune system will not attack self. Braking of tolerance initiates autoimmune reactivity which may be subclinical but, under certain circumstances, may obtain a clinical phenotype. | Basic Immunology | 10.1007/978-3-030-56670-8_1 |
2021-01-01 | Throughout the past decades, seismic isolation of structures has attracted the attention of civil engineers and scientists. Research around this field has progressed tremendously, starting from the use of simple elastomeric bearings for the decoupling of the superstructure from the foundation and moving toward the invention of more complex devices (characteristic examples being the Tuned Mass Dampers—TMDs or the Quasi-Zero Stiffness oscillators—QZSs) aiming to enhance structural dynamic behavior. In this context, the implementation of novel passive seismic isolation devices incorporating negative stiffness elements to a high-rise building structure is introduced and proposed in this effort. The design of these devices follows the scope of general vibration isolation and damping concept, entitled KDamper concept based on Antoniadis et al. (2016). This paper considers the application of a KDamper system to 10-storey concrete building structure. A dynamic system consisting of a simplified flexible structure model and KDamper devices is considered and is subjected to artificial accelerograms designed to match the EC response spectra. The KDamper is designed to higher frequencies compared to the isolated system with seismic isolation bearings, exploiting the extraordinary damping properties it offers. A comparison with a base isolated structure using Lead Rubber Bearings designed to greatly increase the natural period of the system (2.0–2.5 s), confirms that KDamper base seismic absorption designs can provide great reduction to the inter-story drifts and absolute accelerations reducing at the same time the base displacement. | KDamper Concept for Base Isolation and Damping of High-Rise Building Structures | 10.1007/978-981-15-8049-9_16 |
2021-01-01 | The KDamper is a novel passive vibration isolation and damping concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. The KDamper concept ensures the static stability of the structure, does not require heavy masses, and can achieve better dynamic characteristics, compared to the “Quazi-Zero Stiffness” (QZS) isolators and the traditional Tuned Mass Damper (TMD). Contrary to the TMD and its variants, the KDamper substitutes the necessary high inertial forces of the added mass by the stiffness force of the negative stiffness element. Among others, this can provide comparative advantages in the very low-frequency range (Kapasakalis et al. in GRACM, 2018 [ 1 ]). The paper proceeds to a systematic approach for the optimal design and selection of the KDamper parameters, for a typical bridge structure. The design of the KDamper follows the scope of a general vibration isolation and damping concept considering Base Acceleration Excitation/Relative Structure Displacement Response Transfer Function and/or Base Acceleration Excitation/Absolute Structure Acceleration Response Transfer Function. Furthermore, an alternative design approach, incorporating an optimization algorithm is examined. The system is subjected to artificial accelerograms and real earthquake records. The proposed system is compared to the initial undamped model as well as similar structures employing other seismic isolation techniques. Comparative results prove the efficiency of the proposed KDamper system, used as an alternative or supplement to conventional seismic isolation techniques. | Design and Optimization of the KDamper Concept for Seismic Protection of Bridges | 10.1007/978-981-15-8049-9_12 |
2021-01-01 | Smart materials are currently the most sought-after material systems, today. This is because of their peculiarities in response and functionality when compared to conventional materials. Shape memory materials are one of the most relevant and evolving smart materials because of their associated anthropomorphic properties, which rightly complement their inherent engineering properties. The functionality of shape memory systems has been long discovered to be able to scale with the grain sizes in the materials. In this regard, processing of ultrafine/nanostructured shape memory materials has become expedient for the development of “new age” shape memory materials with outstanding functional properties. This new subclass of shape memory materials are sometimes referred to as shape memory nanomaterials. This chapter discusses the shape memory potentials of nanomaterials, as viable materials for addressing mechanical vibrations in structural systems. The first section of this chapter, briefly, discusses the different classes of shape materials in an attempt to skip the details available in several reviews. The grain size effect on the engineering properties of shape memory materials is discussed in the second section. In this section, special attention is placed on shape memory nanomaterials and how they differ from other sub classes of shape memory materials. The third section focuses on the nano structuring of shape memory alloys into shape memory nanomaterials, thereby presenting their comparative performance. The fourth section extensively covers damping in shape memory nanomaterials and possible applications of these materials. The chapter concludes by summarizing this vast topic, highlighting the exciting future possibilities. | Shape Memory Nanomaterials for Damping Applications | 10.1007/978-3-030-11155-7_165-1 |
2021-01-01 | The undesirable effects of roll motion of ships (rocking about the longitudinal axis) became noticeable in the mid-nineteenth century when significant changes were introduced to the design of ships as a result of sails being replaced by steam engines and the arrangement being changed from broad to narrow hulls. The combination of these changes led to lower transverse stability (lower restoring moment for a given angle of roll) with the consequence of larger roll motion. The increase in roll motion and its effect on cargo and human performance lead to the development several control devices that aimed at reducing and controlling roll motion. The control devices most commonly used today are fin stabilizers, rudder, anti-roll tanks, and gyrostabilizers. The use of different types of actuators for control of ship roll motion has been amply demonstrated for over 100 years. Performance, however, can still fall short of expectations because of difficulties associated with control system design, which have proven to be far from trivial due to fundamental performance limitations and large variations of the spectral characteristics of wave-induced roll motion. This short article provides an overview of the fundamentals of control design for ship roll motion reduction. The overview is limited to the most common control devices. Most of the material is based on Perez (Ship motion control. Advances in industrial control. Springer, London, 2005) and Perez and Blanke (Ann Rev Control 36(1):1367–5788, 2012). | Control of Ship Roll Motion | 10.1007/978-3-030-44184-5_123 |
2021-01-01 | This study aims to analyze the fluttering in the gas turbine compressor blade and the aerodynamic damping effects on the gas compressor blades by analyzing the damping coefficient sign in the model. The flutter in aerodynamic profiles is referred to as the self-excited vibration in air-foils due to unsteady pressure oscillations in the air flow field. The modal analysis of the gas compressor blade of aluminum alloy is carried out at modes 1, 2, and 3 in which the natural and modal frequency of blade is tested by using the ANSYS 17 platform. The various cases are studied for the different number of blades of gas turbine compressor to analyze the effect of fluttering on the blades. | Flutter and Modal Analysis of Gas Turbine Compressor Blades | 10.1007/978-981-16-0159-0_62 |
2021-01-01 | A performance based seismic design method for plane steel moment resisting and braced framed structures is described. It is a force-based seismic design method employing different modal (or strength reduction) factors for the first four significant modes of the frame, instead of the same constant behavior factor for all modes as in all current design codes. These modal behavior factors are functions of the modal periods of the structure, different soil types and different performance targets. Thus, the method automatically satisfies deformation demands at all performance levels without requiring deformation checks, as in all current design codes. The method is theoretically based on the construction of the equivalent linear structure to the original nonlinear one and the equivalent modal damping ratios of the previous chapter. The modal behavior factors are determined from the equivalent modal damping ratios with the aid of the modal damping reduction factors. Empirical expressions for the modal behavior factors as functions of period, deformation/damage and soil types for the seismic design of steel plane moment resisting and braced frames are derived. These expressions are appropriately converted to ones which can be used directly in conjunction with code defined elastic pseudo-acceleration design spectra with 5% damping. The proposed method is illustrated with representative numerical examples that demonstrate its advantages over code-based seismic design methods. | Design Using Modal Behavior Factors | 10.1007/978-3-030-80687-3_9 |
2021-01-01 | Models for analyzing squeeze film air damping depending on the oscillation mode of cantilever and double-clamped micro/nanobeam resonators are presented. The models are obtained from the damping theory of a rigid rectangular plate moving parallelly to a nearby object in viscous and molecular flow regime and electrostatic theory. The analysis results based on the models show that the influence of oscillation mode on squeeze film air damping in viscous regime is remarkably large compared to that in molecular flow regime. The damping in the first-order mode is larger than that in the high-order modes, while there is little deference in damping among the high-order modes. The damping of oscillation modes depends strongly on the oscillation amplitude and electrostatic spring softening. The obtained damping analysis models are useful for the optimal design of micro/nanobeam resonators and verifying the discrepancy between the theoretically calculated results and experiment data. | Models for analyzing squeeze film air damping depending on oscillation modes of micro/nano beam resonators | 10.1007/s00419-020-01775-3 |
2021-01-01 | Abstract The radio occultation measurements of the signal intensity (λ = 32 cm) of the Venera-15 and -16 satellites, carried out from October 16 to October 31, 1983, are used to analyze the activity of internal waves in the northern polar atmosphere of Venus. Observations of the intensity of radio waves provide important information about the fine-scale structure of the planet’s atmosphere. Comparison of radio occultation measurements and the results of the standard wave theory shows that small-scale fluctuations of the received signal intensity are caused by the spectrum of vertically propagating internal gravity waves. The vertical length of these fluctuations at altitudes of more than 61.5 km is about ~1 km. The model developed for the radiative damping of intensity fluctuations with altitude in the atmosphere of Venus assumes that the intrinsic frequencies of the identified internal waves (measured in a frame of reference moving together with the undisturbed flow) in the sessions under study vary from 3.5 × 10^–4 to 9.5 × 10^–4 rad/s, and the ratio of horizontal and vertical wavelengths is in the range from 57 to 21. | Activity of Small-Scale Internal Waves in the Northern Polar Atmosphere of Venus by Radio Occultation Measurements of Signal Intensity (Λ = 32 cm) from Venera-15 and -16 Satellites | 10.1134/S0038094621010044 |
2021-01-01 | Quantum optomechanics extends the idea that light forces can achieve the quantum control of mechanical motion to mesoscopic and macroscopic systems. Following a semiclassical introduction to cold damping and the optical spring effect, we show how sideband cooling can bring those systems to their quantum mechanical ground state. We then discuss ways to prepare, manipulate, and characterize other quantum states of mechanical oscillators. This is followed by an analysis of the standard quantum limit of optomechanical interferometers that clarifies the roles of shot noise and radiation pressure noise. We finally return to ultracold atoms to show how their collective density excitations can likewise behave as optomechanical oscillators. | Quantum Optomechanics | 10.1007/978-3-030-76183-7_11 |
2021-01-01 | This paper proposes a nonlinear optimization approach for the ride comfort based on nonlinear damping to improve the optimized reliability of ride comfort of the commercial vehicle. First, a vibration model of a commercial vehicle is established and followed by a road excitation model and a nonlinear damping model that can provide nonlinear damping force by using compression velocity rather than linear force. The weighted Root Mean Square (RMS) from previous comfort models is then obtained and compared with experimental data. The result indicates that the ride model based on nonlinear damping leads a more accurate result and is closer to the experiment than the model based on the equivalent one. A optimization approach for ride comfort based on nonlinear damping to the commercial vehicle is further proposed. The sum of weighted RMS of the vertical vibration acceleration of driver seat at 30 km/h, 60 km/h, and 90 km/h is taken as the objective function with the stiffness and nonlinear damping gradient of suspension as the design variables. Afterwards, the particle swarm optimization (PSO) is utilized to improve the ride comfort. And the optimal stiffness and nonlinear damping are obtained. Finally, the effectiveness of the presented approach is evaluated by the comparison of the logarithmic power spectral density and the weighted RMS before and after optimization. It is shown that the optimization method can reduce the average peak of power spectral density and the average weighted root mean square by 29.9% and 10.2%, respectively. | Ride Comfort Optimization Method for Commercial Vehicle Based on Nonlinear Damping and PSO | 10.1007/978-981-15-7945-5_25 |
2021-01-01 | This chapter considers dynamic modeling of solid mass on soil base. Features of finite-element modeling soil massif are discussed on the base optimal selection of representative volume with damping belts. As the test task, it is considered lattice of partitioning a three-layer half-plane into finite elements, with the introduction of damping belts and taking into account a coastal slope. The dynamic stress-strain states of these structures are studied for different geometrical parameters of the layers and their mechanical characteristics. Finally, comparison of finite-element calculations is performed with analytical solutions, obtained by using integral method of harmonic analysis based on the application of the Fourier transform in time. | Dynamic Modeling of Solid Mass on Soil Base | 10.1007/978-3-030-59230-1_8 |
2021-01-01 | The best of effective design and practices of constructive methods in the analysis of rotor excessive vibration will yield the solutions for the dynamic problems. The extensive effusion of the finite element method (FEM) strongly induced in the area of rotordynamic studies and can give accurate results. Diagnosis of a rotor shaft with crack for its operating conditions is essential to the dynamic systems design. This paper carries the analysis of a finite element model of a flexible rotor-bearing system with a transverse open crack by accounting the various crack depths and internal damping of the shaft. The effect of transverse crack on the system instability regions was found out. It is noted that the natural whirl speeds reduce with increase in crack depths. The system unbalance response and damped natural whirl speeds are presented with undamped orthotropic bearings. The stability of the rotating shaft-bearing system with transverse open crack has also been studied for the various spin speeds and disk eccentricity with the time integration procedure. The phase-plane portraits and frequency-domain diagrams are drawn to study the dynamic behavior. Further, the study is yet to be extended to a fully levitated rotor model supported in active magnetic bearings (AMBs). | Dynamic Response Analysis of Rotating Shaft-Bearing System with an Open Crack | 10.1007/978-981-15-5701-9_42 |
2021-01-01 | The ultimate load of a structure is transferred to the soil by the base of the structure known as the foundation. The loads which act on the foundation are basically of two types, i.e. static load and dynamic load. The influence zone of static load which is due to dead and live load is limited to a certain area around the footing depending upon the magnitude of load and soil type. The dynamic load generated due to seismic loading, wind loading, traffic loading and vibrations generated due to certain machines (hydraulic press, pumps, etc.) affects the nearby structure in terms of foundation settlement, tilting of structure and cracks to structure and sometimes influence zone can be large depending upon intensity. In this study, Plaxis 2D: Finite element-based software is used to observe the effect of vibration. Firstly, the experimental work of Swain and Ghosh was simulated in the Plaxis 2D for validation and a good agreement was observed between results of the numerical study and experimental result. After validation of the work, the effect on displacement at primary footing was observed with the varying frequency of vibration generated by a reciprocating pump at the primary footing. Stone columns of coarse recycled aggregates and a layer of waste shredded tyres blanket is used in between the primary and secondary footing to examine the effect of vibration on secondary footing. This study focuses on the use of waste utilization for engineering purposes as a replacement of natural resources to progress towards sustainable development. It was concluded that shredded waste tyre blanket in between the source and sink is the best solution among two materials. | Waste Material a Sustainable Remediation for Settlement Caused by Pseudo-static Loading at Nearby Footing | 10.1007/978-981-15-9554-7_16 |
2021-01-01 | This study is proposed to devise the behavior of temporomandibular joint (TMJ) while jaw opening and closing movements in human beings using bond graph. TMJ is the most active and extensively used biomechanical joint. To diagnose TMJ disorders and provide correct medical care by exploring jaw behavior, accurate dynamic modeling of TMJ is a necessity. This study is limited to in vitro analysis and modeling techniques because it is challenging to study the actual dynamic functioning of TMJ, being an inner body joint. The primary focus of this work is to model TMJ through bond graph considering its physical resonance with a mechanical system. For this study, the human masticatory system is devised into mathematical one-dimensional model. It included morphology, the behavior of the muscle as well as its dynamic properties. The simulation has been carried out for different force patterns replicating proportional jaw activities like mouth opening and closing. The functional role of TMJ muscles has been represented by assigning nonlinear stiffness values through available literature. The muscle strength has been attributed as a damping characteristic of the jaw. The various elements of jaw, i.e., bite force, jaw mass, reaction force and velocity, have been attributed into the model, which accounts for symmetrical jaw motions. | Modeling and Simulation of Human Temporomandibular Joint Using Bond Graphs—A One-Dimensional Model | 10.1007/978-981-33-4684-0_72 |
2021-01-01 | Statistical energy analysis (SEA) has been extensively used for predicting the transmission loss of sound and vibration through the complex structural-acoustic systems. The SEA method proved to be an effective tool for analysing the response of such complex systems at early design stage of the product. In the present study, the SEA parameters such as modal density, damping loss factor, and coupling loss factor have been evaluated by a theoretical and experimental approaches. In order to analyse the effect of different material properties on the SEA parameters, conventional materials such as mild steel, stainless steel, aluminium, and glass fibre epoxy composite have been considered. Beside in case of composite plates, the effects of different fibre orientation on the SEA parameters have been studied. The free-free boundary condition is considered for evaluating the SEA parameters. | Statistical Energy Analysis Parameters Investigation of Composite Specimens Employing Theoretical and Experimental Approach | 10.1007/978-981-33-4550-8_12 |
2021-01-01 | Tool vibration is more critical in the machining of deep holes, where the tool overhang is greater, and, consequently, is the tendency to chatter. This work presents recent designs and dynamic models of boring bars with different passive damping configurations explored in the internal turning in deep holes using hardened materials, where tight tolerances and low surface roughness were always reached. Furthermore, its passive auxiliary systems increased the damping capacity of the tool with a varied physical mechanisms that dissipate mechanical energy. | Passive Damping Techniques for Vibration Suppression in Boring Operation with Long Overhangs | 10.1007/978-981-15-9529-5_22 |
2021-01-01 | Abstract The paper presents a brief review of design for aircraft engine pipeline supports with multilayer plate dampers and dampers made of MR material. A new way of manufacturing the dampers from MR material is proposed. Problems of designing and studying the elastic-damping, dynamic and life time characteristics of new type dampers made of improved MR material are considered. | New Dampers Made of MR Material for Aircraft Engine Pipeline Supports | 10.3103/S1068799821010062 |
2021-01-01 | Large quantities of coal ashes are being generated by thermal power plants (coal-fired) all over the world. The coal ashes are proving to be potentially hazardous materials causing environmental pollution. Bulk utilization of fly ash requires a relatively good knowledge of the characteristics of fly ashes, their response and engineering behaviour. Various studies are available on the behaviour of fly ash without and with various additives, but a very few researchers focus on the behaviour of fly ash–sand mixtures. A series of resonant column tests has been carried out on fly ash, sand and fly ash–sand mixtures to investigate the influence of sand particles on the maximum dynamic shear modulus ( G _max) and dynamic damping ( D ) of fly ash. Dynamic properties of fly ash–sand mixtures are found to be dependent upon the percentage of sand particles in the mix, confining pressure and shear strain. The maximum dynamic shear modulus of fly ash–sand mixtures is found to be more than the maximum dynamic shear modulus of fly ash. The damping ratio of sand is found to be more than the damping ratio of fly ash irrespective of the confining pressure. | Dynamic Properties of Fly Ash–Sand Mixtures | 10.1007/978-981-33-6564-3_62 |
2021-01-01 | Padhi, Sukanya Nayak, Itishree The main objective of this paper is to examine the influence on velocity and temperature profiles of an unsteady, reactive, incompressible, second-grade fluid with low electrical conductivity and variable viscosity within porous channel with asymmetric cooling at the walls. The highly coupled non-linear partial differential equations are generated and reduced to a system of algebraic equations using fully implicit finite difference scheme. The resulting system is then solved by damped-Newton method. The adopted numerical method observes second-order convergence and is highly stable along with ensuring error reduction after every iteration depending on the choice of damping applied. Lastly, the effect of different physical parameters on velocity and temperature profile is discussed and demonstrated graphically with the aid of MATLAB. | Analysis and Computation of Reactive Second-Grade Fluid Flow with Variable Viscosity Within Porous Couette Device | 10.1007/978-981-16-1402-6_12 |
2021-01-01 | This article discusses the features of using various designs of elastic-damping devices on GTE supports, including: support with a hydrodynamic damper (with and without an elastic element), support with an elastic ring and support with a plate damper. An analysis of their design is given in terms of the impact on the stiffness and damping of the engine support unit, which allows you to determine the choice of a damping device for solving the complex problem of reducing engine vibrations. | Features of the Use of Damper Supports of Various Designs in a Gas Turbine Engine | 10.1007/978-981-33-6060-0_33 |
2021-01-01 | Accurate seismic analysis of concrete dams has a great impact not only on design of the new dams but also on the stability assessment of the existing ones. In this regard, one of the challenging issues is to consider the dynamic effects of radiation damping due to the mass of the foundation rock on the seismic responses. In this paper, an absorbing boundary condition, which is comprised of the viscous boundary traction and a free-field column, has been adopted in time domain. Based on the adopted methodology, a finite element model has been prepared for Pine Flat concrete dam using ABAQUS. In order to evaluate the damage level, the concrete damage plasticity model has been assumed for the concrete constitutive relation. The damage level in concrete has been evaluated under Taft earthquake. In addition, the response spectrum that Pine Flat dam can endure has been determined using an endurance time analysis. | Seismic Analysis and Damage Evaluation of Pine Flat Concrete Dam | 10.1007/978-3-030-51085-5_4 |
2021-01-01 | Abstract— We study the stability of a one-dimensional laminated beam which consists of two identical layers of uniform thickness. An adhesive of small thickness is bonding the two layers and creating a restoring force thereby producing a damping called adhesive or structural damping at the interface. It is well-known in the literature that this single frictional damping is not strong enough to stabilize the system exponentially. On the contrary, we prove in this paper that the unique dissipation due to the structural damping is strong enough to exponentially stabilize the system provided the wave speeds of the system are equal. | Exponential Stability of Laminated Beams with Interfacial Slip | 10.3103/S0025654421010039 |
2021-01-01 | In this article, a device design is described to convert vibration energy exerted on a vehicle during motion on different road conditions. This is achieved by converting the vibrational energy to electrical energy by utilizing Faraday’s law. Selection of mounting point is done by using first principle modelling approach for a two-wheeler vehicle as a spring-mass-damper system. Finally, the device is tested at different speeds and road surface conditions. It is concluded that the voltage induced is directly dependent on frequency and amplitude of vibrations. | Fabrication and Performance Analysis of a Device to Transform Vibration Energy on an Automobile | 10.1007/978-981-15-3639-7_4 |
2021-01-01 | This study deals with the optimization of parameters of multiple tuned mass damper (MTMD) system for seismic vibration control considering uncertain bounded structural parameters. An approach based on Taylor expansion of objective function along with subsequent interval extension is taken into account in this study. The objective function involving the uncertain bounded parameters is transformed into two independent deterministic sub-problems leading to the lower and upper bound solutions with the help of interval extension. The optimization strategy investigated in this optimization framework is the stochastic structural optimization (SSO) where the root mean square displacement of the primary–secondary coupled system is minimized. A numerical study is performed to observe the effect of uncertainties on the optimization of MTMD parameters where the primary system is coupled with MTMD system with two, three, five and ten mass units. The performance of these MTMD systems is also compared under various levels of uncertainties. Fundamental mode of the system is considered for vibration control, where natural frequency and damping ratio associated with the fundamental mode are found to be nearly 10 rad/s and 0.03, respectively. In this study, natural frequency and damping ratio of the primary system, natural frequency and damping ratio of elastic filter, intensity of the power spectral density of white noise excitation at the bed rock are taken as the uncertain parameters. It is observed that SSO is suitable for higher levels of uncertainties associated with structural parameters. It may be mentioned that such observations are found for various numbers of mass-units of MTMD system. | Stochastic Structural Optimization of Multiple Tuned Mass Damper (MTMD) System with Uncertain Bounded Parameters | 10.1007/978-981-15-5235-9_28 |
2021-01-01 | Magneto-rheological dampers have been utilized quite effectively to reduce vibration levels in automobiles in recent years. The objective of this work is to determine the optimum dimensions of a magneto-rheological damper based on magnetic saturation. As stress and magnetic field can be analyzed conveniently in the “ANSYS” (FEM tool); a basic MR damper is modeled in “ANSYS” and then the optimum dimensions of the MR damper have been determined. The result shows that the magnetic flux density can be reduced to 0.828 T from 0.877 T with the dimensions obtained from this work, which is close and under the saturation value of 0.83 Tesla in the case of magneto-rheological fluid (MRF132DG). Hence, the optimum dimensions maintain the magnetic flux density close to magnetic saturation with a high damping characteristic which will provide a better control to reduce the vibration levels. | Geometry Optimization of Magneto-Rheological Damper Based on Magnetic Saturation | 10.1007/978-981-15-8704-7_86 |
2021-01-01 | The damped oscillations of a spherical pendulum in planar motion is examined in a wind tunnel. Angular deflections and accelerations are measured for various wind speeds and their influence on the periods of oscillation and the time to complete pendulum rest are presented. | Damped Oscillations of Spherical Pendulums | 10.1007/978-981-33-4960-5_41 |
2021-01-01 | Performance-based seismic engineering is nowadays adopted for economical design of structures to resist earthquakes and it requires nonlinear static pushover analysis to be performed. In this approach, the energy dissipation due to nonlinear behavior of the structures is taken into account by obtaining the equivalent viscous damping and this damping is evaluated from the global pushover curve of the structures. However, the global structural damping is basically due to energy dissipation at local joints of the structures deforming beyond yield rotation. This paper presents the methodology of estimating equivalent damping from the local hinge characteristics of the structures at element level by carrying out Pushover analysis of three structures viz 3D six storeyed, 2D two storeyed and a simple column RC structure. This damping is assessed by considering cumulative hysteretic energy dissipated at all the plastic hinges developed in the structures and is compared with that calculated based on formulations given in codes such as FEMA-440 and ATC-40. Damping agrees well with that given in FEMA-440, estimated from global pushover curve of structures for ductility value greater than 3. Also, nonlinear time history analysis is performed for all the structures to validate the structural performance. | Assessment of hysteretic damping in reinforced concrete structures using local hinge characteristics | 10.1007/s10518-020-00968-z |
2021-01-01 | This chapter describes some of the recent studies on the optimal control of structures. Initially, different passive, active and semi-active control devices are introduced and the importance of optimization in each case is discussed. A comprehensive literature review on the optimal design of various well-known control devices of each category i.e., Tuned Mass Damper (Active, Passive and Semi-Active modifications), Fluid Viscous Damper (Passive and Semi-Active), Viscoelastic Damper and Base Isolation (Passive and Semi-Active) and Active Tendon with special attention to the first studies and studies performed in the last decades, is presented. To suppress tall building vibrations subjected to wind and seismic loads, Tuned Mass Dampers (TMDs) modification have recently gained attention due to their simplicity, stability and reliability. Therefore, in the last section, the results of some recent studies on the optimization of Active and passive Tuned Mass Dampers and a recently proposed promising modification of TMD (i.e. Tuned Mass Damper Inerter) are comprehensively discussed. | Current Trends in the Optimization Approaches for Optimal Structural Control | 10.1007/978-3-030-61848-3_5 |
2021-01-01 | The present protocol introduces a live-cell imaging of secretion activity (LCI-S) that is useful to visualize the real-time release of molecules from individual cells using an immunoassay coupled with total internal reflection fluorescence (FL) microscopy. This novel “live”-cell imaging technique has helped uncover the dynamics of regulated cell “death” by using this new approach. This protocol can observe the final stages of the regulated cell death process via single-cell imaging by targeting the extracellular release of damage-associated molecular patterns (DAMPs) from the cells expressing fluorescence resonance energy transfer (FRET) biosensors, such as a sensor for MLKL activation by RIPK3 based on FRET (SMART) and a sensor for caspase-1 activation based on FRET (SCAT1), which specifically identify the occurrence of regulated cell death processes. | Live-Cell Imaging Technique to Visualize DAMPs Release During Regulated Cell Death | 10.1007/978-1-0716-1258-3_28 |
2021-01-01 | A solar tracker is a machine that uses a mechanical prime mover to tilt solar photo voltaic panels from east to west during the day to track the sun for maximizing the production of PV power by keeping the incident angle of sun-rays perpendicular to the panel surface. Drag and lift produced by the wind on the surface area of solar panels causes a torsional moment on the tracker structure, and may induce torsional instability in the structure due to wind galloping. The use of hydraulic dampers is recommended to reduce the intensity of galloping and reduce the potential risk of damage to the tracker structure and panels. In this paper, the vibration characteristics of the tracker structure are analysed (theoretically and numerically) with and without external dampers, using the lumped spring-mass-damper approach to identify the suitability of the selected dampers for the application. | Damping of Wind-Induced Galloping Oscillations of Solar Trackers | 10.1007/978-981-15-4477-4_36 |
2021-01-01 | We are witnessing a great increase in the use of auxetic structure in comparison to their conventional counterparts in these recent years. They have exhibited numerous advantages such as a high strength, stiffness and energy absorption. On the other side, we are also witnessing the emergence of eco-composite materials that significantly have the upper hand when compared to synthetic alternatives. This paper describes the static and fatigue bending behaviour of a bio-based sandwich structure with conventional and auxetic honeycomb core. The eco-composite used is a tape of polylactic acid reinforced with flax fibers. Additive manufacturing technology is used to produce these structures. The quasi-static bending tests were performed to identify the mechanical properties of sandwich composites and the ultimate loading. The fatigue tests were conducted with displacement-controlled technique in order to study the effect of the core configuration on the stiffness, hysteresis loops, energy absorption and damping ratio of the sandwich composite. The interesting part is that we observed a great increase in the capacity of energy absorption for the auxetic structure when compared to the conventional ones, which results higher loss factors. This work is used to determine the static and fatigue properties and to give an opinion on the damage mechanisms of these composites during its lifetime. | Bending Fatigue Behaviour of a Bio-based Sandwich with Conventional and Auxetic Honeycomb Core | 10.1007/978-3-030-76517-0_6 |
2021-01-01 | Contemporary seismic isolation systems for bridge structures provide (A) horizontal isolation from the effects of ground motion and (B) an energy dissipation mechanism to reduce displacements. Throughout the years many kinds of seismic isolation mechanisms have been developed, with the concept of introducing negative stiffness being the most promising. In this context, a novel passive vibration isolation and damping concept is introduced, the KDamper. The KDamper is based on the optimal arrangement of stiffness elements, including a negative stiffness element. The main advantage of the KDamper over other similar concepts including negative stiffness elements is that no reduction in the overall stiffness of the system is required. This paper considers the application of a KDamper system to a bridge structure. The system is subjected to artificial accelerograms, designed to be compatible to a rather conservative seismic case corresponding to EC8, ground type C. The mean power spectral density of these accelerograms is used to calculate the effect of the variation of the nominal KDamper frequency to the transfer functions, the response power spectral densities, and the root mean square responses. The KDamper is designed to higher frequencies compared to the isolated system with seismic isolation bearings, exploiting the extraordinary damping properties it offers. A comparison with a seismic isolated structure using Lead Rubber Bearings, designed to greatly increase the natural period of the system (2.0 s), confirms that KDamper base seismic absorption designs can provide great reduction to the absolute accelerations reducing at the same time the deck’s displacement. | Frequency-Based Design of the KDamper Concept for Seismic Isolation of Bridges | 10.1007/978-981-15-8049-9_11 |
2021-01-01 | Different types of dynamic loads will originate from the external sources like aerodynamic forces in case of airborne applications and road unevenness in case of automotive applications. Aircraft structures, aerospace vehicle structures, automotive structures, etc., are manufactured by maximum utilization of plate-like structures only. Suppression of effect of dynamic loads on plate structures is most important at the stage of design of any product. Application of constrained damping layer in plate structure without any changes in structural dimensions particularly thickness of plate is the best method to control the dynamic load distribution in the plate structures. The constrained damping layer thickness varies quantitatively for different modes of vibration of plate. The determination of exact or optimized damping layer thickness requirement for the aluminium sandwiched plate structure is considered as the key factor to overcome the maximum effect of dynamic loads in plate-like structures. As part of this work, natural frequency of the plate along with loss factor, and damping layer thickness are computed on iteration methodology, and at convergence condition these values are taken as optimum for a particular mode of vibration. The proposed analytical method will be converted in the form of a general-purpose computer program in MATLAB. This code will be applied to any dimension of the plate at multiple vibration mode patterns. The outcome of this work would be an analytical method that can be used by any designer to find the optimum damping layer thickness of a plate-like structure in order to reduce the vibration response. | Design and Optimization of Constrained Damping Layer Thickness of Aluminium Plate Structure at Various Wave Modes of Vibration | 10.1007/978-981-15-4739-3_9 |
2021-01-01 | Abstract Transverse vibrations of a double-layered viscoelastic orthotropic graphene sheet system are investigated. The two sheets in the system are coupled by the visco-Pasternak medium. General governing equations for free and forced vibrations of the double-layered graphene sheet system with a high-order surface stress effect are formulated. Theoretical solutions for the damped vibrational frequency, damping ratio, and relative deflection of the two sheets with simply supported boundary conditions are obtained. The effects of the high-order surface stress on the damped frequency and damping ratio of the system for in-phase and out-of-phase free vibrations are discussed. The impacts of the high-order surface stress, structural damping, medium damping, Winkler modulus, and shear modulus of the medium on the relative deflection of the two sheets for forced vibrations are investigated. It is demonstrated that the high-order surface stress effects on the vibrational properties of the system are more significant than those of the conventional surface stress. | FREE AND FORCED VIBRATIONS OF DOUBLE-LAYERED VISCOELASTIC ORTHOTROPIC GRAPHENE SHEETS WITH A HIGH-ORDER SURFACE STRESS EFFECT | 10.1134/S0021894421010168 |
2021-01-01 | The Space Launch System (SLS) and its Mobile Launcher (ML) will be transported to the launch pad via the Crawler-Transporter (CT) system. Rollout (i.e., transportation) loads produce structural loads on the integrated SLS/Orion Multi-Purpose Crew Vehicle (MPCV) launch vehicle which are of a concern with respect to fatigue. As part of the risk reduction process and in addition to the modal building block test approach that has been adopted by the SLS Program, acceleration data will be obtained during rollout for use in modal parameter estimation. There are several occurrences where the ML/CT will be transported either into the Vertical Assembly Building (VAB) or to the launch pad and back without the SLS stack as part of the Kennedy Space Center (KSC) Exploration Ground Systems (EGS) Integrated Test and Checkout (ITCO). NASA KSC EGS has instrumentation installed on both the ML and CT to record data during rollout, at the launch pad, and during liftoff. The EGS instrumentation on the ML, which includes accelerometers, is referred to as the Sensor Data Acquisition System (SDAS). The EGS instrumentation on the CT, which also includes accelerometers, is referred to as the CT Data Acquisition System (CTDAS). The forces and accelerations applied to the ML and CT during a rollout event will be higher than any of the planned building block modal tests. This can be very beneficial in helping identify nonlinear behavior in the structure. Developing modal parameters from the same test hardware in multiple boundary conditions and under multiple levels of excitation is a key step in developing a well correlated FEM. The purpose of this study was three fold. First, determine the target modes of the ML/CT in its rollout configuration. Second, determine if the test degrees of freedom (DOF) corresponding to the layout of the SDAS/CTDAS accelerometers (i.e. position and orientation) is sufficient to identify the target modes. Third, determine if the Generic Rollout Forcing Functions (GRFF’s) (“Development of Generic Crawler/Transporter Rollout Forcing Functions for Coupled System Dynamics Analysis,” NASA Exploration Systems Directorate/Cross-Program Systems Integration Technical Assessment Report, ESD 20038, July 31, 2018) is sufficient for identifying the ML/CT target modes accounting for variations in CT speed, modal damping, and sensor/ambient background noise levels. The finding from the first part of this study identified 28 target modes of the ML/CT rollout configuration based upon Modal Effective Mass Fractions (MEFF) and engineering judgement. The finding from the second part of this study showed that the SDAS/CTDAS accelerometers (i.e. position and orientation) are able to identify a sufficient number of the target modes to support model correlation of the ML/CT FEM. The finding from the third part of this study confirms the GRFFs sufficiently excite the ML/CT such that varying quantities of the defined target modes should be able to be extracted when utilizing an Experimental Modal Analysis (EMA) Multi-Input Multi-Output (MIMO) analysis approach. An EMA analysis approach was used because Operational Modal Analysis (OMA) tools were not available and the GRFFs were sufficiently uncorrelated. Two key findings from this third part of the study are that the CT speed does not show a significant impact on the ability to extract the modal parameters and that keeping the ambient background noise observed at each accelerometer location at or below 30 μgrms is essential to the success of this approach. Even though this study relies heavily upon the accuracy of both uncorrelated ML and CT FEM’s and unconfirmed rollout forcing functions, all of which will most likely differ from actuality, it provides important insights into the ability to extract modal parameters from the upcoming rollout events. | Feasibility Study of SDAS Instrumentation’s Ability to Identify Mobile Launcher (ML)/Crawler-Transporter (CT) Modes During Rollout Operations | 10.1007/978-3-030-47713-4_12 |
2021-01-01 | Forced oscillations in a system with a source of energy of limited power in the presence of delays in the forces of elasticity and damping are considered. The elastic force also includes a non-linear component. The solution of the system of equations with nonlinearity was performed using the method of direct linearization, including the linearization accuracy parameter, and the method of change of variables with averaging built on its basis for solving the linearized equation. The latter method gives a standard form equation for determining the non-stationary and stationary values of the amplitude and phase of the oscillations. Using it and the averaging procedure for solving the energy source equation, the necessary relations for the considered system, as well as the source velocity, are obtained. The stability of stationary motions is considered and stability criteria are derived. Calculations are performed to obtain information about the effect of delays on the dynamics of the system. | Forced Oscillations with Delays in Elastic and Damping Forces | 10.1007/978-3-030-80472-5_16 |
2021-01-01 | This study is motivated to find out whether the possibility of forest fire could be predicted based on identifying the reduction of moisture content in the plant. Toward this direction, we explored, specifically, the effect of decreasing water content in the plants on its mechanical properties by a simple yet novel method. This method applies a Laser Doppler Vibrometer to study the change of dynamic response of plants. It was assumed that the change of moisture content would result in the change of mechanical parameters like stiffness and damping of the plant body, which would, in turn, cause changes in natural Frequency of the plant. To carry out this experiment, two plants named Ficus Elastica and Auracaria Cookii were deprived of water for five consecutive days, and their change in resonant frequencies to the external excitation was observed. The important inference from this study concludes that rubber tree (Ficus Elastica) is more robust against water depletion by displaying negligible change in resonant frequency as compared to the Christmas tree (Auracaria Cookii). | Understanding the Imminence of Forest Fire Using Laser Doppler Vibrometer | 10.1007/978-981-15-8049-9_28 |
2021-01-01 | In this paper, the Discrete Sources Method has been extended to describe the influence of the geometry asymmetry of a core-shell particle accounting for the effect of spatial dispersion inside the plasmonic metal shell. We found that varying the plasmonic shell thickness has more influence on the near field intensity distribution then on the average enhancement factor. Besides, we demonstrates that the effect of spatial dispersion can decrease the near field intensity up to 60% of its value and it provides a small blue shift. | Quality of Control in the Tavis–Cummings–Hubbard Model | 10.1007/s10598-021-09517-y |
2021-01-01 | When the suspension deforms, damping force is generated as the piston of the shock absorber moves, but a time difference occurs before the large hydraulic damping force rises. At the same time the frictional force in the shock absorber is playing an important role in generating effective damping force against deformation of the suspension, the generated force itself is small but its response is high. The frictional force in the shock absorber occurs in reciprocating motion in various speed ranges from amplitude of less than one millimeter to larger amplitudes, its behavior changes dynamically and is non-linear. Recent studies have revealed that controlling the friction is more important than reducing it for improvement of the performance. Because of this we have investigated the dynamic friction characteristics of shock absorber oil and sliding parts, by the means of an own developed device that can measure the speed dependence of friction force in reciprocating motion with high accuracy. The result of our analysis shows that friction dissipates energy at a speed level of 0,002m/s where hydraulic dissipation is not working yet. By knowing this phenomenon, we have developed different kind of oil types in order to generate various dynamic friction characteristics. The influence of our developed oil types on the ride and handling performance was tested and analyzed in different vehicles. Subjective assessments and objective measurement show the vehicle performance improvement, which can be generated by using more advanced oil types. | The Power of Oil – Influence of Shock Absorber Oil on Vehicle Ride and Handling Performance | 10.1007/978-3-662-63193-5_8 |
2021-01-01 | Today modern 3D computational fluid dynamics (CFD) and computational structural mechanics (CSM) codes are coupled to predict the interaction between fluids and solids. Within the scope of this work the multiphysics codes ANSYS CFX-MOR and ANSYS CFX-Mechanical are validated against the Vattenfall Rod Vibration Experiment data. The experimental setup consists of a Plexiglas test section with a slender stainless steel rod in the middle, which is pulled and then released. The calculated time dependent rod vibration amplitude in water and air environments with different fluid velocities is compared with measured data. The analyses show that the nature of the vibrations for the cases with flowing fluid is well predicted, while underestimation of the vibration amplitude and phase shift are observed in the cases with stagnant flow. | Validation of Coupled CFD-CSM Methods for Vibration Phenomena in Nuclear Reactor Cores | 10.1007/978-3-030-55594-8_7 |
2021-01-01 | The cable detection robot is of great significance to the automatic maintenance of Bridges. In order to ensure the climbing stability of the detection robot, a spring - magnetorheological damping coupling loading mechanism was proposed. Firstly, aiming at the influence of vibration and disturbance on cable safety performance of heavy-duty climbing robot, a robot-cable coupling dynamic model was established. Secondly, the vibration suppression mechanism of the robot with variable damping was studied, and a variable damping coupling loading mechanism was proposed for the climbing robot. Thirdly, an adaptive controller for cable-climbing robot acting on multiple coupling loading mechanisms under random disturbance is designed. Finally, experiments were carried out to verify the vibration suppression effect of the coupling loading mechanism and improve the safety and detection performance of the robot-stay cable system. | Research on Damping Control of Cable-Climbing Robot Based on Spring-Magnetorheological Damping Coupling Mechanism | 10.1007/978-3-030-89134-3_71 |
2021-01-01 | Relative density is commonly used to quantify the looseness or denseness of the in situ soil. However, its determination is not possible in the case of cohesive soils. Hence, relative compaction is used as a governing parameter to represent the different states of natural in situ conditions in cohesive soils. Relative compaction is defined as the ratio of field dry density to the maximum dry density determined by the standard Proctor test. The amount and rate of strength and stiffness degradation of soil under dynamic loading depend largely on their compaction state. The aim of the current study is to evaluate the effect of relative compaction on the dynamic behaviour of low plasticity cohesive soil collected from Chobari Dam, Gujarat. A series of two-way displacement-controlled cyclic triaxial tests and 1D consolidation (oedometer) tests were performed on the specimens of Chobari Dam soil. The specimens were prepared at different relative compactions of 65, 70, 75, 80, 85, 90 and 100%. The hysteresis behaviour of Chobari Dam soil was evaluated based on the variation in shear modulus ( G ), damping ratio ( D ) and cyclic stiffness degradation index ( δ ). Shear modulus was found to increase with the increase in relative compaction, while cyclic stiffness degradation was observed to decrease as relative compaction decreased to 80%. The variation in cyclic stiffness degradation was observed to be insignificant for relative compaction below 80%. Rate of degradation of damping ratio was observed to be reduced with the decrease in relative compaction. | Effect of Relative Compaction on Dynamic Behaviour of Low Plasticity Cohesive Soil | 10.1007/978-981-33-4001-5_11 |
2021-01-01 | This chapter discusses the problem of wide-area control (WAC) for large-scale power transmission systems. The discussion covers two main applications, namely, wide-area oscillation damping control and wide-area voltage control. Scalable control methods are reported for both applications, highlighting important challenges in design, implementation, and computational complexity. This is followed by two newly evolving control paradigms, namely, sparsity-promoting WAC and online learning-based WAC. The first design reduces the cost and complexity of data communication by imposing structural constraints on the controller. The second design transitions conventional model-based WAC to a data-driven approach by employing system identification and real-time control actions. The chapter ends with a list of open problems and future research directions in this research area including the need for efficient cyber-physical architectures, cyber-security, machine learning, and game theory for WAC. | Wide-Area Control of Power Systems | 10.1007/978-3-030-44184-5_100125 |
2021-01-01 | The proposed observer-based control mechanism solves the trajectory tracking problem in the presence of external disturbances with the reduction in sensor numbers. This systematically considers the quadcopter nonlinear dynamics and parameter and load variations by adopting the standard controller design approach based on a disturbance observer (DOB). The first feature is designing first-order observers for estimating the velocity and angular velocity error, with their parameter independence obtained from the DOB design technique. As the second feature, the resultant velocity observer-based control action including active damping and DOBs secures first-order tracking behavior for the position and attitude (angle) loops through pole zero cancellation, thereby forming a proportional–derivative control structure. Closed-loop analysis results reveal the performance recovery and steady-state error removal properties in the absence of tracking error integrators. The numerical verification confirms the effectiveness of the proposed mechanism using MATLAB/Simulink. | Velocity-sensorless proportional–derivative trajectory tracking control with active damping for quadcopters | 10.1007/s11071-020-06193-2 |
2021-01-01 | Parametric oscillations in a nonlinear system with a source of energy of limited power in the presence of delays in the forces of elasticity and damping are considered. The system model includes a rod-oscillatory system and an electric motor-energy source. To solve the nonlinear equations of motion of the system, the method of direct linearization was used. Using this method, equations are derived for determining the non-stationary and stationary values of the amplitude, phase of oscillations and the speed of the energy source. The conditions of stability of stationary oscillations are considered on the basis of the Routh-Hurwitz criteria. In order to obtain information about the effect of delays on the dynamics of the system, calculations were carried out and a number of amplitude-frequency dependences were constructed for various combinations of delays in the forces of elasticity and damping. For a number of points of amplitude-frequency dependences, areas of steepness of the characteristics of the energy source are shown at which stationary modes of motion are stable. | Parametric Oscillations at Delays in the Forces of Elasticity and Damping | 10.1007/978-3-030-80531-9_16 |
2021-01-01 | Power-to-volume density is a critical metric for all renewable energy technologies. Harnessing Marine Hydrokinetic (MHK) energy using a single linear or nonlinear oscillator with a cylinder in Flow Induced Oscillations (FIO) has proven to be an efficient and environmentally compatible method. MHK power harnessing by two rigid, circular, tandem cylinders on end-springs for Reynolds number 3 × 10^4 ≤ Re ≤ 1.2 × 10^5 with spacing, damping, and stiffness as parameters is investigated experimentally. The objective is to identify optimal parameter combinations where the cylinders, in close-proximity, undergo synergistic FIO harnessing more power than they would individually. The spring-damper controller V_ck, developed in the Marine Renewable Energy Laboratory (MRELab), enables embedded computer-controlled change of viscous-damping and spring-stiffness for fast and precise oscillator realization. Experimental results for amplitude response, energy harvesting, and efficiency are presented and discussed. Center-to-center spacing of 1.57, 2.0, 2.57 diameters, harnessing damping ratio 0.00 < ζ _ harness < 0.24, and spring stiffness 200 N/m < K < 1200 N/m are tested. Limited results are presented for three cylinders. The main conclusions are: (1) For the tested parameters, two cylinders harness 2.56–7.5 times the power of a single cylinder; the corresponding efficiency ratio is 2.0–6.68. (2) The MHK power harnessed by the upstream cylinder is increased by up to 100%, affected by the downstream cylinder. (3) The MHK power harnessed by the downstream cylinder and its FIO benefit less by the interaction as the spacing becomes smaller. (4) Power-to-volume density increases by nearly two orders of magnitude. | Synergistic Flow Induced Oscillations of Multiple Cylinders in Harvesting Marine Hydrokinetic Energy | 10.1007/978-3-030-55594-8_26 |
2021-01-01 | Vibration damping is a paramount factor in understanding vibrations in structures because the response of a structure under stationary dynamic loads, at resonance, is directly (inversely) proportional to the damping. Also, transient response of a structure decays exponentially at a rate determined by the damping factor and eigenfrequency of each mode. Thus, to compute forced responses, the damping must be known. Despite damping thus being of large importance, there is limited knowledge of the damping of ships in general and of large container ships in particular. Some studies have suggested the damping is speed dependent, whereas others have not. In the last ISSC 2018 report, it was concluded that more data are needed from full-scale measurements. In the present paper the dynamics of a large container ship in operation is investigated, from full scale measurements in different operation conditions. State-of-the art, so-called operational modal analysis (OMA) is used for computing the eigenfrequencies, damping factors, and mode shapes of the ship. It is discussed how particularly the vibration damping varies with different operating parameters such as cargo, speed, and sea state. | Vibration Damping of Large Containership in Operation | 10.1007/978-981-15-4672-3_20 |
2021-01-01 | Grand construction projects all over Egypt require large infrastructure projects. In Northern Egypt where large buildings are needed for new developments, large areas of soft soils are abundant. These buildings transfer heavy static and dynamic loads to soil. Soft clays can be stabilized to carry these loads with minimum settlements and high shear strength. This research focuses on improving the static and dynamic properties of soft clay using chemical stabilization by cement or lime. undisturbed samples were collected from Belkas, Dakahleia – Egypt. The engineering properties were determined and classified as soft silty clay (CH). Low proportions of added cement or lime between 4 and 8% by weight were mixed with the natural samples, The effect on the strength and dynamic properties of reconstituted samples were investigated. Three series of a free-fixed type of resonant column tests were conducted in torsional mode on natural soft silty clay, stabilized soft silty clay with cement, and stabilized soft silty clay stabilized with lime. The influence of confining pressure and stabilizer amount on dynamic shear modulus (G_max) and material damping (D_min) for natural and treated samples were studied. The threshold shear strain γ_th for each treatment type is investigated at small-to-medium shear strain amplitude levels to investigate the effect of torsional shearing on material softening behavior and normalized shear modulus (G/G_max) degradation of treated soil. The results are presented and discussed displaying percentages stabilizers that led to significant improvement in the soil stiffness and shear modulus using cement or lime as the stabilizers, The damping ratio, (D_min) decreased by increasing stabilizers dosage. | Dynamic Response of Stabilized Soft Clay Under Cyclic Loading at Low Shear Strain Level | 10.1007/978-3-030-62908-3_13 |
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