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2020-01-01 | This paper presents a novel two-degree-of-freedom (two-DOF) passive damping system dedicated to the vibration suppression of a dual-axis precision force sensor. The damping system consists of two identical eddy current dampers (ECDs), each of which utilizes a double-layer Halbach-array permanent magnet (PM) structure and a middle-layer copper plate to generate a large damping force. Analytical models are established to predict the damping characteristic of the ECD. The finite element simulations are conducted to verify the effectiveness of the analytical models. The simulation results indicate the large damping coefficient of the developed ECD. | A Dual-Axis Force Sensor with Passive Eddy Current Damper for Precision Measurement | 10.1007/978-3-030-44267-5_11 |
2020-01-01 | Due to the fact that the vehicle suspension system is complicated, how to identify the structure-borne path of road noise efficiently and accurately is the key point of road noise diagnosis. In this research, a transfer path diagnosis approach for road noise diagnosis is proposed. In terms of methodology, the proposed method is based on the multiple coherence method, and it also needs to take into account the mechanical transfer paths of road noise. Therefore, the numerical implementation of multiple coherence method is presented first and then the classification of mechanical transfer paths of road noise. As for the practical application, first of all, the presented approach is used to investigate the transfer paths of a 79 Hz road-induced drumming problem of a vehicle. And then the mechanism for above-mentioned problem is predicted combining the modal results of relevant components. Furthermore, the predicted result is validated by adding a tuned 78 Hz damper to the lower control arm on both sides of the rear suspension. The experimental result indicates that the peak value at 79 Hz corresponding to road-induced drumming noise reduces by 10 dB(A), which proves the correctness of the inference for drumming noise and further demonstrates the validity of the proposed diagnosis approach. | Diagnosis of Road-Induced Drumming Noise of Passenger Car Based on Multiple Coherence Method | 10.1007/978-981-13-9718-9_57 |
2020-01-01 | In this note, we study a damped plate equation. On the one hand, the action of the damping creates a smoothing effect in Gevrey classes, on the other hand, it dissipates the energy of the solution. | Decay Estimates and Gevrey Smoothing for a Strongly Damped Plate Equation | 10.1007/978-3-030-36138-9_10 |
2020-01-01 | In this present study, the efficiency of the combined circular tuned liquid column ball damper (CTLCBD) and tuned liquid column ball damper (TLCBD) is demonstrated in order to suppress the torsional responses of building, excited by wind. The results from the numerical simulation reveal that combined CTLCBD and TLCBD is effective in suppressing torsionally coupled response. The reduction achieved by the damper system is around 38% in peak rotational displacement and around 28% in peak rotational acceleration. | Vibration Control of Torsionally Coupled Building Using Tuned Liquid Column Ball Damper | 10.1007/978-981-15-5693-7_41 |
2020-01-01 | With an increasing demand for safe and efficient rail transportations with high availability, there is an interest to apply condition based maintenance on railway systems to increase the total system reliability. A condition based maintenance system utilizes data collecting, data processing and decision making to schedule maintenance based on the actual condition of components. In this paper a rail vehicle is simulated at varying operational conditions, and with degraded dampers in the primary and secondary suspension. A large database of simulations is generated and is used to train and test classification algorithms to detect upcoming damper faults, introduced as a fault factor multiplied with the damper coefficients. Frequency response functions between accelerometer signals in the carbody, bogieframes and axles are used as fault indicators, predictors, fed to the classification algorithms. The algorithms are evaluated for a varying number of included frequency response functions, as well as varying operational conditions in the training datasets. The linear Support Vector Machine and 1-Nearest-Neighbour classifier both indicate high capability of correctly classifying damper degradations. | Condition Monitoring of Rail Vehicle Suspension Elements: A Machine Learning Approach | 10.1007/978-3-030-38077-9_14 |
2020-01-01 | This paper presents the new vibration model of the horizontal washing machine (HWM) using a nonlinear geographic of the suspension system with nonlinear friction force - velocity (F-V) relationship of dampers obtained from experiment. Furthermore, using the dissipated energy function of dampers (Ed) criteria, some results of the effect of the spring stiffness on the dampers’ loading level are achieved. The simulation was done in Matlab/Simulink^® environment. The results were then compared with experimental validation results to determine the suitability of the model. The conclusions can provide some available evidences for the design and improvement of nonlinear dampers. | New Vibration Model to Analyze the Correlation of Components in the Washing Machine Suspension System | 10.1007/978-3-030-37497-6_58 |
2020-01-01 | In engines, torsional vibration is inevitably caused by the fluctuation of the engine torque. Therefore, the establishment of torsional vibration damper is the necessary measure to diminish the torsional vibration. In this paper, an experimental study was carried out in a gasoline engine to analyze the bolt tightening of torsional vibration damper. The influence of the friction coefficient of the bolt of the torsional vibration damper, the material properties of the torsional vibration damper, and the axial force calibration were studied. The results show that the changes in the friction coefficient of the bolt and the material of the torsional vibration damper have great impacts on the bolt torque. It is effective to improve the bolt tightening state by checking the axial force and establishing suitable tightening parameters. | Experimental Study on Bolt Tightening of Torsional Vibration Damper | 10.1007/978-981-13-9718-9_49 |
2020-01-01 | Cancer recurrence is one of the most imminent problems in the current world of medicine, and it is responsible for most of the cancer-related death rates worldwide. Long-term administration of anticancer cytotoxic drugs may act as a double-edged sword, as necrosis may lead to renewed cancer progression and treatment resistance. The lack of nutrients, coupled with the induced hypoxia, triggers cell death and secretion of signals that affect the tumor niche. Many efforts have been made to better understand the contribution of hypoxia and metabolic stress to cancer progression and resistance, but mostly with respect to inflammation. Here we provide an overview of the direct anticancer effects of necrotic signals, which are not necessarily mediated by inflammation and the role of DAMPs (damage-associated molecular patterns) on the formation of a pro-cancerous environment. | Necrosis in the Tumor Microenvironment and Its Role in Cancer Recurrence | 10.1007/978-3-030-35727-6_6 |
2020-01-01 | A comparative study between a tuned mass damper (TMD) and a nonlinear energy sink (NES), attached to a linear two-degree-of-freedom (DoF) mechanical system under impulsive excitation, is performed. The analysis involves different scenarios; namely, we consider the cases in which only one or both modes of the primary system are initially excited. First, exploiting a harmonic balance approach, the invariant manifolds describing the slow dynamics of the system are identified. Then, introducing the so-called relative dissipation power, the performance of the two absorbers is carefully compared, based on analytical computations. Results illustrate that the two absorbers have similar performance, albeit resorting to different mechanical properties: the NES achieve a broad frequency band of operation exploiting nonlinearity, while the TMD by increasing damping. An interesting feature, highlighted by the invariant manifold, is that the NES is generally unable to resonate with more than one mode of the primary system at the same time, rather, it experiences a sort of modal cascade. | Comparative Analysis of NES and TMD Performance via High-Dimensional Invariant Manifolds | 10.1007/978-3-030-23692-2_13 |
2020-01-01 | The history of formulation of the efficient method for studying the nonlinear dynamic response of structures, damping features of which depend on natural frequencies of vibrations, is presented. This technique is the modified version of the method of multiple scales, the efficiency of which is illustrated by the examples of nonlinear vibrations of suspension bridges and plates subjected to the conditions of the internal resonances. | The fractional derivative expansion method in nonlinear dynamic analysis of structures | 10.1007/s11071-019-05055-w |
2019-12-18 | In this work, the quantisation of particle propagating in a dissipative harmonic medium will be investigated using the creation and annihilation operator formalism, which is more appropriate in some fields of physics. Modelling the problem as damped harmonic oscillator, the equations of motion are then written in terms of Poisson brackets, and the Heisenberg equations are written in terms of the quantum counterpart of the Poisson bracket, known as commutators. The creation and annihilation operators are introduced and used to obtain the energy and eigenstates. Our results are in exact agreement with different quantisation approaches as in Serhan et al , J. Math. Phys. 59 , 082105 (2018). The normalisable coherent states are obtained as eigenstates of the annihilation operator, which overcome the non-normalisability of these states that appeared via the dual coordinate method. | Quantisation of particle motion in dissipative harmonic environment | 10.1007/s12043-019-1882-4 |
2019-12-13 | By using variational methods, we obtain infinitely many nontrivial periodic solutions for a class of damped vibration systems with superquadratic terms at infinity. By using some weaker conditions, our results extend and improve some existing results in the literature. Besides, some examples are given to illustrate our results. | Multiple periodic solutions for damped vibration systems with superquadratic terms at infinity | 10.1186/s13661-019-01306-2 |
2019-12-13 | In this paper, we consider convergence rates to solutions for the damped system of compressible adiabatic flow through porous media with boundary effect. Compared with the results obtained by Pan, the better convergence rates are obtained in this paper. Our approach is based on the technical time-weighted energy estimates. | Convergence rates to the damped system of compressible adiabatic flow through porous media with boundary effect | 10.1186/s13661-019-01304-4 |
2019-12-12 | In this article, we study the existence of positive periodic solutions of second order damped boundary value problem u ″ + p ( t ) u ′ + q ( t ) u = g ( t , u , u ′ ) $u'' + p(t)u'+q(t)u = g(t,u,u')$ , u ( 0 ) = u ( T ) $u(0) = u(T )$ , u ′ ( 0 ) = u ′ ( T ) $u'(0) = u'(T )$ . The main tools are the nonlinear alternative principle of Leray–Schauder and Schauder’s fixed point theorem. We emphasize that the damped term and nonnegative Green’s functions are the key points. We also apply the results to examples for testing. Some recent results in the literature are improved and generalized. | Periodic solutions for second order damped boundary value problem with nonnegative Green’s functions | 10.1186/s13661-019-01302-6 |
2019-12-11 | In this paper, we consider the blow-up for solutions to a weakly coupled system of semilinear damped wave equations of derivative type in the scattering case. The assumption on the time-dependent coefficients for the damping terms means that these coefficients are summable and nonnegative. After introducing suitable functionals proposed by Lai-Takamura for the corresponding single semilinear equation, we employ Kato’s lemma to derive the blow-up result in the subcritical case. On the other hand, in the critical case, an iteration procedure based on the slicing method is employed. Let us point out that we find as critical curve in the p - q plane for the pair of exponents ( p , q ) in the nonlinear terms the same one as for the weakly coupled system of semilinear not-damped wave equations with the same kind of nonlinearities. | Nonexistence of Global Solutions for a Weakly Coupled System of Semilinear Damped Wave Equations of Derivative Type in the Scattering Case | 10.1007/s00009-019-1445-4 |
2019-12-07 | In this paper we obtain the best Ulam constant for the second order linear differential operator with constant coefficients. As application we prove that damped oscillating systems are stable in Ulam sense while the harmonic oscillating systems are nonstable. Moreover, an optimal estimation between the solutions of the perturbed an unperturbed oscillating systems is given. | On the best Ulam constant of the second order linear differential operator | 10.1007/s13398-019-00776-4 |
2019-12-01 | In this article we consider a nonlinear viscoelastic Petrovsky equation in a bounded domain with distributed delay $$\begin{aligned} \begin{aligned}&|u_{t}(x,t)|^{l}u_{tt}(x,t)+\Delta ^{2}u(x,t)-\Delta u_{tt}(x,t)-\displaystyle \int _{0}^{t}h(t-\sigma )\Delta ^{2}u(x,\sigma )\,d\sigma +\mu _{1}u_{t}(x,t)\\&\quad +\int _{\tau _{1}}^{\tau _{2}}\mu _{2}(s)u_{t}(x,t-s)ds=0,\quad x\in \Omega ,\; t>0, \end{aligned} \end{aligned}$$ | u t ( x , t ) | l u tt ( x , t ) + Δ 2 u ( x , t ) - Δ u tt ( x , t ) - ∫ 0 t h ( t - σ ) Δ 2 u ( x , σ ) d σ + μ 1 u t ( x , t ) + ∫ τ 1 τ 2 μ 2 ( s ) u t ( x , t - s ) d s = 0 , x ∈ Ω , t > 0 , and prove a global solution existence result using the energy method combined with the Faedo–Galerkin approximation , under condition on the weight of the damping and the weight of distributed delay. Also we establish the exponential stability of the solution by introducing a suitable Lyapunov functional. | Existence of global solutions and decay estimates for a viscoelastic Petrovsky equation with internal distributed delay | 10.1007/s12215-018-0373-7 |
2019-12-01 | The dynamic behavior of soil material is of importance in construction and geotechnical engineering. This study focuses on the dynamic properties of silty sands, particularly on the effect of plastic fines content (FC) on the shear modulus and damping ratio. Natural sand (Taiyuan sand) and fines (Taiyuan loess) were collected from an engineering site in China. Fujian standard sand, kaolin, and stone powder were also used for comparison. Fines plasticity, FC, effective confining pressure, and relative density were considered. A series of tests were conducted using a Stokoe-type resonant column apparatus manufactured by GDS Instruments, UK. The small strain shear modulus ( G _max) of the samples were investigated under various test conditions. Hardin’s function was used to fit the experimental data. The results indicate that the shear modulus changes non-linearly with increasing FC. The shear modulus of various mixtures initially decreases and then increases. The threshold FC (FC_th) of Taiyuan and Fujian sand mixtures is 30% and 20%, respectively, which indicates that the FC_th is related to the host sand. The addition of plastic fines will decrease the shear modulus. The effect of non-plastic fines on the shear modulus of sand–fines mixtures is dependent on FC. The damping ratio of various mixtures initially increases and then decreases with increasing FC. The addition of fines will increase the damping ratio. Moreover, the damping ratio of plastic fines mixtures is higher than that of non-plastic fines mixtures. The values of the fitting constant, namely, A , n , and d , are related to fines plasticity. The findings of this study can provide a reference for engineering designers. | The effect of plastic fines on the shear modulus and damping ratio of silty sands | 10.1007/s10064-019-01522-1 |
2019-12-01 | Of concern is a nonlinear second order initial value differential problem involving a convolution of a singular kernel with the derivative of the state. The problem describes the dynamics of a single-degree-of-freedom fractional oscillator. It is a generalization of the standard harmonic oscillator. The model also generalizes some well-known fractionally damped second order differential equations such as the Bagley–Torvik equation. Moreover, it extends models using exponential non-viscous damping to the more challenging singular case. We prove an exponential stability result of the equilibrium using the multiplier technique. A new energy functional, different from the classical one and different from the one obtained by the diffusive representation, is introduced. | Long time behavior for a fractional Picard problem in a Hilbert space | 10.1007/s12215-018-0380-8 |
2019-12-01 | The dynamic nature of radiation damping is exploited in a fluoride fiber–based plasmonic sensor in terms of variable temperature ( T ) and Ag layer thickness ( d _m) at certain near-infrared wavelengths. The optimum point of radiation damping, which is stimulated by the presence of a graphene monolayer and its dynamic dispersive and thermo-optic properties as per Kubo formulation, causes extremely huge enhancement in sensor’s performance (analyzed in terms of its figure of merit, i.e., FOM). The simulation indicates that at λ = 1550 nm, the optimum radiation damping is achieved at d _m = 35 nm and T = 322.7 K leading to a peak FOM value of 27,086 RIU^−1. At λ = 1310 nm, the peak FOM is 16,736.65 RIU^−1 for d _m = 35.4 nm and T = 315.6 K. The above peak FOM values are significantly greater than those presently available with plasmonic sensors. | SPR Sensing Enhancement with Dynamic Radiative Damping Stimulated by Graphene Conductivity Under Temperature Variation in NIR | 10.1007/s11468-019-00980-3 |
2019-12-01 | A plate submerged at a certain depth underneath the sea surface has been proposed as a structure type for different purposes, including motion response reduction, wave control, and wave energy harvesting. In the present study, the three-dimensional wave radiation problem is investigated in the context of the linear potential theory for a submerged ring plate in isolation or attached to a floating column as an appendage. In the latter case, the ring plate is attached at a certain distance above the column bottom. The structure is assumed to undergo a heave motion. An analytical model is developed to solve the wave radiation problem via the eigenfunction expansion method in association with the region-matching technique. With the velocity potential being available, the hydrodynamic coefficients, such as added mass and radiation damping, are obtained through the direct pressure integration. An alternative solution of radiation damping has also been developed in this study, in which the radiation damping is related to the Kochin function in the wave radiation problem. After validating the present model, numerical analysis is performed in detail to assess the influence of various plate parameters, such as the plate size and submergence depth. It is noted that the additional added mass due to the attached ring plate is larger than that when the plate is in isolation. Meanwhile, the radiation damping of the column for the heave motion can vanish at a specific wave frequency by attaching a ring plate, corresponding to a condition that there exist no progressive waves in the exterior region. | Wave Radiation by A Submerged Ring Plate in Water of Finite Depth | 10.1007/s13344-019-0064-y |
2019-12-01 | In boring process, tool vibration is an important parameter which results in progressive tool wear, poor surface finish and cutting tool damage. This tool vibration was reduced by passive, semi-active and active techniques which are used by various researchers in the past. In this paper, various techniques employed to prevent tool vibration in boring operation are reviewed, analyzed and presented. It was inferred that the control of tool vibration was effective by utilizing appropriate damping mechanism in the boring process. Also, from the overall review of the literature, it was observed that as the tool wear started to progress, the tool vibration gets increased which leads to failure of the tool. In this review paper, scope of developing a damper where tool vibration can be suppressed by varying the damping ability based on requirement was established. | Suppression of Tool Vibration in Boring Process: A Review | 10.1007/s40032-019-00531-z |
2019-12-01 | This paper deals with the evolution of the shear modulus G and the damping D as a function of the shear deformation of the soil, using data from field and laboratory tests. The studied experimental site is located in port area of the city of Bejaia (Algeria), which has already been the subject of numerous geotechnical and geophysical investigation campaigns as part of construction of important industrial projects. In a first step, the geological, tectonic and hydrological contexts of the region are described, as well as the results of the geophysical and geotechnical tests. The result of this first step is the development of a database from field and laboratory tests. In a second step, monotonic and cyclic triaxial tests are performed to identify the dynamic properties on a reconstituted silty clayey sand soil in the laboratory with a characteristic relatively close to the ground in place. In a third step, a numerical analysis is carried out using a FLAC^2D code. The nonlinear elastic model proposed by Ramberg–Osgood and limited by the Mohr–Coulomb criterion is used. The comparison between the numerical results and the experimental data shows the applicability of the Ramberg–Osgood model to describe the dynamic behavior of muddy silty sand and muddy sands of Bejaia. | Evaluation of Dynamic Soil Properties for Alluvial Plain of Bejaia Using Field Data and Laboratory Tests | 10.1007/s10706-019-00933-x |
2019-12-01 | Basin scale seiches in lakes are important elements of the total energy budget and are a driver of fluxes of important ecological parameters, such as oxygen, nutrients, and sediments. At present, the extraction of the damping ratios of surface seiches, which are directly related to the capacity of seiches to drive these fluxes through the increased mixing of the water column, is reliant on spectral analysis which may be heavily influenced by the transformation of water level records from the time domain to the frequency domain, and which are sensitive to the level of noise present within the data. Existing spectral-based methods struggle to extract the periods of surface seiches which are of similar magnitude due to the overlap between their spectral responses. In this study, the principles of operational modal analysis, through the random decrement technique (RDT), currently used primarily in the analysis of high rise structures and in the aeronautical industry and not previously applied within the fields of limnology or ecology, are applied to barotropic seiches through the analysis of water level data for Lake Geneva, Switzerland, and Lake Tahoe, USA. Using this technique, the autocorrelation of the measurements is estimated using the RDT and modal analysis can then be carried out on this time-domain signal to estimate periods of the dominant surface seiches and the corresponding damping ratios. The estimated periods show good agreement with experimental results obtained through conventional spectral techniques and consistent damping ratios are obtained for the dominant surface seiche of Lake Tahoe. The effect of input parameters is discussed, using data for the two lakes, alongside discussion of the application of RDT to the study of internal seiches and current barriers to its application. RDT has great potential for the analysis of both surface and internal seiches, offering a method through which accurate damping ratios of seiche oscillations may be obtained using readily available data without necessitating spectral analysis. | A novel technique for experimental modal analysis of barotropic seiches for assessing lake energetics | 10.1007/s10652-019-09677-x |
2019-12-01 | Natural fiber composites have become a new tradition as an alternative to conventional materials. To meet this new tradition material testing, newer techniques have been set up that are termed as dynamic mechanical analysis (DMA), which is an adaptable methodology that accompanies the more traditional techniques. Through these techniques, it is summarized that interconnected bonds between reinforced natural fibers within different matrix materials will affect the dynamic variables like storage modulus (E′), loss modulus (E″), and damping factor (tan δ), and also, it was stated that these are temperature dependent. The dynamic variables were unfavorably affected by the improvement in the length of fibers and fiber loading, but geometric changes (developments) were not considered. Frequent uncertainties in the dynamic loading in any structure are because of noises, shocks, winds, tides in the ocean and some of the live and imbalanced loads, etc. Much importance was given to vibration damping parameters for structural applications in order to have an improvement in the effectiveness, performance, and freeness in some of the building constraints. In this review, the employability of different natural fibers in forming composites with different matrix materials and the impact of fiber length, chemical treatment, and compositions on the dynamic mechanical characteristics were discussed in detail. Graphical abstract | Dynamic mechanical properties of natural fiber composites—a review | 10.1007/s42114-019-00121-8 |
2019-12-01 | While doing vibration analysis in terms of the dynamic response of a beam, the end conditions, in most of the cases, are assumed to be fixed, simply supported, free or sliding imposing an ideal condition of end support displacement. But, in real engineering structures, the end supports are non-ideal (for example welded, riveted etc.) and allow certain degree of translational or rotational motion of the support ends. To simulate the effect of real engineering boundary states, a combination of linear and torsional springs has been considered at the two boundaries of the beam structure. The theoretical analysis of free undamped beam structure with elastically restrained end conditions has been undertaken using approximation of the modal displacement as a Fourier cosine series to generate natural frequencies and corresponding mode shape equations. The effect of variation in stiffness values of the boundary springs on the vibration characteristics (natural frequency, mode shapes and dynamic response) has been presented for vibration conditions for the free undamped beam structure. Thereafter, forced undamped and damped (taking combined effects of both viscous and structural damping) beam structures have been theoretically analysed to generate response equation. Finally, numerical assessment has been undertaken to present the effect of damping ratio, forcing frequency and force magnitude on the response of a nearly clamped beam and has been compared with the response of an undamped beam under similar forcing and boundary condition. The results indicate considerable effects of real boundary condition, on the vibration characteristics and dynamic response of beam structures thus cannot be ignored in design of real engineering structures. Further, the presence of damping does not change the vibration characteristics beam structures, but is useful in achieving steady-state condition of response for a harmonic force input. The technique presented provides a simplified and convenient tool for obtaining vibration response for real engineering boundary supports. Further, the beam model can be extended for analysis of plate structures considering non-ideal boundary conditions. | Dynamic Response of a Damped Euler–Bernoulli Beam Having Elastically Restrained Boundary Supports | 10.1007/s40032-018-0485-z |
2019-12-01 | Different thermal analysis techniques were used to study the effect of fillers and ionic liquids (ILs) on the vulcanization process, thermal and dynamic mechanical properties of acrylonitrile–butadiene elastomer (NBR). The products of the studies were composites of NBR filled with hydrotalcite, nanosized silica or carbon black. ILs such as 1-butyl-1-methylpyrrolidinium (BMpyrrolBF_4), 1-butyl-4-methylpyridinium (BMpyrBF_4) or 1-butyl-1-methylpiperidinium (BMpipBF_4) tetrafluoroborates were applied to improve the dispersion degree of the curatives and filler particles in the elastomer and to increase the efficiency of vulcanization. The differential scanning calorimetry results indicated that ILs reduced the vulcanization temperature of NBR compounds and increased the homogeneity of cross-link distribution in the elastomer network. NBRs filled with carbon black or silica exhibited similar thermal stabilities, whereas hydrotalcite reduced the temperature of thermal decomposition. The lowest mechanical loss factors were determined for vulcanizates filled with nanosized silica. | Thermal characterization of the effect of fillers and ionic liquids on the vulcanization and properties of acrylonitrile–butadiene elastomer | 10.1007/s10973-019-08187-8 |
2019-12-01 | A considerable interest has been generated in recent years in the use of thermoplastic polymers as matrices in the manufacture of advanced composites that require high reliability during long-term operations. In this research, a new Elium® acrylic matrix developed by Arkema was studied to evaluate the accelerated test methodology based on time-temperature superposition principle of Carbon Fiber/Elium® 150 composites. The results show that the high frequencies increase the glass transition (Tg) to higher values because the free volume is favored by polymer chains movement. In addition, artificial neural network has been used to model the temperature-frequency dependence of dynamic mechanical over the wide range of temperatures and frequencies due to its complex non-linear behavior. It has been observed that low frequencies result in low damping due to the lower internal friction, while high frequencies provide greater stiffness to the chains, resulting in a high damping. The long-term life prediction using master curves confirms that this new material can be considered to acoustic or vibrational damping purposes, considering its use in temperatures above Tg. | Prediction of temperature-frequency-dependent mechanical properties of composites based on thermoplastic liquid resin reinforced with carbon fibers using artificial neural networks | 10.1007/s00170-019-04486-4 |
2019-12-01 | In the current study, the dynamic behavior of two planar mechanisms with revolute joints, in the presence of clearances is investigated. Subsequently, a control scheme with the aim of restraining the clearance and maintaining a more stable behavior is proposed. This approach is based on using tuned mass damper (TMD) in order to reduce the effects of clearances in mechanisms for passive control purpose. The applied absorber’s mass is insignificant and they are little in size. By attaching two perpendicular absorbers in order to control the clearance, the oscillations are notably reduced. The proposed methodology is applied to planar multibody mechanical systems with revolute clearance joints with a view to demonstrating its features. The absorber performance is evaluated for changes around the designed state and the results show that the designed absorbers have a good robustness with variations to changes in different parameters. | Effects of passive vibration absorbers on the mechanisms having clearance joints | 10.1007/s11044-019-09684-2 |
2019-12-01 | Accurate electromagnetic force control in a high speed on/off valve actuator (HSVA) can improve the performance of a vehicle braking system, and an accurate theoretical model is the key to smoothly controlling the high speed on/off valve. Therefore, a nonlinear model of an HSVA is proposed in this paper. Three subsystems are modeled as a spring/mass/damper system, a nonlinear resistor/inductor system and a multiwall heat transfer system, respectively. Then, a sliding-model controller combined with a sliding-model observer is designed to adjust the electromagnetic force for an accurate HSVA state control, taking the effect of the coil heating into account. The feasibility of the three submodels and the sliding-model controller are verified by comparing the simulation results with the experimental results obtained on a test bench. Our study shows that the three subsystems are coupled to one another through resistance, displacement, and temperature. When the excitation voltage exceeds 9 V, the coil temperature can reach more than 150 degrees Celsius within 300 s, and the electromagnetic force decreases by approximately 30 %. However, by applying the above control strategy, the electromagnetic force can also be stable, fluctuating within 5 % even if the temperature of the coil rises to the thermal equilibrium temperature. | Modeling and Control of A High Speed On/Off Valve Actuator | 10.1007/s12239-019-0114-8 |
2019-12-01 | This study investigates the displacement transmissibility of single-degree-of-freedom systems with a Coulomb friction contact between a mass and a fixed or oscillating wall. While forced vibration and base motion problems have been extensively investigated, little work has been conducted on the joined base-wall problem. Based on the work of Den Hartog (Trans Am Soc Mech Eng 53:107–115, 1930 ), analytical expressions of the displacement transmissibility are derived and validated numerically. The mass absolute motion was analysed in the joined base-wall motion case with a new technique, with results such as: (1) the development of a method for motion regime determination; (2) the existence of an inversion point in transmissibility curves, after which friction damping amplifies the mass response; (3) the gradual disappearing of the resonant peak when the ratio between friction and elastic forces is increased. Moreover, numerical analysis provides further insight into the frequency region where mass sticking occurs in the base motion problem. | Displacement transmissibility of a Coulomb friction oscillator subject to joined base-wall motion | 10.1007/s11071-019-04983-x |
2019-12-01 | This paper presents the shunt damping of a unimorph piezoelectric mirror intended to be used as an active secondary corrector in future space telescopes. We propose to take advantage of the actuation capability of the piezoelectric mirror, to increase its natural damping during the critical launch phase of the spacecraft. The piezoelectric actuators, intended to be used for active optics, are shunted on a passive resistive and inductive RL circuit during the launch operation. The proposed concept is verified numerically and experimentally on a piezoelectric deformable mirror prototype, developed on behalf of the European Space Agency. We show that the shunt damping significantly reduces the response of the most critical mode of the mirror (− 23 dB) as well as the stress in the mirror when subjected to a typical vibro-acoustic launch load. This reduces the risk of damaging the mirror during the delicate launch phase, without increasing the complexity of the design. | Damping of piezoelectric space instruments: application to an active optics deformable mirror | 10.1007/s12567-019-00278-4 |
2019-12-01 | The interaction between a moving two-level atom and squeezed coherent states in the presence of Kerr like medium and an external classical field is studied. We consider the cavity field not to be isolated, so the field suffers from a decay rate. Under the rotating wave approximation, and some certain transformations, the system is transformed to the usual Jaynes-Cummings model with Kerr medium as well as a damping term. The probability amplitude is obtained when the atomic system is prepared in its excited state. The results show that, the evolution of the atomic population inversion, the Pegg-Barnett phase, and the quasi-probability distributions are decaying in the presence of damping. While the detuning parameter delays the decay rate, also enhances a part of the phase space and decrease the rate of another part. The system is very sensitive to the Kerr like medium, where it plays a role in shortening the collapse periods, however it works to cracking and diffusing the phase space. | External Classical Field and Damping Effects on a Moving two Level atom in a Cavity Field Interaction with Kerr-like Medium | 10.1007/s10773-019-04268-4 |
2019-12-01 | In this paper, optimization of the design of a fuzzy-genetic controller was done through the IDA and ET analysis methods. Combination controllers versus classical control methods have the ability to handle nonlinear and complex problem, learnability, adaptability and robustness to errors. However, one of the main shortcomings of fuzzy Type-1 systems is ignorance of the uncertainties in the fuzzy rule base. Studies which have been conducted on the benchmark structures show that the training of controllers is generally based on the control of the index of damage in a particular earthquake. Controller performance in case of different loading conditions depends on the characteristics of the earthquake used in the training phase, and the controller performance, in other conditions, is not optimal. In this study, the results of the IDA and ET methods for training and designing controllers, as a solution for reducing the uncertainty in structural behavior and loading, were used. Also, the IDA method was used to evaluate the performance of controllers. Examining the strengths and weaknesses of controllers in a wider range of dynamic loading conditions through using the IDA method is applicable. Moreover, evaluation of the results based on a wider range of earthquakes with different maximum accelerations can be done through the IDA method. A benchmark building which was equipped with a MR damper was used in order to evaluate the proposed control method. The results of structural analysis in the proposed controller with uncontrolled structure response, and controlled structures under fuzzy controller that was trained under a special earthquake, were compared and evaluated. Numerical results show that controller training under ET-generated accelerogram in the proposed controller is more effective than other controllers and structural responses under different loading conditions will be optimized. The use of the proposed controller reduces damage in the structure by 15–20% in comparison with other controllers. | A Study on the Optimization of the Performance of Type 1 Fuzzy Controller Based on the IDA Method | 10.1007/s40996-018-0220-2 |
2019-12-01 | An adjustable cuckoo-search wavelet-based fuzzy logic controller (ACSWBFLC) is introduced to mitigate structural responses during seismic motion by using magnetorheological (MR) dampers. The ACSWBFLC incorporates four algorithms: discrete wavelet transform (DWT), fuzzy logic controller (FLC), modified Bouc–Wen model and geometrical nonlinearity algorithm. DWT is applied to acquire the local energy distribution of seismic excitation over the frequency bands. These online data are transmitted to FLC to operate MR damper intelligently based on online excitation frequency. Furthermore, modified Bouc–Wen phenomenological algorithm was utilized to generate the nonlinear behavior of the MR dampers. A wavelet low-pass filter is employed to prevent the stabilization of coefficients and minimize the computational burden. Moreover, geometrical nonlinearities were considered to design a more robust controller. Furthermore, a novel evolutionary algorithm of cuckoo search was used to optimize the placement and the number of MR dampers and sensors in the sense of minimum resultant vibration magnitude. Numerical efforts were considered to validate the efficiency of the proposed FLC. From a designer’s point of view, the proposed ACSWBFLC controller can determine the optimal solutions during a reasonable number of iterations. Finally, numerical examples are utilized to demonstrate the efficiency of ACSWBFLC under several far- and near-fault seismic excitations. The results indicate that ACSWBFLC attenuates the excessive responses of the structural building in real time more efficiently than traditional FLC controllers by using appropriate control force. | Optimal Semi-active Structural Control with a Wavelet-Based Cuckoo-Search Fuzzy Logic Controller | 10.1007/s40996-018-0206-0 |
2019-11-30 | Abstract The origin of the friction between sliding bodies establishes an outstanding scientific problem. In this article, we demonstrate that the energy loss in each microscopic slip event between the bodies readily follows from the dephasing of phonons that are generated in the slip process. The dephasing mechanism directly links the typical timescales of the lattice vibrations with those of the experienced energy ‘dissipation’ and manifests itself as if the slip-induced motion were close to critically damped. Graphical abstract | On the Origin of Frictional Energy Dissipation | 10.1007/s11249-019-1247-7 |
2019-11-28 | We prove spatiotemporal algebraically decaying estimates for the density of the solutions of the linearly damped nonlinear Schrödinger equation with localized driving, when supplemented with vanishing boundary conditions. Their derivation is made via a scheme, which incorporates suitable weighted Sobolev spaces and a time-weighted energy method. Numerical simulations examining the dynamics (in the presence of physically relevant examples of driver types and driving amplitude/linear loss regimes), showcase that the suggested decaying rates are proved relevant in describing the transient dynamics of the solutions, prior their decay: They support the emergence of waveforms possessing an algebraic space-time localization (reminiscent of the Peregrine soliton) as first events of the dynamics, but also effectively capture the space-time asymptotics of the numerical solutions. | The linearly damped nonlinear Schrödinger equation with localized driving: spatiotemporal decay estimates and the emergence of extreme wave events | 10.1007/s00033-019-1223-y |
2019-11-28 | This review of MRF (magnetorheological fluids or MR fluids) brings out the challenges in methods of preparation, difficulties encountered in storage and use, and possible solutions to overcome the challenges. Magnetorheological fluid in the rheological fluid domain has found use due to its ability to change its shear strength based on the applied magnetic field. Magnetorheological fluids are composed of magnetizable micron-sized iron particles and a non-magnetizable base or carrier fluid along with additives to counter sedimentation and agglomeration. Magnetorheological fluids can respond to external stimuli by undergoing changes in physical properties thus enabling several improved modifications in the existing technology enhancing their application versatility and utility. Thus, magnetorheological fluid, a rheological material whose viscosity undergoes apparent changes on application of magnetic field, is considered as a smart material. Such materials can be used for active and semi-active control of engineering systems. Many studies on the designs of systems incorporating MR fluids, mainly for vibration control and also for other applications including brakes, clutches, dynamometers, aircraft landing gears, and helicopter lag dampers, have emerged over last couple of decades. However, the preparation as well as the maintenance of magnetorheological fluids involves several challenges. Sedimentation is a major challenge, even when stored for moderate periods of time. A comprehensive review is made on the problems confronted in the preparation of magnetorheological fluids as well as sustenance of the properties, for use, over a long period of time. Other problems encountered include agglomeration and in-use thickening (IUT) as well as rusting and crusting. Of interest is the mitigation of these problems so as to prepare fluids with satisfactory properties, and such solutions are reviewed here. The control of magnetorheological fluids and the applications of interest are also reviewed. The review covers additives for overcoming challenges in the preparation and use of magnetorheological fluids that include incrustation, sedimentation, agglomeration, and also oxidation of the particles. The methodology to prepare the fluid along with the process for adding selected additives was reviewed. The results showed an improvement in the reduction of sedimentation and other problems decreasing comparatively. A set of additives for addressing the specific challenges has been summarized. Experiments were carried out to establish the sedimentation rates for compositions with varying fractions of additives. The review also analyzes briefly the gaps in studies on MR fluids and covers present developments and future application areas such as haptic devices. | A review of challenges and solutions in the preparation and use of magnetorheological fluids | 10.1186/s40712-019-0109-2 |
2019-11-22 | In this paper, we consider the Cauchy problem for the sixth-order multidimensional generalized Boussinesq equation with double damping terms. By using the improved convexity method combined with Fourier transform, we show the finite time blow-up of solution with arbitrarily high initial energy. | Blow-up for the sixth-order multidimensional generalized Boussinesq equation with arbitrarily high initial energy | 10.1186/s13661-019-01297-0 |
2019-11-15 | The discrete element method (DEM) has been widely used in numerical evaluations in geotechnical engineering; however, simple analysis and verification are still needed to obtain the interaction mechanism between a single particle and a wall under a damping effect. A single freely falling particle model is proposed, and the analytical solutions for the stages of particle freefall, fixed wall contact, and rebound are obtained for different damping types and values. Timestepping in quasi-static and non-quasi-static conditions is considered for better understanding of the DEM hypothesis. The numerical results are quite consistent with the analytical solution. The linear and exponential relationships between the restitution coefficient and the local and viscous damping, respectively, are obtained and formulized. Kinetic energy dissipation is larger with the viscous damping effect than for the local damping when comparing the particle rebound height. Verification of the analytical and numerical solutions has been conducted with the previous studies which shows good agreement. The timestep is no longer constant when the particle velocity exceeds approximately 1.55 m/s, which means the DEM system is no longer quasi-static. | DEM verification of the damping effect in a freely falling particle motion for quasi- and non-quasi-static conditions | 10.1007/s12517-019-4848-4 |
2019-11-12 | We study the existence of subharmonic solutions for a forced pendulum equation with time-dependent damping. The proof is based on the theorem of the least action principle due to Mawhin and Willem (Critical point theory and hamiltonian systems. Springer, Berlin, 1989). Some results in the literature are generalized and improved. | Subharmonic oscillations of a forced pendulum with time-dependent damping | 10.1007/s11784-019-0746-3 |
2019-11-07 | In this paper, we consider wave equations with double damping terms expressed by $$u_{t}$$ u t and $$-\Delta u_{t}$$ - Δ u t and a power type of nonlinearity $$\vert u\vert ^{p}$$ | u | p . We are concerned with mixed problems for these equations in exterior domains of a bounded obstacle. A main purpose is to determine a so-called critical exponent of the power p of the nonlinearity $$\vert u\vert ^{p}$$ | u | p . In particular, in the two dimensional case, our results are optimal, and the critical exponent is given by the Fujita one. This shows a parabolic aspect (as $$t \rightarrow \infty $$ t → ∞ ) of our equations considered in exterior domains, and one can see that the usual frictional damping $$u_{t}$$ u t is more dominant than the strong one $$-\Delta u_{t}$$ - Δ u t as $$t \rightarrow \infty $$ t → ∞ even in the nonlinear problem case. | Critical exponent for semi-linear wave equations with double damping terms in exterior domains | 10.1007/s00030-019-0603-5 |
2019-11-04 | A custom ultrasonic calliper was employed to monitor voluntary and externally excited muscle dynamics with synchronous electromyography. The activation, hold, and relaxation phases of the gastrocnemius muscle were monitored for maximum voluntary isometric contraction. Muscle belly shortening occurred during contraction and a post-contractile overshoot (lengthening) and subsequent exponential recovery of muscle dimension to the baseline were observed. Both the overshoot and recovery are attributed to the muscle as suggested by combined monitoring including electromyography and modelling with a lumped mechanical circuit containing idealized elements, such as a bidirectional linear motor unit, a ratchet, dampers, and springs. The rapid contraction and relaxation phases require a high-order filter or alternatively a kernel filter, attributed to the nervous system as suggested by external electric stimulation, which resulted in faster rise and relaxation times. The respective response function is modelled with an electrical lumped circuit. Together with empirically adjusted reaction times and corrections for droop in the hold phase, the monitored response is represented in close approximation by the combined electrical and mechanical lumped circuits. The refined combinatory model includes a ratchet as a novel nonlinear mechanical element. In combination with determined model parameters, it provides a refined evaluation scheme capable to model monitored muscle dynamics in physical activity in close approximation. | Monitoring skeletal muscle dynamics and modelling the nonlinear response | 10.1007/s42452-019-1560-7 |
2019-11-01 | Dissipative properties of a structural system are difficult to be characterized in real structure. Nevertheless, damping features may be dominant in several operating conditions of railway bridges influencing fatigue life or passenger comfort during train passage. Observations treating real data acquired in operational condition on steel and concrete railway bridges belonging to the Italian network permits to highlight dissipative sources and features. Consequently, linearized modal damping ratios are evaluated through a recursive process on the acceleration signals acquired before, during and after train passages and/or in environmental conditions. Stochastic Subspace Identification has been used to identify state-space dynamical models able to reproduce the vibrations. Through these models, characterized by an increasing number of state-space variables, it is possible to extract modal damping ratios. A mechanical interpretation of damping characteristics is pursued through the evaluation of the differences with respect to a classical Rayleigh proportional damping matrix of the viscous matrix belonging to the identified state-space models determined through the system spectral features. A non-proportional damping index is presented as a basis to determine the influence of different sources of non-proportionality in the damping matrix (as the ballast layer under the track) and to justify the high value of damping observed in specific experimental campaigns. | Measured properties of structural damping in railway bridges | 10.1007/s13349-019-00358-3 |
2019-11-01 | Nonstructural components (NSCs) housed in building structures are subject to semi-narrow band excitations generated via filtering of the ground motion by the supporting building. NSC design forces are generally provided based on adopting a 5% NSC viscous damping ratio ( $$ \xi_{\text{C}} $$ ξ C ), whereas recent experiments illustrate that typical NSCs may exhibit $$ \xi_{\text{C}} $$ ξ C values substantially different, mostly lower, than 5%. This study introduces damping modification factors (DMFs) to adjust NSCs elastic seismic design forces for other $$ \xi_{\text{C}} $$ ξ C values. Elastic floor spectra with different $$ \xi_{\text{C}} $$ ξ C values are developed for floor motions obtained from several code-based designed buildings subjected to ground motion sets with different intensities. Numerical analyses illustrate that due to the narrow-band characteristic of building floor motions, applying conventional DMFs proposed for adjusting ground spectral ordinates may lead to the underprediction of floor spectral ordinates up to 55% for the range of $$ \xi_{\text{C}} $$ ξ C evaluated in this study. Assuming a value of $$ \xi_{\text{C}} $$ ξ C , the amplitude of the DMF for a building floor spectrum is primarily a function of the NSC tuning ratio. For example, for a given floor motion and a $$ \xi_{\text{C}} $$ ξ C value of 2%, the DMF can vary from 1.0 (for a non-tuning condition) to 1.6 (for a tuning condition). To a lesser extent, the DMF is also influenced by supporting building characteristics (e.g., the level of inelastic behavior, fundamental period, height, and lateral-force resisting system), the vertical location of the NSC in the building, and ground excitation characteristics. Practical expressions, which are developed through simple modifications of the prescribed ground spectra DMFs by ASCE/SEI 41-13, are proposed to estimate DMFs for elastic floor spectra. | Damping modification factor for elastic floor spectra | 10.1007/s10518-019-00684-3 |
2019-11-01 | In this paper, we study a semilinear Timoshenko system with heat conduction having two damping effects. The observation that two damping effects might lead to smaller decay rates for solutions in comparison to one damping effect is rigorously proved here in providing optimality results. Moreover, the global well-posedness for small data is presented. | Decay Estimate and Global Existence of Semilinear Thermoelastic Timoshenko System with Two Damping Effects | 10.1007/s10473-019-0601-z |
2019-11-01 | This study is aimed at evaluating seismic responses of a bridge pier isolated by high damping rubber bearing (HDRBs), subjected to intra-plate and inter-plate earthquake ground motion records. In this regard, a conventional bilinear model and two elasto-visco-plasticity-based rheology models (the original rheology model [ 36 ] and an improved rheology model proposed in the current study) of HDRBs have been utilized in this study. In the first part of the paper, the adequacy of the two elasto-visco-plasticity-based rheology models has been checked in predicting the mechanical behaviour of the HDRBs, subjected to sinusoidal loadings. The numerical results of the HDRBs have shown that the improved rheology model can predict the mechanical behaviour of the bearings in a quite better way in comparison to the original rheology model, particularly at higher shear strain levels of the bearings. In the second part, seismic response analysis of a 3-DOF bridge superstructure–pier–foundation ( s – p – f ) system has been evaluated. In the end, nonlinear dynamic analysis using a standard direct time integration approach has been carried out. The seismic responses of the s – p – f system considered in the current study are the pier and deck displacements, the shear force of the bridge pier, the shear strain of the bearing and the total hysteretic energy of the bearings. The analytical results have shown that the rheology modeling of HDRBs has a significant effect on seismic responses of bridge pier. | Seismic Responses of a Bridge Pier Isolated by High Damping Rubber Bearing: Effect of Rheology Modeling | 10.1007/s40999-019-00454-x |
2019-11-01 | In this paper, we consider a one-dimensional porous-elastic system with past history and nonlinear damping term. We established the well-posedness using the semigroup theory and we showed that the dissipation given by this complementary controls guarantees the general stability for the case of equal speed of wave propagation. | General decay of a nonlinear damping porous-elastic system with past history | 10.1007/s11565-019-00321-6 |
2019-11-01 | Moisture and aggressive ions transferring into concrete have detrimental effects on durability of reinforced concrete structure. To tackle this problem, damp-proofing admixtures, like calcium stearate, can be incorporated in the mixture design of concrete to restrict water and aggressive ions’ ingress into concrete. Calcium stearate is a damp-proofing admixture which can provide a water-repellent layer along the capillary pores. As a result, it can reduce permeability of concrete under non-hydrostatic condition. This study investigates the effects of calcium stearate on properties of fresh and hardened concretes. To this end, 12 mixtures with different water-to-cementitious materials (w/cm) ratios but constant ratio of cement paste-to-aggregate were prepared and moist-cured for 180 days. The major outcomes of fresh concrete analysis showed that high dosage of calcium stearate in low w/cm ratios increased the air content and reduced the density of fresh concrete. It also decreased the workability of fresh concrete, regardless of the w/cm ratio and the dosage of calcium stearate. The findings of compressive strength analysis indicated that calcium stearate reduced compressive strength, even when low dosage of calcium stearate was added to the concrete mixture. Based on permeability test results, calcium stearate could improve permeability under non-hydrostatic pressure. However, incorporation of calcium stearate was not found to be an effective approach to decrease permeability under hydrostatic pressure. Finally, microstructure analysis showed that CS has adverse effect on the interfacial transient zone. | The impact of calcium stearate on characteristics of concrete | 10.1007/s42107-019-00161-x |
2019-11-01 | One of the challenges of machining process is to improve the quality of machined surface by reducing the vibration of cutting tools. The research aims to suppress vibration using composite boring bars with an enhanced damping capacity. A new design of boring bars with different cross-sections is considered. Static and dynamic behavior of the proposed tools is investigated. A mathematical model for determining the eigenfrequency is proposed, and it is compared with computer simulation and experimental results. The validity of the proposed models is verified by conducting experimental machining tests in order to study the changes in vibro-acoustic signals depending on the cross-sections of the toolholder. The results show that the composite material significantly improves damping of boring bars, which leads to a reduction in the vibration compared to conventional boring bars. | The effect of composite boring bars on vibration in machining process | 10.1007/s00170-019-04298-6 |
2019-11-01 | Sea ice can attenuate wave energy significantly when waves propagate through ice covers. In this study, a third-generation wave model called simulating wave nearshore (SWAN) was advanced to include damping of wave energy due to friction in the boundary layer below the ice. With the addition of an eddy viscosity wave-ice model, the resulting new SWAN model was applied to simulate wave height in the Bohai Sea during the freezing winter. Its performance was validated with available buoy data near the ice edge, and the new model showed an improvement in accuracy because it considered the ice effect on waves. We then performed a wave hindcast for the Bohai Sea during a freezing period in the winter of 2016 that had the severest ice conditions in recent years and found that the mean significant wave height changed by approximately 16.52%. In the Liaodong Bay, where sea ice concentration is highest, the change reached 32.57%, compared with the most recent SWAN model version. The average influence of sea ice on wave height simulation was also evaluated over a five-year (2013-2017) hindcast during January and February. We found that the wave height decrease was more significant in storm conditions even the eddy viscosity wave-ice model itself showed no advantage on damping stronger waves. | Surface wave simulation during winter with sea ice in the Bohai Sea | 10.1007/s00343-019-8253-3 |
2019-11-01 | A fractional frequency transmission system (FFTS) is the most competitive choice for long distance transmission of offshore wind power, while the Hexverter, as a newly proposed direct AC/AC converter, is an attractive choice for its power conversion. This paper proposes a novel control scheme characterizing the global stability and strong robustness of the Hexverter in FFTS applications, which are based on the interconnection and damping assignment passivity-based control (IDA-PBC) methodology. Firstly, the frequency decoupled model of the Hexverter is studied and then a port-controlled Hamiltonian (PCH) model is built. On this basis, the IDA-PB control scheme of the Hexverter is designed. Considering the interference of system parameters and unmodeled dynamics, integrators are added to the IDA-PB controller to eliminate the steady-state error. In addition, the voltage-balancing control is applied in order to balance the capacitor DC voltages to obtain a better performance. Finally, the simulation results and experimental results are presented to verify the effectiveness and superiority of the IDA-PB controller. | A global asymptotical stable control scheme for a Hexverter in fractional frequency transmission systems | 10.1007/s40565-019-0549-y |
2019-11-01 | The lack of research on the double damper system seriously restricted the impact power’s increase of hydraulic rock drills. The structure and working principle of the double damper system are described. The key parameters such as the unloading damping pressure, damping flow, equilibrium position of the damping piston, and double damper clearance are designed. At last, the design method is applied to the YYG170 hydraulic rock drill. Double damper system’s advantages of high efficiency and fast response are verified by simulation. | Design on Key Parameters of Double Damper System for Hydraulic Rock Drill | 10.1007/s10778-019-00989-5 |
2019-11-01 | The expansion of the wide-area measurement system has provided some control strategies to improve the low-frequency oscillation modes in electric power systems. One of these strategies is to use remote signals for a wide-area damping controller (WADC) to enhance the small-signal stability of the power system. However, the expansion of the Electric Power System increased the generator number connected to the grid, and then some challenges to the WADC design surged such as which input–output pairs of the WADC should be designed to improve the closed loop system damping. Typically, the WADC is a centralized controller and may have many design elements. The interactions among the elements may compromise the central controller design and its purpose. This paper proposes a procedure based on genetic algorithms in order to design a robust central controller. This procedure automatically chooses the input–output pairs of the central controller that will contribute to damping the low-frequency oscillation modes. The design procedure considers topological changes and time delay variations. Small-signal analysis and time-domain nonlinear simulations are carried out in the multi-machine Australian Equivalent Power System, an IEEE benchmark model for small-signal stability analysis. | A procedure to design wide-area damping controllers for power system oscillations considering promising input–output pairs | 10.1007/s12667-018-0304-x |
2019-11-01 | The correct estimation of modal parameters has an important role in ensuring the structural reliability of existing bridges. Operational modal analysis provides rather accurate extraction of natural frequency and mode shapes, but the corresponding damping estimates are subjected to higher uncertainties. This paper reports the results of ambient and free-vibration tests performed on five different typologies of road and railway bridges: steel trusses, steel box, multi-girder reinforced concrete, masonry and reinforced concrete arch bridges. In one case, data acquired by a continuous structural health monitoring system over a period of 1 year are available. In another case, the passage of trains is exploited to perform free decays. The processing of ambient vibrations is performed through several frequency and time-domain identification techniques, whereas the measured free decays are analyzed by the logarithmic decrement method applied to the autocorrelation functions of the signals. Outcomes are compared, evaluating the quality of modal damping estimates and the accuracy of results. The influence on modal parameters extraction of structural typologies, length of acquired time histories and ambient noise, loading and environmental effects are studied. At the end, it is demonstrated that the estimation of modal damping is more reliable for flexible structures when SHM and free-vibration data are available. | Ambient and free-vibration tests to improve the quantification and estimation of modal parameters in existing bridges | 10.1007/s13349-019-00357-4 |
2019-11-01 | Abstract Fe–Cu alloys can be characterized as a system with immiscible components (IC). This statement is based on a weak mutual solubility in the solid state. In addition, Fe–Cu system stratifies in the liquid state at low carbon content. Alloys with ICs have a simple phase composition of almost pure components, which determines a significant practical interest in these alloys. Manufacturers have technologically succeeded in achieving damping alloys of Fe–Cu–Pb system. With proper technological preparation, the final product can be obtained by combining the properties of pure alloy components in the fraction required for practical application. For example, diamagnetic copper has high electrical conductivity and thermal conductivity in Fe–Cu alloys, while ferromagnetic iron has enhanced strength characteristics compared to copper. When the alloy structure is organized in a certain way, a final product can be obtained with high electrical conductivity and thermal conductivity of copper, enhanced strength properties of iron, or a hard magnetic material with copper ductility. The studies of iron-copper alloys focused on the structural studies and measurements of service properties. At the same time, the dynamics of macro- and microstructure alloy formation were not analyzed. In the present studies, the macrostructure formation dynamics of the solid phase enriched with iron at the crystallization melt process during cooling was studied using high-temperature viscometry. Due to the effect of the melt-cooling rate on the size and morphology of crystallizing inclusions, as well as a significant amount of the two-phase area, special attention was paid to the thermophysical analysis of the measurement mode. Analysis of the reliability of the results obtained was made by the viscosity measurement method. The phase state of Fe–Cu system melts was investigated during cooling by changing the damping factor. The analysis of thermophysical processes occurring during measuring the damping factor was carried out. The measuring process of damping decrement takes place under quasi-equilibrium conditions and the cooling rate is close to zero. There are no temperature gradients, both in radius and in height. For compositions Fe_50Cu_50, Fe_40Cu_60, and Fe_30Cu_70, the precipitation dynamics of the solid phase was determined. | Investigation of Two-Phase State of Fe–Cu Melts during Cooling in a Viscometer | 10.3103/S0967091219110032 |
2019-11-01 | Every year earthquake damage causes hundreds of death all over the world. As much as possible, buildings should be kept in the elastic zone during an earthquake, therefore, the failure of building the main member is reduced. This paper investigated an oval steel shaped yielding damper used for seismic protection of chevron steel braced frames. The damper is designed to deform in-elastically under shear deformation to become energy dissipated. This oval steel shaped damper improves the braces buckling problem and reduces the required area cross section of chevron steel bracing members. To do this, eight models of the damper are proposed. For this purpose, finite element (FE) analysis with ABAQUS software is used to investigate and model the oval-shaped damper (OSD). The present study also investigated the damper strength parameters and seismic performance for applying to the steel braces frame. It is shown that the damper added between the chevron braces and the upper beam can reduce the lateral displacement and base frame force. Hence, the oval steel shaped damper is capable to absorb a great amount of energy with a stable hysteresis behavior. To do this, relationships are proposed and developed based on the maximum capability of the damper. The results show that this damper is responsible for absorbing input energy and increasing ductility frame coefficient. By comparing the analytical method and theoretical results, it is calculated that the proposed equations can be adapted to calculate seismic parameters like ultimate stress, ultimate shear force, plastic moment, elastic stiffness, stiffness degradation, deformation capacity, and resistance of the damper and calculate the exact location of plastic hinge. The structural designer, researchers and someone who like to develop the researches, it can be used and benefit for structural engineering. | Cyclic Performance and Mechanical Characteristics of the Oval-shaped Damper | 10.1007/s12205-019-1382-6 |
2019-11-01 | The dynamics of a nonlinear passive vibration absorber conceived to mitigate vibrations of a nonlinear host structure is considered in this paper. The system under study is composed of a primary system, consisting of an undamped nonlinear oscillator of Duffing type, and a nonlinear dynamic vibration absorber, denominated nonlinear tuned vibration absorber (NLTVA). The NLTVA consists of a small mass, attached to the host structure through a linear damper, a linear and a cubic spring. The host structure is subject to free vibrations and the performance of the NLTVA is evaluated with respect to the minimal time required to dissipate a specific amount of the mechanical energy of the system. In order to characterize the dynamics of the system, a combination of numerical and analytical techniques is implemented. In particular, on the basis of the first-order reduced model, slow invariant manifolds of the transient dynamics are identified, which enable to estimate the absorber performance. Results illustrate that two different dynamical paths exist and the system can undergo either of them, depending on the initial conditions and on the value of the absorber nonlinear stiffness coefficient. One path leads to a very fast vibration mitigation, and therefore to a favorable behavior, while the other one causes a very slow energy dissipation. | Impulsive vibration mitigation through a nonlinear tuned vibration absorber | 10.1007/s11071-019-05312-y |
2019-10-28 | For the linear damped wave equation (DW), the $$L^p$$ L p – $$L^q$$ L q type estimates have been well studied. Recently, Watanabe (RIMS Kôkyûroku Bessatsu B 63:77–101, 2017) showed the Strichartz estimates for DW when $$d=2,3$$ d = 2 , 3 . In the present paper, we give Strichartz estimates for DW in higher dimensions. Moreover, by applying the estimates, we give the local well-posedness of the energy critical nonlinear damped wave equation (NLDW) $$\partial _t^2 u - \Delta u +\partial _t u = |u|^{\frac{4}{d-2}}u$$ ∂ t 2 u - Δ u + ∂ t u = | u | 4 d - 2 u , $$(t,x) \in [0,T) \times {\mathbb {R}}^d$$ ( t , x ) ∈ [ 0 , T ) × R d , where $$3 \le d \le 5$$ 3 ≤ d ≤ 5 . Especially, we show the small data global existence for NLDW. In addition, we investigate the behavior of the solutions to NLDW. Namely, we give a decay result for solutions with finite Strichartz norm and a blow-up result for solutions with negative Nehari functional. | The Strichartz estimates for the damped wave equation and the behavior of solutions for the energy critical nonlinear equation | 10.1007/s00030-019-0598-y |
2019-10-26 | We are concerned with global well-posedness of the three-dimensional Vlasov–Poisson system with radiation damping. First, we show that global $$C^1$$ C 1 solutions verifying specified decay conditions are stable under small perturbations. As a consequence, we obtain that a small perturbation of a monopolar and spherically symmetric plasma launches a global $$C^1$$ C 1 solution that preserves quasi-spherical symmetry at the macroscopic level. Second, we show that an initially quasi-neutral datum with $$C^1$$ C 1 regularity launches a global classical solution that propagates quasi-neutrality at the macroscopic level. Finally, we obtain better decay estimates for the radiation damping in both cases. | On global classical solutions of the Vlasov–Poisson system with radiation damping | 10.1007/s00033-019-1211-2 |
2019-10-23 | In this article, we consider a one-dimensional Timoshenko system subject to different types of dissipation (linear and nonlinear damping). Based on a combination between the finite element and the finite difference methods, we design a discretization scheme for the different Timoshenko systems under consideration. We first come up with a numerical scheme to the free-undamped Timoshenko system. Then we adapt this numerical scheme to the corresponding linear and nonlinear damped systems. Interestingly, this scheme reaches to reproduce the most important properties of the discrete energy, namely we show for the discrete energy the positivity, the energy conservation property and the different decay rate profiles. We numerically reproduce the known analytical results established on the decay rate of the energy associated with each type of dissipation. | Discrete energy behavior of a damped Timoshenko system | 10.1007/s40314-019-0982-6 |
2019-10-15 | A feedback control strategy for mitigating pressure oscillations in centrifugal pumping systems is proposed herein. Severe system damage may occur if such oscillations are not adequately damped. According to the experimental data observed, this dominant oscillating mode is operating point-dependent and may become poorly damped under low-speed regime. By using a theoretical control approach, the key parameters that affect the damping of the dominant oscillating mode are investigated. Linear model analysis show that the relative damping of the oscillations depends on the pumping system’s average rotational speed and it is almost zero at low-speed operating condition. To cope with such a dangerous condition, a supplementary feedback damping controller is designed. The damping controller actuates via motor–pump variable-speed drive subsystem. The proposed controller modulates the rotational speed setpoint of the centrifugal pump rotor to produce an extra damping torque. Controller design is performed by using frequency domain techniques, and performance thereof is assessed through experimental tests in a laboratory rig pumping system. The results obtained show that by using the proposed control methodology, it is possible to safely operate the pumping at a low-speed regime, thus preventing damage to the equipment. | Mitigating Oscillations in Hydraulic Pumping Systems by Using a Supplementary Damping Controller | 10.1007/s40313-019-00481-y |
2019-10-10 | The present paper focuses on the oscillation of the third-order nonlinear neutral differential equations with damping and distributed delay. The oscillation of the third-order damped equations is often discussed by reducing the equations to the second-order ones. However, by applying the Riccati transformation and the integral averaging technique, we give an analytical method for the estimation of Riccati dynamic inequality to establish several oscillation criteria for the discussed equation, which show that any solution either oscillates or converges to zero. The results make significant improvement and extend the earlier works such as (Zhang et al. in Appl. Math. Lett. 25:1514–1519 2012 ). Finally, some examples are given to demonstrate the effectiveness of the obtained oscillation results. | Oscillation of third-order neutral differential equations with damping and distributed delay | 10.1186/s13662-019-2363-2 |
2019-10-05 | The performance of Magnetorheological dampers should be analyzed to study the stability of Magnetorheological fluid and its configuration. To this end, in this study a prototype Magnetorheological fluid is presented. The fluid consists of stabilized Silicone dioxide (SiO_2) nanoparticles, Stearic acid, Phosphoric acid and micron-sized soft ferromagnetic carbonyl iron particles. To assure the authentic performance, sedimentation and magneto-rheometry tests are conducted. Also, a prototype of double-tube Magnetorheological damper with double magnetic components is fabricated by using the mentioned magnetorheological fluid characteristics. Damping force measurement test is carried out to measure the damping force in various electrical currents. The Kwok model is employed to examine the analytical model predictions against the experiments. Furthermore, a general evolution is presented using the neural network algorithm. It is demonstrated that the damping force in saturated current is almost five times higher than in the zero current. In addition, the derived evolution for the damping force has a high performance to predict the response of the Magnetorheological damper in other electrical currents. | Mathematical modeling and experimental evaluation of a prototype double-tube Magnetorheological damper | 10.1007/s42452-019-1408-1 |
2019-10-01 | The use of tools with chamfered cutting edges is an essential part of high performance cutting (HPC) as a rough milling process strategy for manufacturing structural components in the aerospace industry. Due to an interaction between the chamfer and the undulated workpiece surface, tool vibrations can be damped allowing high depths of cut without the occurrence of harmful dynamic effects. Hence, a significant increase in efficiency is possible. As a result of process damping, the stability boundary predicted by linear stability analysis provided for instance by analytical or geometric physically-based simulations will generally underestimate the experimentally determined one. Consequently, the object of this procedure, namely to reduce the number of test runs until sufficient process parameter values are determined, could not be met. Therefore, the damping effect induced by chamfered tools was analysed in this paper. It is shown that the use of chamfered cutting edges leads to a significant limitation of chatter amplitudes when exceeding the stability limit. The strength of this effect depends on the cutting speed and the engagement situation, which influence the intensity and number of interactions between the chamfer and the workpiece surface and, thus, the resulting process damping. Moreover, a dynamic process damping model presented in the literature was chosen and implemented in a geometric physically-based milling simulation. An evaluation of its validity points out the challenges regarding the simulation of process damping. | Analysis and simulation of process damping in HPC milling | 10.1007/s11740-019-00912-4 |
2019-10-01 | Abstract This paper is devoted to studying the motion of non-holonomic systems with higher-order constraints. The problem of the motion of such systems is formulated as the generalized Chebyshev problem. This refers to the problem in which the solution to a system of equations of motion should simultaneously satisfy an auxiliary system of higher-order ( n $$ \geqslant $$ 3) differential equations. Two theories are constructed to study the motion of these systems. In the first, a joint system of differential equations for the unknown generalized coordinates and Lagrange multipliers is constructed. In the second theory, the equations of motion are derived by applying the generalized Gauss principle. The higher-order constraints are considered the program constraints in this investigation. Thus, the problem of finding the control satisfying the program given in the form of auxiliary system of differential equations linear in the ( n $$ \geqslant $$ 3)-order derivatives of the sought generalized coordinates is formulated. A novel class of control problems is therefore introduced into consideration. Several examples are provided of solving the real mechanical problems formulated as the generalized Chebyshev problems. The paper is a review of the research performed for many years at the Department of Theoretical and Applied Mechanics of St. Petersburg University. | Formulation and Solution of a Generalized Chebyshev Problem: First Part | 10.1134/S1063454119040137 |
2019-10-01 | Abstract —The stiffness and damping properties of various-thickness samples made of a composite material based on a rubber mixture, rubber fiber composite material, and thermoplastic elastomers of various stiffnesses are studied under static and dynamic loading conditions at a temperature of 23 and –40°C. The composites based on a rubber mixture and the rubber fiber composites are recommended for the dampers that work in regions with low climatic temperatures. The stiffness and damping properties of a real object are assumed to be estimated using the elastic hysteretic properties of a test sample. | Elastic Hysteretic Properties of Damping Composite Materials for Rail Transport at Low Temperatures under Static and Dynamic Loading | 10.1134/S0036029519100161 |
2019-10-01 | Tuned mass damper (TMD) is an effective passive device in reducing harmful vibrations as long as they are designed correctly. An optimal TMD design method is proposed based on transfer functions and also differential evolution (DE) algorithm is used. The method includes optimization of all parameters which are the mass, stiffness and damping coefficients of a TMD. By using random vibration theory, the mean-square of top floor absolute acceleration, top floor displacement and the sum of mean-squares of interstorey drifts have been chosen as objective functions to be minimized with respect to upper and lower limits of TMD parameters. In the classical design, the mass is usually chosen by the designer to find the optimum values of the stiffness and damping coefficient. In addition to optimizing stiffness and damping coefficients, in this study TMD mass quantity is also optimized by using DE algorithm to minimize objective functions for TMD design. After that, structure system with TMD is tested under six near fault and three far fault ground motions by evaluating responses of the structure. The results obtained here are compared with the methods available in the literature for verification. Numerical results show that the proposed method is effective for optimal TMD design. | A New Tuned Mass Damper Design Method based on Transfer Functions | 10.1007/s12205-019-0305-x |
2019-10-01 | The reduction in vibration in gear transmission systems is an engineering task. Particle damping technology attenuates vibration by means of friction and inelastic collisions between damping particles. This study proposes a dynamic model for a spur gear transmission system that contains damping particles inside the holes on gear bodies, using two-way coupling with multi-body dynamics and discrete element method. The equations of motion for the multi-body system are derived using Euler–Lagrange formalism. The discrete element method with a soft contact approach is used to model the dynamic behavior of damping particles. Hertzian contact theory and Coulomb friction theory are applied to modeling contacts. The effects of particle radius, coefficient of friction and restitution coefficient on the dynamic characteristics are explored. Numerical results show that vibration in the transmission is appreciably attenuated by the particle damping mechanism and that the contact friction, and not contact damping, dominates the energy dissipation of the multi-body system in such a centrifugal scenario. | Dynamic modeling of a gear transmission system containing damping particles using coupled multi-body dynamics and discrete element method | 10.1007/s11071-019-05177-1 |
2019-10-01 | Damping is critical for the roll motion response of a ship in waves. A common method for the assessment of damping in a ship’s rolling motion is to perform a free-decay experiment in calm water. In this paper, we propose an approach for estimating nonlinear damping that involves a linear exponential analytical approximation of the experimental roll free-decay amplitudes, followed by parametric identification based on the asymptotic method. The restoring moment can be strongly nonlinear. To validate this method, we first analyzed numerically simulated roll free-decay data using rolling equations with two alternative parametric forms: linear-plus-quadratic and linear-plus-cubic damping. By doing so, we obtained accurate estimates of nonlinear damping coefficients, even for large initial roll amplitudes. Then, we applied the proposed method to real free-decay data obtained from a scale model of a bulk barrier, and found the simulated results to be in good agreement with the experimental data. Using only free-decay peak data, the proposed method can be used to estimate nonlinear roll-damping coefficients for conditions with a strongly nonlinear restoring moment and large initial roll amplitudes. | Estimation of Nonlinear Roll Damping by Analytical Approximation of Experimental Free-Decay Amplitudes | 10.1007/s11802-019-3912-8 |
2019-10-01 | Rotating machinery support design with the aim of reducing the synchronous unbalance response has significant importance regarding the various applications of these machineries. In this paper, we present H _ ∞ and H _2 methods for calculating the optimum support flexibility and damping of flexible rotors to minimize vibrational amplitudes in the vicinity of the rotor first critical speed. First, the governing equations for the Jeffcott rotor model mounted on flexible supports are derived and the optimal parameters for the supports have been analytically achieved using H _ ∞ and H _2 optimization procedures. The approach method of the tuned damper support system is similar to that designed for dynamic vibration absorber optimization. The H _ ∞ optimum parameters such as tuning frequency and damping ratios are expressed based on fixed-point theory to minimize the rotor amplitudes, as well as, the H _2 optimum parameters to minimize the mean square motion of flexible rotor as analytical formulas. It is proven by numerical simulations that the system optimization design can effectively improve the synchronous unbalance response. Comparison of two optimization procedure showed the vibrational amplitudes with H_2 optimization was smaller than H _ ∞ one. | H_∞ and H_2 optimization procedures for optimal design of support parameters of a flexible rotor | 10.1007/s40314-019-0945-y |
2019-10-01 | The paper discusses the effectiveness of currently used methods of surface damping of bending vibrations for thin-walled structures. The special features of surface damping of vibrations using a free and constraining layer damping are analyzed from a physical point of view and practical application. A combined damping coating is proposed, which allows integrating the positive qualities of both of the above methods. An experimental comparison of the effectiveness of the known and proposed methods for damping of bending vibrations of thin-walled structures is made using the method of free damped oscillations. | An Integral Method of Surface Damping of Bending Vibrations for Thin-Walled Structures | 10.3103/S1068799819040056 |
2019-10-01 | Based on the Hilbert transform, measurement errors of the amplitude and frequency of a vibrating signal of variable frequency are studied. The chief factors affecting measurement error of the parameters of a signal were determined by means of numerical modeling. The use of a frequency response model of a vibration isolator in the form of a Chebyshev digital filter confirmed the effectiveness of the Hilbert transform. The results of numerical modeling were successfully verified during field tests of the vibration isolator at an electrodynamic workstation. | Numerical and Full-Scale Study of Measurement Errors of the Frequency Response of Vibration Isolators | 10.1007/s11018-019-01669-z |
2019-10-01 | Wind turbine technology is well known around the globe as an eco-friendly and effective renewable power source. However, this technology often faces reliability problems due to structural vibration. This study proposes a smart semi-active vibration control system using Magnetorheological (MR) dampers where feedback controllers are optimized with nature-inspired algorithms. Proportional integral derivative (PID) and Proportional integral (PI) controllers are designed to achieve the optimal desired force and current input for MR the damper. PID control parameters are optimized using an Ant colony optimization (ACO) algorithm. The effectiveness of the ACO algorithm is validated by comparing its performance with Ziegler-Nichols (Z-N) and particle swarm optimization (PSO). The placement of the MR damper on the tower is also investigated to ensure structural balance and optimal desired force from the MR damper. The simulation results show that the proposed semi-active PID-ACO control strategy can significantly reduce vibration on the wind turbine tower under different frequencies (i.e., 67%, 73%, 79% and 34.4% at 2 Hz, 3 Hz, 4.6 Hz and 6 Hz, respectively) and amplitudes (i.e. 50%, 58% and 67% for 50 N, 80 N, and 100 N, respectively). In this study, the simulation model is validated with an experimental study in terms of natural frequency, mode shape and uncontrolled response at the 1st mode. The proposed PID-ACO control strategy and optimal MR damper position is also implemented on a lab-scaled wind turbine tower model. The results show that the vibration reduction rate is 66% and 73% in the experimental and simulation study, respectively, at the 1st mode. | Smart Semi-active PID-ACO control strategy for tower vibration reduction in Wind Turbines with MR damper | 10.1007/s11803-019-0541-6 |
2019-10-01 | Structural safety of building particularly that are intended for exposure to strong earthquake loads are designed and equipped with high technologies of control to ensure as possible as its protection against this brutal load. One of these technologies used in the protection of structures is the semi-active control using a Magneto Rheological Damper device. But this device need an adequate controller with a robust algorithm of current or tension adjustment to operate which is further discussed in the following of this paper. In this study, a neural network controller is proposed to control the MR damper to eliminate vibrations of 3-story scaled structure exposed to Tōhoku 2011 and Boumerdès 2003 earthquakes. The proposed controller is derived from a linear quadratic controller designed to control an MR damper installed in the first floor of the structure. Equipped with a feedback law the proposed control is coupled to a clipped optimal algorithm to adapt the current tension required to the MR damper adjustment. To evaluate the performance control of the proposed design controller, two numerical simulations of the controlled structure and uncontrolled structure are illustrated and compared. | Neural network control for earthquake structural vibration reduction using MRD | 10.1007/s11709-019-0544-4 |
2019-10-01 | This paper summarizes the development of a new replaceable horizontally steel arc-cut damper (HACD) designed as a fuse element in steel-coupling beams for earthquake protection of reinforced concrete shear walls with openings. The HACD is fabricated from a steel arc-cut plate and restraining plates positioned by vertical steel stiffeners. The proposed damper is an in situ, weld-free energy dissipater device, which eliminates the on-site installation difficulties. The seismic induced energy is dissipated through shear yielding of the arc-cut plate when the device is subjected to inelastic cyclic deformation. The optimized shape of HACD with adequate ductility and dissipation energy capacity is obtained using finite-element analysis. The result of numerical analysis under pseudo-dynamic displacements indicates its suitable energy dissipation, stable hysteric response, and remarkable ductility through shear yielding of the arc-cut shear plate. The performance of the numerical approach is justified through the analysis of tested dissipative device available in the literature. | New Fused Steel-Coupling Beam with Optimized Shear Panel Damper | 10.1007/s40999-019-00430-5 |
2019-09-18 | The improvement of the average fidelity of the quantum teleportation protocol of an arbitrary qubit state has been researched. The initial quantum channel is chosen as the non-maximally entangled state, and this state depends on a free parameter. One qubit of this quantum channel is influenced by the amplitude-damping noise environment in the Markovian regime or the non-Markovian regime. The average fidelity is enhanced efficiently through the appropriately selected free parameter of the initial quantum channel. The optimization could not be attributed to the probability as well as the noise environment that makes the initial quantum channel becomes the closest quantum channel to the maximally entangled one. Our study shows that the average fidelity is enhanced as the quantum entanglement of the initial quantum channel is harmoniously redistributed into the entanglement of quantum channel influenced by the noise environment and the entanglement between each of the qubits in this quantum channel and the noise environment. | Optimal fidelity for quantum teleportation protocol of an arbitrary qubit state affected by amplitude-damping noise: causes and results | 10.1007/s11128-019-2455-7 |
2019-09-16 | In this research, semi-active control of sandwich plates with electro-rheological (ER) core and carbon nanotubes-reinforced composite facesheets using smart ER dampers is studied. Sandwich plate is subjected to the external electric field and rested on orthotropic visco-Pasternak foundation. The material properties of ER core and nanocomposite facesheets are obtained by Yalcintas model and Eshelby–Mori–Tanaka approach, respectively. The governing equations of motion are solved by a combination between finite element and Newmark methods for clamped and simply supported boundary condition. The effects of various parameters such as applied voltage, controlled electric field and initial gap of the electrodes on the vibration suppression time are discussed. The results show that the settling time of system introduced in this work is much less than previous researches in this field which is a very important advantage. | Application of smart electro-rheological dampers in semi-active control of electro-rheological sandwich plates with nanocomposite facesheets rested on orthotropic visco-Pasternak foundation | 10.1007/s40430-019-1903-8 |
2019-09-13 | Offshore jacket platforms are exposed to environmental loads such as wind, wave, current, and earthquake throughout the lifetime of operation. Due to dynamic and periodic nature and fatigue phenomenon in the structure, wave forces are the most important loads among others. There are diverse methods to explore the fatigue life of jackets, including deterministic, spectral, and time domain analysis. Among these methods, spectral method is a reliable method, which considers the random nature of sea waves in fatigue analysis. In the current study, a spectral method is introduced for assessment and rehabilitation of jacket platform structure. To this end, a computer program has been developed, meanwhile, probability spectral density functions of displacement and stress are calculated in each joint of jacket elements. Furthermore, using S – N curve approach, cumulative fatigue damage in critical members of an example jacket is obtained. Finally, several configurations of viscous dampers are applied to jacket, and damage and fatigue lifetime are discussed with and without dampers. Consequently, the best arrangement of dampers is achieved. Results indicate the best cumulative fatigue damage with dampers which was about 0.01 times of cumulative fatigue damage without a damper. | Spectral fatigue analysis of jacket platform under wave load equipped with viscous damper | 10.1007/s00773-018-0592-9 |
2019-09-12 | In this paper, we are concerned with variable coefficients plate system subjected to three partially distributed feedbacks: time-varying delay, frictional and viscoelastic dissipations. This work is devoted to, without any prior quantification of both decay rate of relaxation function and growth rate of frictional dissipation near the origin, establish a general decay result which corresponds to a certainly stable ODE. Our result extends the decay result obtained for some kind of problems with finite history to problem with infinite history. Moreover, this paper allows a wider class of kernels of infinite history, and the usual exponential and polynomial decay rates are only special cases. The proof is based on the multiplier method and some techniques about convex functionals. | Viscoelastic versus frictional dissipation in a variable coefficients plate system with time-varying delay | 10.1007/s00033-019-1192-1 |
2019-09-06 | In this study, the mechanical properties of a high-strength laminated vibration damping steel sheet (LVDSS) with stretch-dominated deformation behavior were characterized and successfully applied to formability prediction. The high-strength LVDSS was fabricated with dual-phase 590 steel sheets as outer skins and polymeric adhesive layer as a core via roll bonding. The uniaxial and biaxial mechanical behaviors were evaluated by performing uniaxial tension and in-plane biaxial tension tests, respectively, while the forming limit was investigated by conducting punched dome tests. Then, based on the experimental data, the mechanical properties of the LVDSS were characterized, viz., the hardening curve, yield function, and forming limit curve. As an example of LVDSS application, a square cup drawing test was conducted and a dashboard prototype was fabricated using an LVDSS, and the deformation and failure behaviors were successfully predicted via a finite element simulation performed by inputting the characterized mechanical properties. | Characterization of the Mechanical Properties of a High-Strength Laminated Vibration Damping Steel Sheet and Their Application to Formability Prediction | 10.1007/s12540-019-00281-8 |
2019-09-05 | Magnetorheological (MR) fluids belong to a class of controllable fluids, and the composition and concentration of its components govern its magnetorheological properties. In this study, an optimum particle loading (or mass fraction) and size of iron particles in MR fluid for use in a shear mode monotube MR damper were determined based on the damping force and off-state viscosity of synthesized MR fluid samples. Initially, the morphological and magnetic properties of carbonyl iron particles were characterized. Six MR fluid samples were prepared composed of combination of three different particle loadings and two sizes of iron particles. Magnetorheological tests were conducted on these samples to determine the flow curves at off-state and on-state magnetic field conditions. Herschel–Bulkley model was used for mathematical representation of flow curves at different magnetic fields and to determine their dynamic yield stress. Further, a shear mode monotube MR damper with accumulator was designed by using optimization technique for desired dynamic range and damping force. Magnetostatic analysis was performed to determine the magnetic field strength generated in the shear gap at different currents. The damping force was calculated for synthesized MR fluids based on their dynamic yield stress corresponding to the magnetic field strength in the shear gap. Analysis of variance was performed to analyse the significance of independent factors on the damping force and off-state viscosity of MRF. The optimal particle loading and size which yielded maximum damping force with minimum off-state viscosity were determined using a multi-objective genetic algorithm. | Determination of optimal magnetorheological fluid particle loading and size for shear mode monotube damper | 10.1007/s40430-019-1895-4 |
2019-09-01 | Low-frequency electromechanical oscillations damping is powerfully crucial in power system operation. In order to fulfill this requirement, power oscillation damping (POD) controllers are installed in synchronous generators and flexible alternating current transmission system devices. These controllers can have either a conventional fixed structure composed by stages of gain and phase compensation or a multi-band modern structure (PSS4B) composed by three bands that correspond to a specific frequency range (low, intermediate and high frequency). In the PSS4B structure, each band consists of two branches based on differential filters (with a gain, lead–lag blocks and a hybrid block). This paper investigates the application of PSS4B as a POD controller for the static VAR compensator (PSS4B-SVC-POD) to damp oscillations in multi-machine power systems. The proposed PSS4B-SVC-POD and power system stabilizers (fitted on generators) are simultaneously designed through an optimization approach aiming at maximizing the closed-loop damping ratio. Modal analysis, frequency responses and time simulations for the well-known two-area four-generator power system show the good performance of the proposed controller fitted on static VAR compensator. | Multi-band power oscillation damping controller for power system supported by static VAR compensator | 10.1007/s00202-019-00830-9 |
2019-09-01 | Communication latency which inherently occurs in wide area measurement system greatly degrades small-signal stability (SSS) and is stochastic in nature, and thus, the current power oscillation damping controllers (PODCs) designed to improve SSS must consider this crucial factor. This paper proposes a probabilistic method to tune the parameters of PODCs incorporated in renewable farms to improve SSS under stochastic time delay and under other power system uncertainties arising due to renewable energy resources and loads. The proposed method is composed of two stages: The first stage quantifies the effect of time delay and other power system uncertainties on SSS, and the second stage uses this information to formulate an optimization problem. This optimization problem is solved with the help of four swarm intelligence-based optimization algorithms which are: bat algorithm, cuckoo search algorithm, firefly algorithm, and particle swarm optimization algorithm. The solutions from all these four optimization algorithms are compared, and the best result is used to optimize the parameters of the PODCs. All the analyses were conducted on a modified IEEE 68 bus system. The results show that the PODCs tuned using the proposed method greatly enhances the SSS margin under different scenarios and are probabilistically robust to the varying time delay and other power system uncertainties. | Optimized tuning of power oscillation damping controllers using probabilistic approach to enhance small-signal stability considering stochastic time delay | 10.1007/s00202-019-00833-6 |
2019-09-01 | Abstract We propose a method for describing damped vibrations of a beam with a built-in end considering the dynamic hysteresis that determines mechanical energy dissipation due to viscoelasticity. As the mathematical basis, we have used the fractional integro-differentiation apparatus. Rapidly damped vibrations of a foamed polypropylene beam have been studied experimentally. It is shown that the theoretical model successfully describes experimental data. | New Method for Describing Damped Vibrations of a Beam with a Built-in End | 10.1134/S1063784219090135 |
2019-09-01 | For advanced attitude control of the satellite, reaction wheels are used, which are actuated by motor. Fault detection and prediction of Remaining Useful Life (RUL) of the motor is of great importance. This study aims to demonstrate health management of reaction wheel motor in satellites by estimating the RUL of the damping coefficient. Multi-scale Extended Kalman Filter (EKF) is employed for this purpose using the data of input current and output velocity measured during the life test of the motor. The motor dynamic behavior is modeled by the ordinary differential equations. The damping coefficient is taken as the health indicator, which is obtained by solving the micro EKF problem. To set threshold for the damping coefficient, degradation behavior of characteristic curve that evaluates the motor performance is used to correlate with the degradation of the damping coefficient. Then, the RUL is predicted by solving the macro EKF problem. | Remaining useful life prediction of reaction wheel motor in satellites | 10.1007/s42791-019-00020-5 |
2019-09-01 | Subsystems of Russian automatic excitation regulators that ensure the maximum dynamic stability and effective damping of oscillations in an electric power system are described. They are compared to stabilizers included in international and national standards of other countries. It is shown that the Russian system stabilizer PSS2RU is effective in oscillation damping in various circuits and modes. | Implementing the System Functions of the Automatic Proportional-Derivative Excitation Control of Synchronous Generators | 10.1007/s10749-019-01084-y |
2019-09-01 | Vibration is a concern in the boring process due to the low dynamic stiffness of long cantilever boring bars. Vibration has a negative impact on the processing quality and processing performance. Dynamic vibration absorbers (DVAs) are used to consume vibration energy to improve the performance of boring operations. In this study, a nonlinear model is established to study the dynamic characteristics of a boring bar. Due to the consideration of nonlinear factors, the amplitude-frequency characteristics of the boring bar appear as an interesting phenomenon. As the damping of the DVA has an important influence on the vibration amplitude of the boring bar, the engineering implementation of this damping is conducted. Since the damping oil fills a hollow cylinder within the DVA, the length, inner diameter, and outer diameter of the hollow cylinder, along with the oil pressure and excitation frequency, are selected as parameters to study their influences on the damping value. | Nonlinear system modeling and damping implementation of a boring bar | 10.1007/s00170-019-03907-8 |
2019-09-01 | Thermoacoustic instabilities are a major issue for industrial and domestic burners. One possible framework to study these instabilities is to represent the system by a network of Dimensionless Acoustic Transfer Matrices (DATM) that link pressure and velocity fluctuations upstream and downstream each element of the network. In this article, the DATM coefficients of a turbulent swirling combustor are determined for a thermoacoustically stable configuration using harmonic acoustic forcing. Since the dynamics of the whole system is controlled by nonlinearities, the impact of the forcing level needs to be considered. The four DATM coefficients are thus measured for reactive operating conditions (premixed flame) and cold flow conditions for increasing acoustic excitation levels. The velocity level is controlled by a hot wire located inside the injector, in a region with a laminar top-hat velocity profile. The upstream and downstream specific acoustic impedances are also measured. Results for the acoustic response under cold flow conditions are first presented. In this case, the DATM coefficients are found to be independent of the forcing level except for the modulus of the coefficients linking the downstream velocity fluctuations to the upstream pressure and velocity fluctuations. This behavior is linked to the nonlinear response of the injector but is not entirely captured by the acoustic network model developed in this work. For reactive operating conditions, measurements indicate that all DATM coefficients depend on the forcing level to a certain extent. The Flame Describing Function, linking heat release rate fluctuations to velocity fluctuations, is used to reconstruct the transfer matrix through an acoustic network model. This network model accurately predicts the trend of the measured coefficients but the impact of the forcing level is not reproduced. Saturation for reactive operating conditions is shown to be not only related to the nonlinear flame response but also to the nonlinear injector dynamics. Finally, a data-driven reconstruction of the FDF using the acoustic network model along with the hot wire and microphone measurements is performed. This data-driven acoustic reconstruction is subsequently compared with the FDF determined with an optical technique. | Impact of the Acoustic Forcing Level on the Transfer Matrix of a Turbulent Swirling Combustor with and Without Flame | 10.1007/s10494-019-00033-z |
2019-09-01 | A quasi-zero stiffness (QZS) isolator is devised to acquire the feature of high-static-low-dynamic stiffness. Cam–roller–nonlinear spring mechanisms, where two horizontal dampers are installed symmetrically, are employed as a negative stiffness provider to connect in parallel with a vertical spring. From the static analysis, the piecewise restoring force in the vertical direction of the system is inferred considering possible separation between the cam and roller. The stiffness characteristics and parameters for offering zero stiffness at the equilibrium position are then determined. The dynamic equation is established and used for the deduction of the amplitude–frequency equation by means of the Harmonic Balance Method. The definitions of force and displacement transmissibility are introduced, and their expressions are derived for subsequent investigations of the effects of horizontal spring’s nonlinearity, excitation amplitude, horizontal damping, and vertical damping on the transmissibility performance. The comparative study is implemented on the isolation performance afforded by the QZS isolator and an equivalent linear counterpart, whose static bearing stiffness is same as the QZS isolator. Results indicate that the system with softening nonlinear horizontal spring can exhibit better performance than that with opposite stiffness spring. With the increase in horizontal damping ratio, the force transmissibility is further suppressed in resonance frequency range but increased in a small segment of higher frequencies and tends to unite in high frequency range. However, the horizontal damper deteriorates the ability to isolate the displacement excitation to a certain extent. Besides, the isolation capability of the QZS system depends on the magnitude of excitation amplitude. The quasi-zero stiffness system possesses lower initial isolation frequency and better isolation ability around resonance frequency compared with the linear system. Therefore, the quasi-zero stiffness isolator has superior low-frequency ability in isolating vibration over its linear counterpart. | Dynamic characteristics of a quasi-zero stiffness vibration isolator with nonlinear stiffness and damping | 10.1007/s00419-019-01541-0 |
2019-09-01 | This study focused on rheological and mechanical properties of poly(vinylidene fluoride) nanocomposites incorporated with functionalized graphene nanoplatelets and hydroxylated titanium dioxide. Mechanical properties of the ternary composites were improved with a slight reduction in damping coefficient compared to the pure polymer and graphene binary composites. The storage modulus of the ternary composites significantly increased from about 67.5 Pa for the pure polymer to 3.24 × 10^5 Pa and 3.49 × 10^5 Pa at 0.1 rad/s for 6.67 wt% graphene composites containing 10 wt% and 20 wt% titania respectively. All ternary composites showed higher tensile strength and Young modulus compared to the pure polymer. Strong bonding between the polymer and co-fillers with a reduction in interfacial slipping in the ternary composites resulted in their lower damping factor and higher strength compared to their counterparts. The composite samples were prepared by solution and melt mixing methods. The scanning electron microscope was used to examine the samples’ morphology and dispersion of the co-fillers in the matrix. Such composites can find applications in automobile and aerospace industries where materials with good strength and noise or vibration absorption capability are required. | Advanced rheological and mechanical properties of three-phase polymer nanocomposites through strong interfacial interaction of graphene and titania | 10.1007/s00170-019-03999-2 |
2019-09-01 | Similarly to electromagnetic waves, plasma waves can also carry an orbital angular momentum. A key distinction from electromagnetic waves is that plasma waves are intrinsically coupled to electrons and may deposit their momentum with electrons, resulting in their secular motion and generation of quasistatic magnetic fields. In this paper, we present an analysis of kinetic plasma waves carrying an orbital angular momentum in the paraxial approximation by considering the energy and momentum exchange between the wave and electrons and the average electron motion induced by plasma wave damping. | Twisted Kinetic Plasma Waves | 10.1007/s10946-019-09822-3 |
2019-09-01 | Modeling dynamic and static responses of an elastic medium often employs different numerical schemes. By introducing damping into the system, we show how the widely used time-marching staggered finite difference (FD) approach in solving elastodynamic wave equation can be used to model time-independent elastostatic problems. The damped FD method can compute elastostatic stress and strain fields of a model subject to the influence of an external field via prescribed boundary conditions. We also show how to obtain an optimized value for the damping factor. We verified the damped FD approach by comparing results against the analytical solutions for a borehole model and a laminated model. We also validated our approach numerically for an inclusion model by comparing the results computed by a finite element method. The damped FD showed excellent agreement with both the analytical results and the finite element results. | A Damped Dynamic Finite Difference Approach for Modeling Static Stress–Strain Fields | 10.1007/s00024-019-02207-2 |
2019-09-01 | In this paper, we present a subspace method for solving large scale nonlinear equality constrained optimization problems. The proposed method is based on a SQP method combined with the limited-memory BFGS update formula. Each subproblem is solved in a theoretically suitable subspace. In the case of few constraints, we show that our search direction in the subspace is equivalent to that of the SQP subproblem in the full space. In the case of many constraints, we reduce the number of constraints in the subproblem and we show that the solution of the subspace subproblem is a descent direction of a particular exact penalty function. Global convergence properties of the proposed method are given for both cases. Numerical results are given to illustrate the soundness of the proposed model. | A subspace SQP method for equality constrained optimization | 10.1007/s10589-019-00109-6 |
2019-09-01 | In recent years, the semi-active control of structural vibrations has interested several researchers. It has been demonstrated that semi-active control strategies are economical solutions for the safety of structure against earthquake or wind excitations. In this study, a semi active device which utilizes the Magneto-Rheological fluid characteristics to dissipate the earthquake excitation energy is proposed. The Magneto-Rheological damper is adopted to control the undesired vibrations of an earthquake-excited structure. Furthermore, a sliding mode controller coupled to the Clipped optimal algorithm is proposed to control this semi-active device. Otherwise, the sliding mode controller is reinforced by an adaptive gain law and the effectiveness of the new proposed adaptive controller to control the structural earthquake vibrations is proved by the compared numerical simulation results of the controlled and uncontrolled structure. Thus, the improvement of the sliding mode controller through the adaptive gain law is proved by the evaluation indices of an excited three-story scaled structure. Hence, a comparison between the results of the proposed adaptive sliding mode controller and the uncontrolled structure under the El Centro 1940 and the Boumerdès 2003 earthquakes excitations are discussed. | Adaptive sliding mode vibrations control for civil engineering earthquake excited structures | 10.1007/s40435-019-00559-0 |
2019-09-01 | Control polices with semi-active and active devices such as magnetorheological (MR) damper, magnetorheological isolator, magnetorheological mount, electrorheological dampers, actuators and pneumatics are integrated with automotive seating system (ASS) for seating and ride comfort. Semi-active device has been developed to replace the traditional static spring and damper system for reducing the acceleration of the human body. The current work reviews various control policies like PID, GA-PID, PSO-PID, MR on–off, FLC, Skyhook, etc., used for controlling the vibration level of ASS. This review study finds that adoption of cost effective intelligent vibration control policies with adoptive solutions will improve the ride comfort and will be made available in all ASS in the near future. | Control policies used for semi-active damper for automotive seating system: a review | 10.1007/s40435-018-0460-9 |
2019-09-01 | Field controllable magnetorheological (MR) damper has gained prominence as a suitable vibration control device for a wide variety of applications as they offer the combined advantages of high-performance metrics of a fully active vibration control system with the cost metrics of a passive vibration control system. The functional quantity that influences the damping performance of a magnetorheological damper is the yield stress of the magnetorheological fluid across the fluid flow gap when the magnetic field is applied. To achieve maximum damping output from the magnetorheological damper, the geometry of the damper piston needs to be optimized. The main geometrical design parameters of the damper piston are the pole width, magnetorheological fluid flow gap, distance between piston rod and coil and the outer pole thickness. The optimization of the damper geometry is carried over with magnetic field strength and yield stress as response variables in two different iterations. A quadratic polynomial function is considered for both the response variables. The yield stress response variable is found to exhibit a more accurate following through the regression equation and it is selected as the response variable of choice. The individual effect of each of the design variable and the interaction effect of the design variables over the yield stress response variable is studied in this research paper. The optimal values of the piston geometry could be used to fabricate a magnetorheological damper prototype in future study. | Design optimization of magnetorheological damper geometry using response surface method for achieving maximum yield stress | 10.1007/s12206-019-0828-6 |
2019-09-01 | The high-temperature superconducting (HTS) maglev system is characterized with self-stable levitation, low energy consumption, and pollution-free operation, and it has been considered as a promising technology for implementing high-speed transport systems. But the previous studies have shown that the damping of such system is relatively low, which indicates the large-amplitude nonlinear vibration may occur easily under external disturbances and affect the long-term motion stability, operation safety, and comfort of HTS maglev in rail transit application. In order to suppress the harmful vibration, an electromagnetic shunt damper (EMSD) was designed and incorporated into the HTS maglev system. Compared with other systems which employ the EMSD to diminish the vibration, the HTS maglev system does not need to set up external devices to supply magnetic field for the damper, because the permanent magnet guideway (PMG) in this system is directly taken advantages of. The natural frequency of the damper is adjusted to a value close to that of the maglev system. In this way, the damper becomes most effective because the moving vehicle body and the circuit resonate simultaneously. The feasibility of the damper was demonstrated through systematic experiments, and the effects of different field cooling heights (FCHs) of the HTS maglev system on EMSD’s performance were experimentally studied as well. Also, how the change of resistors in the EMSD circuit affects its working efficiency was preliminarily explored in this work. The results show that under the definite external disturbance, the damper can effectively attenuate the acceleration of vibration, furthermore, and it is found that the damper works better in condition of lower FCH. Within the scope of our experiments, the EMSD with a resistor in lower resistance performs better as results have shown. This investigation indicates that the vehicle will run in a more smooth and comfortable way along the track with this damper. The work is important for the further practical application of the technology. | Vibration Suppression of High-Temperature Superconducting Maglev System via Electromagnetic Shunt Damper | 10.1007/s10948-019-5050-3 |
2019-08-30 | The need for larger and more efficient structures has led to the development of numerical models to approach real-world complex behaviors. Normally, engineering systems consider deterministic parameters, while in real-world situations, they are subjected to parametric uncertainties, resulting in differences between the calculated responses. This work is devoted to performing numerical and computational studies of fatigue damage analyses of viscoelastically damped systems in the frequency domain subjected to parametric uncertainties. Here, the discretization of the random field is performed using the finite element method combined with the Karhunen–Loève expansion and the fatigue damage index is estimated by applying the so-called Sines’ global criterion. Optimization techniques were applied in order to obtain the optimal design of surface viscoelastic treatments in terms of fatigue. Therefore, the main contribution intended for the present study is to show the importance of considering optimal–robust parameters to estimate the failure probability of engineering structures with constrained viscoelastic layers. After presenting the underlying foundations, the numerical results are presented and the main features of the proposed methodology are highlighted. | Fatigue damage investigation and optimization of a viscoelastically damped system with uncertainties | 10.1007/s40430-019-1879-4 |
2019-08-16 | Nowadays, the trajectory model for a subsonic fin-stabilized projectile at a low angle of attack is typically a point-mass model (PMM), taking only gravity and a constant zero-yaw drag into account. This choice can be qualitatively justified for non-lethal projectiles given the short ranges. The disadvantage of this approach is the lack of prediction on the precision and the attitude of the projectile when hitting the target, because of a possible instability in flight. However, the use of non-lethal projectiles requires that the impact conditions are met, otherwise more serious injuries may occur. Therefore, the consideration of other forces and moments acting on the projectile in flight is mandatory to predict static and dynamic stabilities, already in the body shape design as well as in the controller design process in the field of non-lethal ammunitions. Starting from a geometry in caliber 12-gauge, static coefficients (drag, lift, and pitch) for different angles of attack using steady RANS simulations with a low-order turbulence model were found. Different trajectories were then analyzed using those coefficients and the difference between the PMM and a 3-DOF accounting for drag, lift, and pitch in function of the angle of attack is indeed negligible in height and in range as long as the launch conditions are completely undisturbed. The slightest destabilization makes the PMM completely inappropriate. Knowledge of the pitch damping coefficient then becomes a necessity to optimize stabilization following minor disturbances. | Aerodynamical CFD Study of a Non-Lethal 12-Gauge Fin-Stabilized Projectile | 10.1007/s41314-019-0020-x |
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