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2023-04-01 | Purpose The main purpose of this study was to investigate the effect of dampers equipped with shape memory alloys where steel connections equipped with slit dampers were used. For this purpose, 16 models equipped with SMA dampers were developed, SMA dampers have different lengths and stiffness. Methods In this study, application of SMAs as dampers is investigated to improve the seismic behavior of slit dampers. This study is to evaluate the effects of superelastic Nitinol damper on the seismic behavior of the slit system using Abaqus finite element software to verify and analyze the numerical models. Results Increasing the stiffness in SMA dampers resulted in yield moment and its equivalent rotation in the system. The longer the SMA damper length, the greater the yield moment. Increasing the length and stiffness of the shape memory alloy significantly reduces the permanent rotation of the connections. It can be almost concluded that increasing the length of the SMA in the damper slightly reduces the permanent deformation. The installation of SMA dampers in the models has reduced the energy dissipation capacity. This reduction is different in different models. Conclusion In fact, in models in which SMA dampers were embedded, the percentage of reduction in permanent deformation was greater than the percentage of reduction in energy dissipation. | Evaluating the Effectiveness of a Shape Memory Alloy on a Connection Equipped with Slit Damper | 10.1007/s42417-022-00640-7 |
2023-04-01 | In this paper, the influence of ground motion duration on the inelastic displacement ratio, C_1, of highly damped SDOF systems is studied. For this purpose, two sets of spectrally equivalent long and short duration ground motion records were used in an analysis to isolate the effects of ground motion duration on. The effect of duration was evaluated for observed values of C_1 by considering six ductility levels, and different damping and post-yield stiffness ratios. A new predictive equation of C_1 also was developed for long and short duration records. Results of non-linear regression analysis of the current study provide an expression with which to quantify the duration effect. Based on the average values of estimated C_1 ratios for long duration records divided by C_1 for a short duration set, it is concluded that the maximum difference between long and short duration records occurs when the damping ratio is 0.3 and the post-yield stiffness ratio is equal to zero. | Effect of ground motion duration on inelastic displacement ratio of SDOF systems | 10.1007/s11803-023-2169-9 |
2023-04-01 | This study proposes a novel design and micromachining process for a dual-cantilever accelerometer. Comb and curved-surface structures are integrated into the sensing structure to modulate the squeeze-film damping, thus effectively optimizing the response frequency bandwidth. Owing to the high stress concentration on the dual-cantilever integrated with a fully sensitive piezoresistive Wheatstone bridge, a high sensitivity to acceleration is achieved. In addition, the dual-cantilever accelerometer is fabricated using a specifically developed low-cost and high-yield (111)-silicon single-side bulk-micromachining process. The test results show that the proposed dual-cantilever accelerometer exhibits a sensitivity of 0.086–0.088 mV/ g /3.3 V and a nonlinearity of ±(0.09%–0.23%) FS (full-scale). Based on dynamic characterization, an adequate frequency bandwidth of 2.64 kHz is verified. Furthermore, a resonant frequency of 4.388 kHz is measured, and a low quality factor ( Q ) of 7.62 is obtained, which agrees well with the design for air-damping modulation. The achieved high performance renders the proposed dual-cantilever accelerometer promising in applications such as automotive and consumer electronics. 本研究提出了一种新型双悬臂加速度计的设计和微加工工艺技术。传感结构中集成有梳齿和空气微间隙结构，以调节压膜空气阻尼效应，进而有效地优化了传感器的频率响应和带宽特性。由于压阻惠斯通全桥集成在双悬臂梁上实现了高效率的应力集中，实现了对加速度检测的高灵敏度。此外，双悬臂加速度计采用了具有低成本和高成品率的(111)硅单面体微加工工艺来实现制造。传感器测试结果表明，所提出的双悬臂加速度计的灵敏度为0.086~0.088 mV/g/3.3V，全量程的非线性为±(0.09%~0.23%)。动态特性表征结果显示了2.64 kHz的充足频率带宽。传感器具有4.388 kHz谐振频率，并将品质因子（Q值）控制在7.62，与空气阻尼调制效应的设计结果高度一致。该双悬臂加速度计实现了较高的性能，在汽车和消费电子等领域具有很好的应用前景。 | High-Performance Single-Side Fabricated (111)-Silicon Dual-Cantilever Accelerometer with Squeeze-Film Air Damping Modulation | 10.1007/s12204-021-2288-2 |
2023-04-01 | Many vibrating systems, over some ranges of parameter values, exhibit a single unstable mode. Adding a small resonant secondary system to the unstable system is a well-known stabilization strategy. Here we show that even a nonresonant secondary system, if equipped with a limit cycle of its own, can stabilize the unstable mode of the primary system. The primary system is modeled here as a linear spring block system with negative damping. The secondary system is a van der Pol oscillator. Smallness of the latter’s parameters allows use of the method of multiple scales. The resulting slow amplitude equations decouple from the phases and a two-dimensional system is obtained. The secondary system’s amplitude evolves faster than that of the primary system, which simplifies analysis. A parameter-dependent transformation casts the system in a canonical form with a single free parameter $$c_1>0$$ c 1 > 0 in addition to the small perturbation parameter. The canonical phase portrait involves two key straight lines. When $$c_1 < 4$$ c 1 < 4 these lines intersect and a separatrix passes through that intersection. Solutions on one side of the separatrix show quenching of the primary instability with limit cycle oscillation of the secondary system. Solutions on the other side of the separatrix show significant oscillations of the primary system at its natural frequency, with the secondary limit cycle being quenched. When $$c_1 > 4$$ c 1 > 4 , stabilization fails for all initial conditions. In summary, for the case of a negatively damped oscillator interacting with a small nonresonant secondary limit cycle oscillator, we show stabilization, provide a pair of canonical equations with one free parameter, and present a complete qualitative characterization of the dynamics. | Vibration stabilization by a nonresonant secondary limit cycle oscillator | 10.1007/s11071-022-08145-4 |
2023-04-01 | In this paper, a fault-tolerant control method for an input-series output-parallel modular grid-tied pulse-width modulation (PWM) current source inverter is proposed to address the most commonly seen single symmetrical gate-commutated thyristor (SGCT) open-circuit fault problems. This method actively offsets the neutral point of the current space vector to ensure a sinusoidal output of the grid current, and it can achieve the upper limit power of the inverter under the condition of a single SGCT open-circuit fault. In addition, an active damping control method based on grid harmonic current feedback is proposed after analyzing the influence of the transformer ferromagnetic resonance caused by the neutral point offset on the power quality of the grid current. It has been demonstrated that the proposed method effectively suppresses the resonance caused by the transformer and the modified modulation, improving the grid current’s power quality. | Fault tolerant control strategy for modular PWM current source inverter | 10.1007/s11708-022-0852-6 |
2023-04-01 | One of the widely used control devices is a tuned mass damper (TMD) due to its simplicity and cost-efficiency. Although using the TMD is so promising, there are still some challenging tasks; obtaining optimum design parameters and optimum placements of a structure plays a vital role in the effectiveness of a TMD. In addition to those challenging tasks in design, using a single TMD can only be operative in a small frequency range unless multi-tuned mass dampers (MTMDs) are employed. Therefore, the MTMD placements are the focus of this study, distributed along with the building height under selected excitations. When the first three modes are aimed to be controlled by MTMDs, this is called the multi-mode controlling placement (MMCP) strategy, and all TMDs are tuned to the first, second, and third modes of the uncontrolled structure in order. Another strategy is the first mode dominant placement (FMDP); three TMDs are mostly tuned to the first (dominant) mode of the structure. For both strategies, MTMDs can be applied on any floor of the structure. Six optimal MTMD placement cases are initially determined considering FMDP and MMCP strategies. The results of all placements are examined in dynamic response and energy evaluation. The obtained results show that while the FMDP performs better to reduce the maximum floor displacement and velocity, MMCP outperforms by controlling the maximum acceleration. | Analysis of Different Placement Strategies of Multi-Tuned Mass Dampers Placed in Building Height | 10.1007/s13369-022-07440-x |
2023-04-01 | This paper presents an Active Tuned Mass Damper (ATMD) control approach for vibration reduction applied to a one-bay three-story scaled shear frame. The ATMD is composed of a Tuned Mass Damper (TMD) driven by the combined action of a modified Positive Position Feedback (mPPF) control law and a Model Predictive Controller (MPC). The mPPF and the MPC are in an inner and outer loop configuration. In the inner control loop, the mPPF strategy compensates for the first vibration modes at low frequencies and pre-stabilizes the structure; while, in the outer loop, the MPC controller considers the actuator limits ensuring constraint satisfaction and softening the control action. A critical advantage concerning to mPPF controller is its design is based only on the natural frequencies, which are relatively easy to estimate around an experimental test. Furthermore, the MPC allows generalizing the controller design for multi-story arrangements without modifying the controller structure. Numerical results show that, for the case study, the control effort of the proposed scheme is more than seven times lower than the control effort when compared with an ATMD driven by a conventional MPC, without sacrificing performance. | Vibration Control Using a Positive Position Feedback-based Predictive Controller Applied to a One-Bay Three-Story Scaled Shear Frame | 10.1007/s42417-022-00613-w |
2023-04-01 | When the control moment gyroscope, momentum wheel, solar array drive mechanism, antenna drive mechanism, and refrigerator on spacecraft work, they produce micro-vibration, which seriously affects the accuracy of observation equipment. It is an effective way to suppress micro-vibration to install a vibration isolation device at the payload. In this paper, a three-parameter fluid viscous damper (TPFVD) for spacecraft micro-vibration suppression is researched. Considering the compressibility of the fluid and the volume deformation of the bellows, according to the effective area principle of bellows, the bellows is equivalent to a single tube, and a reduced-order model of the vibration isolator is established by using the approximate analytical modeling method. The nonlinearity caused by the inlet and outlet effects of the damping orifice is also considered in the model. The model error is further modified by introducing the correction coefficient of bellows volume deformation. Compared with the FEM model, the validity of the model and the modified method is verified. The results show that the models in the existing literature are applicable only when the frequency is less than 100 Hz. The calculation error of the model proposed in this paper is less than 8.20% in the frequency range of 1–300 Hz, and the maximum error of the unmodified model in the literature can reach 34.28%. In addition, the influences of damping orifice parameters, viscosity, payload mass, and nonlinear characteristics on the force transmissibility and payload displacement of the isolator are analyzed. | A reduced-order model of the three-parameter fluid viscous damper with consideration of fluid compressibility and bellows volume deformation | 10.1007/s11071-022-08211-x |
2023-04-01 | A novel cambered surface steel tube damper (CSTD) with a cambered surface steel tube and two concave connecting plates is proposed herein. The steel tube is the main energy dissipation component and comprises a weakened segment in the middle, a transition segment, and an embedded segment. It is believed that during an earthquake, the middle weakened segment of the CSTD will be damaged, whereas the reliability of the end connection is ensured. Theoretical and experimental studies are conducted to verify the effectiveness of the proposed CSTD. Formulas for the initial stiffness and yield force of the CSTD are proposed. Subsequently, two CSTD specimens with different steel tube thicknesses are fabricated and tested under cyclic quasi-static loads. The result shows that the CSTD yields a stable hysteretic response and affords excellent energy dissipation. A parametric study is conducted to investigate the effects of the steel tube height, diameter, and thickness on the seismic performance of the CSTD. Compared with equal-stiffness design steel tube dampers, the CSTD exhibits better energy dissipation performance, more stable hysteretic response, and better uniformity in plastic deformation distributions. | Hysteretic behavior of cambered surface steel tube damper: Theoretical and experimental research | 10.1007/s11709-023-0925-6 |
2023-04-01 | Purpose The axial vibration of short fiber reinforced composite nanorods is investigated for the first time in this paper. Short fibers are randomly distributed or aligned in composite nanorods. Methods Nonlocal elasticity theory has been employed in the analysis. In addition to analytical solution of axial vibration problem of composite nanorods, finite element method is carried out to derive the natural frequencies for general boundary conditions. A two-noded rod finite element is used in the vibration problem. Results The natural frequencies of composite nanorods predicted by the present analytical model are verified with the developed finite element solution for general boundary conditions. In addition, the natural frequencies are obtained for the viscously damped case of composite nanorods. Conclusion The present study would be useful for the dynamic analyses of nanocomposite structures. | On the Axial Vibration of Viscously Damped Short-Fiber-Reinforced Nano/Micro-composite Rods | 10.1007/s42417-022-00643-4 |
2023-04-01 | This paper examines the optimized parameters for tuned mass dampers (TMDs) to reduce seismic vibrations of tall buildings; with soil–structure interaction effects (SSI). To illustrate the results, earthquake data are applied to the model and the jellyfish search optimization (JSO) method is used to obtain the best parameters for TMD. TMD mass, damping coefficient and spring stiffness are assumed as design variables and the goal is to reduce both the maximum deflection and the acceleration of the aircraft. It shows how the JSO can be effectively applied to design the optimal TMD device. It is also noted that the type of soil significantly affects the optimized parameters of the TMD and the temporal response of structures. This study helps researchers better understand seismic vibrations and guides designers to achieve the optimized TMD for skyscrapers. The proposed method is the implementation of the MATLAB platform. Here the proposed technique is compared to other existing techniques such as the shuffled Shepherd optimization algorithm (SSO) and the genetic algorithm (GA). | Jellyfish search optimization for tuned mass dumpers for earthquake oscillation of elevated structures including soil–structure interaction | 10.1007/s42107-022-00530-z |
2023-04-01 | With advances in construction techniques and building materials, lightweight and flexible structures have been widely developed. Its light mass, low damping, and low frequency properties make it extremely vulnerable to human-induced vibration. Researchers have found that occupancy of a crowd would increase the damping of structures and decrease their natural frequencies. The adoption of a single-degree-of-freedom (SDOF) mass-spring-damper (MSD) model of the human body can illustrate the phenomenon. Therefore, to obtain the dynamic properties of the human body, we designed a full-scale experimental platform and measured the dynamic properties of the empty structure and the human-structure interaction system separately. The dynamic parameters of the human body in a standing position, a sitting position at different vibration levels were obtained. A total of 30 participants were involved in this study and the average frequency and damping ratio identified were 5.12 Hz and 36.76% respectively, when the body was in a standing position, and 4.92 Hz and 43.93% respectively when the body was in a sitting position. The results of the identification show that the human fundamental frequency decreases with increasing vibration magnitude and the human damping ratio tends to increase with increasing vibration magnitude, regardless of whether the human body is in a standing or sitting position. | Identification of Human Body Dynamics from a Human-Structure System: An Experimental Study | 10.1007/s40799-022-00548-7 |
2023-04-01 | This study aims to investigate the performance of nonlinear viscous damper (NVD) in seismic vibration control of reinforced concrete moment-resisting frames. To this aim, five RC moment frames (1-, 2-, 4-, 8-, and 12-stories) with and without NVD were examined. To evaluate the seismic behavior of the models, different records were considered, including high period (HP), low period (LP), near field (NF), far field (FF), low dominant high mean period (LDHM), and the ground motions that carry directivity effects (D). The effects of height and frequency of reinforced concrete frames were studied. The simulations and analyses were conducted using nonlinear dynamic time-history analysis in SAP 2000. According to the results, by increasing the exponential coefficient of the damper (alpha) from 0.15 to 0.50, the damping performance is optimally improved under the effect of more ground motions. Nonlinear viscous dampers under high period (HP), and near-fault (NP) ground motions, especially ground motions that carry directivity effects, have a completely better performance than far-field or high-frequency ground motions. In high-period (HP) earthquakes for short structures and in low-period earthquakes (LP) for 12-story structures, dampers have shown more energy dissipation. Based on the average of the obtained results, the effect of viscous dampers on the absorption of the input energy and reduction of roof displacement, base shear, and roof acceleration was about 90, 70, 25, and 47%, respectively. | Seismic Vibration Control of Moment-Resistant Concrete Frames Using Nonlinear Viscous Dampers | 10.1007/s40996-022-00916-8 |
2023-04-01 | In this study the efficiency of Semi Active Tuned Mass Damper (STMD) on seismic response reduction in a moment resisting frame steel building considering soil-pile-structure interaction is investigated in comparison with common Tuned Mass Damper (TMD). Substructure method is used for simulating the Soil-Pile-Structure interaction. p–y curves recommended by API are used for simulating the nonlinear spring coefficients. Damping ratio of STMD is optimized during dynamic loading simultaneously by using Groundhook Algorithm and a layered soil profile with varying stiffness (two and three layers) is considered. In addition, the mass ratio for STMD is assessed for obtaining the highest efficiency for STMD to mitigate the seismic vibration. The results indicated that, the STMD efficiency reduces when the soil stiffness is increased. TMDs performed poorly for seismic control of structural performance in comparison with STMDs when soil pile structure interaction was ignored. Finally, the optimized mass ratio considering soil-pile-structure interaction for STMD is evaluated, which have shown that a range of 3 to 5% is suitable for efficient design of STMDs. However, it is worth noting that the seismic responses of soil-pile structure systems under near-field and far-field earthquakes do not have significantly different effects on STMD performance. | Seismic Performance Assessment of Semi Active Tuned Mass Damper in an MRF Steel Building Including Nonlinear Soil–Pile–Structure Interaction | 10.1007/s13369-022-07138-0 |
2023-03-31 | We develop a virtual element method for weakly damped wave equations on polygonal meshes. Very general polygonal meshes are used for the spatial discretization. In both $$L^{2}$$ L 2 norm and $$H^{1}$$ H 1 semi-norm, optimal order of convergence is obtained for the spatially discrete approximation. We employ the Crank–Nicolson temporal discretization scheme for the fully discrete problem and derive the convergence analysis. Numerical experiments are illustrated to confirm our theoretical findings. | Virtual element methods for weakly damped wave equations on polygonal meshes | 10.1007/s40314-023-02252-7 |
2023-03-29 | In this note, we investigate again the blow-up phenomenon of weak solutions to the following initial-boundary value problem of the fourth-order equation with variable-exponent nonlinearity $$\begin{aligned} u_{tt}+\Delta ^2 u-M(\Vert \nabla u\Vert _2^2)\Delta u-\Delta u_t+|u_t|^{m(x)-2}u_t=|u|^{p(x)-2}u. \end{aligned}$$ u tt + Δ 2 u - M ( ‖ ∇ u ‖ 2 2 ) Δ u - Δ u t + | u t | m ( x ) - 2 u t = | u | p ( x ) - 2 u . Our investigations reveal that the blow-up phenomenon will happen for arbitrarily high initial energy under $$m^-:=ess\inf _{x\in \Omega }m(x)>2$$ m - : = e s s inf x ∈ Ω m ( x ) > 2 . It is worthy to point out that an upper bound of the blow-up time is also shown. These results answer the earlier unsolved question in our previous paper (Liao and Tan in Sci China Math 66 , 285–302 (2023). https://doi.org/10.1007/s11425-021-1926-x ). | Blow-Up of Solutions to the Fourth-Order Equation with Variable-Exponent Nonlinear Weak Damping | 10.1007/s00009-023-02391-5 |
2023-03-13 | In this paper, we are devoted to the study of a problem proposed in Aujol and Dossal (SIAM J Optim 29:3131–3153, 2019), which concerns the optimal convergence rates for damped inertial gradient dynamics with flat geometries. Fortunately, we find a solution to the problem. More specifically, we obtain an optimal decay rate for the system energy of the second-order differential equation with time-dependent damping in a Hilbert space $${\mathcal {H}}$$ H $$\begin{aligned} \ddot{x}(t)+\gamma (t){\dot{x}}(t)+\nabla F(x(t))=0, \end{aligned}$$ x ¨ ( t ) + γ ( t ) x ˙ ( t ) + ∇ F ( x ( t ) ) = 0 , where $$F : {\mathcal {H}} \rightarrow R$$ F : H → R is a differentiable convex function possessing at least one minimizer and $$\gamma (t)=\alpha /t$$ γ ( t ) = α / t with $$\alpha >0.$$ α > 0 . It is known that this system, with the time-dependent damping coefficient $$\gamma (t)$$ γ ( t ) , models a nonlinear oscillator with viscous damping, and is associated with the Nesterov acceleration scheme, FISTA, or the accelerated gradient method in the area of numerical optimization. | Optimal Convergence Rates for Damped Inertial Gradient Dynamics with Flat Geometries | 10.1007/s00245-023-09966-4 |
2023-03-09 | We consider the Euler-Bernoulli beam equation with a local Kelvin-Voigt dissipation type in the interval ( − 1 , 1 ) $(-1,1)$ . The coefficient damping is only effective in ( 0 , 1 ) $(0,1)$ and is degenerating near the 0 point with a speed at least equal to x α $x^{\alpha }$ where α ∈ ( 0 , 5 ) $\alpha \in (0,5)$ . We prove that the semigroup corresponding to the system is polynomially stable and the decay rate depends on the degeneracy speed α $\alpha $ . Here we develop a new method which consists to use a local analysis approach combined with the classical iterative method. | Stability for Euler-Bernoulli Beam Equation with a Local Degenerated Kelvin-Voigt Damping | 10.1007/s10440-023-00559-5 |
2023-03-01 | A new gravity sensor based on electromagnetic damping for the JMGrav marine gravimeter is presented. The new gravity sensor considered the advanced construction methods of the electromagnetic damping system of the gravimeter. The design features of the new system are discussed and the research survey data in the South China Sea are shown. Numerical simulations are applied to model the magnetic and mechanical characteristics of the system using finite element analysis and to evaluate the force distribution and the resulting damping effects. The performance characteristics of the system were tested on a motion simulator in laboratory, and the gravimeter was subjected to vertical accelerations of up to 100 Gal in 1–1 000 s. It was found that the amplitude reduction of vertical accelerations in 3–15 s is 30–45 dB, with a time lag of 2–5 s, while the effect on gravity in period greater than 600 s is less than 0.5 dB, with a time lag of less than 100 s. The accelerations cause discrepancies of approximately only 1 mGal between the static value and the mean dynamic value. The sea tests were conducted in September 2020. Gravity measurements were taken with a JMGrav marine gravimeter onboard the R/V Dongfanghong 3 , and the effective survey line exceeded 2 000 km. Completely irregular accelerations with peaks up to 100 Gal yielded a reduction of approximately 40 dB in amplitude. The survey data were evaluated using ocean gravity field models and grid line tests. The results show that the accuracy of the gravity measurements is better than 2 mGal. | A marine gravimeter based on electromagnetic damping and its tests in the South China Sea | 10.1007/s00343-022-2110-5 |
2023-03-01 | The soil nonlinear hysteretic behaviour is usually described, in the moderate strain range, through the shear modulus reduction and material damping ratio (MRD) curves. In common practice, in absence of specific laboratory tests, the curves are estimated by employing empirical regression models. Such predictive models, typically calibrated on large experimental datasets, correlate the soil response to its physical properties. This research fits within this context, presenting a comprehensive database of cyclic and dynamic laboratory tests conducted on natural Italian soils. The database, publicly available as supplementary data of the paper, contains the results of the tests conducted by the geotechnical laboratories of the Politecnico di Torino (Turin, Italy) and the Sapienza Università di Roma (Rome, Italy) over the past 30 years. The experimental data are employed to assess the performance of some widely used empirical models in predicting the MRD curves of natural uncemented fine-grained soils, emphasizing the importance of using an independent dataset for conducting a reliable statistical analysis. The results show that the use of many soil parameters as proxies for predicting the soil response does not necessarily lead to an improvement in the performance of the model. Therefore, according to Occam’s razor principle, simple models are to be preferred. | The PoliTO–UniRoma1 database of cyclic and dynamic laboratory tests: assessment of empirical predictive models | 10.1007/s10518-022-01573-y |
2023-03-01 | This work entails an analysis of secondary resonances in the parametrically damped van der Pol equation, with and without external excitation. A potential application of this system is a vertical-axis wind-turbine blade, which can have cyclic damping, aeroelastic self-excitation, and direct excitation. We analyze the system using the method of multiple scales and numerical solutions. For the case without external excitation, the analysis reveals nonresonant phase drift (quasiperiodic responses) and subharmonic resonance with possible phase drift or phase locking (periodic responses). The case of external excitation consists of a constant load and a harmonic load with the same frequency as the parametric term. Hard excitation is treated for nonresonant conditions and secondary resonances. Subharmonic and superharmonic resonances show possible phase drift and phase locking. Primary resonance is observed but not analyzed here. | Resonances of a forced van der Pol equation with parametric damping | 10.1007/s11071-022-08026-w |
2023-03-01 | This paper is devoted to stabilizing an ODE-PDE coupled system with boundary disturbance, where the PDE is chosen to be a wave equation with viscous damping. Applying the active disturbance rejection control (ADRC) technic, the unknown disturbance is estimated by the extended state observer (ESO). Assuming the absence of disturbance, the dynamic boundary connection is designed. The methods of spectral analysis and separation of operator are applied, which ensures the Riesz basis property as well as the spectrum determined growth condition. The exponential stability of the coupled system without disturbance is then concluded. Finally, combining the disturbance estimation and the dynamic boundary connection, a feedback controller designed to stabilize the coupled system, and the closed-loop system is proved to be asymptotically stable. | Stabilization of a Coupled ODE-wave System with Disturbances | 10.1007/s12555-021-1068-y |
2023-03-01 | To dampen periodic off-levelling motions within an inertial platform while undergoing horizontal accelerations of the same period and to achieve a levelling accuracy of a few tens of arcseconds with that system, an internally damped inertial platform for a marine scalar gravity system was the developed. Methods for attenuating horizontal acceleration and reducing off-levelling error by a satisfactory gyro-levelling loop, which are fundamental to the internally damped inertial platform, were designed and implemented. In addition, phase delays are introduced by the levelling loop. The resulting off-levelling gravity errors were analyzed and modeled. A series of tests on a motion simulator were performed in laboratory for a variety of simulated sea conditions. We found that the motion of the platform is a function of the amplitude and period of the simulated ship motions and ranges between 10 and 40 arcseconds. In addition, the phase lag between platform motion and ship motion is not constant but ranges 180°–270°, depending on the period and amplitude of the motion. Then, the platform, on which a gravimeter was mounted, was installed on the R/V Shiyan 2 to conduct a gravity survey in the South China Sea. Despite rough sea conditions, it was shown that in short periods of 2–30 s, the off-levelling angle was less than 30 arcseconds, and the phase lagged the horizontal acceleration by 230°–260°. From a repeated survey line and intersecting survey points, the estimated errors of gravity measurements were between 1.3 and 1.7 mGal. The marine measurements results were compared with those of satellite altimetry data and show a mean value of 0.5 mGal in a standard deviation of 1.5 mGal. | An internally damped inertial platform for marine gravimetry and a test case in the South China Sea | 10.1007/s00343-023-2337-9 |
2023-03-01 | An integral evolutionary model is constructed for calculating the thickness and flow rate of a fluid in a turbulent wave film, moving under the influence of gravity and tangential stress of a gas stream. Derivation of the model equations requires conditionally averaged Navier–Stokes equations with turbulent viscosity, which appears at averaging over the high-frequency (turbulent) component of the velocity field. The description of turbulent viscosity has been earlier proposed by the author in the form of a formula with a cubic attenuation law in a viscous sublayer, with linear behavior away from the wall and taking into account turbulence attenuation near the free surface of the film. For linear waves of small amplitude, a dispersion equation is derived; its results at small Reynolds numbers are consistent with known calculations by the laminar integral model. | An integral model for turbulent wave liquid film | 10.1134/S0869864323020105 |
2023-03-01 | Underground structures such as tunnels are one of the important elements in the transportation network that may show different seismic behavior compared to structures built on the ground due to being buried in the ground and bearing high stresses. Therefore, it is very important to pay attention to the behavior of these structures during seismic loading. In this study, in order to apply the damping approach in the soil-tunnel interaction system, a two-dimensional finite element model is employed with the help of ABAQUS software. For this purpose, the data of four known earthquakes are used to apply seismic load to the soil-tunnel system. Furthermore, depths of 15, 20, 25, 30 and 40 m for the tunnel and thicknesses of 0, 15 and 25 cm for the damper are considered, during which various parameters such as horizontal displacement, stress and tunnel strain response are evaluated. Moreover, to evaluate the effect of the type of damper, the results of the strain and stress applied to the tunnel crown for two types of dampers were compared with each other. It is important to state that the optimum thickness of the damper layer was reported to be 25 cm. The results show that putting a damper layer between the tunnel and the soil can reduce the tunnel’s maximum stress and strain for different seismic waves excitation up to 47% and 37%, respectively. The horizontal displacement of the tunnel in the saturated state is slightly higher than that of the unsaturated state. By and large, the application of shock-absorbing material, especially those with higher elastic modulus, can have an acceptable damping effect on the seismic response of the tunnel-soil interaction system, which is quite helpful for the anti-seismic design of tunnels. | Effect of a Shock-Absorbing Material on Seismic Responses of the Longitudinal Buried Tunnel Using Theoretical Analysis and Finite Element Modeling | 10.1007/s10706-022-02330-3 |
2023-03-01 | Generator tripping strategies are generally decided by offline transient stability analysis. However, traditional methods can hardly ensure dynamic stability after GT. Simulation tests show that GT strategies change the topology and the state variables of a power system, which may weaken the system damping after GT. In order to estimate the system damping, this paper proposes a time-varying linearized model under unsteady states based on the virtual equilibrium point (VEP) theory. Then, the changes in dynamic characteristics caused by GT can be represented by the eigenvalues at VEPs before and after GT. An inertia equivalence system is mathematically formulated to analyze the effects of generator inertia, damping ratio, and controllers. Two indices are designed to estimate the system damping changes. Based on the indices, a framework is proposed to improve the current GT strategy decision-making system. The sensitivity analysis and the fault scanning verify the effectiveness and robustness of the proposed method and indices. | A Novel Method to Estimate the System Damping After Generator Tripping | 10.1007/s42835-022-01261-6 |
2023-03-01 | In this study, we design ultralow density Mg−8.4Li (~ 1.46 g/cc), and Mg-9Li (~ 1.44 g/cc) alloys processed by Disintegrated Melt Deposition (DMD) having extraordinary properties outperforming the existing commercial magnesium (Mg) alloys in terms of specific strength, strain hardening ability and ductility. The developed alloys were characterized for microstructural, microhardness, compressive and damping properties. Unique image threshold technique coupled with SEM and EDS was used for better visualization of the phases and layers formed on the surface of Mg-Li binary alloys. The high reactivity of lithium (Li) with Mg resulted in evaporation and oxidation of alloying elements, thereby effectively reducing the wt.% of Li added to ~ 8.4 and 9 wt.% than the original amount of 15 and 20 wt.%, respectively. Microstructural analysis revealed presence of both α-Mg and β -Li solid solution phases in both Mg-8.4Li and Mg-9Li alloys. The materials presented impressive compressive and energy absorption properties, exhibiting > 80% fracture strain for both alloys, with Mg-8.4Li exhibiting the highest compressive yield strength (CYS) value of 192 MPa and Mg-9Li exhibiting the highest ultimate compressive strength (UCS) value of 2312 MPa. The overall damping properties were also enhanced for the binary Mg-Li alloys and showed the highest specific value as compared with other popular commercial magnesium, aluminum, titanium or ferrous alloys. Finally, microstructural changes in Mg owing to alloying with Li and its effect on the mechanical and damping properties are elaborately discussed. | Development of Ultralight Binary Mg-Li Alloys: Enhancing Damping, Ductility, and Ultimate Compressive Strength beyond 2000 MPa | 10.1007/s11665-022-07335-w |
2023-03-01 | The motion of both internal and surface waves in incompressible fluids under capillary and gravity forces is a major research topic. In particular, we review the derivation of some new models describing the dynamics of gravity-capillary nonlinear waves in incompressible flows. These models take the form of both bidirectional and unidirectional nonlinear and nonlocal wave equations. More precisely, with the goal of telling a more complete story, in this paper we present the results in the works (Cheng in Water Waves 1(1):71-130, 2019; Granero-Belinchón and Ortega in On the motion of gravity-capillary waves with odd viscosity. arXiv:2103.01062 , 2021; Granero-Belinchón and Scrobogna in J Diff Equ 276:96–148 1921; SIAM J Appl Math 79(6):2530–2550, 2019; Proc Am Math Soc 148(12):5181–5191, 2020; Phys Fluids 33(10):102115, 2021; Granero-Belinchón and Shkoller in Multiscale Model Simul 15(1):274–308, 2017) together with some new results regarding the well-posedness of the resulting PDEs. | Interfaces in incompressible flows | 10.1007/s40324-021-00283-w |
2023-03-01 | Inter-story isolation system (IIS) is increasingly being sought to add floors on top of existing buildings while controlling their base shear forces. One of the main issues with this application is the need to control the drift between the two structural parts and the acceleration of the superstructure, while optimizing the substructure performance. Therefore, this study investigates the use of the IIS as a structural Tuned Mass Damper (TMD), proposing a specific multi-objective optimization approach and providing new design equations for the IIS parameters. Unlike conventional TMD approaches, which focus on the performance of the primary structure (i.e., substructure), the proposed approach aims to consider the overall structural response. The optimal solutions obtained are then compared with the consistent ones currently available in the literature. Finally, time-history analyses of three simple case study structures are performed to validate these optimized solutions. The results demonstrate the potential of the IIS in improving the seismic performance of the substructure, as well as the possibility of limiting the isolation drifts and superstructure accelerations according to specific needs. | Multi-objective optimization of the inter-story isolation system used as a structural TMD | 10.1007/s10518-022-01592-9 |
2023-03-01 | Supercritical transmission shafts, which have one or more critical speeds below their working speeds, are becoming more popular in new rotorcraft designs. To attenuate the excessive transcritical vibration, dry friction damper is a prevailing choice. In this paper, we focus on the basic working mechanism and parameter influence of the dry friction damper for supercritical transmission shaft. Mathematical model of the dry friction damper, which fully considers the nonlinear rub-impact and side-dry-friction effects, is proposed and integrated with finite element model of the transmission shaft to investigate nonlinear interactions between the shaft and damper. It is demonstrated through systematic numerical simulations that a typical transcritical response with dry friction damper can be divided into 4 sub-regions and the dry friction damper takes effect only within region II and III respectively through hard-stopping and side-dry-friction effects. In addition, effects of nonlinear bearing force, transcritical acceleration and initial location of the damper are discussed in detail. Moreover, influences of 3 key damper parameters, that is the rub-impact clearance, the critical slip force and the circumferential friction coefficient, are further investigated, which provides a guidance for designs of the dry friction damper. Finally, prototypes of the dry friction damper are designed, manufactured and tested on a rotor dynamics test rig. For the first time, the theoretical analysis and numerical simulation results are quantitatively verified by an experiment. | Nonlinear modelling and parameter influence of supercritical transmission shaft with dry friction damper | 10.1007/s10999-022-09625-6 |
2023-03-01 | In this paper, the main purpose is to study existence of the global attractor for the weakly damped wave equation with gradient type nonlinearity. To this end, we first verify the existence and uniqueness of global weak solution by the Galerkin method and compulsively variational method. Furthermore, we obtained the global strong solution under some mild assumptions on f . Secondly, we utilize the $$\omega$$ ω -limit compactness to show the semigroup generated by the equation has a compact, connected and invariant attractor. | Global Attractors for a Class of Weakly Damped Wave Equations with Gradient Type Nonlinearity | 10.1007/s44198-022-00079-0 |
2023-02-28 | In this paper, we consider the initial-boundary value problems with several fundamental boundary conditions (the Dirichlet/Neumann/Robin boundary condition) for the multi-component system of semi-linear classical damped wave equations outside a ball. By applying a test function approach with a judicious choice of test functions, which approximates the harmonic functions being subject to these boundary conditions on $$\partial \varOmega $$ ∂ Ω , simultaneously we have succeeded in proving the blow-up result in a finite time as well as in catching the upper bound of lifespan estimates for small solutions in all spatial dimensions. Moreover, such kind of these results, which become sharp in the subcritical cases for one-dimensional case, will be discussed at the end of this paper. | Blow-up and lifespan estimates for solutions to the weakly coupled system of nonlinear damped wave equations outside a ball | 10.1007/s00028-023-00875-1 |
2023-02-27 | Quantum speed limit (QSL) represents the minimum evolution time of a quantum system. We investigate the QSL time of a two-level qubit in a phase-damping channel. By manipulating measurement-based feedback controls on the qubit, we show that the QSL time of the qubit can have an obvious decline when the measurement rate is high. We also study the effect from feedback and find that the QSL time can reach the largest value when the feedback angle is $${\pi \mathord{\left/ {\vphantom {\pi 2}} \right. \kern-0pt} 2}$$ and it decreases symmetrically on both sides of the angle. Additionally, the QSL time of qubit in the whole dynamic process is calculated. High rate of measurement and control is helpful to drive the QSL time to a stable value at earlier time and the variation of the optimal evolution time can be witnessed by the purity of the qubit system. | Quantum Speed Limit Under the Influence of Measurement-based Feedback Control | 10.1007/s10773-023-05318-8 |
2023-02-21 | The paper investigates the well-posedness and the complete regularity of the weak solutions, and the existence of strong global attractor for the strongly damped wave equation with critical nonlinearities on $$\mathbb {R}^3: u_{tt}-\Delta u-\Delta u_{t}+h(x,u_t)+g(x,u)=f(x)$$ R 3 : u tt - Δ u - Δ u t + h ( x , u t ) + g ( x , u ) = f ( x ) . We show that when both nonlinearities $$h(x,u_t)$$ h ( x , u t ) and g ( x , u ) are of at most critical growth, (1) the model is well-posed and its weak solution is of higher complete regularity as $$t>0$$ t > 0 , which ensures that the weak solution is exactly the strong one; (2) the related dynamical system $$(S(t),\mathcal {H})$$ ( S ( t ) , H ) possesses a strong $$(\mathcal {H}, \mathcal {H}_{2})$$ ( H , H 2 ) -global attractor of optimal topological property, which is also the standard global attractor of optimal regularity of S ( t ) in $$\mathcal {H}$$ H . The method developed here allows breaking through the long-standing restriction for this model on $$\mathbb {R}^3$$ R 3 : the partial regularity of the weak solutions and almost linearity of $$h(x,u_t)$$ h ( x , u t ) , and helps obtaining the optimal complete regularity of the weak solutions and the existence of strong global attractor. | Complete regularity and strong attractor for the strongly damped wave equation with critical nonlinearities on
$$\mathbb {R}^{3}$$
R
3
| 10.1007/s00028-023-00872-4 |
2023-02-13 | The energy dissipation capacity (EDC) of most current configurations of yielding steel dampers is susceptible to be improved by applying optimization concepts. Thus, this study proposes a methodology to enhance the EDC of a slotted hollow cylinder steel (HCS) damper under a cyclic displacement protocol while keeping the same quantity of material via shape optimization. The simulated annealing algorithm was selected for solving the optimization problem as it uses only one candidate solution per iteration, reducing the computational cost associated with the EDC computation. In addition, the finite element software ABAQUS is used to model the behavior of the steel damper under cyclic loads. A code is elaborated using the Python programming language for the optimization process, containing the instructions to be executed in ABAQUS. Five slot configurations were proposed for the initial damper to determine the effect of the initial solution on the optimized HCS damper. The results show that the proposed optimization process obtains optimized models with stable hysteretic behavior and a significantly higher energy dissipation capacity than the initial models. The optimal configuration presented an EDC of 5543 J, 16% higher than the HCS damper without slots and with the same material quantity. The material is mainly located parallel to the beam, simulating two 2D shear steel plates. The difference in EDC with other optimized configurations reaches 955 J, indicating the dependence of the solution on the initial damper configuration. In addition, the difference in the optimized damper topologies proves the multi-modality characteristic of the problem. The proposed algorithm is easy to implement in a computer and reaches the optimal solution with less than 50 iterations. | A proposal for the optimization of the geometric configuration of a hollow cylindrical steel damper with slots | 10.1007/s40430-022-03919-8 |
2023-02-12 | The present study investigates the dynamic mechanical response of crump rubber filled epoxy composites. The effect of crump rubber content (0, 10, 20 and 30 vol.%) on the storage modulus, loss modulus and damping properties is assessed by experimental and theoretical approaches. The experimental storage modulus decreases with an increase in temperature for all the compositions while the experimental loss modulus of EC-30 registers higher values in comparison with other compositions. Damping capabilities also increase with higher filler content. The strengthening mechanism of the crump rubber composite is validated through the effectiveness of dispersion, degree of entanglement and activation energy. The increment in the degree of entanglement and activation energy are 84 and 154% higher than the neat epoxy, respectively, which implies the thermal stability of the composite. The results of theoretical modeling evaluated for the storage and loss modulus are in good agreement with the experimental results. | Evaluation of dynamic mechanical analysis of crump rubber epoxy composites: experimental and empirical perspective | 10.1007/s40430-023-04033-z |
2023-02-10 | This article focuses on the oscillation and asymptotic behavior of the third-order neutral differential equation with damping and distributed deviating arguments. Some new sufficient conditions for the discussed equation are established by using a generalized Riccati transformation, which extend and improve several known results in the literature. Finally, two examples are given to illustrate the obtained results. | Oscillation and Asymptotic Behavior of the Third-Order Neutral Differential Equation with Damping and Distributed Deviating Arguments | 10.1007/s12346-022-00733-4 |
2023-02-07 | Control systems based on fuzzy logic (FL) and proportional–integral–derivative (PID) are among the effective controllers which operate using an inference mechanism rule base and control loop mechanism that continuously calculates an error value. Because of that both of them are being used as a practical solution for major vibration problems in many applications recently. However, in automotive suspension applications, the number of study on reducing the amplitude vibration of vehicle ride comfort using these controllers, especially in the experimental study, is still limited. Thus, this study aims to improve the performance of the said controllers by integrating with a modified version of the algorithm known as the advanced firefly algorithm (AFA) in the suspension system application. An experimental quarter vehicle test rig complete with a magnetorheological (MR) damper is used in this study to test and compare the effectiveness of the proposed FL-AFA and PID-AFA controllers against the passive controller system. An external disturbance in the form of sinusoidal waves is applied to the system to verify the sensitivity and durability of the proposed control schemes, and consequently, a comparative study is performed to analyze the system characteristics. Two major issues known as the disturbance rejection and damping constraint are investigated and overcome by proposing a good controller scheme with intelligent optimizers. The experiment result indicates that the PID-AFA shows a good response compared to the FL-AFA and the passive system, with the ability to reduce the vibration amplitude by up to 57.1%. | Experimental evaluation of ride comfort performance for suspension system using PID and fuzzy logic controllers by advanced firefly algorithm | 10.1007/s40430-023-04057-5 |
2023-02-06 | This paper investigates a transmission problem of viscoelastic wave equations with degenerate nonlocal damping. We prove the global well-posedness of the problem with the aid of Faedo–Galerkin technique and the multiplier method. Meantime, by introducing a new Lyapunov functional, we establish the optimal explicit and general energy decay results. | Global well-posedness and optimal decay rates for a transmission problem of viscoelastic wave equations with degenerate nonlocal damping | 10.1007/s00033-023-01949-3 |
2023-02-02 | In this paper, we study global stability dynamics for quasilinear damped Klein–Gordon equation with variable coefficients in $${\mathbb {R}}^n$$ R n for dimension $$n\ge 1$$ n ≥ 1 , without assuming that the quasilinear term satisfies the null condition. Due to the influence of damping term, we are able to prove that if it admits a global smooth solution (including time quasi-periodic solution), then this quasilinear system must be asymptotic stable in Sobolev space under some assumptions on the variable coefficients of it. This result also implies that a smooth large solution can be constructed for such quasilinear system, which includes time quasi-periodic stable dynamics of Klein–Gordon equation. We note the global stability for a class of semilinear wave equation satisfying null condition has been shown by Zha (J Funct Anal 282:109219, 2022). | Global Stability Dynamics of the Quasilinear Damped Klein–Gordon Equation with Variable Coefficients | 10.1007/s12220-022-01169-7 |
2023-02-01 | Friction force microscopy (FFM) explores the interaction in a sliding contact on the nanoscale, providing information on the frictional dynamics and lateral contact stiffness with lattice resolution. Recent FFM measurements on a NaCl crystal immersed in liquid (ethanol) surroundings displayed an increase of the effective contact stiffness, K _eff, with the applied load, differently from similar measurements performed under ultra-high vacuum (UHV) conditions, where K _eff showed negligible load dependency. Additionally, under UHV conditions multiple slip length friction with increasing load was reported, while in ethanol surroundings only single (lattice unit length) slips were observed. Our current understanding of this behavior relates the transition from single jumps to multiple jumps dynamics to the normal load (manifested through the amplitude of the interaction potential at the contact, U _0) and to the damping of the system. Here we have incorporated the effect of the load dependency on both U _0 and K _eff within Prandtl—Tomlinson based simulations, accompanied by variations in the damping coefficient of the system. Introducing the experimentally observed load dependency to K _eff resulted indeed in single slip jumps at critical damping, while multiple slip jumps were obtained at constant K _eff. The average slip length increased with the normal load, particularly when the system became underdamped. Our work provides a glimpse on the relation between the characteristic observables in atomic-scale sliding friction (maximal slip forces, stiffness, and slip dynamics) with respect to their governing parameters (corrugation energy, effective stiffness, and damping). While common understanding in nanotribology relates the effect of surrounding media mainly to the interaction potential at the contact, here we show that the media can also greatly affect the elastic interaction, and consequently play an important role on the transition from single to multiple stick-slip. | Surroundings affect slip length dynamics in nanoscale friction through contact stiffness and damping | 10.1007/s40544-021-0590-5 |
2023-02-01 | Inerter-based-dampers have received substantial interest from the earthquake engineering community in the last two decades. These typically consist of an inerter, a linear spring and a viscous damper arranged into various possible configurations. In this paper, for the first time, experimental results are presented from shake table tests on a scaled three-storey structure with an inerter-based damper included, in order to suppress vibration amplitudes at the resonant frequencies. In particular two types of device are used to demonstrate the differences between using viscous and hysteretic damping in the inerter-based device. The two different types of experimental dampers were manufactured using eddy current dampers and gel damping material. The inerter was manufactured based on a flywheel design. The experimental results were compared with four analytical models tuned to suppress vibrations in the first resonance; namely the tuned-inerter-damper, the tuned-inerter-hysteretic-damper, the tuned-mass-damper-inerter, and the tuned-mass-hysteretic-damper-inerter. These experimental results confirm the observations made from the models that the suppression of higher resonance peaks is significantly different between the viscous and hysteretic damped inerter-based-dampers. Consequently, it is recommended that future studies exploring the performance of inerter-based seismic mitigation systems pay close attention to the damping mechanisms that are prevalent within the structure. | Experimental shake table validation of damping behaviour in inerter-based dampers | 10.1007/s10518-022-01376-1 |
2023-02-01 | The damping characteristic of a specific type of high-strength alloys was researched by using a dynamic mechanical analyzer (DMA) and via the application of viscoelastic damping theory. The characteristics of temperature/frequency-dependent damping and coupling factor are provided from the perspective of dynamic applications. Consider the evolution of damping characteristics. The evolution can be expressed as a time-dependent term and a non-time-dependent term. This time-dependent-term variable damping nonlinear stochastic dynamic analysis method was proposed according to the random vibration of magnesium alloy structures. The quasi-non-stationary random analysis method of stationary problems was established based on the solution characteristics of the pseudo-excitation method. In contrast, from the numerical analysis results and experiments conducted on magnesium alloy structures, it is demonstrated that the analysis results of constant damping systems have obvious inconsistencies with the experimental results. The calculation results based on variable damping systems were more consistent with experimental results. It is suggested that variable damping theory should be used in the dynamic structural analysis of the magnesium alloy material under consideration in fields and applications with higher accuracy requirements. | The Characteristics of Temperature/Frequency-Dependent Damping and Quasi-Non-Stationary Random Dynamic Method | 10.1007/s40799-021-00531-8 |
2023-02-01 | This paper deals with the following Petrovsky equation with damping and nonlinear sources: $${u_{tt}} + {\Delta ^2}u - M\left({\left\| {\nabla u} \right\|_2^2} \right)\Delta u - \Delta {u_t} + {\left| {{u_t}} \right|^{m(x) - 2}}{u_t} = {\left| u \right|^{p(x) - 2}}u$$ u t t + Δ 2 u − M ( ‖ ∇ u ‖ 2 2 ) Δ u − Δ u t + | u t | m ( x ) − 2 u t = | u | p ( x ) − 2 u under initial-boundary value conditions, where M ( s ) = a + bs ^ γ is a positive C ^1 function with the parameters a > 0, b > 0, γ ⩾ 1, and m ( x ) and p ( x ) are given measurable functions. The upper bound of the blow-up time is derived for low initial energy by the differential inequality technique. For m ( x ) ≡ 2, in particular, the upper bound of the blow-up time is obtained by the combination of Levine’s concavity method and some differential inequalities under high initial energy. In addition, we discuss the lower bound of the blow-up time by making full use of the strong damping. Moreover, we present the global existence of solutions and an energy decay estimate by establishing some energy estimates. | Behavior of solutions to a Petrovsky equation with damping and variable-exponent sources | 10.1007/s11425-021-1926-x |
2023-02-01 | Abstract This paper introduces a comprehensive study on vibration damping of a lumped aeroelastic wing model with translational linear and torsional nonlinear spring elements considering different actuation scenarios. The wing models have two degrees of freedom (DoFs) representing translational and torsional oscillations. On the other hand, the flap angles represent the control inputs that attempt to regulate the wing vibrations. Depending on the number of flaps designed, three actuation scenarios are investigated including fully actuated, overactuated, and underactuated wing models. For a fully actuated wing system (Scenario 1), conventional adaptive control strategies can be used for damping wing oscillations; however, adaptive approximation control is adopted in this work due to its capabilities for controlling (regulating) the dynamic system in the presence of the unknown system parameters. On the other hand, in the overactuated wing model (Scenario 2), the wing system has more control inputs than the DoFs and hence infinite solutions for the control input response are obtained. The Pseudoinverse matrix is a powerful tool to resolve this problem. In Scenario 3, the control inputs are less than the DoFs and hence a partial feedback linearization control strategy with an adaptive approximation compensator is used for regulation purposes; however, the internal dynamics of the underactuated wing system should be stable. Simulation experiments are performed to prove the effectiveness of control methods of the investigated scenarios. | Function Approximation Technique (FAT)-Based Adaptive Feedback Linearization Control for Nonlinear Aeroelastic Wing Models Considering Different Actuation Scenarios | 10.1134/S2070048223010106 |
2023-02-01 | An array of air chambers embedded on the tunnel track is numerically investigated for different configurations. The air chambers act as an in-tunnel countermeasure to alleviate non-linear steepening of compression waves during propagation process thereby mitigating emission of high amplitude micro-pressure waves (MPWs) from the exit portal. The air chambers are designed to entrap the incoming flow and induce damping behavior so as to reduce wave steepening in tunnels. Initially, qualititative comparisons are made between Helmholtz resonator and damping type air chambers. Thereafter, the quantitative assessment of the compression wave properties are checked in detail. From results, over damped air chamber shows 60 % reduction in peak over pressure for weak compression wave whereas the Helmholtz resonator and critically damped shows 35 % and 22 %, respectively. Similarly, due to the presence of over damped air chamber, 17 % reduction in maximum pressure gradient is noticed while critically damped shows close to 10 % reduction. | Effect of air chambers on the compression wave propagating along a high-speed railway tunnel | 10.1007/s12206-023-0122-5 |
2023-02-01 | One of the most effective approaches for seismic protection of structural systems is isolation. The majority of existing seismic protection systems are related to horizontal ground motion and only few focus on vertical seismic components, as this would require vertical flexibility, a feature conflicting with the need for sufficient support of the isolated structure. In order to overcome this difficulty, a novel vertical Stiff dynamic absorber (SDA) is proposed that combines a Quasi-Zero Stiffness design including negative stiffness elements, an enhanced Tuned Mass Damper, and Inerter elements. The present work deals with the optimization problem for the determination of the various design parameters of the proposed configuration, aiming at minimizing the vertical accelerations induced on the structure while keeping the displacement within reasonable limits. The values of the optimized design parameters depend only on the characteristics of the isolated structure irrespectively of the excitation input. This feature differentiates the proposed SDA from similar versions found in the literature and renders the design applicable for use across a wide range of vertical vibration control applications. The proposed configuration is designed to achieve great acceleration isolation without compromising the weight-bearing capacity of the structure. This is realized through the appropriate determination of the static and dynamic stiffnesses via a novel calculation approach that is based on the initial static equilibrium point. The role of various design factors is investigated based on time-history responses of a reference structure to artificial accelerograms matching EC8 criteria, and the effect of the optimized SDA is evaluated on real earthquake records, confirming its capacity to greatly reduce the response to structure accelerations. The selection of the design parameters is based on engineering criteria and an indicative implementation of the design elements is included, demonstrating the feasibility of the proposed configuration. | Vertical seismic protection of structures with inerter-based negative stiffness absorbers | 10.1007/s10518-021-01284-w |
2023-02-01 | This paper presents the network-based modeling, validation and analysis of the nonlinear liquid spring damper model under vertical landing conditions of reusable launch vehicle. The impedance function of damper model is derived first. Then, its mechanical and hydraulic networks are newly established based on the hydro-mechanical analogy and network-based analysis. By comparing the networks between the corresponding symmetric and asymmetric structures, the meaning of each branch in the network is elucidated. After that, the validity of the network-based model for the liquid spring damper is confirmed by comparison against the experimentally verified nonlinear model in both frequency and time domain. The force and energy absorption characteristics of the damper model are further decomposed, and, specifically, the influence of the orifice area and orifice length on the attenuation performance is studied. The results show that the network-based model provides predictions consistent with those generated by the nonlinear model. The main discrepancy is attributed to the inaccuracy caused by the equivalent fluid bulk modulus. The network-based analysis indicates that the orifice area mainly influences the damping force in the network, which further affects the loads and efficiency of the damper. The orifice length mainly influences the inertia force in the network, which should be limited to a small value. The proposed novel interpretation of the damper models and responses under impact conditions constitutes a framework suitable for systematic design of typically highly nonlinear landing systems in reusable launch vehicles. | Analysis of liquid spring damper for vertical landing reusable launch vehicle with network-based methodology | 10.1007/s11071-022-07944-z |
2023-02-01 | Evaluating safety and stability of concrete dams in highly seismic regions is an increasing concern. Therefore, proposing an effective model that can predict crack propagation with good accuracy and low computation time is essential. The purpose of this study is to develop a special purpose finite element program for nonlinear dynamic analysis of concrete gravity dams. Despite its simple formulation and preferably easy programing, it should be able to predict acceptable crack patterns compared with previous studies. For this aim, a finite element program is developed based on a simplified isotropic continuum damage model. It also relies on the Hilber–Hughes–Taylor time integration method. Moreover, three different damping algorithms are employed in this program to study the nonlinear response of Koyna dam. It is concluded that variable damping algorithms leads to a more localized crack pattern in comparison to constant damping algorithm alternative. Furthermore, by increasing the numerical damping (i.e., α-factor) in the Hilber–Hughes–Taylor time integration method, the results of varying damping in each step get close to the results of varying damping in each iteration. Therefore, varying damping in each step with higher α-factors can be a suitable replacement to more common strategy in this respect due to its significant computational time saving. | Nonlinear dynamic analysis of concrete gravity dams utilizing a simplified continuum damage model and different damping algorithms | 10.1007/s42107-022-00511-2 |
2023-02-01 | Ferrofluids are a type of nanometer-scale functional material with fluidity and superparamagnetism. They are composed of ferromagnetic particles, surfactants, and base liquids. The main characteristics of ferrofluids include magnetization, the magnetoviscous effect, and levitation characteristics. There are many mature commercial ferrofluid damping applications based on these characteristics that are widely used in numerous fields. Furthermore, some ferrofluid damping studies such as those related to vibration energy harvesters and biomedical devices are still in the laboratory stage. This review paper summarizes typical ferrofluid dampers and energy harvesting systems from the 1960s to the present, including ferrofluid viscous dampers, ferrofluid inertia dampers, tuned magnetic fluid dampers (TMFDs), and vibration energy harvesters. In particular, it focuses on TMFDs and vibration energy harvesters because they have been the hottest research topics in the ferrofluid damping field in recent years. This review also proposes a novel magnetic fluid damper that achieves energy conversion and improves the efficiency of vibration attenuation. Finally, we discuss the potential challenges and development of ferrofluid damping in future research. | Typical dampers and energy harvesters based on characteristics of ferrofluids | 10.1007/s40544-022-0616-7 |
2023-02-01 | Abstract Botrytis cinerea , Rhizoctonia solani and Hemileia vastatrix are three species of phytopathogenic fungi behind major crop losses worldwide. These have been selected as target models for testing the fungicide potential of a series of bis (ylidene) cyclohexanones. Although some compounds of this chemical class are known to have inhibitory activity against human pathogens, they have never been explored for the control of phytopathogens until now. In the present work, bis (ylidene) cyclohexanones were synthesized through simple, fast and low-cost base- or acid-catalyzed aldol condensation reaction and tested in vitro against B. cinerea , R. solani and H. vastatrix . bis (pyridylmethylene) cyclohexanones showed the highest activity against the target fungi. When tested at 200 nmol per mycelial plug against R. solani ., these compounds completely inhibited the mycelial growth, and the most active bis (pyridylmethylene) cyclohexanone compound had an IC_50 of 155.5 nmol plug^−1. Additionally, bis (pyridylmethylene) cyclohexanones completely inhibited urediniospore germination of H. vastatrix , at 125 μmol L^−1. The most active bis (pyridylmethylene) cyclohexanone had an IC_50 value of 4.8 µmol L^−1, which was estimated as approximately 2.6 times lower than that found for the copper oxychloride-based fungicide, used as control. Additionally, these substances had a low cytotoxicity against the mammalian Vero cell line. Finally, in silico calculations indicated that these compounds present physicochemical parameters regarded as suitable for agrochemicals. Bis (ylidene) cyclohexanones may constitute promising candidates for the development of novel antifungal agents for the control of relevant fungal diseases in agriculture. Graphical Abstract | Synthesis of bis(ylidene) cyclohexanones and their antifungal activity against selected plant pathogenic fungi | 10.1007/s11030-022-10431-7 |
2023-02-01 | Background Façade technologies are in continuous evolution and the idea to realize buildings equipped with cladding systems capable to undergo significant displacements relatively to the main structure has been considered by many authors as an opportunity to improve their vibration performances. Method From a structural dynamics viewpoint, a building with a monolithic Moving Façade is essentially the same thing as a building with a Tuned Mass Damper. However, in the presence of excitations directly acting on the external surface of the building, there may be significant diferences of behavior. In this work, a first step towards a systematic comparison between the performances of buildings with Moving Façades and Tuned Mass Dampers is carried out in the simplest setting of 2 degrees of freedom modeling and harmonic excitation. Results Despite the deceptive simplicity of the setting, some of the aspects related to the potential applicability of moving façades to vibration damping and the correlated limitations are discussed and critically analyzed. The analyses show that, depending on the tuning of the system, monolithic Moving Façades could effectively act as vibration absorbers with a potentially high efficiency. However, it turns out that good performances could be realized at the price of extremely large displacements of the façade. The possibility to pursue potential applications of this type of systems seems therefore to be subordinated to the search of solutions to limit such displacements within functionally acceptable ranges. | Vibration Damping Performances of Buildings with Moving Façades Under Harmonic Excitation | 10.1007/s42417-020-00247-w |
2023-02-01 | Flexible microporous metal rubber (FMP-MR) is a high-damping material that dissipates energy by dry friction through internal spiral metal wires in contact with each other. However, the FMP-MR energy dissipation mechanism is not fully understood owing to its disordered grid interpenetrating structure. In this work, computer-aided preparation technology is used to accurately reconstruct the complex spiral network structure of FMP-MR multipoint random contact, and a cell group model with an energy dissipation mechanism is proposed to obtain the dynamic energy distribution of the contact friction in both space and time dimensions. By judging the effective contact point, a global displacement ablation phenomenon of hooked staggered porous materials is induced. The macro- and micro-equivalent frictions are introduced to effectively explain the characteristics of the strong energy dissipation in FMP-MR under fretting excitation. A real and effective damping hysteresis constitutive model is then constructed to dynamically capture the mapping relationship between the complex nonlinear topological structure effect of the materials and spatial random contact dry friction in real time. The results indicate that the contact behavior between turns of the FMP-MR wire follows a clear quasi-Gaussian distribution under an external load, forcing the topological results to change. The energy dissipation of the materials revealed peak energy consumption lagging behind the loading limit for a certain distance, which can be determined by the effective contact point and contact dry friction slip. The consistency between the quasi-static compression tests and constitutive curves of the model was quantitatively verified through residual analysis. The data demonstrated the differential behavior of the FMP-MR meso-structure to follow a phased growth law during loading with different action mechanisms in the guiding, main growth, and relaxation stages of the energy consumption displacement curve. In summary, these findings provide an acceptable theoretical basis for the damping energy consumption mechanism and lifetime prediction of FMP-MR. | Dry friction damping mechanism of flexible microporous metal rubber based on cell group energy dissipation mechanism | 10.1007/s40544-022-0599-4 |
2023-02-01 | An inerter is a two-terminal inertial element that can produce an amplified inertance and enhanced damping when operating with spring and damping elements. Its superior vibration mitigation effect has been proved by previous studies. Although H∞ optimal design of inerter-controlled single-degree-of-freedom structure can be derived based on fixed-point method, rational and theoretical design methods for inerter-controlled multi-degree-of-freedom (MDOF) structures yet need to be developed. In this study, a practical and semi-analytical method based on the damping enhancement principle is proposed for the design of inerter-controlled MDOF structures under earthquakes. To improve the vibration mitigation efficiency, the parameters of inerter systems are distributed based on structural responses, and the required damping coefficient in the inerter systems is minimized to fully utilize the damping enhancement effect of inerter systems. The response mitigation ratio is taken as the targeted performance index to fulfill the demand-oriented design philosophy presented in this study. The stochastic response of the structure is obtained by conducting complex mode superposition. A detailed design procedure and corresponding computer program is developed. Three benchmark structures are employed to exemplify the effectiveness of the proposed design. The analysis results show that the story drifts and story shear forces of the designed structure are effectively mitigated to the target value. In comparison with an existing method (the fixed-point method), the proposed design strategy efficiently exploits the damping enhancement effect, resulting in reducing the damping coefficient and damping force while satisfying the performance demand, thereby producing a rational and economical design. | Design of MDOF structure with damping enhanced inerter systems | 10.1007/s10518-022-01381-4 |
2023-02-01 | An improved incremental harmonic balance method (IHBM) is proposed by Wang (J Sound Vib 441:111–125, 2019) to solve the periodic responses of the continuous nonlinear stiffness systems. However, the nonlinear damping systems remain unsolved. This paper aims to investigate the nonlinear damping parts by the proposed IHBM method, which is based on the principle that any continuous curve can be approximated by a piecewise-linear curve with discrete nodes. The piecewise-linear function can be considered a unified benchmark function that can convert the complex IHBM Galerkin process of arbitrary nonlinear damping systems to that of unified piecewise-linear damping systems. The general process of the proposed method for this piecewise-linear system is derived considering the stability of the solutions. Then, a polynomial nonlinear damping system is investigated to validate the accuracy of the method. Furthermore, five typical cases of single-degree-of-freedom (SDOF) nonlinear damping systems are carried out, and this method is also extended to multi-degree-of-freedom (MDOF) systems where each nonlinear force in the systems is expressed by the function of only one independent DOF. The results illustrate that the proposed method shows convenience and accuracy in obtaining the dynamics of nonlinear systems. | Vibration analysis of nonlinear damping systems by the discrete incremental harmonic balance method | 10.1007/s11071-022-07953-y |
2023-02-01 | To meet the excitation frequency in the range of 0-200 Hz engine mount to achieve better noise, vibration, and harshness performance (NVH). This paper proposes a new bell plate controllable multi-inertia channel MRF (magnetorheological fluid) mount for dynamic characteristic analysis and research. Firstly, designing a multi-flow channel MRF damper and verifying by the experimental method that a larger current can achieve switching and closing of the flow channels. Secondly, the lumped parameter models of controllable multi-inertia channel MRF mount and controllable multi-inertia channels MRF mount with two bell plates and decoupler membrane combinations (new bell plate multi-inertia channel MRF mount) are solved separately, and the dynamic characteristics of the mounts at high and low frequencies are analyzed. Finally, the 3-degree-of-freedom mount system of the 1/4 car model is built to analyze the effects of different inertia channel switching and closing on the relative displacement of the vehicle frame and engine, and the transfer force of the engine to the vehicle frame. The results show that the designed new bell plate controllable multi-inertia channel MRF mount can achieve adjustable dynamic stiffness and damping in the frequency range of 0-50 Hz, and has a small dynamic stiffness value in the range of 50 Hz-200 Hz. Therefore, the designed MRF mount can achieve wide frequency vibration isolation. | Dynamic Characteristic Analysis of New Bell Plate Controllable Multi-Inertia Channel MRF Mount with Wide Frequency Isolation | 10.1007/s40799-021-00539-0 |
2023-02-01 | In recent years, the tuned mass damper inerter (TMDI) has been demonstrated in several theoretical studies to be an effective vibration absorber for the seismic protection of non-isolated buildings. Its effectiveness relies on careful tuning of the TMDI stiffness and damping properties, while its performance improves with the increase of the inertance property which is readily scalable. Nevertheless, in all previous studies, the energy dissipative TMDI element has been modelled by a linear viscous damper. Still, commercial viscous dampers display a nonlinear velocity-dependent power law behavior. In this regard, this paper investigates, for the first time in literature, the potential of the TMDI fitted with nonlinear viscous damper (NVD) for seismic response protection of multi-storey buildings. This is supported by an efficient optimal nonlinear TMDI (NTMDI) tuning approach which accounts for any absorber connectivity to the building structure and employs statistical linearization to treat the nonlinear damping term. For the special case of white-noise excited undamped buildings, optimal NTMDI tuning is derived analytically in closed-form which is shown to be sufficiently accurate for lightly damped structures. Comprehensive numerical data are presented to delineate trends of optimal NVD damping coefficient with the NVD power-law exponent and the inertance. Further, nonlinear response history analysis results pertaining to optimally tuned NTMDI application for a benchmark 9-storey steel structure demonstrate that reduced NTMDI stroke and inerter force can be achieved with negligible change in storey drifts and floor acceleration performance by adopting lower NVD exponent values, leading to practically beneficial NTMDI deployments. | Optimal design and assessment of tuned mass damper inerter with nonlinear viscous damper in seismically excited multi-storey buildings | 10.1007/s10518-022-01609-3 |
2023-02-01 | Inerter-based vibration absorbers (IVAs), such as the tuned-mass-damper-inerter (TMDI), have become popular in recent years for the earthquake protection of building structures. Previous studies using linear structural models have shown that IVAs can achieve enhanced vibration suppression, but at the expense of increased control forces exerted from the IVA to the host building structure. The authors recently developed a bi-objective IVA design framework for linearly behaving buildings to balance between structural performance (drift/acceleration suppression) and IVA forces. This paper extends the framework to multi-storey hysteretic/yielding structures under seismic excitation. Though the proposed design framework can accommodate any type of IVA, the focus is herein on TMDI applications, with tuned-mass-damper (TMD) and tuned-inerter-damper (TID) treated as special cases of the TMDI. Earthquake hazard is modeled through representative, design-level acceleration time-histories and response of the IVA-equipped structure is evaluated through nonlinear response-history analysis. A high-fidelity finite element model (FEM) is established to accurately describe hysteretic structural behavior. To reduce the computational burden, a reduced order model (ROM) is based on the original FEM, using the framework proposed recently by the first and second authors. The ROM maintains the accuracy of the original FEM while enabling for a computationally efficient solution to the optimization problem. As an illustrative example, the bi-objective design for different IVA placements along the height of a non-linear benchmark 9-storey steel frame structure is examined. The accuracy of the ROM-based design is evaluated by comparing performance to the FEM-based response predictions across the entire Pareto front resulting from the bi-objective optimization. Then, the designs and associated performance predicted by using a linear or a nonlinear structural model are compared to evaluate how the explicit consideration of nonlinearities, as well as the degree of nonlinear behavior, impact the IVA design and efficiency. | Tuned-mass-damper-inerter optimal design and performance assessment for multi-storey hysteretic buildings under seismic excitation | 10.1007/s10518-021-01236-4 |
2023-02-01 | Inerter-based passive control devices have great potential to efficiently mitigate damage to structures subjected to earthquakes as they can provide large added mass effects, while having a relatively small physical mass. The added mass effect of inerters is typically achieved through the conversion of translational motion to the rotation of a flywheel. In a clutch inerter damper (CID), energy transferred to the flywheel cannot transfer back to the structure. Despite this potentially advantageous behavior, few studies have considered the seismic performance of structures with CIDs. As a result, the effect of the device parameters (i.e., effective mass and damping), the ability of the device to delay yielding and collapse of the structure, and the relative effectiveness of the device in far-field and near-field earthquakes, which more often include a dominant pulse, are uncertain. This paper addresses these gaps in knowledge through a numerical study of SDOF structures. The numerical model considers the nonlinear behavior of the structure in addition to nonlinear behavior of the CID. Incremental dynamic analyses were performed with suites of recorded earthquake ground motions. The results of these analyses showed that the CID is typically significantly more effective than a comparable viscous damper. Also, while performance differences were observed for different earthquake types, the median performance is broadly similar. Overall, this work shows the CID is capable of delaying the onset of yielding and collapse and otherwise mitigating the effects of a wide range of types of seismic excitation; thus, further investigation on its use is warranted. | Performance of structures with clutch inerter dampers subjected to seismic excitation | 10.1007/s10518-022-01514-9 |
2023-02-01 | A damping strategy using a friction ring damper for an industrial flywheel was numerically and experimentally investigated. The friction ring damper, located on the arms of the flywheel, was experimentally found to effectively reduce the vibration amplitude of the flywheel. The vibration energy was dissipated when relative motions occur at the friction contact interfaces. Nonlinear dynamic analysis based on a lumped-parameter model of a flywheel equipped with a friction ring damper was conducted. The normal load, N , was used to evaluate the damping performance of the friction ring damper. For several values of N , steady-state responses under harmonic excitation and nonlinear modes were obtained using the harmonic balance method combined with the alternating frequency–time domain method. The forced response analysis proved the existence of an optimal value of N , which could minimize the vibration amplitude of the flywheel. The nonlinear modal analysis showed that all the damping ratio–frequency curves were completely coincident even for different values of N , and the frequency corresponding to the maximum damping ratio was equal to the frequency at the intersection of the forced response curves under the fully slip state and the fully stick state of the friction contact interface. By analyzing the behaviors of the friction contact interface, it was shown that the friction contact interface provides damping in the combined stick–slip state. The forced response under random excitation was calculated using the Runge–Kutta method, and the friction interface behaviors were analyzed. Finally, spectral testing was conducted to verify the numerical results. | Numerical and experimental investigations on a friction ring damper for a flywheel | 10.1007/s11071-022-07960-z |
2023-02-01 | Novel combinations of true negative stiffness dampers (NSDs) and inerter devices are used concurrently as supplemental dampers for response control of base-isolated structures. The combination of the inerter and NSD is denoted as negative stiffness inerter damper (NSID). Classical H∞ optimisation based on a well-known fixed-point theory of tuned mass dampers is used to derive optimal parameters for NSD and three configurations of NSIDs. Optimal NSIDs and NSD are supplemented to the base-isolated structure as passive control devices. The closed-form expressions for optimal parameters are derived, which will be useful for the initial design process of these devices for isolated structures. A numerical searching technique is used to verify the derived closed-form expressions for the optimal parameters of NSIDs. A comparative analysis is also run by utilising three configurations of NSIDs and a true NSD as supplemental control devices to the flexible base-isolated structure. The governing equations of motion are written in state-space form, and the performance of the proposed supplemental dampers for the base-isolated structure is investigated under real earthquake records. Time history analysis shows that the optimal NSIDs and NSD effectively control the objective variables of base displacement, inter-storey drift, and top storey acceleration. Especially under near-fault, which may bring isolation systems to critical working conditions, the proposed supplemental dampers cushion against failure by improving energy dissipation capacity compared to conventional passive dampers. Optimal NSID parameters are lower in magnitude than NSD parameters, resulting in a smaller damper size, which is desirable from a practical design standpoint. | Optimum parameters and performance of negative stiffness and inerter based dampers for base-isolated structures | 10.1007/s10518-022-01372-5 |
2023-02-01 | The unwanted vibrations of offshore structures induced by wave or earthquake loads can lead to the reduction of the service life and fatigue failure of the offshore platforms. This paper introduces tuned inerter damper (TID) to a jacket offshore platform as passive control device for mitigating the excessive vibrations of platform structure induced by wave and earthquake loads. An analytical design method is proposed for jacket platforms and the influence of installation location on the modal response is investigated. The proposed design method can determine the optimal installation position and obtain the optimal design parameters by transform the original multi-degree of freedom (MDOF) system to a single DOF (SDOF) modal system. Two sets of closed-form solutions of which corresponding to wave and earthquake excitations are derived based on the $${\mathrm{H}}_{2}$$ H 2 optimization criterion. Further, a practical 90 (m) high and 80 (m) deep in-water jacket offshore platform is used in numerical simulation and the wave forces are modeled using Morison’s equation. The case study finds that the optimal installation location of TID is deck level for both wave and earthquake loads. The proposed design method is validated by the numerical example and the results demonstrate that TID system can effectively mitigate the maximum, minimum, and RMS responses of jacket platforms. Besides, the TID is more effective when the jacket platform is under the action of waves and the tuning of TID according to earthquake load is more reliable when the jacket platform subjected to both wave and seismic loads. | Mitigating jacket offshore platform vibration under earthquake and ocean waves utilizing tuned inerter damper | 10.1007/s10518-022-01378-z |
2023-02-01 | An electromagnetic inertial mass damper (EIMD) is an inerter-based damper that can significantly enhance the seismic performance of a frame structure. However, the stochastic seismic analysis of a base-isolated structure (BIS) with the EIMD subjected to earthquake ground motions has rarely been reported. Based on a probabilistic framework, this paper studies the stochastic seismic responses of the BIS with the EIMD subjected to seismic excitations considering three typical soil conditions. The analytical solutions of the response variances of a two-degree-of-freedom (2DOF) BIS-EIMD system are derived considering both stationary and non-stationary seismic excitations. A parametric study on the BIS-EIMD system subjected to stochastic seismic excitations modeled by filtered Kanai-Tajimi spectrum is conducted to investigate the different seismic responses under firm, medium, and soft soil conditions, and the corresponding optimal inertance and damping of the EIMD are obtained by minimizing the stochastic seismic responses of the superstructure or the base floor. The results of the 2DOF BIS-EIMD system indicate that the optimal EIMD achieves comparable control performance under the three soil conditions, but the optimal parameters of the EIMD vary significantly under different soil conditions. Under soft soil conditions, the BIS-EIMD system requires a much larger inertance setting compared with that of the firm and medium soil conditions. A numerical simulation of a seven-story isolated building with an EIMD is conducted considering both artificial seismic excitations and real earthquake ground motions. Numerical results show that the EIMD is capable of significantly suppressing the seismic responses of both the base floor and the superstructure, which is better than that of a conventional viscous damper. | Stochastic seismic analysis of base-isolated structures with electromagnetic inertial mass dampers considering different soil conditions | 10.1007/s10518-021-01231-9 |
2023-02-01 | In this paper, a hybrid control system (HCS) endowing a base isolation system (BIS) with a Tuned Mass Damper Inerter (TMDI) is proposed for the protection of steel storage tanks from severe structural damages induced by seismic events. Among all the components of industrial plants, cylindrical steel storage tanks are widely spread and play a primary role when subjected to seismic hazard, since they suffer of many critical issues related to their dynamic response such as high convective wave height and base shear force. The adopted base isolation system is realized with spring and damper elements, whereas the TMDI is realized with a tuned mass damper connected to the ground by the inerter. The developed mechanical model consists of a MDOF system, which considers the impulsive and convective modes as well as the TMDI dynamics. An optimal design problem is tackled, making use of a multi-objective approach, with the scope to mitigate simultaneously the convective and impulsive response of the storage tank. A zero mean white noise excitation is assumed as input in the optimal design procedure. Once the HCS is optimally designed, a systematic investigation of its seismic effectiveness is reached through parametric analysis. Modal parameters and frequency response functions are discussed. A literature case study comparing the effectiveness of the proposed optimally designed HCS with traditional base isolation is illustrated and performances are assessed through stochastic excitation and natural earthquakes. | Multi-objective optimal design and seismic assessment of an inerter-based hybrid control system for storage tanks | 10.1007/s10518-022-01457-1 |
2023-01-21 | The present study investigates the performance of steel structures plagued with plan irregularities subjected to underground blast-induced excitations. The building plan irregularity is considered by comparing the structural performance of various geometrical shape buildings, namely square, rectangle, L shape and C shape. The blast load is calculated by considering constant blast charge weight and varying the standoff distance. The study installs resilient control systems, namely fluid viscous dampers and X-plate dampers within the selected eleven storey steel buildings. An analytical approach is adopted to investigate the efficiency of passive control techniques with the help of finite element programme. A parametric study is also carried to determine the most efficient damper properties and damper type in improving the performance of steel buildings. Three damper placement techniques are also evaluated such as zig–zag pattern, alternate floor damper placement and dampers at all locations to optimize the number of dampers in achieving the maximum reduction in structural responses. The study concludes that the fluid viscous and X-plate dampers yield a maximum reduction in top storey peak displacement at a standoff distance of 400 m in the range 58% and 88%, respectively. The study also reports that the viscous damper and X-Plates prove to be an efficient passive control technique for irregular shaped steel buildings as compared to regular shaped buildings. | Effect of plan irregularity on the performance of steel buildings subjected to blast-induced vibrations | 10.1007/s41062-023-01034-8 |
2023-01-16 | The dissipation behavior of granular balls in a Q-2D closed container subjected to vertical vibration is investigated by means of Discrete Element Method (DEM). Damping contour and phase diagram of vibrated granular balls in the interested excitation amplitude-frequency plane are obtained respectively, revealing ten different granular motion patterns where density inversion, wave-solid state and Leidenfrost effect demonstrate relatively higher damping effect. Uncertainty of vibrated granular balls in dissipation behavior under the same excitation parameters is indicated. Moreover, the influence of cavity dimension (i.e., height, width and aspect ratio) of granular container on dissipation behavior of vibrated granular balls is further explored based on the three high damping granular phases, which not only lays a foundation for the optimal design of Q-2D granular damping structure based on dissipation behavior of vibrated granular materials, but also further verifies the existence of granular wave-solid state as a newly revealed high damping granular phase. Graphical abstract Effect of cavity dimension | Does cavity dimension of vibrated granular container matter? | 10.1007/s10035-022-01299-3 |
2023-01-16 | Classical particle dampers suffer from their non-robust damping behavior, i.e. they can only be efficiently applied to a specific frequency range and amplitude range. The reason for that is that particle motion, also called motion mode, and damper efficiency show a strong correlation. By changing particle or container properties the motion modes are shifted to other excitation conditions but their efficient range is not much affected. To increase the damping performance and robustness of particle dampers, two approaches are presented here by introducing new motion modes. Therefore, the particle dampers are analyzed experimentally using a shaker setup and numerically using the discrete element method. The first design approach uses inner structures inside the particle damper, manufactured by a 3D printer. The inner structures consist of different numbers of beams, placed perpendicular to the container moving direction. They lead to a much more robust damper as the transition between the motion modes gets smoother. For the second approach, the container walls are equipped with different soft polymers. In this way a new motion mode at low excitation intensities is observed, leading to a high efficiency possibly on a large excitation intensity range. For an easy calculation of the necessary wall’s Young’s modulus an analytical formula based on Hertz impact theory is derived. | Design of robust particle dampers using inner structures and coated container walls | 10.1007/s10035-022-01298-4 |
2023-01-16 | During flight, vibrations potentially cause aerodynamic instability and noise. Besides muscle control, the intrinsic damping in bird feathers helps to reduce vibrations. The vanes of the feathers play a key role in flight, and they support feathers’ aerodynamic function through their interlocked barbules. However, the exact mechanisms that determine the damping properties of the vanes remain elusive. Our aim was to understand how the structure of the vanes on a microscopic level influences their damping properties. For this purpose, scanning electron microscopy (SEM) was used to explore the vane’s microstructure. High-speed videography (HSV) was used to record and analyze vibrations of feathers with zipped and unzipped vanes upon step deflections parallel or perpendicular to the vane plane. The results indicate that the zipped vanes have higher damping ratios. The planar surface of the barbs in zipped vanes is responsible for aerodynamic damping, contributing 20%–50% to the whole damping in a feather. To investigate other than aerodynamic damping mechanisms, the structural and material damping, experiments in vacuum were performed. High damping ratios were observed in the zipped vanes, even in vacuum, because of the structural damping. The following structural properties might be responsible for high damping in feathers: (i) the intact planar surface, (ii) the interlocking of barbules, and (iii) the foamy inner material of the barb’s medulla. Structural damping is another factor demonstrating 3.3 times (at vertical deflection) and 2.3 times (at horizontal deflection) difference in damping ratio between zipped and unzipped feathers in vacuum. The shaft and barbs filled with gradient foam are thought to increase the damping in the feather further. | Aerodynamic vs. frictional damping in primary flight feathers of the pigeon Columba livia | 10.1007/s00339-023-06395-6 |
2023-01-13 | In this paper, a three-layer Rao–Nakra sandwich beam is considered where the core viscoelastic layer is constrained by the purely elastic or piezoelectric outer layers. In the model, uniform bending motions of the overall laminate are coupled to the longitudinal motions of the outer layers, and the shear of the middle layer contributes to the overall motion. Together with nonlinear damping injection and nonlinear source terms, the existence and uniqueness of local and global weak solutions are obtained by the nonlinear semigroup theory and the theory of monotone operators. The global existence of potential well solutions and the uniform energy decay rates of such a solution, given as a solution to a certain nonlinear ODE, are shown are proved under certain assumptions of the parameters and by the Nehari manifold. Finally, the existence of a smooth global attractor with finite fractal dimension, which is characterized as an unstable manifold of the set of stationary solutions, and exponential attractors for the associated dynamical system are proved. The present paper extends the linear analysis of the stability of the Rao–Nakra sandwich beam to nonlinear analysis in the existing literature. | Long-Time Behavior of a Nonlinearly-Damped Three-Layer Rao–Nakra Sandwich Beam | 10.1007/s00245-022-09931-7 |
2023-01-11 | The goal of this paper is to consider damped elastic systems with nonlocal conditions in the framework of Banach spaces. Our first aim is to investigate the existence of mild solutions to damped elastic systems by means of fixed point for condensing maps avoiding the hypothesis of compactness on the semigroup. The second step of the paper is to study the existence of decay mild solutions to the mentioned problems. The obtained results can be applied to the nonlinear vibration equation of structural damping elastic beams with nonlocal conditions | A Study on Decay Mild Solutions of Damped Elastic Systems with Nonlocal Conditions in Banach Spaces | 10.1007/s00009-023-02260-1 |
2023-01-07 | We study semilinear damped wave equations with power nonlinearity $$|u|^p$$ | u | p and initial data belonging to Sobolev spaces of negative order $$\dot{H}^{-\gamma }$$ H ˙ - γ . In the present paper, we obtain a new critical exponent $$p=p_{\textrm{crit}}(n,\gamma ):=1+\frac{4}{n+2\gamma }$$ p = p crit ( n , γ ) : = 1 + 4 n + 2 γ for some $$\gamma \in (0,\frac{n}{2})$$ γ ∈ ( 0 , n 2 ) and low dimensions in the framework of Sobolev spaces of negative order. Precisely, global (in time) existence of small data Sobolev solutions of lower regularity is proved for $$p>p_{\textrm{crit}}(n,\gamma )$$ p > p crit ( n , γ ) , and blow-up of weak solutions in finite time even for small data if $$1<p<p_{\textrm{crit}}(n,\gamma )$$ 1 < p < p crit ( n , γ ) . Furthermore, in order to more accurately describe the blow-up time, we investigate sharp upper bound and lower bound estimates for the lifespan in the subcritical case. | On the critical exponent and sharp lifespan estimates for semilinear damped wave equations with data from Sobolev spaces of negative order | 10.1007/s00028-022-00864-w |
2023-01-05 | As one damper controls the response of two adjoining interconnected structures, the interconnecting adjoining structures concept turns into an economic alternative. The functioning of adjoining similar two-degree-of-freedom structures interconnected by a nonlinear damper under random excitation is investigated. The governing equation of motion of the interconnected structure is derived, and responses (displacement and acceleration) are investigated. The response-enhancing efficiency of the nonlinear damper is assessed by analyzing the linked structures using Monte Carlo simulation. The optimal value of the damper constant and representing response in closed-form formulation under stationary white noise excitation is deduced. The initial design of damper interconnecting adjoining similar structures can be ascertained using deduced closed-form formula. The response-enhancing efficiency of the nonlinear damper interlinking two similar adjoining multi-degree-of-freedom structures subjected to real earthquake excitation is also investigated. | Nonlinear damper interconnecting adjoining similar structures subjected to random excitation | 10.1007/s41062-022-01026-0 |
2023-01-01 | The quality factor defines the rate with which a nanomechanical resonator dissipates energy. Low energy loss, i.e., a high quality factor, is desirable for most applications of nanomechanical resonators. In this chapter, the three main sources of energy loss in nanomechanical resonators are presented. Energy can be lost (i) to the surrounding medium, which can be a liquid or a gas, (ii) through the clamping to the substrate via elastic waves, and (iii) through dissipation mechanisms that are intrinsic to the resonator. Medium interaction losses can readily be circumvented by operation in vacuum, and clamping losses can be minimized by an optimized resonator design. This typically leaves intrinsic losses as the limiting mechanism defining the maximal obtainable quality factor. Intrinsic losses consist of material friction and fundamental loss mechanisms such as thermoelastic loss and phonon-phonon interaction loss. Generally, intrinsic losses can be reduced by decreasing the temperature. Dissipation dilution reduces the effect of intrinsic loss in resonators under tensile stress, resulting in quality factors of several million even at room temperature. | Damping | 10.1007/978-3-031-29628-4_3 |
2023-01-01 | The lack of rapid, simple, and reliable techniques in damage detection of large civil engineering structures has hindered the frequent application of available vibration-based structural health monitoring and damage detection methods. The basics of baseline data of undamaged structure detailed finite element models, or the need for numerous expensive sensors have further distanced the technique from practice. Thus, in this study, the application of a simple, baseline free time domain damage detection technique using acceleration data is discussed. The investigation is made using analysis of nonlinearity in damping extracted from ambient vibration data for identification of the existence of damage in a structure. It is known that the dominant mechanism of energy dissipation in the presence of structural defects such as cracks, defective connections, etc. is due to dry Coulomb friction and this type of damping is considered nonlinear. Contrary to this, in the undamaged state of structures, the dissipation of energy is mostly due to material damping which is considered a macroscopically viscous and constant type of damping. Thus, analysis of nonlinearity in damping and identification of the contribution of Coulomb friction in modal damping could reveal the existence of damage or defects in a structure. This study presents the application of the method to an experimental system at the laboratory to show the competency of the method. The experimental estimates obtained from the proposed method illustrate the effectiveness and efficiency of the method in portraying the existence of the damage and approximate quantification. | Damage Prediction by Using Nonlinearity of Damping | 10.1007/978-981-99-3471-3_4 |
2023-01-01 | The flow of current in the circuit branches and the voltage drop across circuit elements depend on their behavior and ability to store energy. For instance, the voltage drop across a resistor is in phase with its current passing through. However, that is not the same in a capacitor or an inductor. This makes the circuit KVL and KCL equations integrodifferential equations. The order of these equations depends on the number of energy-storing elements. The circuit elements are introduced in this chapter, and their equations are discussed. The order of a circuit is discussed, and responses of first- and second-order circuits to their initial condition and external sources are analyzed. | Circuit Response Analysis | 10.1007/978-3-031-21908-5_4 |
2023-01-01 | This paper considers a gyroscopic rigid rotor with restoring and damping characteristics of an elastic support. Differential equations of the rotor motion, which take into account the anisotropy of stiffness and damping, are solved analytically by the harmonic balance method. It is found that if the linear stiffness of the elastic support material differs in two mutually perpendicular directions, there are two critical velocities and corresponding resonance regions. Each critical velocity is defined by two resonance curves, the principal direction and the perpendicular direction, respectively. The area limited by the principal direction resonance curve is larger than the area limited by the second direction resonance curve. Linear damping or non-linear cubic damping suppresses the maximum amplitudes of these resonant curves. If damping acts only in one direction, then its effect is observed in the resonance curves of the corresponding critical velocity. In the case of the presence of a non-linear component of the rigidity of the support material, the resonance curves of the main directions are accompanied by jumps. Combined linear and non-linear cubic damping suppresses the oscillation amplitude more significantly than linear damping. The equations of rotor motion were also solved numerically and the results are in good agreement with the results of the analytical solution at the initial stage of time. | Dynamic Simulation of Gyroscopic Rigid Rotor with Anisotropy of Elastic Support Restoring and Damping Characteristics | 10.1007/978-3-031-29815-8_33 |
2023-01-01 | This study addresses the modeling of different energy dissipation mechanisms for numerical prediction of the vertical acceleration demand in regular moment-resisting steel frame structures. One of the issues discussed is the consideration of viscous damping in the structural model. It is shown that well-established Rayleigh-damping may highly overestimate the damping of the vertical modes, resulting in much too low vertical acceleration response predictions. A study with different damping models provides an appropriate damping modeling strategy that leads to reasonable predictions of both horizontal and vertical frame acceleration demands. Another open question is the effect of inelastic material behavior on the vertical acceleration demand on the considered regular structures. The results of a shell model of a frame structure exposed to high intensity ground motion excitation demonstrate that inelastic material behavior has virtually no impact on the vertical acceleration demand, while structural inelasticity leaves the horizontal acceleration response significantly smaller compared to the elastic demand. This leads to the conclusion that common frame models that capture the inelastic horizontal response but behave elastic in the vertical direction are suitable for the computation of both the horizontal and vertical acceleration demand. | Effect of damping model and inelastic deformation on the prediction of vertical seismic acceleration demand on steel frames | 10.1007/s10518-022-01530-9 |
2023-01-01 | This chapter provides an introduction to the optics and plasma physics concepts that will be used throughout the rest of the book. The optics section focuses on basic concepts of light wave propagation and Fourier optics, which will be useful when discussing optical smoothing techniques in Chap. 9 . After a general introduction of plasma concepts, the plasma physics section emphasizes the description of plasma waves: it presents their fluid and kinetic descriptions, the wave energy, and action concepts and discusses the properties of acoustic waves in multi-species plasmas which can play a major role in laser–plasma instabilities and their mitigation, as discussed in Chap. 7 . Electron-ion collisions, which will later play a central role in laser absorption (Chap. 4 ) and in the saturation of nonlinear kinetic effects (Chap. 10 ), are introduced next. Finally, the last section introduces the isothermal expansion of plasma in vacuum, which represents a type of plasma profiles often encountered in laser–plasma experiments. | Fundamentals of Optics and Plasma Physics | 10.1007/978-3-031-23424-8_1 |
2023-01-01 | A linear physical system with multiple sets of input and output can be represented by mathematical functions that relate any outputs to any inputs. These functions are unique and are defined based on the systems governing equations. The transfer function of a system is defined as the Laplace transform of the output response over the Laplace transform of the input excitation. Transfer functions are defined for any desired set of input and output functions that may relate the input and output together. X ( s ) Y ( s ), H ( s ) | Transfer Functions | 10.1007/978-3-031-21908-5_8 |
2023-01-01 | Gilbert damping is one of the critical parameters in magnetic thin films for developing low-power spintronic devices, and $${\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$$ Co 40 Fe 40 B 20 (CFB) is one of the sought-after materials in this regard. Here, we report the effect of annealing on the structural, magnetization reversal, and spin dynamics of CFB thin films. X-ray diffraction results show that as-deposited films are amorphous and retain their nature upon annealing up to 350 °C. Magnetization reversal results exhibit anisotropic behavior in both as-deposited and annealed samples. The random anisotropy model explains the change in coercivity in the transverse axis with respect to the longitudinal axis for CFB annealed at 350 °C. Broadband ferromagnetic resonance spectra reveal that the damping parameter decreases with increasing annealing temperature. Ultra-low damping of 0.004 is obtained with annealing at 350 °C. Surface topographical images from atomic force microscopy are rewarded for supporting the observed variation of the damping constant. Our systematic study gives an insight into CFB magnetization reversal and dynamics for developing ultra-low damping magnetic thin films via annealing. | Effect of Annealing on Magnetization Reversal and Spin Dynamics in Co_40Fe_40B_20 Thin Films | 10.1007/s10948-022-06442-y |
2023-01-01 | Follower forces acting on elastic beams are considered, and their nonconservative character is discussed. The linearized bifurcation analysis of a double pendulum, known as Ziegler column , is performed. In absence of damping, the mechanism of flutter Flutter circulatory system (or circulatory, or reversible, Hopf bifurcation) is illustrated, caused by the collision of two pairs of purely imaginary eigenvalues. The effect of added damping is then discussed, changing flutter into a generic Hopf bifurcation , in which only one pair of purely imaginary eigenvalues are involved. Damping, although dissipative, is generally found to exert a destabilizing effect , since it reduces the critical load; furthermore, the damped critical load is not in continuity with that of the undamped system, when damping tends to zero. All these surprising phenomena constitute the so-called Ziegler paradox ./COMP: Set “ Ziegler paradox ” to Roman. By still making reference to the double pendulum, a nonlinear analysis is developed, aimed at describing the amplitude of the limit cycle , as a function of the bifurcation parameter. To achieve this result, the Lindstedt-Poincaré perturbation method is used, which allows to determine the periodic solutions of a weakly nonlinear system. The analytical results are then compared with those deriving from numerical integrations. Finally, a viscoelastic fixed-free beam, loaded at the tip by a compression follower force, known as the Beck beam , is studied. The linear analysis carried out for the Ziegler discrete system is repeated for the continuous Beck system. The role of the internal and external damping acting on the beam is discussed with regard to the Ziegler paradox. | Dynamic Bifurcations Induced by Follower Forces | 10.1007/978-3-031-27572-2_11 |
2023-01-01 | This chapter describes seventeen fundamental experiments in vibration which can easily be conducted in the laboratory to understand the basic vibration theory which has been described in Chapter 2. The presentation is such that an academician can mix and match these experiments to suit the laboratory courses being taught at undergraduate or postgraduate levels. The material will also be useful for researchers who would like to set up basic experiments in the laboratory. Simple rigs that can easily be fabricated in the workshop for specific experiments are suggested. The description of every experiment starts with the aim, theory behind the experiment, test setup and procedure, as well as how to report the results. Suggestions are given for the choice of transducers (described in Chapter 3) and for alternate experimental setups. | Vibration Experiments | 10.1007/978-3-031-03968-3_10 |
2023-01-01 | We consider a fluid-plate interaction model where the two dimensional plate is subject to viscoelastic (strong) damping, as it occurs in some biological systems (Ozkaya et al., Fundamentals of biomechanics-equilibrium, motion, and deformation. Springer, New York, 2021). The strength of the Kelvin-Voigt damping is measured by a constant 0 < ρ ≤ 1. Coupling occurs at the interface between the two media, where each component evolves. In this paper, we apply “low” physically hinged boundary interface conditions, which involve the bending moment operator for the plate. We prove four main results: (1) analyticity, on the natural energy space, of the corresponding contraction semigroup (and of its adjoint); (2) sharp location of the spectrum of its generator (and similarly of the adjoint generator), neither of which has compact resolvent, and in fact both of which have the point λ = − 1 ρ $$ \lambda = -\frac {1}{\rho }$$ in their respective continuous spectrum; (3) both original generator and its adjoint have the origin λ = 0 as a common eigenvalue with a common, explicit, 1-dimensional eigenspace; (4) The subspace of codimension 1 obtained by the original energy space by factoring out the common 1-dimensional eigenspace is invariant under the action of the (here restricted) semigroup (or of its adjoint), and on such subspace both original and adjoint semigroups are uniformly stable. | Fluid–Plate Interaction with Kelvin-Voigt Damping and Bending Moment at the Interface: Well-posedness, Spectral Analysis, Uniform Stability | 10.1007/978-3-031-21460-8_6 |
2023-01-01 | This chapter starts with the description of a charged particle motion in a plane light wave, including the figure of eight motion at higher intensities. The single particle dynamics in electron or ion plasma waves is discussed next; particle trapping, which plays an important role in the generation of suprathermal electrons (Chap. 8 ) and the kinetic inflation phenomenon (Chap. 10 ), is explained via a simple analogy with the simple pendulum and is connected to the physics of Landau damping derived in Chap. 1 . The last section describes the ponderomotive force concept in detail, distinguishing the force from a plasma wave vs. a light wave. The figure of eight motion of a particle in a light wave described in the first section (and the equivalent nonlinear motion in a plasma wave from the second section) is interpreted in terms of the ponderomotive force. | Single Particle Dynamics in Light Waves and Plasma Waves | 10.1007/978-3-031-23424-8_2 |
2023-01-01 | In this chapter, analysis and characterization of responses of mechatronics and measurement systems under static and dynamic conditions are presented. Details of first-order and second-order system characteristics and their experimental determination are covered. Examples including computer-aided analysis and simulation are presented. Experimentation using the virtual simulation platform Tinkercad is presented along with actual laboratory implementation. End-of-chapter exercise problems are provided to help consolidate problem-solving skills and understanding of materials covered. | Dynamic System Characteristics | 10.1007/978-3-031-29320-7_4 |
2023-01-01 | Cables stay bridges, due to the slenderness, have generally a very low inherent damping. Wind induced, vortex excitation, wake galloping, or rain-wind combination may cause excessive vibrations conduit to the risk of decrease the fatigue service life of the cables system. External damper systems in combination with a special cable surface treatment are considered as the most efficient approach to mitigate the cables vibration. In this paper, the performance of friction damper system, typically installed on several new stay cable bridges in Vietnam recently had been investigated and presented through a theoretical prediction and an in-situ damping tests campaign. The comparison between the theoretical evaluation and the experiments is also discussed for possible improvement of the damping prediction process. | Friction Damper Performance on Stay Cable Bridges in Vietnam, Solution Prediction, and In-Situ Testing | 10.1007/978-981-19-4835-0_12 |
2023-01-01 | The objective of this chapter is to show that nonsmooth processes may naturally occur as high-energy asymptotics in different oscillatory models with no intentionally introduced stiff constraints or external impacts. In other words, nonsmooth temporal mode shapes may be as natural as sine waves generated by same oscillators under low-energy conditions. Essentially nonlinear phenomena, such as nonlinear beats and energy localization, are also considered. It is shown that energy exchange between two oscillators may possess hidden nonsmooth behaviors. | Nonsmooth Processes as Asymptotic Limits | 10.1007/978-3-031-37788-4_3 |
2023-01-01 | This chapter discusses the absorption of light waves (and to a lesser extent, plasma waves) in plasmas. The collisional absorption coefficient of light waves (or plasma waves) is derived from first principles using a ballistic model and compared to the derivation from a fluid model. The associated plasma heating rate is presented, as well as a discussion of the Coulomb logarithm that is most appropriate for the absorption process in plasmas. The formation of non-Maxwellian electron distributions from collisional absorption is briefly discussed. The following section provides simple analytical estimates for the absorption factor in idealized plasma profiles. The last section describes the resonance absorption process and discusses the different regimes where collisional vs. resonance absorption is the dominant mechanism. | Absorption of Light Waves (and EPWs) in Plasmas | 10.1007/978-3-031-23424-8_4 |
2023-01-01 | Epoxidised natural rubber (ENR) is foreseen as a good material of choice for a comprehensive range of technical rubber goods due to its unique properties. Properties of ENR such as oil resistance and low gas permeability are suitable for products that require resistance to oil and low permeation rates, such as seals and hose covers. With a reactive epoxide group, blending ENR with polar synthetic elastomers such as acrylonitrile butadiene rubber (NBR) and chloroprene rubber (CR) allows for an improvement in tear strength, abrasion resistance and oxidative ageing whilst retaining the degree of oil resistance. In addition, the superior damping properties of ENR confer a promising potential in a wide range of engineering products such as rubber bushes and engine mountings. The advantage of ENR’s damping properties suggests a niche application such as rubber sound dampers for automotives and buildings. The recent achievements in ENR have revealed new potentials for natural rubber (NR) applications. | Epoxidised Natural Rubber in Technical Rubber Goods | 10.1007/978-981-19-8836-3_6 |
2023-01-01 | With the development of wind power and large-scale grid connection, more and more new challenges are brought to the safe operation of power system. It is of great significance to analyze the damping characteristics and stability of low-frequency oscillation of wind power grid connected system, so as to improve the permeability of wind power and new energy generation. This paper based on the main physical structure and linearization model of DFIG, building the grid connected system and its linear model, analyzes the influence of the damping characteristics of power system after the wind power grid connected by using the damping torque method, and verifies the change of the damping characteristics of the system after the wind power grid connected by using the power factory simulation software. It can be seen that the influence of the permeability and control parameters of wind power on the low-frequency oscillation of power system under different operating conditions, has a more clear guiding significance for the safe and stable operation of power system. | Research on the Influence of Wind Power Grid Connected to Power System Damping Characteristics | 10.1007/978-981-99-0408-2_1 |
2023-01-01 | A new proportional damping model, named as bell-shaped, has recently been proposed to address the limitations of existing models for simulating un-modeled energy dissipation in large-scale structures subjected to seismic loading. This model relies on an expanded damping coefficient matrix in a sparse matrix form in order to maintain the same computational efficiency as Rayleigh model for the response solution process, so that it can be used for structures with a large number of degrees of freedom. This study investigates two storage schemes: COO (coordinate list) and BST (binary search tree) for constructing and storing the expanded coefficient matrix. The results show that both schemes require a computational complexity of $$O\left(nnz\mathrm{log}\left(nnz\right)\right)$$ O n n z log n n z , which is the optimum in the state-of-the-art technologies and is less than the complexity of the solution process. This study also develops an application for computing model parameter values via optimization to match a user-specified damping ratio curve in the structural frequency domain. | Implementation and Performance of Bell-Shaped Damping Model | 10.1007/978-3-031-30125-4_13 |
2023-01-01 | Squeezed film damping (SFD) becomes a dominant damping mechanism in micro-electro-mechanical system (MEMS). Depending on the pressure variation in MEMS, SFD governs the dynamic parameters like quality factors (Q factors) and damping ratio. In the present paper, we calculate the Q factor and damping ratio of the trapezoidal shaped microcantilever beam by eigenfrequency analysis using finite element method (FEM) in COMSOL Multiphysics. The effective viscosity method is used to calculate the SFD in FEM for the continuum, slip, transition and molecular flow regimes as described by the Knudsen no. ( K _n). K _n is varied by altering the operating pressure, keeping the thickness of air gap constant. It is observed that the Q factor and damping ratio of trapezoidal microcantilever beam varies by an order of million for different flow regimes with the change of operating pressure from atmospheric to 0.1 Pa. | Finite Element Analysis of Squeezed Film Damping on Trapezoidal Microcantilever Resonators at Different Pressure Levels | 10.1007/978-3-031-20353-4_17 |
2023-01-01 | The primary purpose of this article is to explore different types of wave solutions such as shock, solitary, and periodic solutions for the ion acoustic waves (IAWs) propagating in a collisional dusty plasma containing dust grain with a negative charge, positive ions, neutral particles, and electrons abiding q-nonextensive velocity distribution. To observe IAW in a plasma medium under the influence of externally applied periodic force, the forced Korteweg-de Vries-Burgers (FKdVB) equation is formally derived from the governing basic equations utilizing reductive perturbation technique (RPT). From the modified tanh method (MTM), some exact analytical solutions are derived based on some relation between the coefficients in the equation, from which the impact of different physical parameters on wave propagation is discussed from a numerical perspective. Apart from this, propagation of IAW is also studied separately considering the dust ion collision effect. To check the behaviors of IAW in a collisional plasma, the damped Korteweg-de Vries-Burgers (DKdVB) equation is already derived in an earlier literature in which using conservation law, only the solitary wave solution is derived for small burgers term. The presence of burgers term necessarily initiates the existence of shock waves. In order to search shock solution, the method of undetermined coefficient (MUC) and the Exp-function method (EFM) is employed, and new type of solitary wave, shock wave, and periodic wave solutions is explored. The obtained new solutions extend earlier results and aid effectively in understanding wave properties. Some numerical graphs are depicted to investigate the nonlinear properties of IAW with the variance of physical plasma parameters. | Shock, Solitary, and Periodic Wave Solutions of the Ion Acoustic Waves for Nonextensive Dusty Plasma in the Framework of Korteweg-de Vries-Burgers Equation with Forcing and Damping Terms | 10.1007/978-981-19-8054-1_10 |
2023-01-01 | This paper focuses on the representative renewable energy bases in eastern Xinjiang and southern Qinghai regions, and conducts in-depth studies on the current status and problems of power grids in these regions. On the basis of the power grid characteristics, this paper proposes a DC grid based on the voltage source converter based high voltage DC (VSC-HVDC) technology, establishes its simulation model, and analyzes the power flow distribution, the power flow transfer capacity and the fault ride-through (FRT) characteristics of the proposed system. The results show that the proposed DC system effectively improves the steady/transient-state characteristics of the power grids in eastern Xinjiang and southern Qinghai areas. It helps promote the delivery of renewable energy. In the meantime, the proposed method provides solutions for solving the problems faced in the northwest region. | Design and Simulation Modeling of ±800 kV HVDC Project for Improving Power Transfer Capability of Renewable Energy in Xinjiang-Qinghai Region | 10.1007/978-981-99-0063-3_44 |
2023-01-01 | Numerical Integration Algorithm plays a very important role in real-time hybrid experiments. Based on the Newmark (γ = 1/2, β = 1/4) average constant acceleration algorithm, the stability analysis equations of Chang Algorithm, CR Algorithm and TL Algorithm under the condition of negative stiffness were derived by using the principle of positive stiffness analysis. The stability of the four algorithms under the condition of negative stiffness was analyzed by Matlab, and the stability characteristics of the four algorithms were studied by changing the integral time interval, damping ratio and stiffness ratio. The research findings indicate that when stiffness is negative, the Newmark average constant acceleration algorithm (γ = 1/2, β = 1/4) is no longer unconditionally stable, whearas the other three algorithms are all unconditionally stable. The Chang Algorithm has the best stability, while the CR algorithm is nearly as stable as the TL algorithm. It is suggested that while performing hybrid testing with probable negative stiffness, the numerical integration algorithm should be carefully chosen. | Comparison of Stability of Four Numerical Integration Methods Under Negative Stiffness | 10.1007/978-981-19-5217-3_101 |
2023-01-01 | The mechanics of nanomechanical resonators can be described by a lumped-element model. In this chapter, linear, coupled, and nonlinear damped and driven resonators are discussed by means of lumped-element models. Additionally, the phenomenon of parametric amplification is introduced. Such simplified models with a single degree of freedom are the basis to discuss the behavior of individual eigenmodes of continuum mechanical resonators, as introduced in the next chapter. | Lumped-Element Model Resonators | 10.1007/978-3-031-29628-4_1 |
2023-01-01 | The accuracy of the machined workpiece depends on the true conditions of the hydrodynamic linear guides. Linear guides based on hydrodynamic lubrication are still in use due to their high damping coefficient and high load carrying capacity. Measuring the true conditions of the hydrodynamic linear guide is important to achieve high accuracy. Until today, pressure measurement has not been established for linear guides. Oil film pressure is one of the important factors explaining the operating conditions of the hydrodynamic linear guides. The main goal of this study is to develop a method in which pressure sensors were installed in the lubrication gap to measure the oil film pressure under realistic condition of a hydrodynamic linear guide. A hydrodynamic linear guide testing rig with varying load capability was used as main test device. Multiple miniature pressure sensors were installed in a stationary rail in different manners to get the realistic oil film pressure distribution along the length of the slide. Additionally, the sensors were also calibrated hydrostatically and hydrodynamically with variable frequency and amplitude. Due to the problem of the enormous influence of air inside the lubrication gap of the testing rig, the measured pressure by the sensors showed that the numerical results have to be adapted to the experimental oil film pressure, which is lower. A new sensor’s integration method has shown great improvements in estimating the oil film pressure of hydrodynamic guides experimentally. | Development of Pressure Sensors Integration Method to Measure Oil Film Pressure for Hydrodynamic Linear Guides | 10.1007/978-3-031-18318-8_29 |
2023-01-01 | The possibility of increasing lifting mechanisms’ productivity through damping elastic mechanical vibrations that negatively affect the control quality, increase the dynamic winch loads, contribute to the accumulation of fatigue stresses in kinematic circuits, lead to the equipment premature failures and unplanned downtime, as well as an increase in the cost of repairs and operation, is considered. Previous studies demonstrated that establishing mechanical characteristics with the required stiffness decreases the passenger elevators’ lifting mechanism’s vibrations. However, due to the mass ratio, small values such as stiffness formed do not eliminate the vibrations. Recommendations are proposed to improve the winches’ dynamic modes quality at the expense of damping the passenger elevators’ lifting mechanisms vibrations. A generalized block diagram of an elevator system with corrective feedback is given, and the damping coefficient’s maximum possible value and an expression for optimal feedback coefficient value are found. The dependence obtained using a physical model and confirming the derived mathematical regularity is shown. The elevator lifting mechanism start-up oscillograms are given, where significant fluctuations of values in two sections of the mechanical characteristic are registered in the dynamic mode. The oscillograms of the elevator lifting mechanism start with corrective feedback in the control system are also considered, illustrating the significant damping of vertical vibrations. It is found that the damping coefficients’ values can reach and even exceed one, which corresponds to the elevator lifting mechanisms’ aperiodicity. | Vibration Damping of Lifting Mechanisms for Elevators Using Control Systems | 10.1007/978-3-031-32774-2_2 |
2023-01-01 | Turbulent fluctuation of the liquid medium under lateral excitation is a major area of concern due to the potential severities it may cause if the contained structure is damaged. Therefore, this study focuses on variation in the self-damping efficiency of the liquid mass in a liquid tank under lateral excitation. For this, a parametric study has been carried out by changing the aspect ratio of the tank with respect to the horizontal and vertical dimensions. Pressure-based transient analysis has been carried out considering harmonic excitation as well as seismic ground motions. The transient response of the liquid medium is observed in terms of free surface elevation and hydrodynamic pressure. The study reveals that an accurate geometric design of the tank structure improves the self-damping of the sloshing liquid. An aspect ratio of less than ‘1’ results in the improved self-damping efficiency of the contained liquid mass. The effect of the vertical dimension of the tank on slosh damping is less significant compared with that of the horizontal dimension. | Influence of Geometric Parameters in Self-damping Efficiency of Rectangular Liquid Storage Tanks | 10.1007/978-981-19-3371-4_12 |
2023-01-01 | This paper presents an investigation of complex mode shape analysis caused by non-linear damping. Nowadays, most academics are accustomed to complex mode shapes, which are a characteristic of most axisymmetric structures. The topic was deeply investigated during the 1980s, sparking the sharpest debates about their physical existence or not. However, after nearly three decades, one question still stands, do we know all about complex mode shapes? This paper takes the dust off this topic again and explores how complex eigenvectors arise when the percentage frequency separation between two mode shapes is the same order of magnitude as the percentage damping. The difference between the past and present investigations relates to the non-linear damping that might arise from joint dynamics under various vibration amplitudes. Hence, the new research question is about the investigation of amplitude-dependent damping on the modal complexity. Why bother? There are several engineering applications in both space and aerospace where axisymmetric structures and joint dynamics can impair the numerical analysis that is currently performed. This paper does not offer any solutions but does expand the research on an unsolved challenge by identifying the questions posed. | An Investigation of Complex Mode Shapes | 10.1007/978-3-031-04086-3_2 |
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