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2022-01-01 | Vibration reduction is a phenomenon that is used to obtain the stability of a member subjected to various loadings. The objective to be fulfilled in this research process is to attain the dynamic stability of the components. Beams used in any machine or mechanism are simple structural members. Structures build in layers are gaining importance these days because of their good vibration damping characteristics. This experimental approach aims to highlight the effect of interfacial slip on the damping of layered and bolted simply supported beams undergoing free vibration. Fabricating the structures in layers and joining them by the means of bolts is the technique used in this problem. The structure engaged with such joints is majorly responsible for energy dissipation where the energy is damped through frictional effects associated with relative displacements due to shear at the interfaces. The parameters that affect the damping capacity of the jointed structures are beam length, thickness ratio, torque of tightening the bolt, number of layers, etc. When a layered beam with bolted joints is acted upon by dynamic loading, the vibrations are produced with some amplitude of excitation at a particular frequency of vibration, and thus damping in a structure occurs by the energy dissipation. It has been established that the factor responsible for 90% of energy getting dissipated in layered structure is interfacial micro-slip. | Identification of Damping in Sandwich Beam | 10.1007/978-981-16-2900-6_2 |
2022-01-01 | Owing to superior mechanical properties of fiber reinforced polymer (FRP) composites, they are employed in various structural and automobile applications. Though many researchers explored various FRP composites, it is indeed need of hour to find eco-friendlier composites for contemporary modern usages. Therefore, manufacturing of new FRP composites and exploring its static and dynamic mechanical properties has been essential. In this present investigation, epoxy hybrid composites were prepared by reinforcing with silane treated plain jute woven fabric and groundnut shell particles (GSP) using compression moulding technique. Jute-epoxy (JE) composites with and without GSP were developed for varying filler content (0, 5, 10, and 15 wt.%) and tested for DMA properties such as storage modulus (E’), loss modulus (E”) and Tanδ (damping or loss factor). The experimental result showed that at all frequency conditions, 10 wt.% of GSP filled JE composites exhibited promising DMA properties than epoxy and other JE composites. In fact, as anticipated, frequencies at which DMA tested has also affected the dynamic properties of the composites. | Dynamic Mechanical Analysis of Silane Treated Groundnut Shell Particles Filled Jute/Epoxy Hybrid Composites | 10.1007/978-981-19-0244-4_102 |
2022-01-01 | Inverters are the power electronic devices which convert DC voltage to required AC. A simple conventional voltage source inverter has three levels of output, i.e., positive, negative, and zero while a multilevel inverter which is an advanced inverter generates a near-sinusoidal desired output voltage from several levels of DC voltages. From various conventional topologies, Cascaded H-Bridge topology (CHB) is chosen owing to its various advantages compared to the other topologies. Using CHB topology, various level (3, 5, and 7 levels) inverters are compared with each other. Different types of Sine Pulse Width Modulation (SPWM) control techniques of multilevel inverters have been examined and out of them Phase Opposition Disposition (POD) technique is put in use till the end of this work as it gives best results based on values of % Total harmonic Distortion (%THD). By varying the switching frequency and modulation index (M_a), changes in %THD values are observed. Further to reduce the harmonics and to improve %THD, various passive filters are used. These filters are designed accordingly with optimal values of inductance and capacitance. | Analysis of Control Techniques and Filter Design of Multilevel Inverter | 10.1007/978-981-16-6879-1_56 |
2022-01-01 | Due to their long and slim geometry, single-lip deep hole drills have a high level of flexibility, especially in the radial and tangential direction. This leads to torsional and chatter vibrations, respectively, especially at high feed rates. In this paper, the conventionally brazed connection between the shaft and the adapter sleeve is replaced by an adhesively bonded joint that allows slight rotational movements. This is intended to passively dampen the vibrations that occur. In addition to examining the obvious question of whether different types of adhesive can withstand the machining forces and torques, practical environmental conditions are also considered. These are, for example, long-term contact with cooling lubricants or the extreme temperature and ambient conditions during a PVD coating process of the tool. | Investigation of Single-Lip Deep Hole Drilling Tools with Adhesively Bonded Joints in the Context of Practical Conditions | 10.1007/978-3-030-78424-9_35 |
2022-01-01 | The issues of assessing the dynamic properties of structural formations were considered in a number of works; interesting results were obtained, which predetermined the interest in assessing the features of dynamic interactions, when structural formations are included in the structure of real systems interacting with the base or motion limiters. The oscillation of a system with several degrees of freedom is considered from the point of view of identifying structural formations and taking into account the features of their interactions. It is proposed to consider a mechanical oscillatory system with the allocation of an object in the form of a structural formation. The frequency function, the damping function, and the parametrizing function are considered as mathematical tools for taking into account the dynamic properties of structural formations. Made the transition from a task object, the dynamic properties of which are characterized by their own numbers in the form of a concentrated mass, to the task of assessment of interaction of elements of vibrating systems with several degrees of freedom with the object in the form of the structures dynamic and structural properties resulting in an estimated frequency response function, damping function, and parametrizing function. | System Representations of Dynamics of Mechanical Oscillatory Structures Based on Frequency Function and Damping Function | 10.1007/978-981-16-2814-6_29 |
2022-01-01 | Flexural vibrations of a cantilever beam in a viscous incompressible fluid near a plane boundary are considered. On the basis of three-dimensional numerical modeling, the study of hydrodynamic forces acting on the beam is carried out. The results of the study describe the changes of hydrodynamics around the beams occurring with an increase of the dimensionless frequency, amplitude of vibrations, and the gap-to-width ratio. | Nonlinear Hydrodynamic Damping of Elastic Vibrations of Beams Near a Plane Boundary | 10.1007/978-3-030-81162-4_8 |
2022-01-01 | A new method used to evaluate the performance of the lathe tool is proposed and optimal thickness of the damping layer is obtained through optimization analysis. FEA model is built as well to verify its feasibility. A serial of experiments are conducted, from the aspects of power spectrum, cutting force, surface smoothness and fatigue, to study the characteristic of lathe tool with high damping alloy layer. It could be seen that the new proposed performance evaluating method is acceptable and verified by FEA and experimental study, and two kinds of physical lathe tools are made according to optimization study. Power spectrum and cutting reaction force of two types of lathe tool under different working conditions are completed and the results shows that the damping tool’s peak value of the spectrum and cutting force is at least 20% lower than that of the tool without damping layer, and this is also matched well with the transient dynamic study based on the FEA. The experiments for surface smoothness and fatigue life are conducted under the same working condition, and it could be found that lathe tool with high damping alloy layer could improve the surface smoothness and fatigue life dramatically. | Dynamic and Experimental Study of Lathe Tool with High Damping Alloy Layer | 10.1007/978-981-16-7381-8_2 |
2022-01-01 | This work is devoted to studying the damping behavior of rotating functionally graded (FG) laminated cylindrical shells undergoing active constrained layer damping (ACLD) treatment comprising of viscoelastic layer sandwiched between the 1–3 piezoelectric composite (PZC) smart layer and host shell. FG cylindrical shells in laminae form consist of fibers which are aligned longitudinally in the parallel curved planes of the shell. The continuous variation of fiber angle conferring to a power law in thickness direction results into gradation of mechanical properties. To present numerical results, two types of FG shells are considered, namely a symmetric two-layered substrate with 0° orientation at top and bottom surfaces and 90° at the interface (Type-1) and asymmetric three-layered shell with 0° and 90° fiber orientation angles at the top–bottom surfaces (Type-2), respectively. The shear deformation of unit order (FSDT) has been applied for the displacement field to represent the deformation kinematics of the smart shell. The virtual work principle has been employed for arriving at the finite element (FE) motion equations of the FG laminated cylindrical (FGLC) rotating shell. To present the closed-loop frequency response characteristic of static and rotating shells, MATLAB code has been developed. | Smart Damping of Rotating Functionally Graded Laminated Composite Cylindrical Shells Using 1–3 Piezoelectric Composites | 10.1007/978-981-16-6738-1_46 |
2022-01-01 | Structures are subjected to various types of loading conditions such as earthquake, wind loads, etc. For structures in earthquake zones, they are designed to resist seismic forces. Earthquake is one of the greatest catastrophic threats to humankind and other living creatures as well as properties by nature. It is impossible to prevent earthquakes from occurring. Whenever earthquake occurs, it causes devastating results. As earthquake waves travel in soil, it starts to penetrate the base of building. Due to which the building will tend to vibrate to a frequency, and if the frequency of building matches the frequency of ground, it is called as resonance, which can cause heavy damages. To avoid or to lower such damages, seismic dampers can be used in buildings. Seismic dampers can decrease the damaging effect and improve the building’s seismic performance. The structure with damping system is analyzed in structural program for earthquake data. The structure is analyzed for different positions of dampers at different story levels, and by adopting optimization technique, we can obtain the required numbers and optimum location of damper. | Seismic Response Control of RCC Building Using Dampers | 10.1007/978-981-16-6879-1_11 |
2022-01-01 | This chapter studies the control schemes Control scheme of reducing the second harmonic current Second harmonic current (SHC) for the two-stage Two-stage single-phase Single-phase photovoltaic Photovoltaic (PV) grid-connected inverter where the front-end dc-dc converter DC-DC converter is operated as a bus-current controlled converter (BCCC) Bus-current controlled converter . To limit the SHC in the BCCC and the PV Photovoltaic panel, the input voltage Input voltage loop gain Loop gain of the BCCC should be high enough at twice the output frequency Output frequency (2 f _o). Since there is a −180° phase abrupt at the resonant frequency Resonant frequency of the input side filter capacitor Filter capacitor and the inductor, the system may be unstable. To cope with this problem, the inductor current feedback active-damping Active-damping scheme (ADS) is adopted. For further improving the input voltage Input voltage loop gain Loop gain at 2 f _o, the proportional-integral Proportional-integral - resonant regulator with active-damping Active-damping scheme is proposed in this chapter. Besides, a step-by-step closed-loop Closed-loop parameters design method is presented. Finally, a 3-kW two-stage Two-stage single-phase Single-phase grid-connected PV Photovoltaic inverter prototype is fabricated and tested in the lab, and the experimental results are provided to verify the feasibility of the proposed control schemes Control scheme . | Second Harmonic Current Reduction for Two-Stage Single-Phase Inverter with Front-End Bus-Current Controlled Converter | 10.1007/978-981-19-1547-5_6 |
2022-01-01 | Dynamic Monitoring System (DMS) and Signal matching analysis is widely used in the offshore industry to validate the axial capacity of foundation piles. While the uniqueness of the signal matching solution is still being discussed (Buckley et. al. 2017 ), field experience highlights that an accurate choice of the damping parameter is key to evaluate correctly the static capacity of the foundation. This paper, proposes to review two independent set of signal matching analyses performed using the same recorded data at Platform A, field X, in the Arabian Gulf, to appreciate fully the importance of the damping factor in the analysis and confront the results to literature and past experience. Findings presented in this paper aims to guide the DMS user towards a more accurate selection of the damping and hence a better assessment of the pile’s axial capacity. | Estimation of Damping Factors for a Better Assessment of Offshore Driven Piles Capacity | 10.1007/978-981-16-7735-9_8 |
2022-01-01 | This work is aimed at improving the technology of descent of spacecraft to the surface of planets covered with atmosphere. This paper proposes to use inflatable braking devices for landing on the planet’s surface. These inflatable brakes help to reduce the approach speed to the surface to an acceptable level. A feature of the considered descent vehicle is asymmetry due to the displaced center of pressure relative to the longitudinal axis. The work simulates the movement of the descent vehicle with an inflatable braking device. Mathematical modeling of the descent process in a stationary flow and a flow with variable parameters have been carried out. The studies were carried out using the numerical integration of the differential equations of motion. The results of changes in the angle of attack versus time are shown in the form of graphs. The influence of damping on the stability of the rotational motion of the descent vehicle relative to the center of mass is shown. | Study of the Movement of the Descent Vehicle with an Inflatable Device Made of a Special Material Taking into Account the Arising Asymmetry | 10.1007/978-981-16-9632-9_5 |
2022-01-01 | The article explores the passive method for damping wind auto-oscillations of an aboveground gas pipeline. The method consists in installing a vibration damping device in one of the spans, which operates on the principle of one-way connection. This characterizes the system as structurally non-linear. Integration of the differential equation of motion of a finite-dimensional dissipative system is based on the developed algorithm, which is associated with the analysis of the matrix quadratic characteristic equation. This allowed to obtain an analytical form of the dynamic reaction of a dissipative system in the matrix form of the Duhamel integral, which does not require the spectral expansion of the solution. Internal friction of the material is considered using a non-proportional damping model. The efficiency of devices with one one-way connection (OWC) in the span (DDM-1) and with two OWC (DDM-2) is compared on different values of the cable compliance. The estimation of the accuracy of solving the differential equation of motion by constructing the residual vector is carried out. | Vibrations of a Constructively Nonlinear System with One-Way Connections | 10.1007/978-3-030-91145-4_3 |
2022-01-01 | The damping systems design is a fundamental feature in a crutch because it decreases the forces in the upper members of the users and consequently reduces the chance of eventual injuries coming up. However, the damping system present in the currently marketable crutches cause discomfort to their users. Thus, the main object of this project was to develop a new damping system approach in order to minimize the problem previously stated. Initially, a study of the existing crutches was carried out and then, a biomechanical characterization of the gait assisted by crutches was performed. Considering the results of the gait analysis and the morphology of the crutch, a hydraulic damping system was scaled and designed in the Inventor software for a specific target audience which was settled to include children between the ages of 5 and 10. This target audience was selected because usually, children don’t have the required strength to effectively operate with this kind of devices and they adapt more easily to new ones. | The Damping System in Crutches: Development of New Model | 10.1007/978-3-030-79165-0_35 |
2022-01-01 | Energy dissipation capacity and seismic performance of steel moment resisting frame with hybrid damping system along with buckling restrained brace is investigated and an innovative approach of design of energy dissipating system is recommended. The nine storied structure is analyzed by nonlinear time history analyses using seven time histories and scaled to achieve a set of results and then compared the various possibilities. The multi-linear elastic and plastic links are used to model energy dissipating devices with the help of SAP 2000. The various results such as story displacement, story drift, roof drift, base shear and roof acceleration of steel moment resisting frame are compared with the system after installation of energy dissipaters in the same moment resisting frame that means a dual buckling restrained brace with steel moment resisting frame system and a dual hybrid damping system with steel moment resisting frame system. It was expected that the system will work in individual phases as earthquake intensity will go on increasing and in end results, the models have shown the same. It also has got depicted that the energy dissipation of the systems gets improved after installation of hybrid damping systems. | Evaluation of Role of Hybrid Damping System in Seismic Assessment | 10.1007/978-3-031-04793-0_32 |
2022-01-01 | The article is concerned with the effect of linear and cubic non-linear damping of an elastic bearing on forced resonant vibrations of a gyroscopic vertical rigid rotor taking into account non-linear stiffness of the cubic nature of the bearing material. It is confirmed that non-linear cubic damping of the support can suppress not only the maximum amplitude, but also the amplitudes of forced unsteady oscillations behind the rotation speed corresponding to the maximum amplitude and the variation of its values in time along the main curve, around its mean values. It shifts the speed of rotation of the amplitude maximum, with rigid and soft non-linear elastic characteristics of the support material downwards and upwards, respectively. It is shown that with a “slow” increase in the shaft rotation speed, an increase in the absolute value of the angular acceleration is accompanied by a shift of the amplitude peak towards high speeds, with a “slow” decrease in the shaft rotation speed – towards low speeds with a decrease in the amplitude of oscillations. It is shown that during the rotor takeoff run, the maximum amplitude for the case with a rigid non-linear elasticity characteristic of the support material is greater than the same value for the case with a soft non-linear elasticity characteristic of the support material, and conversely, during the rotor run-down for similar cases. | Unsteady Resonant Oscillations of a Gyroscopic Rigid Rotor with Non-linear Damping and Non-linear Rigidity of the Elastic Support | 10.1007/978-3-030-83594-1_9 |
2022-01-01 | Due to the many irregularities and speed humps present on the roads, the conventional passive suspension system fails to provide the most comfortable ride possible. The following work proposes the use of an active suspension system to achieve a more comfortable ride. An active suspension system refers to varying the suspension characteristics like stiffness and damping coefficient in real-time. Moreover, changing the suspension characteristics can provide other benefits like sporty handling and off-roading capabilities. The main objective of this study is to find out the effectiveness of active suspension systems using Matlab. A quarter car model with two degrees of freedom is used to perform the simulations. The parameters of the quarter car model represent a two-wheeler's (motor-cycle) rear suspension characteristics. The road profile in real-life situations (including speed humps and irregularities) can be very arbitrary. But, ultimately, one can approximate these random profiles to sinusoidal waves by using the Fourier series (to make computations easier). In this particular analysis, vibration inputs are already considered sinusoidal in nature. The assessment is based on the sprung mass acceleration and displacement. On completion of the simulations, results show that an active suspension system can provide the optimum values of the suspension parameters to improve the ride quality (Comfort) significantly. | Modeling and Analysis of Active Suspension System | 10.1007/978-981-16-6490-8_47 |
2022-01-01 | A zig-zag 1–3 viscoelastic composite (VEC) layer is designed for improved passive damping treatment of the vibrating structural beam. A zig-zag 1–3 VEC comprises by incorporating graphite blocks in zig-zag manner within the conventional viscoelastic material (VEM) layer. For the estimation of its damping capacity in the passive damping treatment of a beam, the corresponding finite element (FE) model is formed. To investigate the effect of inclusions in their zig-zag form compared to regular form, primarily, the optimal dimensional properties of corresponding configurations are obtained for the maximum damping of the beam. Then, their optimal modal loss factors and the performance in controlling the forced vibration of beam are compared. The results reveal that VEC with a zig-zag form of inclusions improves damping significantly compared to their regular form and conventional VEM. Moreover, this enhancement in damping appears due to the improvement in both extensional and shear counterparts of modal loss factor. | Design of Zig-Zag 1–3 Viscoelastic Composite Layer for the Improved Passive Damping Treatment of Beam | 10.1007/978-981-16-2794-1_17 |
2022-01-01 | The article is concerned with the effect of nonlinear cubic damping of an elastic support on unsteady resonant vibrations of a gyroscopic rigid rotor when interacting with a non-ideal energy source. It is confirmed that nonlinear cubic damping can suppress not only the maximum amplitude, but also the amplitude of unsteady oscillations behind the rotation speed corresponding to the amplitude peak. It shifts the control parameter corresponding to the maximum amplitude, downward with a rigid nonlinear elastic characteristic of the support material, and upward with a soft nonlinear elastic characteristic of the support material. An increase in the nonlinear cubic damping coefficient can significantly weaken the Sommerfeld effect with a nonlinear jump in unsteady oscillations, up to its complete elimination. The difference in the values of the maximum amplitude and in the corresponding values of the control parameter in the resonance curves with an increasing and decreasing control parameter is explained by the difference in the values of the same parameters relating to the jumping effects during the acceleration and runout of the rotary machine. | Nonstationary Resonant Oscillations of a Gyroscopic Rigid Rotor with Nonlinear Damping and Non-ideal Energy Source | 10.1007/978-3-030-91892-7_72 |
2022-01-01 | Use of high damping rubber bearings (HDRBs) in seismic isolation is a viable practice to protect bridges from earthquakes. The behavior of HDRB under cyclic load is dominated by nonlinear rate-dependent elasto-plastic responses and low temperatures. Rate-dependency effect due to viscosity depends strongly on the current strain but the effect is vividly different in loading/unloading phases. A rheology model, proposed recently for HDRB, can reproduce the behaviors of HDRB under cyclic loads. In this paper, the effects of incorporating the rheology model in simulating the seismic responses of a bridge superstructure-pier-foundation (S-P-F) system are investigated. In addition, the change of the model parameters at low temepratures affacting to the dynamic responses of the bridge is also investigated in this study. To this end, nonlinear dynamic analysis of a six span continuous seismically isolated bridge is conducted for two different strong earthquake ground motions. The nonlinear hysteretic behaviors of bridge piers are considered using Takeda tri-linear model. The nonlinearity is restricted to be lumped in plastic hinges located at the bottom of piers. Three temperature conditions are considered in the analysis: the room temperature (+23 °C) and the two low temperatures (−10 °C and −30 °C) for checking the low temperature effect. Two models for the isolation bearings are considered for comparison: the conventional bilinear model [ 1 , 2 ] used in design practice and the ratedependent rheology model [ 3 ]. To evaluate the time-history response of the bridge system, a solution algorithm has been developed to solve the equations of motion of the system and the first order differential equation governing the nonlinear rate-dependent behavior of HDRB. The solution algorithm is successfully implemented in general purpose finite element code. The implication of using the rheology model in response prediction of the S-P-F system is studied by comparing the rotation of pier and shear strain of the bearing obtained using the bilinear model and the rheology model. The comparison suggests that the modeling of HDRB considering the nonlinearities due to elasticity and viscosity effects is vital for rational prediction of the seismic response of highway bridges. | Dynamic Performance of Highway Bridges: Low Temperature Effect and Modeling Effect of High Damping Rubber Bearings | 10.1007/978-981-16-3239-6_36 |
2022-01-01 | Purpose The full damping treatments have been widely used in many fields for structural vibration and noise reduction. Compared to the partial damping treatments, the full damping treatments have not significantly enhanced the effect of vibration reductions. It is essential to find the optimal damping treatments in lightweight designs. Moreover, the solution methods should be beneficial to engineering applications. Method In this work, a layerwise finite element (FE) model of plates with constrain layer damping (CLD) treatments is proposed, based on Kerwin’s hypothesis. The dynamic characteristics of CLD system are analyzed by the modal strain energy (MSE) method. Based on the variable density method and the rational approximation of material properties (RAMP) interpolation scheme, a topology optimization model of the CLD system is built, and the optimal layouts are determined by the proposed modified guide-weight (MGW) method. The results are compared with optimal layouts using other common methods. Results The layerwise FE model, the topology optimization model and the MGW method are validated by numerical examples. The proposed layerwise FEM-MSE solutions converge to the analytical or semi-analytical solutions more accurately than the NASTRAN/MSE solutions. The optimization results indicate that the added weight of viscoelastic material (VEM) layer decreases by 50 percent, and meanwhile the modal loss factors can just decrease by 5.18 percent compared to plates with VEM full coverage in some cases. Conclusion The results of this work are beneficial to the vibration and sound radiation suppression of plates with CLD treatments in engineering applications. | Topology Optimization of Plates with Constrained Layer Damping Treatments Using a Modified Guide-Weight Method | 10.1007/s42417-021-00361-3 |
2022-01-01 | A simple yet useful construction of a system comprising of a “second-order control system” attached to an “SSB-SC amplitude modulator”. Using the basic concepts of both, the latter can be controlled externally as a result of simple mathematical relationships established between the defining parameters of the two. These so-called defining parameters are the “damping ratio” and the “modulation index”. Other important and indirectly influenced/influencing parameters are the “natural frequency”, the “damped frequency”, and more importantly the “current” and “power” of the modulated signal. We have explicitly established mathematical relationships that allow us to influence most of the parameters of an SSB amplitude modulator except for its own carrier signal/modulation index (can be either of these two and solely depends on what the variable parameter(s) of the modulator apparatus involved is(are)). Similar designs have been proposed previously but they have failed to make use of the more power efficient single side band techniques that surprisingly also enable a greater ease of control and various other advantages which we have mentioned in our paper. Finally, after evaluating based on these previously mentioned parameters we prove that our design is better than the other one. | Controlling an SSB-SC Amplitude Modulator Using a Second-Order Control System | 10.1007/978-981-16-1476-7_44 |
2022-01-01 | An analytical study on a true negative stiffness damper (NSD) in the form of negative stiffness amplifying damper (NSAD) is presented. NSD proposed in this study for controlled base isolator displacement uses damping magnification effect that guarantees the efficient reduction in base displacement and inter-storey drift whilst utilising minimum damping coefficient of NSAD dashpot. Dynamic equations of motion are represented in the state-space form. A simple optimisation design for NSAD is proposed using complex eigenvalue analysis of the system matrix. Optimal parameters for NSAD are developed considering the stability of the system and effective fundamental mode damping. Optimal NSAD is supplemented to MDOF base-isolated shear structure as NSD. A suite of six ground motions consisting of three near-fault (NF) and three far-field (FF) motions are used in this study. For comparison purpose, viscous damper (VD) and visco-elastic damper (VED) are used as conventional supplemental dampers to the base-isolated shear structure. Base shear, top storey acceleration and inter-storey drift are three objective variables that are monitored for the effectiveness of supplemental dampers. Results of the time history analysis show that NSAD works as an efficient supplemental damping system for both NF and FF ground motions in contrast to conventional dampers. | Optimal Design of True Negative Stiffness Damper as a Supplemental Damping Device for Base-Isolated Structure | 10.1007/978-981-16-7397-9_34 |
2022-01-01 | The model of rate-dependent mechanical behavior for the damping rubber material is proposed based on Petiteau’s time convolution integral model in terms of the K-BKZ model and Xiang’s constitutive model to characterize the hyperelastic response under various deformation states. Furthermore, the specimen of PVMQ with different Phenyl contents were prepared, and the mechanical behaviors of the samples were tested at various strain rates. Within a small stretch ratio, the materials are mainly characterized by elastic or hyperelastic behaviors rather than viscous behavior. When the material’s stretch beyond the elastic section, the viscous behavior gradually manifests itself and the materials are showing sensitivity to strain rates. With the increase of phenyl content in the materials, the influence of strain rate will be weakened. The model can characterize the mechanical behaviour of the damping materials accurately under various strain rates. In addition, this viscoelastic model could be used to predict the mechanical response of Phenyl silicone rubber in the dynamic mechanical environments. | Characterization of the Rate-Dependent Behavior of Phenyl Silicone Rubber | 10.1007/978-981-16-7423-5_4 |
2022-01-01 | In this paper we consider a quasilinear Cauchy problem for the scale invariant damped wave equation v t t − Δ v + μ ( 1 + t ) v t + μ 2 μ 2 − 1 v ( 1 + t ) 2 = μ 2 ( 1 + t ) v + v t p , $$\displaystyle v_{tt}-\Delta v+\frac {\mu }{(1+t)}v_t+\frac {\mu }{2} \left (\frac {\mu }{2}-1 \right )\frac {v}{(1+t)^2} =\left | \frac {\mu }{2(1+t)}v+v_t\right |{ }^p, \\ $$ with μ ≥ 0, v = v ( t , x ) and x ∈ ℝ n $$x\in \mathbb {R}^n$$ . The particular structure of the nonlinear term, guarantees a blow up result and a lifespan estimate, assuming radial initial data having slow decay. In particular the range of admissible exponents p depends on μ , n and the rate of the initial data decay. | Lifespan Estimates for a Special Quasilinear Time-Dependent Damped Wave Equation | 10.1007/978-3-030-87502-2_61 |
2022-01-01 | This study develops displacement- and kinetic energy-based tuning methods for the design of the tuned inerter dampers (TIDs) coupled to both linear and nonlinear primary systems. For the linear primary system, the design of the TID is obtained analytically. The steady-state frequency–response relationship of the nonlinear primary system with a softening or hardening stiffness nonlinearity is obtained using the harmonic balance (HB) method. Analytical and numerical tuning approaches based on HB results are proposed for optimal designs of the TID to achieve equal peaks in the response curves of the displacement and the kinetic energy of the primary system. Via the developed approaches, the optimal stiffness of the TID can be obtained according to the stiffness nonlinearity of the primary system and the inertance of the absorber. Unlike the linear primary oscillator case, for a nonlinear primary oscillator the shape of its resonant peaks is mainly affected by the damping ratio of the TID, while the peak values depend more on the stiffness ratio. The proposed designs are shown to be effective in a wide range of stiffness nonlinearities and inertances. This study demonstrates the benefits of using inerters in vibration suppression devices, and the adopted methods are directly applicable for nonlinear systems with different types of nonlinearities. | Tuning methods for tuned inerter dampers coupled to nonlinear primary systems | 10.1007/s11071-021-07112-9 |
2022-01-01 | Technological advancements in the field of transport and mobility are numerous with advancements and improvements in every possible scope. The subsystems of vehicles are a constant area of research for improvement, by the fact a new development in the field of magnetorheological fluid dampers has been proposed in published previous research. The proposed design of the damper and its features can capture the market with proper background planning to establish a small-scale manufacturing industry. This paper deals with discussing and planning a layout to establish an industry and to analyze the break-even sales quantity based on the inquired costs. The market sales analysis is performed using a different parameter that affects sales figures. Employing the bass business model to the discussed conditions the different sales scenarios are predicted and analyzed to come up with strategic plans to alter the sales trends in the time of declension. The potential outcomes and suggestions are discussed to conclude a complete background study to establish a small-scale automotive industry. | Sales Forecast and Layout Analysis of a Damper Manufacturing Industry for Autonomous Transport | 10.1007/978-3-030-94774-3_39 |
2022-01-01 | It would be economical if the overhead water tank (OWT), a common component of any conventional building structure, is designed to act as a passive tuned liquid damper (TLD) for vibration control of the primary structure under lateral excitations. However, the fluctuation in water height due to functional requirements in conventional rectangular or circular shaped OWT alters the liquid sloshing frequency, thereby causing mistuning between the frequency of the TLD and the structural frequency. Again, to ensure maximum energy dissipation in a conventional TLD, the ratio of the liquid height to the largest lateral dimension of the damper along the expected excitation is kept to about 0.1, which is practically impossible to maintain in conventional OWTs. To address these issues, a novel design of OWT with floating base (OWT-FB) is adopted. The floating base is a movable partition provided horizontally in the OWT in such a way so that the desired height of water, determined from the tuning requirement, is always maintained above the floating base. The design ensures that the water above the floating base functions as in a conventional TLD, maintaining proper tuning, even though the water level in the OWT fluctuates. The design of the OWT-FB system for an example building structure is illustrated. The effectiveness of the proposed design is demonstrated by subjecting the structure–damper system to seismic base excitation. | Design of Overhead Water Tank with Floating Base for Utilization as Tuned Liquid Damper Against Lateral Excitation | 10.1007/978-981-16-6490-8_54 |
2022-01-01 | The seat is the device that minimize the vibration transmitted to the tractor driver’s body by the tractor platform. All seats for agricultural machines require homologation before their installation on the machine, in accordance with the Council Directive 78/764/EEC (Annex XIV), amended with the Delegated Regulation 1322/2014 and with the Delegated Regulation 830/2018. In Italy there is still a large number of underused tractors (less than 200 h per year) that are more than 30 years old. Low cost upgrades are often necessary, even though the seat is an expensive item. The first worn out element of the seat is usually the damper (or shock absorber), but when replaced by the users, only the dimension is considered, not its damping properties. Aim of the work was to perform resonance tests to investigate the dynamic characteristics of seats using different type of dampers. Tests were conducted in laboratory with six different types of dampers and with two different static masses: 40 and 80 kg. The results showed that the seat suspension was nonlinear, with the transmissibility mostly depending on the amount of the inertial mass. The distribution of the vibration energy was also different, in function of the rigidity of the shock absorber. | Dynamic Characteristics of the Seats Equipping Old Agricultural Tractors | 10.1007/978-3-030-98092-4_23 |
2022-01-01 | For the preservation of historic architecture, historic building structures in areas prone to seismic excitations should have sufficient aseismic performance. A useful approach for enhancing the aseismic performance of historic buildings is aseismic retrofitting, where energy dissipation elements, such as frictional devices, are installed. However, for conventional friction dampers (FDs), an increase in damper force increases the story shear force and response acceleration under earthquakes. The authors previously developed a passive variable friction damper (VFD) that produces a decreased frictional force when the device displacement exceeds a predetermined value. In the present study, a time history response simulation was conducted using a nonlinear analytical model assuming a historic building made of a reinforced concrete structure retrofitted by the VFD subjected to earthquakes. The seismic responses were compared to those obtained with the FD. The results show that the VFD reduced the peak response story shear force and acceleration compared with those for the FD. | Response Simulation of Aseismic Retrofit for a Reinforced Concrete Historic Building Structure Using a Variable Friction Damper | 10.1007/978-3-030-90788-4_19 |
2022-01-01 | Taking the stabilized platform with viscous fluid damper of balloon radar as the research object, the mechanical balance model and multi-body dynamics simulation model of the stabilized platform are established comprehensively, considering the pitch angle, roll angle of the balloon, damper damping coefficient and gravity. Based on the three-dimensional model of the stabilized platform with viscous fluid damper, a dynamic simulation analysis model of the stabilized platform with viscous fluid damper platform system was established. The recovery time of the stabilized platform and the changes of the pitch angle and roll angles of antenna under the pitch or roll angle of the balloon are analyzed. Finally, the changes in the pitch and roll angles of the antenna under a certain eccentricity of the antenna centroid are measured, and compared with the simulation results to verify the correctness of the simulation model. It has guiding significance for the design of the balloon radar stabilized platform and lays a theoretical foundation . | Research on the Stability of Stabilized Platform for Balloon Radar | 10.1007/978-981-19-1309-9_9 |
2022-01-01 | Seismic fragility, loss and resilience provide a rational basis for decision making in new construction/retrofitting. The inter-storey-isolation (ISI) is a relatively recent seismic vibration control technology for taller buildings. The isolation bearings are placed at an intermediate storey to isolate the upper storey block (USB), which also acts as a non-conventional tuned mass damper (TMD) to the lower storey block (LSB) to reduce the vibration. This study presents the seismic fragility, total expected annual loss ratio (TEALR), the life cycle cost (LCC) and the resilience index (RI) for buildings with ISI. The ISI is shown to considerably reduce the seismic fragility, TEALR and LCC and enhances the RI. Alternative building frames and high damping rubber bearings (HDRBs) are considered to be subjected to a suite of near fault, pulse type ground motions. The reduction in seismic fragility by the ISI system is shown first; followed by the reduction in the TEALR/LCC and enhancement of the RI in respect to the pertinent damage scenarios. A functionality recovery approach is adopted while estimating the RI. These improvements are shown to be maximized by a sufficiently high (nearly 100%) mass ratio (ratio of mass of the upper storey block to the lower storey block) and higher level of viscous damping (e.g. 20%) in the HDRBs. Not only the structural damage(s) but the non-structural and economic damage(s) are also noted to be prominent. Best performances are observed under moderate seismic hazard level but diminishes gradually for extreme hazard, owing to the reduced efficiency of isolation and de-tuning by the incipient nonlinearity. | Implications of inter-storey-isolation (ISI) on seismic fragility, loss and resilience of buildings subjected to near fault ground motions | 10.1007/s10518-021-01277-9 |
2022-01-01 | This paper presents a novel energy-harvesting shock absorber for a vehicle to provide the required damping function to reduce the vibration between the vehicle and the road, as well as to reclaim vibration energy from the automotive suspension system during driving. The energy-harvesting shock absorber consists of a traditional hydraulic damping system and an energy harvesting system to convert mechanical energy into electricity. An energy-harvesting shock absorber was designed, simulated using a full car model. The results showed the energy-collecting ability of the energy-collecting dampers and a comparison of the vertical vehicle’s vibrations when using energy-collecting dampers and normal-type shock absorbers on vehicles traveling under the same conditions. | Design of an Energy Harvesting Shock Absorber for Vehicle | 10.1007/978-3-030-99666-6_49 |
2022-01-01 | This study aims at design and hysteresis modeling of a novel damper featuring shape memory alloy (SMA) to mitigate structural vibrations. The damper consists of SMA springs for actuation and a wedge mechanism to amplify and convert the actuating force into friction against the inner cylindrical face of the damper housing. From the friction between the wedges and housing, the damping force is archived. Following an introduction of SMA spring actuators and SMA dampers, the proposed SMA damper is configured. Experiments are then conducted on SMA springs to obtain their performance characteristics such as transformation temperature, heating time and actuating force. Based on the experimental data, design of the proposed SMA damper is performed and a damper prototype is fabricated. Experimental tests are then conducted to evaluate the damper performance. From the experimental results, hysteresis phenomenon of the SMA damper is presented and investigated. To predict the damper behavior, several hysteresis models are adopted and validated with comparisons and discussions. | Design and Hysteresis Modeling of a New Damper Featuring Shape Memory Alloy Actuator and Wedge Mechanism | 10.1007/978-981-16-3239-6_10 |
2022-01-01 | Magnetorheological (MR) damper is an effective semi-active vibration actuator which can produce controllable damping force by supplying proper voltage or electrical current as an input. By altering the input, the behaviour of MR fluid will change accordingly from free flow to semi-solid state. A semi-active suspension system consists of MR damper combines the advantages of both passive and active suspensions which is more economical, safe, mechanical simplicity and does not required a large power supply. Therefore, a lot of continuous efforts have been done to develop a vehicle suspension system incorporating with MR damper to reduce the vibration and road disturbance in order to provide a good ride comfort to driver and passenger. This study intends to investigate the performance of quarter car model in terms of body acceleration and body displacement adopted by the Skyhook-Differential Equation controller. Simulation and experimental validation data of MR damper model tests show that the modified Bouc-wen model can be used to represent the MR damper as the model is more accurately predicts the behaviour of the MR damper compared to other parametric models. Skyhook controller utilizing by Differential Evolution (DE) is used in order to optimize the system and its performance is improved with up to 63.04% as compared to the other controller responses. | Magnetorheological Damper Control for Semi-active Suspension System Using Skyhook-Differential Evolution | 10.1007/978-981-33-4597-3_16 |
2022-01-01 | In order to enhance the safety of the aircraft’s take-off and landing process, it is necessary to control the shimmy phenomenon of the aircraft wheel. In this situation, the magnetor-rheological damper is used to reduce the wheel shimmy, several years. This paper, firstly, builds the model of the aircraft landing gear and magneto-rheological damper is established. Then the linear active disturbance rejection control technique (LADRC) method is used to control the shimmy and compared with the PID method. The simulation results show that LADRC can control the wheel shimmy well. And when the aircraft speed is high, the stabilization time and the amplitude are smaller than PID. | Study on Magneto-rheological Damper Control of Aircraft Landing Gear Based on LADRC | 10.1007/978-981-16-6328-4_83 |
2022-01-01 | Radial stiffness of flexible ring dampers used in rotor supports is analyzed in this paper. Two major approaches are proposed for this purpose. The first is the conventional finite element modeling of this contact mechanics problem. The second is an analytical method that can be used as alternative to the costly numerical computations. This method is based on the Kalker’s principle of minimum complementary energy. A special variational formulation is developed in the closed form using Euler–Bernoulli beam approximation for the elastic ring and a simplified model of normal contact at the ring flanges. It has been shown that the surface tolerances of the parts have a substantial effect on the radial response of the flexible ring that may become nonlinear. The tight fit of the ring on both sides makes it much stiffer, while the loose fit results in free motion of the rotor and much weaker damping of its motion. Both methods produced results that are in excellent agreement for the considered cases. | Numerical and Analytical Analysis Methods for Radial Response of Flexible Ring Dampers | 10.1007/978-3-030-88465-9_49 |
2022-01-01 | The article dwells upon the study of the properties of a passive vibration isolation system with a nonlinear characteristic of a controlled damper. The existing problems in the field of research and the objectives of the research are indicated. As an actuator, a magnetorheological vibration damper is used, the design of which is similar to serial samples. The design diagram of an oscillatory system with a nonlinear element of viscous resistance is presented. The characteristics of the nonlinear element depend on the linear speed of the damper piston as well as on the control current. To study the characteristics of the vibration isolation system, the MATLAB program was used. With the help of a special block of two variables for the specified program, a simulation model of the damper is set, based on which a simulation model of the vibration isolation system is built. The mechanism of formation for the damper nonlinear temporal characteristics is studied. Based on equivalent frequency characteristics, the dynamics of the vibration isolation system with the damper nonlinear and linearized characteristics is investigated. The calculation results are confirmed by experiments on the developed bench. The satisfactory adequacy of the developed model to the real vibration isolation system is shown. The obtained results are analyzed, and conclusions on the work done are formulated. | Research of a Nonlinear Vibration Isolation System with a Controlled Magnetorheological Damper | 10.1007/978-3-030-85233-7_90 |
2022-01-01 | In recent days, the safety and serviceability of bridges are increasingly being affected by high-speed and heavy moving vehicles due to the construction of more slender and light structures. Though tuned mass dampers (TMDs) offer a very desirable solution to the vibration problem of a bridge, high TMD effectiveness generally entails a large damper mass ratio, which poses practical difficulties in implementation within a bridge deck. Further, the space within a bridge deck is limited for accommodating the static stretching of the connecting spring between the bridge deck and the TMD mass due to gravity, and the large TMD stroke resulting from the transfer of structural vibrational energy to the TMD. These problems can be overcome by the use of the tuned mass damper inerter (TMDI). With this perspective, the present study presents a comparative study on the performance of a TMD and TMDI in reducing the maximum mid-span acceleration of an example bridge deck as well as the dynamic stroke of the damper mass. Results indicate the superior performance of TMDI in reducing response of the bridge deck. | A Comparative Study on the Vibration Control of a Bridge Under Moving Springing Mass by TMD and TMDI | 10.1007/978-981-16-6490-8_53 |
2022-01-01 | Although Independently Rotating Wheels (IRW) meet the low-floor height requirements of the Light Rail Transit systems, its self-centering and self-steering moments resulting from the longitudinal creep forces are small to maneuver sharp curves due to the lack of a rigid rotational speed coupling between its wheels. While the Active Steering control of IRWs can potentially achieve perfect steering with satisfactory running stability, in the present study a simpler passive stabilization control method using a Gyroscopic damper is proposed to realise automatic sharp curve steering and high-speed stability to improve the dynamic performance of a railway vehicle running with IRWs. The present study discusses the stabilization effect of the Gyroscopic damper in three basic configurations of IRWs, namely the conventional IRW, the Negative Tread Conicity Independently Rotating Wheels (NTCIRW) and the EEF (Einzelrad-Einzel Fahrwerk) bogie. In this study, the theoretical investigation and numerical simulations with a full-scale railway vehicle is done which shows the effectiveness of the proposed gyroscopic damper. | Utilisation of Gyroscopic Damper to Improve Dynamic Stability and Steering in a Railway Vehicle with Independently Rotating Wheels | 10.1007/978-3-031-07305-2_40 |
2022-01-01 | The automotive industry has started to show interest in harvesting energy from the motion of the suspension. Unlike conventional shock absorber which dissipates energy by passing a fluid, generally oil, through small orifices, thus generating heat, the regenerative shock absorber transforms the linear motion of the suspension into a rotation of an electric generator. The electrical load of the generator should be optimized because the too large value suppresses the useful electric current while the too small value gains too little energy. This paper presents the analytical solutions of the optimal electrical load of the generator for two objectives: ride comfort and regenerated power, under two cases of excitation: harmonic and random. | Optimal Electrical Load of the Regenerative Absorber for Ride Comfort and Regenerated Power | 10.1007/978-981-16-3239-6_43 |
2022-01-01 | The optimal design and seismic performance of a nonlinear tuned mass damper with pinched hysteresis (TMD-PH) are studied. The peculiar behavior of this device is offered by hybrid wire ropes made of shape memory alloy and steel under an axial-flexural loading. This device has been previously described by means of a modified 6-parameter Bouc–Wen hysteresis model. The optimal design of this TMD-PH mounted on a linearly elastic and viscously damped structural system subject to earthquakes is here dealt with by resorting to a stochastic approach. To this end, the nonlinear behavior of the TMD-PH is taken into account via stochastic linearization technique whereas the seismic ground motion is modeled as a filtered amplitude-modulated white Gaussian noise. The optimum design problem aims to minimize the cumulative time integral of the variance of the structural response. After evaluating the accuracy of the stochastic linearization, the present study examines the seismic performance of the TMD-PH optimized for a multi-storey reinforced concrete frame according to the proposed approach. | Optimal Design and Seismic Performance of a Nonlinear TMD with Pinched Hysteresis | 10.1007/978-3-030-81166-2_19 |
2022-01-01 | In order to solve the problem that the output damping force of magnetorheological Damper is not large enough and the adjustable range is small, a bypass magnetorheological Damper is designed in this paper. The Valve is connected in a hydraulic cylinder with pipes to form a controllable magnetorheological Damper device. Two structures are designed by adding non-magnetic materials to the structure so that the magnetic field lines pass vertically through the damping gap as much as possible. One is to use two coils and add a non-magnetic material above the coil, and the other is to use only one coil and add a non-magnetic material above the coil. The finite element method is used to simulate and analyze the parameters of two structures which affect the damping performance, and the results are discussed. The results show that more magnetic force lines can pass through the damping channel vertically by adding non-magnetic material to the structure, which can increase the damping force and adjustable coefficient. | Design and Finite Element Analysis of Magnetorheological Damper | 10.1007/978-981-19-2456-9_91 |
2022-01-01 | The present Chapter presents on its entirety the dynamics of mechanical structures such as beam and rectangular plate when they are subjected to one or more DC motors with limited power supply. Attention is paid on the various applications of such study in civil and mechanical engineering. To deal with this topic, we developed two main approaches with the purpose to give a good insight on vibration control and stability of the studied system. The first step consists on the use of some electric transducers and tuned mass damper to reduce the amplitudes of vibration of a plate. An adequate choice of the physical parameters of the control device enhances the efficiency of the control strategy. A stability analysis using the Routh-Hurwitz criteria confirms the pertinence of the control strategy. The second method is rather based on the synchronization with and without delay between the external sources (DC motors) working on the structure. Here, the physical parameters of the structure enable to present the phase and anti-phase or rapid and late synchronization phenomena between the motors. This difference of phase or the input delay between the motors and the voltage applied on the motors lead to situations where the amplitude vibrations of the mechanical structure are considerably reduced. | Control of the Dynamics of Mechanical Structures Supporting DC Motors with Limited Power Supply | 10.1007/978-3-030-96603-4_16 |
2022-01-01 | Passive control devices are widely used in the reduction of lateral vibrations of building structures. The control of these lateral vibrations is vital in preventing collisions between adjacent building structures during a seismic event. These collisions modify the dynamic behavior of the intervenient structures and cause substantial local damage. In this way, the implementation of a Tuned Mass Damper (TMD) can be a solution in mitigating the earthquake-induced building pounding. However, there are concerns regarding the effectiveness and practical applicability of solutions for this purpose. In fact, non-linear inelastic behavior of building structures, expected during earthquakes, is one of these concerns that should be considered in the assessment of the TMD effectiveness. Hence, this study addresses the investigation of the control action effectiveness of a TMD in reducing the lateral displacements of one of two building structures modelled with elastic and inelastic behavior that are prone to earthquake-induced structural pounding. Results show that TMD is effective in reducing displacements, pounding forces, and number of impacts, under elastic building behavior. However, when inelastic behavior is considered the TMD becomes less effective. | Control Action of a Tuned Mass Damper in Mitigating Earthquake-Induced Structural Pounding Between Building Floors | 10.1007/978-3-031-10047-5_36 |
2022-01-01 | A semi-active control scheme for the vibration control of offshore steel jacket platforms is developed. Decentralized sliding mode control (SMC) algorithm is adopted for applying the control force to the structure with the help of Magneto-rheological (MR) damper for alleviating the earthquake-induced vibrations. SMC method is used due to its robustness against the parametric variations of the structures. The command voltage to the MR dampers is regulated through the clipped-optimal algorithm. A steel jacket platform, available in the literature, is modelled in MATLAB as an example to investigate the dynamic responses under the environmental loads. The earthquakes ground motions, scaled to 0.3 g PGA, considered in the present study are the El Centro (1940), Northridge (1994), San Fernando (1971) and Chichi (1999). Results indicate that sliding mode controller is able to reduce the responses of the offshore jacket platform significantly, subjected to different earthquake loads. It is observed that the positions and the number of MR dampers affect the performance of the controller to a great extend in the offshore jacket platforms. The control algorithm is stable against the variations and uncertainties in structural parameters. | Semi-active Seismic Vibration Control Offshore Jacket Platforms | 10.1007/978-981-16-5673-6_4 |
2022-01-01 | As the evolution of civilization took place, the shelter became the primary need for civilization. There emerged a demand for the construction of the permanent structure to repel environmental risk and community resilience. The development of the tall structure evolved in the construction of different structural forms to resist the lateral load, mainly interior and exterior structural systems. An outrigger structural system has been considered as one of the finest structural systems in controlling the lateral load by mitigating the response of the structure. In this study, the outrigger structural system is considered with an undamped and damped system to diminish the vibration of the structure against the earthquake load. In a conventional outrigger structure, the outrigger arm is directly connected to the core and the perimeter column. In damped outrigger structure, there is an introduction of the external device called passive dampers which are connected between the outrigger arm and outer column. In this paper, the viscous damper is used as an external passive damper between the outrigger arm and the perimeter column. The simulation results show that with the introduction of the damping device between the outrigger and column, the performance of the outrigger structure has been further enhanced. | Seismic Vibration Mitigation of Damped Outrigger Structure Using a Passive Damper | 10.1007/978-981-16-6738-1_44 |
2022-01-01 | This chapter on the recent history of experimental structural dynamics puts much of the Handbook in a historical perspective that begins with the development of digital data methodology and computerized data processing that began in the mid-1960s. Experimental structural dynamics began much earlier with analog, single frequency data acquisition and mostly visual data processing that began in the 1800s with the rail and marine industries, particularly when the steam engine impacted those technologies. The analog, single frequency data acquisition methodology, continued in the automotive and the aircraft industries in the first half of the 1900s. This Handbook mostly chronicles data acquisition and processing methods that began more recently, in the mid-1960s, with the advent of the Fourier transform, analog to digital data conversion, and digital minicomputers to the present time period. The Handbook also discusses many methods and techniques in use during the 1960s and 1970s that utilize experimentally derived models, both linear and nonlinear, to calibrate and validate corresponding analytical models. Part of this discussion includes the issue of the varying dimensionality of the number of degrees of freedom (DOF) between experimental and analytical models. This chapter also discusses the researchers and educators that were part of the development of the experimental structural dynamics methodology in the 1960s to 1980s that led to the current technical state of the art. This discussion includes the identification of researchers and educators that were instrumental to the Society for Experimental Mechanics (SEM) in the development of this area of interest within the Society over the last 50 years. | Recent History of Experimental Structural Dynamics | 10.1007/978-1-4939-6503-8_1-1 |
2022-01-01 | Phytopathogenic fungi are known to secrete specific proteins which act as virulence factors and promote host colonization. Some of them are enzymes with plant cell wall degradation capability, like pectate lyases (Pls). In this work, we examined the involvement of Pls in the infection process of Magnaporthe oryzae , the causal agent of rice blast disease. From three Plgenes annotated in the M. oryzae genome, only transcripts of MoPL1 considerably accumulated during the infection process with a peak at 72 h post inoculation. Both, gene deletion and a constitutive expression of MoPL1 in M. oryzae led to a significant reduction in virulence. By contrast, mutants that constitutively expressed an enzymatic inactive version of Mo Pl1 did not differ in virulence compared to the wild type isolate. This indicates that the enzymatic activity of Mo Pl1 is responsible for diminished virulence, which is presumably due to degradation products recognized as danger associated molecular patterns (DAMPs), which strengthen the plant immune response. Microscopic analysis of infection sites pointed to an increased plant defense response. Additionally, Mo Pl1 tagged with mRFP, and not the enzymatic inactive version, focally accumulated in attacked plant cells beneath appressoria and at sites where fungal hyphae transverse from one to another cell. These findings shed new light on the role of pectate lyases during tissue colonization in the necrotrophic stage of M. oryzae’s life cycle. | Gene deletion and constitutive expression of the pectate lyase gene 1 (MoPL1) lead to diminished virulence of Magnaporthe oryzae | 10.1007/s12275-022-1074-7 |
2022-01-01 | The application of ring spring dampers in seismic design and strengthening/rehabilitation of civil structures is almost unknown and poorly investigated. Ring spring dampers are extremely robust, heat-resistant, durable, and have almost no maintenance requirements. Through an innovative design, they combine self-centering characteristics with a high seismic energy absorption capacity. Preloading gives them the typical flag-shaped force-deformation hysteresis curve, which can very efficiently absorb seismic energy in a structure, independently of the deformation velocity (non-viscous damping). Due to these properties, a structure with ring spring dampers can withstand seismic loads with little or no damage. The springs themselves also remain free of damage. The objective of this paper is to give an overview of the behavior of ring spring dampers, which are used as braces that will be activated in case of a seismic event. The resulting behavior of structures is discussed based on the analytical and numerical investigation of the equivalent stiffness and damping of the dampers. By the special combination of ring spring dampers with additional parts, the braces can be designed to resist seismic forces and absorb the resulting energy in both the tension and compression directions. Several structural and spring design parameters (structural and spring layout, spring type, spring composition, etc.) determine the overall seismic performance of the structure. The main influencing factors on the stiffness and damping of the ring springs were identified and investigated and their use for design purposes was elaborated. Generally, high initial stiffness and a high preload have a positive effect. By applying ring spring dampers, masses and cross-sections can be reduced. The dimensioning and practical applicability of ring spring dampers used as bracing units has been proven in several projects. | Application and Optimization of Ring Spring Dampers for Seismic Design | 10.1007/978-3-031-03811-2_89 |
2022-01-01 | In this chapter, an introduction is presented for system dynamics and control. The main aim in the control of structures is to reduce vibrations and the vibration is defined then, the main concern of system dynamics and control such as control, automatic control, system, transfer function and control system types are given. Then, a short brief for structural control types such as active, passive, semi-active and hybrid are defined. Lastly, the content of the book “Optimization of Tuned Mass Dampers-Using Active and Passive Control” is presented. | Introduction and Overview: Structural Control and Tuned Mass Dampers | 10.1007/978-3-030-98343-7_1 |
2022-01-01 | With an electric formula racing vehicle as the research object in the paper, a suspension design method with independent roll control function was introduced, and the conclusion that the suspension has different damping requirements in ride conditions and roll conditions was drawn. Compared with traditional vehicles without heave shock absorbers, this type of suspension realizes the decoupling of stiffness and damping in the heave and roll conditions, and different damping characteristics of the vehicles are obtained in ride conditions and roll conditions by adjusting the heave shock absorbers and inboard shock absorbers separately, to improve the vehicle attitude control and steering response. The effectiveness of the design was verified by simulation in the vehicle dynamics simulation software VI-Car Real Time. | Suspension Design of Formula Racing Vehicle with Roll Independent Control Function | 10.1007/978-981-16-2090-4_3 |
2022-01-01 | Frequency response of half-car model that is moving at a constant speed on sinusoidal road surface is investigated. The suspension system is considered with damper having nonlinear stiffness and damping characteristics. Primary and superharmonic resonance with internal resonance between front and rear wheels is studied. The equilibrium analysis is carried out with the method of multiple scales. The amplitude response versus frequency at the front and rear wheels is presented for different parameter values to analyse the nonlinear response. | Analysis of Half-Car Model with Nonlinear Damper Under Sinusoidal Road Excitation | 10.1007/978-3-030-81166-2_16 |
2022-01-01 | Conventional approaches in seismic design dissipate most of the energy input by the earthquake through plastic deformations in regions of the main structure that also support the gravity loads. This involves important damage spread throughout the structure. Innovative approaches based on the use of energy dissipation devices (EDDs) apply a completely different strategy. The EDDs release the main structure from dissipating energy and limit its responsibility to only (or mainly) sustaining the gravity loads as the building deforms laterally. The seismic capacity of the structure is entrusted entirely (or mainly) to EDDs. Ultimately, the usefulness of EDDs is fully acknowledged, but their use in Europe is still very incipient. Two impediments to the widespread implementation of EDDs would be the lack of requirements, or else the over-conservative requirements of code provisions for the seismic design of structures with EDDs. This presentation introduces the concept of a buildings with energy dissipation systems and briefly reviews recent research on this topic. Finally, the procedures for verifying buildings with energy dissipation systems that have tentatively been adopted in the draft-new-Eurocode 8 are explained. | From Conventional to Innovative Approaches in Seismic Engineering: Buildings with Energy Dissipation Systems and the Upcoming Second Generation of Eurocode-8 | 10.1007/978-3-031-15104-0_23 |
2022-01-01 | It is well–known that magneto–rheological dampers (MRDs) are usually designed based on their quasi–static models. However, in dynamic response, the dampers exhibit nonlinear hysteresis phenomena. For connection between the design phase and dynamic modeling of the MRDs, in this research, a new dynamic model named QSHM model based on quasi–static (QS) model and a hysteresis multiplication (HM) factor is developed. After the new approach in experiment–based dynamic modeling of the MRDs is proposed, several hysteresis multiplication factors are introduced. The proposed approach is then implemented for a prototype MRD and the results are compared with a typical hysteresis model previously developed for MRDs. From the comparison results, advantages of the proposed approach are clarified. | A New Approach for Dynamic Modeling of Magneto–Rheological Dampers Based on Quasi–static Model and Hysteresis Multiplication Factor | 10.1007/978-3-030-91892-7_70 |
2022-01-01 | The high-temperature superconducting (HTS) maglev system has great potential to become a new type of rail transit due to its unique self-stabilizing levitation, low noise pollution, and environment-friendly operation. However, previous studies have shown that the damping properties of HTS system are low, and hence, its large-amplitude nonlinear vibration is prone to occur under external interference, which will affect the stability, safety, and comfort of the long-term operation of the maglev vehicle. Therefore, it is necessary to improve the damping performance of HTS maglev system, minimize the impact of vibration on the maglev system, improve the anti-interference ability of the system, and ensure the smoothness and stability of the system. In this work, an eddy current damper (ECD) is designed to suppress the vibration that may occur during the operation of the HTS maglev vehicle; the ECD is placed at the same height as the HTS bulks. And by collecting the displacement and acceleration signals of the HTS levitator, the efficiency of dampers in suppressing vibration with different copper thicknesses under different field cooling heights (FCHs) is analyzed. The experimental results show that the additional ECD can effectively reduce the vibration of the HTS levitator, especially among the resonance frequency range. And when the FCH is set to the commonly used engineering height of 30 mm, the ECD has the highest damping efficiency. The relevant research results in this work provide a possible solution to the problems encountered in the operation of the maglev train in the real scene. | Vibration Reduction Using Eddy Current Damper in High-Temperature Superconducting Maglev System | 10.1007/s10948-021-06056-w |
2022-01-01 | The spring damper and viscous fluid damper were designed in detail, and the finite element model of the stabilized platform was established on the basis of the three-dimensional model of the stabilized platform, the mechanical simulation of the main structural parts is carried out. The pitch and roll angle of the antenna were measured and compared with the simulation results based on the test platform of the spherical stabilized platform with viscous fluid damper. The results show that compared with the stabilized platform with spring damper, the stabilized platform with viscous damper can better isolate the influence of balloon pitch or roll motion on antenna, and has the advantages of high stability accuracy, quick stability response time and small fluctuation. The theoretical results of the platform stabilized by viscous fluid damper agree well with the measured results, which verifies the reliability of the design. | Research and Design of Stabilization Platform for Ball-Borne Radar | 10.1007/978-981-19-1309-9_24 |
2022-01-01 | The non-linear propagation of dust acoustic waves (DAWs) in collisional, unmagnetized, viscous dusty plasma systems containing two temperature ions, electrons, high negatively charged dust grains are investigated. By using the reductive perturbation method (RPM) the damped Kadomtsev-Petviashvili Burgers (dKPB) equation that governs the DAWs is derived. Generally, the impact of viscosity is ignored during the studies of wave dynamics in a plasma medium. In the present investigation, a Burgers term is introduced in order to express the dissipation effect in the viscous plasma circumstance. The strong dissipation due to the presence of Burgers term may cause for rising of a shock solution. However, in a very weak dissipative system, the solitary-like wave solution may arise due to the balance between the dispersion and nonlinearity. Assuming conservation law in the present system, solitary type wave solution is explored, and shock type wave solution is determined by means of Simplified Hirota bilinear method (SHBM). Finally, the effect of the kinematic viscosity, collisional frequency, etc. on wave propagation is demonstrated from numerical understanding. | Propagation of Rarefactive Dust Acoustic Solitary and Shock Waves in Unmagnetized Viscous Dusty Plasma Through the Damped Kadomstev-Petviashvili Burgers Equation | 10.1007/978-3-030-99792-2_15 |
2022-01-01 | The dynamic response of base-isolated bridge with various isolators is presented. Bridge modal of 2-span of length 19.5 m and width of 12.16 m has been picked for the present study. Two models are used in this study, one is non-isolated railway bridge with ballastless slab track and another one is base-isolated railway bridge with ballastless slab track of base-isolated bridge with different HDRB. Isolators are designed by considering suitable soil type and site conditions. And, the properties of isolators are introduced between super structure and sub structure. Influence of the base isolator is studied, and both the models are analyzed for seismic response spectrum method in both horizontal directions. The influence of the HDRB in the dynamic behavior of the bridge is observed. Parametric studies are performed for different system configurations, isolation systems, and frequency ratios under torsional coupled and uncoiled conditions. The dynamic response of the base-isolated bridge varies significantly due to the disparity in the isolator properties. | Seismic Analysis of Isolated and Non-isolated Railway Bridges with Slab Track—A Comparative Study | 10.1007/978-981-16-4617-1_27 |
2022-01-01 | In high-rise building conception, seismic load becomes more and more a big issue because seismic induced displacement (e.g. displacement or inter-stories shift) is very important. Tuned Liquid Damper (TLD) is considered as one promising solution thank to its efficacity and cheap installation cost. However, lack of standard or design code may conduct earthquake engineers to some difficulties during the conception phase of high-rise building. In this paper, the optimization of TLD parameters, such as geometry, water level are conducted through a systematic analyses of simplified models, representing a various range of TLD parameters, undergoing an input signal recorded during 1940s El Centro earthquake. As highlighted result, the effectiveness of TLD can be clearly asset through non-dimensional frequency equal to the ratio between first sloshing frequency and first eigen-frequency. The optimized design of TLD is reached when the non-dimensional frequency is close to the unity. | Optimized Design of Tuned Liquid Damper for Mitigating Seismic Induced Vibration in Case of High-Rise Building | 10.1007/978-981-16-7160-9_43 |
2022-01-01 | Recently, linear magnetorheological (MR) dampers have been widely utilised for impact protection of seat suspensions. However, the viscous force of the linear MR damper increases seriously with the increase of impact velocity. This results in a sharp increase of the total output force of the seat suspension, which may damage the suspension structure and lead to occupant injuries. To address this issue, the performance of a seat suspension installed with a rotary MR damper to improve the impact protection performance is investigated in this paper. Specifically, the mathematical models for the linear MR seat suspension and the rotary MR seat suspension are established. The impact protection performance of these two suspensions are numerically compared by the transient analysis and the dynamic impact simulation. Both the transient analysis and the dynamic simulation indicate that the rotary MR damper seat suspension is less sensitive to the impact velocity and can provide better impact protection performance. | Numerical Study of Rotary Magnetorheological Seat Suspension on the Impact Protection | 10.1007/978-981-16-5912-6_74 |
2022-01-01 | In this chapter, an approximate analytical technique for computing the damped backbone curves resulting from the inclusion of viscous damping is presented. Traditionally, the analysis of nonlinear systems involves studying the relation between the nonlinear frequency and the resulting vibration amplitudes. One approach is to compute the conservative (undamped-unforced) backbone curves of the system and compare them to the numerically computed forced-damped frequency responses. Although this technique can have acceptable accuracy in the case of very lightly damped systems, increasing the damping reduces the matching between the conservative backbone curves and the forced-damped frequency response curves. The new method presented in this chapter is related to the previous methods of Wentzel, Kramers and Brillouin and Burton. It is combined with a normal form transformation to obtain the damped backbone curves. Two examples are shown demonstrating how it can be directly applied to single-degree-of-freedom nonlinear oscillators with polynomial nonlinear terms. | Exploring the Dynamics of Viscously Damped Nonlinear Oscillators via Damped Backbone Curves: A Normal Form Approach | 10.1007/978-3-030-81162-4_14 |
2021-12-29 | In this paper, we are concerned with the asymptotic behavior of solutions to the system of hyperbolic conservation laws with damping. In particular, a system includes compressible Euler equations with damping, $$M_1$$ M 1 -model, etc. Under some smallness conditions on initial perturbations, we prove that the solutions to the Cauchy problem of the system globally exist and time-asymptotically converge to corresponding equilibrium state, and further give the optimal convergence rate. The approach adopted is the technical time-weighted energy method combined with the Green’s function method. | Optimal decay rates of solutions to hyperbolic conservation laws with damping | 10.1007/s00033-021-01657-w |
2021-12-27 | In this paper, we propose a time-dependent viscous system and by using the vanishing viscosity method we show the existence of delta shock solutions for a generalized zero-pressure gas dynamics system with linear damping. | Delta Shock Solution for a Generalized Zero-Pressure Gas Dynamics System with Linear Damping | 10.1007/s10440-021-00463-w |
2021-12-16 | High penetration of renewable sources into conventional power systems results in reduction of system inertia and noticeable low-frequency oscillations (LFOs) in the rotor speed of synchronous generators. In this paper, we propose effective damping of LFOs by incorporating a supplementary damping controller with a photovoltaic (PV) generating station, where the parameters of this controller are coordinated optimally with those of a power system stabilizer (PSS). The proposed method is applied to damp local electromechanical modes by studying a system comprising a synchronous generator and a PV station connected to an infinite bus. The PV station is modeled following the instructions of the Western Electricity Coordinating Council. The problem is modeled as an optimization problem, where the damping ratio of the electromechanical modes is designed as the objective function. Constraints including upper and lower limits of decision parameters and damping ratio of other modes are considered by imposing penalties on the objective function. Different optimization algorithms are used to pursue the optimal design, such as political, improved gray wolves and equilibrium optimizers. The results validate the effectiveness of the proposed controller with PSS in damping local modes of oscillations. | Effective damping of local low frequency oscillations in power systems integrated with bulk PV generation | 10.1186/s41601-021-00219-6 |
2021-12-10 | Fabric and resin materials, fiber orientations, volume fraction and knitting patterns are highly effective for the mechanical and dynamic properties of the composite materials. These materials can be subjected to impact loads at various energy levels depending on their application areas, and thus causes the material properties to change. Therefore, experimental studies have been carried out to determine the dynamic properties for the polyamide fiber-reinforced epoxy composites, which can be defined as a novel composite material variation, before and after low-velocity impact. In this context, the composite specimens were subjected to one and two repeated low-velocity impacts under 25.2 J constant energy. Apart from that experimental vibration tests were conducted under free-free boundary conditions to determine how dynamic properties such as natural frequency, flexural modulus, and specific damping capacity will change with the consequent distortion in the structural integrity. For the current study, at least three samples were subjected to the experimental tests to verify obtained results, and standard deviations revealed that results were reliable and repeatable. As a consequence of the current study, it has been concluded that the composite specimens have high matrix volume fractions due to the knitting architecture of the polyamide fabrics. Moreover, since the polyamide fabrics have spacious mesh weave, an improvement for the damping properties has been achieved due to the increased fiber-resin interface. It has been observed that polyamide composite specimens exhibited approximately 11.5% specific damping capacity, and had relatively higher damping properties compared to the conventional materials. It was also revealed that the degradation in the specific damping capacities was observed by virtue of the low-velocity impact but it was not significantly effective on the dynamic properties due to the limited damage area. Additionally, it was found that polyamide fiber-reinforced composites can be used as the optimum material for the application areas in which high damping and impact resistance are required. | Effects of low-velocity impact on vibration behaviors of polyamide fiber-reinforced composites | 10.1007/s40430-021-03322-9 |
2021-12-08 | Analytical frequency analysis of a nonlinear viscoelastic microcantilever is performed based on strain gradient theory. The Kelvin–Voigt scheme is utilized to model the viscoelasticity effect. Due to the microcantilever shortening effect via Euler–Bernoulli inextensibility condition, geometric, inertia, stiffness, and inherent damping nonlinearities are considered. The equation of motion is derived from Hamilton’s principle, and discretized using Galerkin method. The multiple timescale perturbation method is performed to solve the time response equation. Implying steady-state condition, the nonlinear relation between detuning parameter and amplitude of the vibration of a nonlinear viscoelastic microcantilever in the framework of the strain gradient theory is developed, and stability and bifurcation criteria near primary resonance is analytically evaluated. Results show that the damping nonlinearities cause the microcantilever to be softer while size effects via geometric and inertia nonlinearities have the opposite effect. It is also found that utilizing strain gradient theory has a considerable effect on natural frequency, stability criteria, the amplitude of oscillation, force, and frequency bandwidth, in comparison with classical and modified coupled stress theory, especially when the ratio of beam thickness to length scale parameter reduces. | Size effects on stability and bifurcation of nonlinear viscoelastic microcantilevers based on strain gradient | 10.1007/s40430-021-03316-7 |
2021-12-01 | The viscous damping is a highly idealized but mathematically convenient way of representing the energy dissipation mechanisms not related to the hysteretic response. In this study, the tangent-stiffness proportional Rayleigh damping (TSPRD) appropriate for inelastic hysteretic structures outfitted with the supplemental damping devices is utilized in inelastic dynamic analysis of simple single-degree-of-freedom (SDOF) structures. A numerical procedure of dynamic equilibrium equation for SDOF systems with TSPRD model is derived for development of the general numerical solution scheme. By specifying various combinations of tangent-stiffness and mass proportional damping terms in TSPRD model, the influence of viscous damping models on displacement ductility demands is investigated. The results indicate that the difference in ductility demands for various damping models is considerable, depending on the periods of vibration, relative lateral strength, hysteretic models, stiffness deterioration and initial damping ratios. The constant-strength displacement ductility spectra, by considering both tangent-stiffness proportional and mass proportional damping, are developed in terms of site conditions, hysteretic rules and initial damping ratios. | Effect of Viscous Damping Models on Displacement Ductility Demands for SDOF Systems | 10.1007/s12205-021-1899-3 |
2021-12-01 | We are concerned with asymptotic stability of energy for plate equations with vanishing viscoelastic dampings and complementary frictional dampings, where the internal viscoelastic dampings are assumed to be time-dependent. In terms of the relaxation function $$\theta (t)$$ θ ( t ) and the coefficient $$\gamma (t)$$ γ ( t ) of viscoelastic term, we obtain the decay rates for the plate equations’ energies. Since we do not need the viscoelastic damping coefficient to be bigger than a fixed positive number, which is required in previous investigations of the asymptotic stability of the plate equations’ energies, our decay theorems extend and improve essentially the existing decay results for the plate equations in both viscoelastic damping case and mixed-type damping case. | Asymptotic Stability of Energy for a Weak Viscoelastic Plate Equation with Complementary Frictional Damping | 10.1007/s00245-020-09738-4 |
2021-12-01 | We consider a fluid–structure interaction model defined on a doughnut-like domain. It consists of the dynamic Stokes equations evolving on the exterior sub-domain, coupled with an elastic structure occupying the interior sub-domain. A key factor—a novelty over past literature—is that the structure equation includes a strong (viscoelastic) damping term of Kelvin–Voigt type at the interior. This affects the boundary conditions at the interface between the two media and accounts for a highly unbounded “perturbation”. Results include: (i) analyticity of s.c semigroup of contractions defining the overall coupled system, (ii) its (uniform) exponential decay, along with (iii) sharp spectral properties of its generator. Some results are geometry-dependant. | Fluid–Structure Interaction with Kelvin–Voigt Damping: Analyticity, Spectral Analysis, Exponential Decay | 10.1007/s00245-021-09812-5 |
2021-12-01 | In this paper we study the long-time dynamics of the perturbed system of suspension bridge equations $$\begin{aligned} m_c u_{tt}-\beta u_{xx}+\kappa (u-w)^+ +f_1(u,w)+ (-\partial _{xx})^{\gamma }u_{t}= & {} 0,\\ m_b w_{tt}+\mu w_{xxxx}+(p-\epsilon \Vert w_x\Vert ^2)w_{xx}-\kappa (u-w)^++f_2(u,w)+ (-\partial _{xx})^{\gamma }w_{t}= & {} 0, \end{aligned}$$ m c u tt - β u xx + κ ( u - w ) + + f 1 ( u , w ) + ( - ∂ xx ) γ u t = 0 , m b w tt + μ w xxxx + ( p - ϵ ‖ w x ‖ 2 ) w xx - κ ( u - w ) + + f 2 ( u , w ) + ( - ∂ xx ) γ w t = 0 , where $$\epsilon \in (0, 1]$$ ϵ ∈ ( 0 , 1 ] is a perturbed parameter and $$\gamma \in (0, 1)$$ γ ∈ ( 0 , 1 ) is said to be a fractional exponent. Under quite general assumptions on source terms and based on semigroup theory, we establish the global well-posedness and the existence of global attractors with finite fractal dimension. We analysis the upper semicontinuity of global attractors on the perturbed parameter $$\epsilon $$ ϵ in some sense. Moreover, we demonstrate an explicit control over semidistances between trajectories in the weak energy phase space in terms of $$\epsilon $$ ϵ . Finally, we prove that the family of global attractors is upper semicontinuous with respect to the fractional exponent $$\gamma \in (0,1/2)$$ γ ∈ ( 0 , 1 / 2 ) . | Robustness of Global Attractors for Extensible Coupled Suspension Bridge Equations with Fractional Damping | 10.1007/s00245-021-09774-8 |
2021-12-01 | Abstract When an object is being transported by two robots of arbitrary structure, it must be stabilized around the static equilibrium position in the event of kinematic and mechanical perturbations. Dynamic equilibrium of the object in the clamps is described by the Mathieu equation. In controlling the robot executive system, the manipulation system must be adjusted with minimum potential energy in the clamps. Optimal control of the speed is considered in motion of the system to a position close to static equilibrium. | Synchronous Group Operation of Robots with Arbitrary Manipulator Kinematics | 10.3103/S1068798X21120091 |
2021-12-01 | In this article, we consider the wave equation on hyperbolic spaces $$\mathbb {H}^n(n\ge 2)$$ H n ( n ≥ 2 ) with nonlinear locally distributed damping as follow: 1 $$\begin{aligned} {\left\{ \begin{array}{ll}u_{tt}-\Delta _g u+a(x)g(u_t)=0\qquad (x,t)\in \mathbb {H}^n\times (0,+\infty ), \\ u(x,0)=u_0(x),\quad u_0(x,0)=u_1(x)\qquad x\in \mathbb {H}^n. \end{array}\right. } \end{aligned}$$ u tt - Δ g u + a ( x ) g ( u t ) = 0 ( x , t ) ∈ H n × ( 0 , + ∞ ) , u ( x , 0 ) = u 0 ( x ) , u 0 ( x , 0 ) = u 1 ( x ) x ∈ H n . It is well-known that the energy of the system ( 1 ) is of polynomial decay in the Euclidean space. However, on hyperbolic spaces, owing to the following inequality 2 $$\begin{aligned} \int _{\mathbb {H}^n} u^2 dx_g \le C \int _{\mathbb {H}^n} |\nabla _g u|_g^2dx_g , \quad for \quad u\in H^1(\mathbb {H}^n), \end{aligned}$$ ∫ H n u 2 d x g ≤ C ∫ H n | ∇ g u | g 2 d x g , f o r u ∈ H 1 ( H n ) , we prove the exponential stabilization of the wave equation by multiplier methods and compactness-uniqueness arguments. | Exponential Stabilization of the Wave Equation on Hyperbolic Spaces with Nonlinear Locally Distributed Damping | 10.1007/s00245-021-09751-1 |
2021-12-01 | Recent equations of motion for the large deflections of a cantilevered elastic beam are analyzed. In the traditional theory of beam (and plate) large deflections, nonlinear restoring forces are due to the effect of stretching on bending; for an inextensible cantilever, the enforcement of arc-length preservation leads to quasilinear stiffness effects and inertial effects that are both nonlinear and nonlocal. For this model, smooth solutions are constructed via a spectral Galerkin approach. Additional compactness is needed to pass to the limit, and this is obtained through a complex procession of higher energy estimates. Uniqueness is obtained through a non-trivial decomposition of the nonlinearity. The confounding effects of nonlinear inertia are overcome via the addition of structural (Kelvin–Voigt) damping to the equations of motion. Local well-posedness of smooth solutions is shown first in the absence of nonlinear inertial effects, and then shown with these inertial effects present, taking into account structural damping. With damping in force, global-in-time, strong well-posedness result is obtained by achieving exponential decay for small data. | Theory of Solutions for an Inextensible Cantilever | 10.1007/s00245-021-09798-0 |
2021-12-01 | We propose a new approach toward the existence and uniqueness of periodic solutions to linear and semilinear evolution equations. Our approach is based on the connection of the conditional stability of evolution families (i.e., stability only in a subspace of the Banach space containing the initial data) with the choice of the initial data from which emanates the periodic solution. We also give applications to exponentially dichotomic evolution families as well as to nonautonomous damped wave equations. | Conditional stability and periodicity of solutions to evolution equations | 10.1007/s00028-021-00707-0 |
2021-12-01 | The life assessment of materials that structurally shifts, creating mechanical corrosion and damage, during the operation at high temperatures is one of the most critical areas in the gas turbine power plants. This study investigates the widely used carbon steel grade 55 SA516 in the gas turbine blades at metallographic microscopic level and relating it to natural frequency and damping coefficients. In which heat treatments (aging tests) were applied and compared between multiple samples. The results show pearlite is broken up and converted into the ferrite and spherical carbides at grain boundaries. With an increase in microstructural variations in samples due to heat treatments, the first mode of natural frequency slightly decreases but damping ratio increases significantly. In addition, the experimental results show that by increasing the heat treatment time, the Young's modulus decreases by 10.74% and the natural frequency of the second to sixth states of carbon steel also decreases between 4.14 and 4.59%, respectively. As such, the damping coefficients of the second to sixth states increased between 5,609 and 6391 times than their original values, and no connection was obtained between the vibration number and the damping coefficient. | Experimental Modal Analysis of Distinguishing Microstructural Variations in Carbon Steel SA516 by Applied Heat Treatments, Natural Frequencies, and Damping Coefficients | 10.1007/s11665-021-06125-0 |
2021-12-01 | For the energy-critical nonlinear damped wave equation, we show the unconditional well-posedness. The unconditional well-posedness means local well-posedness and the unconditional uniqueness. First, we give the local well-posedness and stability, whose statement will be useful to investigate the global dynamics. At second, we show the unconditional uniqueness. Since these problems seem not to be solvable as a direct perturbation of the wave equation, we apply the Strichartz estimates for the damped wave equation including the wave endpoint case. | Unconditional well-posedness for the energy-critical nonlinear damped wave equation | 10.1007/s00028-021-00744-9 |
2021-12-01 | When one of the natural frequencies of the drive shaft coincides with the excitation frequency of the engine, the vibration amplitude of the drive shaft increases significantly owing to the resonance of the drive shaft at the natural frequency. To reduce this resonance vibration, a single-mode dynamic damper (SMDD) has been used. A dynamic damper yields second resonances because of the mass and stiffness of the damper, although the resonance vibration of the drive shaft is reduced considerably. To reduce vibration due to the second resonance, the vibration parameters of the SMDD, such as frequency, damping coefficient, mass, and stiffness, should be optimized. However, it is difficult to apply an optimized SMDD to a vehicle because it is difficult to achieve an SMDD with optimal stiffness and damping coefficient. This paper presents a new dualmode dynamic damper (DMDD) for the further reduction of vibration due to the second resonance. The stiffness and damping coefficient of the DMDD are changed according to the rotating angle of the drive shaft. The vibration reduction effect of the SMDD is constant at the positions of all rotating angles of a drive shaft; however, that of the DMDD is different at the position of every rotating angle of the drive shaft. In this study, the vibration reduction performance of the DMDD is compared with that of the SMDD. Finally, the DMDD is applied to the drive shaft of a passenger car, and its effect on vibration reduction is confirmed in a vehicle test. | Development of a Dual Mode Dynamic Damper for Vibration Reduction of Drive Shaft in a Passenger Car | 10.1007/s12239-021-0137-9 |
2021-12-01 | With rigorous dynamic performance of mechanical products, it is important to identify dynamic parameters exactly. In this paper, a response surface plotting method is proposed and it can be applied to identify the dynamic parameters of some nonlinear systems. The method is based on the principle of harmonic balance method (HBM). The nonlinear vibration system behaves linearly under the steady-state response amplitude, which presents the equivalent stiffness and damping coefficient. The response surface plot is over two-dimensional space, which utilizes excitation as the vertical axis and the frequency as the horizontal axis. It can be applied to observe the output vibration response data. The modal parameters are identified by the response surface plot as linearity for different excitation levels, and they are converted into equivalent stiffness and damping coefficient for each resonant response. Finally, the HBM with first-order expansion is utilized for identification of stiffness and damping coefficient of nonlinear systems. The classical nonlinear systems are applied in the numerical simulation as the example, which is used to verify its effectiveness and accuracy. An application of this technique for nonlinearity identification by experimental setup is also illustrated. | Parameter Identification of Structural Nonlinearity by Using Response Surface Plotting Technique | 10.1007/s12204-020-2242-8 |
2021-12-01 | A generalized model of the damper is proposed in the form of the equivalent Voigt model for viscoelastic materials, which fully correlates with the differential equation for induced oscillations in the system with a damper. The relations of parameters of the differential equation and parameters of the equivalent Voigt model with parameters of various models for viscoelastic materials and with components of the complex elastic modulus of these models are established. An approach for the assessment of the damper influence on the oscillation level of various elements in the analyzed system that occur under the impact of a coercive force of different frequencies is proposed for the mechanical system. It is presented in the form of the model with lumped parameters. Parameters of viscoelastic materials, which are suitable for use in dampers in the designed mechanical system, are determined based on obtained estimations. Thus, the proposed approach to the analysis of the behaviour of viscoelastic dampers allows us to determine the requirements for viscoelastic materials suitable for use in the designed systems. Also, it allows us to determine frequency response characteristics of dampers with known frequency dependences of storage modulus and loss modulus of the used viscoelastic materials. | Frequency characteristics of viscoelastic damper models and evaluation of a damper influence on induced oscillations of mechanical system elements | 10.1007/s11012-021-01446-9 |
2021-12-01 | This paper evaluates the dynamics of a heavy road truck on different random road conditions, whereas the issue of beam flexibility is also being accompanied. Heavy vehicles like trucks and buses having a large structure to carry their load ride in all kinds of terrains, for thousands of miles without failing structure. Structure (chassis or frame) of the truck should be able to sustain all types of vibration (i.e., longitudinal, transverse and flexural). This study starts with developing an analytical model with consideration of the Rayleigh beam approach, where the rotary inertia of the beam has also been admitted. This work also considered internal damping of the chassis, which has been neglected in past studies specifically for flexural vibration. Further bond graph model of the flexible structure of a heavy road vehicle is developed, where this model is derived through modal expansion approach. The dynamic response of the structure is analyzed under various random road conditions at different vehicle speeds. These random models of the road are developed according to ISO 8608 standard, whereas four (H1–H4) kinds of road categories are considered. Results show the dynamic response of the chassis under a real road response so that parameters of the various parts of the structure can be evaluated, which further raises the ride comfort and road holding capability of the structure. Further, this work also examines the effect of structural damping or internal damping on the dynamics of the system. | Effect of Distributed Damping on the Dynamic Behavior of Flexible Chassis of Heavy Road Vehicle Under Standardized Random Road Responses | 10.1007/s40997-020-00366-5 |
2021-12-01 | Dust ion acoustic waves (DIAWs) are investigated analytically in the framework of damped forced Korteweg–de Vries–Burgers (DFKdVB) equation in an unmagnetized collisional dusty plasma consisting of negatively charged stationary dust grains, positively charged ions and q -nonextensive distributed electrons. Reductive perturbation technique is used to obtain the DFKdVB equation for DIAWs. The effects of different physical parameters such as the entropic index ( q ), ratio of unperturbed number densities of electrons and ions $$(\mu )$$ ( μ ) , dust ion collision frequency $$(\nu _{\mathrm{id}0})$$ ( ν id 0 ) , kinematic viscosity ( $$\eta _0$$ η 0 ), the speed of the traveling wave $$(M_0)$$ ( M 0 ) , strength $$(f_0)$$ ( f 0 ) and frequency $$(\omega )$$ ( ω ) of the external periodic force on the analytical DIAWs are shown . The results of the present paper will be useful in laboratory and space plasmas. | Analytical solitary wave solution of dust ion acoustic waves in nonextensive plasma in the framework of damped forced Korteweg–de Vries–Burgers equation | 10.1007/s12648-020-01929-7 |
2021-12-01 | The nonlinear dust ion acoustic solitary waves (DIAW) in a magnetized collisional dusty plasma comprising with negatively charged dust grain, positively charged ions along with q-nonextensive nonthermal electrons and neutral particles in the presence of small damping force is studied analytically through the framework of damped modified Kadomtsev-Petviashvili-Burgers (DMKPB) equation. Reductive perturbation technique (RPT) is employed to derive the DMKPB equation. It is observed that there is a critical point for the plasma parameters where the amplitude of the solitary wave of damped KP Burgers equation diverges. The DMKPB equation is derived from there and the soliton like solutions with finite amplitude is extracted. The influence of various plasma parameters like entropic index, dust ion collisional frequency, ion kinematic viscosity, speed of the traveling wave and the parameter indicating the ratio between unperturbed dust ion density and electron are investigated on the propagation of dust ion acoustic wave (DIAW). A significant effect on the wave structures due to the variation of present plasma parameters has been observed. Finally, the temporal evolution of a solitary wave solution is depicted through a numerical standpoint. | Propagation of dust-ion-acoustic solitary waves for damped modified Kadomtsev–Petviashvili–Burgers equation in dusty plasma with a q-nonextensive nonthermal electron velocity distribution | 10.1007/s40324-021-00242-5 |
2021-12-01 | A topology optimization method for coupled vibro-acoustic problem based on hybrid finite element-wave based method is proposed. The hybrid finite element-wave based method is used to model the coupled free layer damping structure-acoustics system, and a gradient-based topology optimization formulation is developed by solid isotropic microstructures with penalization method, to obtain optimized layout of free layer damping with the objective of minimizing sound pressure in the acoustic cavity and with constraint defined as the amount of free layer damping. The adjoint variable method for the coupled vibro-acoustic model based on the hybrid finite element-wave based method is also derived as a part of the sensitivity analysis. Numerical example shows that the optimized distribution reduce sound pressure effectively and the calculation time of proposed method is less than the conventional method for topology optimization base on finite element method. Experimental results verify the accuracy of the hybrid finite element-wave based method and the effect of optimized damping material layout is also validated by experiment. | Topology optimization of damping material layout in coupled vibro-acoustic system using hybrid finite element-wave based method | 10.1007/s00158-021-03063-2 |
2021-12-01 | Considering the special requirements for damping materials in the field of building isolation and vibration control, this research aims to improve the mechanical and damping properties of nitrile butadiene rubber (NBR, ACN content: 36–42%)-based matrix material by blending four kinds of minimal particles. Carbon black, light silicon dioxide, graphite powder and AO-80 were blended with the matrix material. Orthogonal test was designed and dynamic mechanical analysis test was carried out. The results were evaluated by multiple indicators, including the glass transition temperature ( T _g), the peak value of loss factor ( η _max), the width of large damping range in which loss factor is larger than 0.5 (∆T_0.5) and the integral area of Loss factor-Temperature (TA). The results showed that the NBR modified by minimal particles could effectively improve the damping properties of the matrix material and made the T _g closer to the service temperature of buildings. Graphite powder could significantly increase the η _max, and effectively broaden the ∆T_0.5. AO-80 could significantly increase the η _max and TA value. In addition, the optimal scheme was determined by Analytic Hierarchy Process (AHP), with carbon black: light SiO_2: graphite powder: AO-80: matrix material = 15: 30: 40: 50: 100. | Experimental study on the damping properties of NBR-based viscoelastic materials enhanced by minimal particles | 10.1007/s42464-021-00128-1 |
2021-12-01 | The microstructures, texture, damping and mechanical properties of Mg-Nd-Zn-Zr alloy processed by hot extrusion were investigated in this work. The results showed that the microstructures were markedly refined, and uniformly distributed after hot extrusion. The average grain size was refined to 8.1 ± 1.6 μm (extrusion ratio was 7.65, E1) and 6.28 ± 1.7 μm (extrusion ratio was 12.56, E2), respectively, and the yield strength of the alloy was increased significantly. The dislocation density and texture of the alloy increase with the increase in the extrusion ratio. The damping values Q^−1 of as-cast (Initial), E1 and E2 alloys were 0.03504, 0.01634 and 0.01539 at the strain of 1 × 10^−3, respectively. Mg-Nd-Zn-Zr alloy could be classified as high strength (259 MPa), high plasticity (21.4%) and high damping (0.01539) Mg alloy. | Evolution of Microstructures, Texture, Damping and Mechanical Properties of Hot Extruded Mg-Nd-Zn-Zr Alloy | 10.1007/s11665-021-06134-z |
2021-12-01 | Abstract In this work, in situ oxidation and particle-dispersed methods are successfully used to prepare novel oxide/Mg composites with ultra-high damping capacity starting from pure Mg as the matrix. Successful incorporation of the MgO particles into the Mg matrix is experimentally demonstrated, and the role of the oxide in enhancing the damping capacities of the composites is examined in detail. The increased damping capacity of the composites with respect to the pure magnesium is attributed to an increased dislocation density and the introduction of interface damping. In the temperature-dependent damping tests, two damping peaks P_1 and P_2 were found. The P_1 peak is considered to be related to the interaction between dislocations and impurity atoms or vacancies. The P_2 peak is considered to be caused by the grain boundaries sliding. Graphic Abstract | Ultra-High Damping Capacity of Oxide Reinforced Magnesium Matrix Composites by In Situ Synthesis | 10.1007/s12540-020-00834-2 |
2021-12-01 | Abstract The theoretical substantiations of an indirect analytical method for assessing the wear of a dry friction damper structure are presented. The wear is simulated by variations in the parameters of the load–damper dynamic system, leading to changes in the kinematic characteristics of the motion of the system, based on which the wear effect has been estimated. Analytical solutions are obtained for the differential equations of the motion of the system and for their variations as functions of the parameters characterizing wear. This makes it possible to determine the dynamic response of the damper and to assess its dissipative properties. | Dynamics of a Dry Friction Wedge Damper with a Finite Number of Degrees of Freedom Taking into Account Structural Wear | 10.3103/S1052618821090041 |
2021-12-01 | The main goal of this study is to investigate the effectiveness of backward-shared tuned mass damper inerter (BSTMDI) in reducing inter-storey drift as well as pounding between adjacent buildings. A backward-shared-TMDI (BSTMDI) linking two adjacent medium-rise buildings is presented, considering the practical and economical part of design parameters. Inerter in BSTMDI can generate higher reaction forces based on the large relative acceleration response between the two adjacent buildings, which efficiently enhance the seismic performance of both buildings. Moreover, a benchmark structure consisting of two adjacent medium-rise buildings equipped with (BSTMDI) is examined. Eight design parameters of the BSTMDI are optimized through single-objective optimization problems using a genetic algorithm (GA) to minimize either the inter-storey drift or the pounding gap distance of the two adjacent benchmark structures. Mitigating effects of the optimally designed (BSTMDI) on the responses of the benchmark structures are assessed considering a set of one hundred (100) natural ground motions records. It is found that the BSTMDI scheme can reduce the inter-storey drift and pounding distance responses similarly or even better than a single shared tuned mass damper inerter (SSTMDI) using a smaller inertance ratio. The same trend is observed while using backward-shared tuned inerter damper (BSTID) compared to a single shared tuned inerter damper (SSTID). Both BSTMDI and BSTID have proven their robustness under a large set of natural real earthquake records with various frequency characteristics for several dynamical parameters such as displacement, inter-storey drift, pounding gap and stroke displacement. | Seismic response control of adjacent buildings using optimal backward-shared tuned mass damper inerter and optimal backward-shared tuned inerter damper | 10.1007/s42107-021-00394-9 |
2021-12-01 | Abstract Rotor systems are widely used in various machines, apparatuses, and other engineering systems, the crucial condition of the efficiency of which is the stability of stationary modes in a wide range of operation rotation speeds. In this work, mitigation of torsional oscillations is considered by the mechanical approach, without the use of control theory. The problem about choosing the parameters of the pendulums of the tuned mass damper of rotor angular vibrations arising in the plane of its rotation and caused by an external periodic excitation moment is considered. The solution to the problem is based on the antiresonance effect and on the use of the method of complex amplitudes. An analytical expression relating the parameter of the tuned mass damper and the rotor with its rotation speed and frequency of excitation is obtained. The results of the numerical solution to the nonlinear and linearized equations describing the motion of the system are presented, and the conditions of mitigation of oscillations obtained are analyzed. | A Centrifugal Pendulum Tuned Mass Damper for Rotor Systems | 10.3103/S1052618821080033 |
2021-12-01 | Under parametric excitations and external forces induced by base motions, dynamic behavior of an on-board rotor system supported by squeeze film damper (SFD) considering fluid inertia was investigated. Based on perturbation method, oil-film pressure and three-dimensional velocities were represented by first-order functions of the Reynolds number. Using finite difference and numerical integration, an oil-film inertia SFD model was established to calculate pressure distribution and oil-film forces. Excited by time-varying base motions, dynamic responses and bifurcation behavior of SFD-rotor system were analyzed by Newmark–HHT method. The results indicate that when the journal whirls at a large eccentricity ratio, the pressure distribution is sensitive to oil-film inertia, reducing radial force while increasing tangential force. For high rotating speed and large eccentricity, the inertia effect dampens resonant amplitude. Under base transverse rotations, the journal’s whirling orbits deviate from the bearing’s center, and sub-harmonic frequencies appear with fundamental frequency. Under base harmonic translation, the journal’s motion is transformed from periodic to quasi-periodic, and the stability is gradually deteriorated with harmonic frequency. Overall, a flexible approach is established to calculate dynamic behavior of SFD-rotor system considering oil-film inertia under base motions, which provides technical support for dynamic design of on-board rotor systems in gas turbines. | Dynamic behavior of a flexible rotor system with squeeze film damper considering oil-film inertia under base motions | 10.1007/s11071-021-06978-z |
2021-11-26 | The present investigation incorporates a detailed study of unsteady MHD flow and heat transfer of a second grade fluid between two infinitely long porous plates. With the aid of implicit finite difference scheme the pertinent partial differential equations are transformed and framed as system of algebraic equations. The resulting equations are solved numerically by the help of damped-Newton method, thereafter coded using MATLAB. The impact of variations in dimensionless parameters such as $$m^2$$ m 2 , $$\alpha $$ α , Re for constant acceleration $$(n = 1)$$ ( n = 1 ) and variable acceleration $$(n = 0.5)$$ ( n = 0.5 ) on velocity and temperature is illustrated. It is noted that the magnetic parameter and Reynolds number have significantly opposite effect on the temperature and velocity profiles for both the instances. Increasing values of Ec and $$m^2$$ m 2 plays a key role in enhancing the temperature at any point of the fluid whereas higher values of Re and $$\alpha $$ α has a pronounced effect on the velocity profile of the fluid. | Numerical Study of Unsteady MHD Second Grade Fluid Flow and Heat Transfer Within Porous Channel | 10.1007/s40819-021-01196-y |
2021-11-26 | This article intends to examine thermoelastic damping (TED) in circular cylindrical nanoshells by considering small-scale effect on both structural and thermal areas. To fulfill this aim, governing equations are extracted with the aid of nonlocal elasticity theory and dual-phase-lag (DPL) heat conduction model. Circular cylindrical shell is also modeled on the basis of Donnell–Mushtari–Vlasov (DMV) equations for thin shells. By inserting asymmetric simple harmonic oscillations of nanoshell into motion, compatibility and heat conduction equations, the size-dependent thermoelastic frequency equation is obtained. By solving this equation and deriving the frequency of nanoshell affected by thermoelastic coupling, the value of TED can be calculated through complex frequency approach. Results of this investigation are given in two sections. First, to appraise the validity of presented formulation, a comparison study is conducted between the results of this work in special cases and those reported in the literature. Next, by providing several numerical data, a detailed parametric study is performed to highlight the profound impact of nonlocality and dual-phase-lagging on TED value in simply supported cylindrical nanoshells. The influence of some determining factors such as mode number and type of material on TED is also evaluated. | Analytical and parametric analysis of thermoelastic damping in circular cylindrical nanoshells by capturing small-scale effect on both structure and heat conduction | 10.1007/s43452-021-00330-3 |
2021-11-23 | Energy levels are considered for the two-photon parity $$\lambda $$ λ -deformed Jaynes–Cummings model of a single two-level atom interacting with a single-mode cavity field corresponding to para-Bose oscillator algebra of order $$p=2\lambda +1$$ p = 2 λ + 1 . Time evolution of the atom-field states with the initial states of the excited and even cat for the atom and field is used to indicate that not only the minimal and maximal closeness of the states in the fidelity is dependent on the deformation parameter $$\lambda $$ λ but also the height of the peaks in quasi-oscillations in the case of off- and on-resonance increases and decreases by increasing $$\lambda $$ λ , respectively. It has been shown that the partial revivals in the Rabi oscillations of the $$\lambda $$ λ -deformed atomic population inversion become less distinct and thinner as well as more periodic in the cases of resonance and out-of-resonance, respectively. The decay term in the interaction Hamiltonian causes the oscillating behavior of revivals in atomic population inversion at the initial moments to resonate by increasing $$\lambda $$ λ . Furthermore, we show that for both deformed and undeformed fields, the statistics of the states in the resonant case becomes more sub-Poissonian with respect to off-resonant one. Finally, it is deduced that the number and height of the peaks for the quasi-oscillations of the time evolution of the atomic entropy are increased by increasing $$\lambda $$ λ , which is a sign of more entanglement. | Two-photon Jaynes–Cummings model: a two-level atom interacting with the para-Bose field | 10.1007/s11128-021-03338-z |
2021-11-19 | In this paper, we investigate a one-dimensional porous elastic system of memory-type coupled with thermal effects, knowing that the heat flux used was introduced by Green and Naghdi. We establish a general decay result irrespective of any condition among the coefficients of the system. | General decay for memory-type porous elastic system with thermoelasticity of type III | 10.1007/s11587-021-00673-2 |
2021-11-17 | In this paper, we consider coupled plate equations with indirect damping including friction and structural damping. By using suitable diagonalization procedure associated with WKB analysis, we derive asymptotic behavior of solutions in the Fourier space. Then, smoothing effect and decay properties in the $$L^p-L^q$$ L p - L q framework of solutions are derived by employing Fourier analysis and representation of solution. We investigate several thresholds to describe smoothing effect and different types of decay properties, for example, Gevrey smoothing and regularity-loss. Finally, we derive approximation of solutions by finding the gained decay rate. | Coupled plate equations with indirect damping: smoothing effect, decay properties and approximation | 10.1007/s00033-021-01640-5 |
2021-11-14 | In this paper, we are considering the one-dimensional porous-elastic system with nonlinear localized damping acting in a arbitrary small region of the interval under consideration. Assuming appropriate assumptions on the nonlinear terms, we establish the energy decay of the corresponding system. To do this, we used the observability inequality obtained for the conservative system combined with a unique continuation property recently introduced in Ma et al. (Attractors for locally damped Bresse systems and a unique continuation property, 2021. arXiv:2102.12025 ) and the reduction principle (see Daloutli et al. in Discrete Contin Dyn Syst 2(1):67–94, 2009) where the problem of decay rates with nonlinear damping is reduced to an appropriate stabilizability inequality for the linear equation. This study generalizes and improves previous literature outcomes. | Energy decay for a porous-elastic system with nonlinear localized damping | 10.1007/s00033-021-01636-1 |
2021-11-14 | Modeling techniques applied to mechanical vibration damping problems in systems made of viscoelastic materials contribute to the development of compact and efficient industrial devices. To reduce the weight of rotors, polymeric materials and light metal alloys can be included in their manufacturing. The objectives of this study are to present analytical models that describe the dynamic behavior of rotors made of viscoelastic materials and to evaluate and compare their performances. Using the anelastic displacement fields method applied to the strain dynamics of the rotor material and introduced into Lagrange equations with a differential operator in the time domain, motion equations are obtained by Rayleigh–Ritz approximation. Based on the numerical solution of the motion equations, comparative analyses are performed for two rotors with different geometries, made of PVC and aluminum. Both models, the first for aluminum and the second for PVC, result in good approximations. | Viscoelastic rotors: a proposed analytical solution and results for rotors made of different materials | 10.1007/s40430-021-03260-6 |
2021-11-13 | Recently , biochar has been widely used in geotechnical and environmental engineering to solve various engineering problems. However, very few studies have been carried out to understand the cyclic behavior of the biochar treated soil. This study explores the possibility of using environment-friendly and stable carbon material (i.e., biochar) for enhancing the cyclic strength of Ganga sand. In this study, Ganga sand (located in Northern India) samples are dry mixed with 3%, 6%, and 10% biochar by weight and tested under low strain-controlled cyclic triaxial tests. The test results demonstrated a 30–50% increase in the number of loading cycles for biochar mixed sand than clean Ganga sand. Based on the cyclic test results, it may be inferred that biochar can be used as soil amendments to increase the liquefaction resistance of sandy soil. Future studies need to be conducted to understand the influence of the type of biochar (i.e., pyrolysis temperature and feedstock type, such as plant/animal waste) on the liquefaction potential of soils. However, such studies will promote commercial production of biochar as it is considered as an essential material owing to it carbon sequestration effects. | Laboratory Investigations of Liquefaction Mitigation of Ganga Sand Using Stable Carbon Material: A Case Study | 10.1007/s40891-021-00333-3 |
2021-11-08 | In this paper, we study the indirect stability of Timoshenko system with local or global Kelvin–Voigt damping, under fully Dirichlet or mixed boundary conditions. Unlike Zhao et al. (Acta Mathematica Sinica Engl Ser 21(3):655–666, 2004), Tian and Zhang (Mathematik und Physik 68(1), 2017), and Liu and Zhang (SIAM J Control Optim 56(6):3919–3947, 2018), in this paper, we consider the Timoshenko system with only one locally or globally distributed Kelvin–Voigt damping D [see System ( 1.1 )]. Indeed, we prove that the energy of the system decays polynomially of type $$t^{-1}$$ t - 1 and that this decay rate is in some sense optimal. The method is based on the frequency domain approach combining with multiplier method. | A transmission problem for the Timoshenko system with one local Kelvin–Voigt damping and non-smooth coefficient at the interface | 10.1007/s40314-021-01446-1 |
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