Elastic Coupling Research Articles

Active control of nonlinear coupled transient vibrations of multifunctional sandwich plates with agglomerated FG-CNTs core/magneto-electro-elastic facesheets

This article investigates the controlled nonlinear transient response of sandwich plates made of magneto-electro-elastic (MEE) facesheets and agglomerated carbon nanotube (ACNT) core. The control is achieved by active constrained layer damping (ACLD) treatment which consists of piezoelectric (PE) and viscoelastic (VE) layers. The agglomeration is mathematically modelled using the Eshelby–Mori–Tanaka approach. The governing equations are derived under the framework of finite element (FE) methods using Hamilton’s principle and condensation technique. The VE patch of the ACLD treatment is modelled through the Golla–Hughes–McTavish method. This evaluation has considered two states of agglomerations, such as complete and partial agglomeration. The proposed FE model facilitates the integration of the three-field (magnetic, electric and elastic) coupling with the agglomeration and electromagnetic circuit effects, which makes this work interesting. It acts as a ready tool for the realistic design of a smart structure and system. In addition, the computational efforts and efficiency of the proposed FE model prove to be better than the commercial numerical software. Extensive numerical examples are solved to assess the influence of CNT distributions, electromagnetic circuits, coupling, mechanical boundary conditions, thickness configuration and ACLD patch position. This work serves as a novel benchmark solution for further research on the active control of agglomerated CNT structures.

Theoretical, numerical and experimental study on the in-plane elastic behavior of a 2D chiral cellular structure

To satisfy the requirements of being used as core of flexible sandwich skins for morphing materials, a 2D chiral cellular structure composed of arc-formed beams is studied. The in-plane elastic properties within the linear elastic range of the structure are studied using the energy method, and verified by finite element analysis and experimental test. Besides, the impact of parameters on the properties is discussed. Finally, the elastic properties of the structure are compared with a V-shaped structure. Excellent agreement is reached between finite element results and theoretical analysis. The structure shows zero Poisson’s ratio, considerably low in-plane equivalent moduli and extremely high global-local strain ratios, as well as noteworthy in-plane elastic coupling effects. Compared with the V-shaped structure, the elastic and shear moduli of the structure are in average rate 39.32% and 19.94% lower, and the maximum global-local strain ratios under tensile and shear loading are in average rate 62.97% and 24.04% higher. To have better performance in elastic constants, structures with large central angle of the arc are recommended.

Simulation of the effect laminate sequence on delamination mode-I with elastic couplings

Simulation of the effect laminate sequence on delamination mode-I with elastic couplings

A model for the quasi-static and dynamic simulations of bevel gears

An original mesh interface model for the static and dynamic simulations of bevel gears is presented. It is based on the superposition of several elastic foundations and accounts for elastic couplings between points of contact, while no hypothesis on tooth contact locations is needed. Comparisons with experimental contact patterns and transmission errors prove that the mesh model is sound. The combination of a time-step integration scheme and a unilateral normal contact algorithm gives access to instant contact patterns, loads and transmission errors as opposed to the classic models based on quasi-static characteristics. It is shown that load is highly influential on contact conditions in bevel gears and that dynamic effects can induce overloads and oscillatory contact patterns in the vicinity of critical speeds, thus emphasizing the possible interactions between the local (contact) and global (system) scales.

Vibration Characteristics of the Dual Electric Propulsion System of Vessels under Electromechanical Coupling Excitation

An electromechanical coupling driving system is a commonly used system for large overloading ships. In this paper, a dual input electromechanical coupling model, including an inverter power supply, three-phase induction motor, fixed-axis gear, and load, is established. The influences of the gear error, inverter, and coupling stiffness on the vibration characteristics of the system are studied, and the influences of each parameter on the vibration characteristics are analyzed. The inverter power supply part considers the constant voltage–frequency ratio control and sinusoidal pulse width modulation, as well as the inverter. The motor part uses the dynamic motor model based on the equivalent circuit. The fixed-axis gear section uses a translation–torsion model with time-varying mesh stiffness and damping. The mechanical part and the motor part are coupled with the load torque of the motor. The results show that the greater the error of the gear, the greater the vibration of the system, and the rotation frequency error is the main factor. Secondly, by comparing the influence of error value and accuracy difference on vibration, we found that when an accuracy difference exists, the dominant factor of system vibration is the accuracy difference. Thirdly, the use of an inverter also increases the vibration of the electromechanical coupling system. Finally, we found that the lower stiffness of the elastic coupling reduced the vibration of the system.

Vibration-based damage detection in anisotropic laminated composite beams by a shear-deformable finite element and harmony search optimization

A numerical procedure to detect and quantify damages in laminated composite beams with arbitrary lay-up using limited vibration data and harmony search optimization is presented. Since any damage in a structure changes its vibration characteristics, they can be considered as the diagnostic parameters with the help of an optimization technique. For the present study, frequencies and mode shapes are used as the damage diagnostic parameters, and the harmony search algorithm is used as the optimization tool. For finite element analyses, a five-node, thirteen-degree-of-freedom shear-deformable beam element is employed. This element can take into account the elastic couplings among extension, bending, and torsion arising due to material anisotropy existing in generally laminated composites as well as the Poisson’s effect. The damage to the beam is introduced by a stiffness loss coefficient at the elemental level while mass is assumed to be unchanged. Two different objective functions to be minimized are considered for damage detection. The efficacy of the proposed method with and without the presence of noise is demonstrated by two numerically simulated composite beams including single and multiple damages. Although its accuracy somewhat decreases in case of multiple minor damages, the proposed method is successful to detect moderate and severe single and multiple damages in practice. To overcome this weakness, (i) the algorithm can be hybridized with other metaheuristics, (ii) objective function can be enhanced by combining it with other vibration characteristics such as curvature, flexibility, and so on, or (iii) two- or multi-stage damage identification methods can be considered.

Theoretical study of nonlinear oscillations of power drives with elastic coupling

Based on the equation of motion of a nonlinear oscillator and the Van der Pol method, the derivation of an equation for constructing of resonance curves of a nonlinear system with an elastic multilayer shell is considered. Based on the equations obtained, resonance curves are constructed to estimate the dynamic loads in the power drive depending on the torsional rigidity of the shell. Keywords: resonance, multilayer elastic shell, power drive, nonlinearity, damping. a_evdo@mail.ru

F1-ATPase Rotary Mechanism: Interpreting Results of Diverse Experimental Modes With an Elastic Coupling Theory.

In this chapter, we review single-molecule observations of rotary motors, focusing on the general theme that their mechanical motion proceeds in substeps with each substep described by an angle-dependent rate constant. In the molecular machine F1-ATPase, the stepping rotation is described for individual steps by forward and back reaction rate constants, some of which depend strongly on the rotation angle. The rotation of a central shaft is typically monitored by an optical probe. We review our recent work on the theory for the angle-dependent rate constants built to treat a variety of single-molecule and ensemble experiments on the F1-ATPase, and relating the free energy of activation of a step to the standard free energy of reaction for that step. This theory, an elastic molecular transfer theory, provides a framework for a multistate model and includes the probe used in single-molecule imaging and magnetic manipulation experiments. Several examples of its application are the following: (a) treatment of the angle-dependent rate constants in stalling experiments, (b) use of the model to enhance the time resolution of the single-molecule imaging apparatus and to detect short-lived states with a microsecond lifetime, states hidden by the fluctuations of the imaging probe, (c) treatment of out-of-equilibrium “controlled rotation” experiments, (d) use of the model to predict, without adjustable parameters, the angle-dependent rate constants of nucleotide binding and release, using data from other experiments, and (e) insights obtained from correlation of kinetic and cryo-EM structural data. It is also noted that in the case where the release of ADP would be a bottleneck process, the binding of ATP to another site acts to accelerate the release by 5–6 orders of magnitude. The relation of the present set of studies to previous and current theoretical work in the field is described. An overall goal is to gain mechanistic insight into the biological function in relation to structure.

Feedback Regulation of Elastically Decoupled Underactuated Soft Robots

The intrinsically underactuated and nonlinear nature of continuum soft robots makes the derivation of provably stable feedback control laws a challenging task. Most of the works so far circumvented the issue either by looking at coarse fully-actuated approximations of the dynamics or by imposing quasi-static assumptions. In this letter, we move a step in the direction of controlling generic soft robots taking explicitly into account their underactuation. A class of soft robots that have no direct elastic couplings between the dynamics of actuated and unactuated coordinates is identified. Considering the actuated variables as output, we prove that the system is minimum phase. We then propose regulators that implement different levels of model compensation. The stability of the associated closed-loop systems is formally proven by Lyapunov/LaSalle techniques, taking into account the nonlinear and underactuated dynamics. Simulation results are reported for two models of 2D and 3D soft robots.

BirdBot achieves energy-efficient gait with minimal control using avian-inspired leg clutching.

Designers of legged robots are challenged with creating mechanisms that allow energy-efficient locomotion with robust and minimalistic control. Sources of high energy costs in legged robots include the rapid loading and high forces required to support the robot's mass during stance and the rapid cycling of the leg's state between stance and swing phases. Here, we demonstrate an avian-inspired robot leg design, BirdBot, that challenges the reliance on rapid feedback control for joint coordination and replaces active control with intrinsic, mechanical coupling, reminiscent of a self-engaging and disengaging clutch. A spring tendon network rapidly switches the leg's slack segments into a loadable state at touchdown, distributes load among joints, enables rapid disengagement at toe-off through elastically stored energy, and coordinates swing leg flexion. A bistable joint mediates the spring tendon network's disengagement at the end of stance, powered by stance phase leg angle progression. We show reduced knee-flexing torque to a 10th of what is required for a nonclutching, parallel-elastic leg design with the same kinematics, whereas spring-based compliance extends the leg in stance phase. These mechanisms enable bipedal locomotion with four robot actuators under feedforward control, with high energy efficiency. The robot offers a physical model demonstration of an avian-inspired, multiarticular elastic coupling mechanism that can achieve self-stable, robust, and economic legged locomotion with simple control and no sensory feedback. The proposed design is scalable, allowing the design of large legged robots. BirdBot demonstrates a mechanism for self-engaging and disengaging parallel elastic legs that are contact-triggered by the foot's own lever-arm action.

Influence of coupling ratio on seismic behavior of hybrid coupled partially encased composite wall system

SummaryPartially encased composite (PEC) members are novel composite members that efficiently exploit the advantages of mechanical properties of concrete and steel. However, the application of PEC members is limited to low‐ and mid‐rise buildings. To overcome this limitation, a study was conducted to assess the seismic performance of a newly proposed steel–concrete hybrid coupled wall consisting of PEC wall piers coupled by means of steel beams. Parametric analysis was conducted to investigate the elastic coupling ratio (CRelastic) and the way of changing CRelastic on the seismic behavior of the hybrid coupled PEC wall. The results showed that the CRelastic was the main parameter that affected the seismic performance of the wall. The way of changing CRelastic had little influence on the trend of the energy dissipation capacity and strength reservation of the wall. The failure mode and the development of plastic hinges of the wall were also not affected by the way of changing CRelastic. Both too large and too small CRelastic were detrimental to the seismic performance of the wall. To form an ideal plastic hinge development mode and experience good seismic performance, it is suggested that the reasonable range of CRelastic for the wall was 60%–70%.

A geometrically nonlinear analysis method for offshore renewable energy systems—Examples of offshore wind and wave devices

Recently, offshore renewable energy has been experiencing a rapid growth with tremendous demands and a significant challenge of high cost. To reduce the cost, people start to introduce advanced designs such as composite structures and flexible devices. As a consequence, traditional structural dynamic analysis tools are not able to provide a comprehensive analysis for the new designs especially their nonlinearity, which dwarf the development of the offshore renewable technology. In order to facilitate the technology development, we propose a new method to conduct the nonlinear analysis by introducing variable Winkler-type viscoelastic foundation into geometrically exact beam theory. By comparing against commercial tools, the newly proposed method is well validated. Then, applications in wind turbines and wave energy converters are used to demonstrate the advantages of the new methods with detailed analysis. Specifically, structure–soil–wave interaction are studied. For the supporting structure, we found that geometric nonlinearity due to large displacements and elastic couplings caused by composite materials cannot be ignored especially under large loads or for those flexible structures. Furthermore, influences of the damping and the stiffness of the springs on the structural dynamics are analyzed for the flexible wave energy converter. Overall, the flexible features of the present solver also show advantage of meeting the need of simulating different scenarios, and it is expected to serve more designs in relevant areas.

BEM-FEM coupling for the hydroelastic analysis of propeller-shafting systems in non-uniform flows

The understanding of the fluid-propeller-shafting system's hydroelastic behavior is critical for underwater vehicle vibration and noise reduction. A three-dimensional panel method coupled with a three-dimensional finite element method for analyzing the hydroelastic dynamics of fully coupled propeller and shafting systems in the non-uniform flows is developed. The fully coupled fluid-propeller-shafting model is utilized to assess the applicability of the traditional uncoupled fluid-propeller (elastic vibration)/fluid-propeller (six degrees rigid body oscillation)-shafting models, which consider the elasticities of the blades and shaft separately. It is found that the designers need to consider the elastic coupling effect between the shaft and the propeller, especially in the case of high skew propellers. In addition, the uncoupled model underestimates the fluid-induced damping.

Master-slave synchronization in the Rayleigh and Duffing oscillators via elastic and dissipative couplings

In this work, a master-slave configuration to obtain synchronization between the Rayleigh and the Duffing oscillators is studied. For this configuration, we analyze the system when the dissipative coupling and one that combines the elastic and dissipative couplings are used. We analyzed the coupling parameters to find the range where synchronization between the oscillators is achieved. We found synchronization in the oscillators for large values of the coupling parameter. Our numerical findings show that for the dissipative coupling, there exists partial synchronization while for the others there is complete synchronization.

Vibration analysis of laminated planar frame structures

A wave-based model is developed to analyze the free vibrations of symmetrically and asymmetrically laminated cross-ply planar frame structures. The model includes the effects of shear deformation, rotary inertia and the elastic coupling due to structural anisotropy. The frame is modeled as an assemblage of beam segments, whereby each segment acts as a one-dimensional waveguide. The system matrices governing wave propagation, reflection and transmission along the connected segments are derived. An advantage of the proposed model over numerical methods, such as the finite element method, is that exact solutions for the equations of motion are used to derive the system matrices of the frame. The matrices are subsequently assimilated to give a complete description of the wave train present during free vibration. The approach, which is well suited for implementation in conventional computing programs, can be used to determine the exact natural frequencies and mode shapes of the frame. By using the proposed model, the free vibration characteristics of inclined laminated portal frames are analyzed. The effects of stacking sequence, frame angle, relative frame length, orthotropicity ratios and boundary conditions on the exact natural frequencies, and in certain cases the mode shapes, are evaluated and discussed. The numerical results presented in this work are in close agreement with finite element (FE) simulations and where possible, published results.

Voltage Stabilisation of a Drive System Including a Power Transformer and Asynchronous and Synchronous Motors of Susceptible Motion Transmission

A mathematical model is developed of the master circuit of an electric driver system including a power transformer and susceptible motion transmission of asynchronous and synchronous drives. Electric motors drive water pumps by means of motion transmission that comprises two elastic couplings of lumped mechanical parameters and a long shaft of distributed mechanical parameters. Differential equations for oscillatory processes for the long shaft and the elastic couplings are different. The shaft is described with partial derivative Euler–Poisson equations, which, combined with the boundary conditions, form mixed problems from the mathematical point of view. The elastic couplings, on the other hand, are described with the ordinary second type Lagrange equations. Based on the theory of electromagnetic field, the partial differential equations describe the skin effects across the rotor age bars. Vertical pumps are presented by means of a loading torque waveform as a function of the input shaft’s angular velocity. The complex mathematical model serves to analyse electromechanical transient processes across the integrated drive system. Starting from there, conditions of stabilisation of the drive system voltage are determined. Electromechanical state equations are presented in the normal Cauchy form and integrated using the fourth-order Runge–Kutta method. Results of computer simulations are shown with graphics, which are interpreted and described.

Multi-objective optimization of composite airfoil fibre orientation under bending–torsion coupling for improved aerodynamic efficiency of horizontal axis wind turbine blade

Modern multi-megawatt wind turbines have long, slender and flexible blades, which experience significant vibration due to aerodynamic loads. These blades are generally made of composite layups with cambered airfoil sections, which induce elastic and dynamic coupling between bending and torsional modes. In addition to these phenomena, the aerodynamic pitching moment also arises due to the offset of the blade pitch axis from the aerodynamic centre. With this in mind, the present work aims to develop a computationally efficient complete multi-body dynamic aero-servo-elastic model of an onshore horizontal axis wind turbine, including bending–torsion coupling and aerodynamic pitching moment. 3D wind fields are generated using TurbSim, and the responses of the coupled system are solved under different operational scenarios, which signify the impact of the aforementioned coupling. It is found to be particularly detrimental at higher wind speeds than the rated value. But, proper design and implementation of structural layup can enhance the aerodynamic performance of the blade. Finally, the optimal design of composite fibre orientation of a benchmark turbine blade is investigated to show its beneficial effects in load/response mitigation.

The modeling method of anisotropic U-shaped plate and U-shaped plate–cavity​ coupled system

The anisotropic U-shaped plate are widely applied in aviation, aerospace, ship, machinery and other fields, and the vibration of U-shaped plate will inevitably produce U-shaped plate–cavity​ coupled system in engineering practice. To investigate the vibration characteristics of anisotropic U-shaped plate and the vibro-acoustic characteristics of U-shaped plate–cavity​ coupled system with varying elastic boundary conditions, a modeling method of anisotropic U-shaped plate and U-shaped plate–cavity coupled system is established: Firstly, the modified Fourier series method is effectively applied to establish the analysis models of U-shaped plate and U-shaped plate–cavity coupled system. Secondly, the simulation of complex elastic boundary and coupling boundary is realized by artificial virtual spring technology. Then, the energy equation of the composite laminate plate is established by Rayleigh–Ritz energy technology. Finally, the solution equation is obtained through Hamilton differential principle. The vibration and vibro-acoustic characteristics are obtained. From the analysis of numerical results, the fast and uniform convergence of analysis modeling and the accuracy of the calculated results are verified. The effects of varying boundary conditions, geometric parameters, acoustic wall conditions and anisotropy degree on the vibration characteristics of U-shaped plate and the vibro-acoustic characteristics of U-shaped plate–cavity coupled system are investigated respectively, which can provide a theoretical basis for future research.

Subcellular Remodeling in Filamin C Deficient Mouse Hearts Impairs Myocyte Tension Development during Progression of Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is a life-threatening form of heart disease that is typically characterized by progressive thinning of the ventricular walls, chamber dilation, and systolic dysfunction. Multiple mutations in the gene encoding filamin C (FLNC), an actin-binding cytoskeletal protein in cardiomyocytes, have been found in patients with DCM. However, the mechanisms that lead to contractile impairment and DCM in patients with FLNC variants are poorly understood. To determine how FLNC regulates systolic force transmission and DCM remodeling, we used an inducible, cardiac-specific FLNC-knockout (icKO) model to produce a rapid onset of DCM in adult mice. Loss of FLNC reduced systolic force development in single cardiomyocytes and isolated papillary muscles but did not affect twitch kinetics or calcium transients. Electron and immunofluorescence microscopy showed significant defects in Z-disk alignment in icKO mice and altered myofilament lattice geometry. Moreover, a loss of FLNC induces a softening myocyte cortex and structural adaptations at the subcellular level that contribute to disrupted longitudinal force production during contraction. Spatially explicit computational models showed that these structural defects could be explained by a loss of inter-myofibril elastic coupling at the Z-disk. Our work identifies FLNC as a key regulator of the multiscale ultrastructure of cardiomyocytes and therefore plays an important role in maintaining systolic mechanotransmission pathways, the dysfunction of which may be key in driving progressive DCM.

Fuzzy Adaptive Type II Controller for Two-Mass System

This paper presents original concepts of control systems for an electrical drive with an elastic mechanical coupling between the motor and the driven mechanism. The synthesis procedure of the speed controller uses a proposed quality index (cost function) of system operation ensures the minimization of both tracking errors and torsional vibrations. Proper selection of the cost function focusses more on the reduction of torsional vibrations due to their negative influence on the drive’s mechanical coupling vitality. The omission of the plant identification of an adaptive fuzzy controller was proposed. Two types of fuzzy controllers were analyzed, namely with type I and type II fuzzy membership functions. The novelty of the presented approach is in the application of a Petri transition layer in a type II fuzzy controller which reduces the numerical complexity in case of a large number of complicated type II fuzzy sets. The presented simulation and experimental results prove that the best dumping of mechanical vibrations ensures the adaptive fuzzy controller with type II functions and a Petri transition layer.