Dissipative Forces Research Articles

Finite contact duration modeling of a Vibro-Impact Nonlinear Energy Sink to protect a civil engineering frame structure against seismic events

This paper reassesses carefully the effects and consequences of instantaneous contact mechanics versus finite contact duration modeling of Vibro-Impact Nonlinear Energy Sinks (VI NES). The device is composed of a container enclosing an inelastic sphere, interacting via a nonlinear viscoelastic dissipative force with the inner walls of the container. The VI NES is considered in a practical context, the control of the vibrations of a civil engineering frame structure under seismic input. It is connected by a rigid link to the structure: the particle bounces within the container when it vibrates, exploring dynamical regimes ranging from periodic collisions to chaos while dissipating energy. Our VI NES is designed in order to mitigate vibrations of a ten-story frame structure under two historic earthquake signals, in order to rule out specific effects. The dynamics of the system, obtained from both finite and instantaneous contact models, are compared and discussed. The main result reveals a significant effect of the contact duration on the estimation of the dissipated energy, even for very brief collisions. Instantaneous contact model indeed provides incommensurate values in terms of acceleration during the impacts, leading to a higher sensitivity to Initial Conditions (IC) revealed by large fluctuations of the mechanical response. In turn, any finite duration contact models is proved to be less sensitive to IC, and thus more precise. Our findings demonstrate that both finite and instantaneous models converge in fact to the same value, in average, but the finite duration models require much less realizations to converge to the mean value. In practice, the finite contact duration low pass filters the mechanical responses of the VI NES, avoiding the system to fall into nonphysical chaotic states experienced by the instantaneous model.

On a pseudo-periodicity in the elastodynamics

The periodic laws of motion of a real mechanism imply the periodicity of all dynamic characteristics of the mechanism during such a movement, including the elastic displacements of its constituent links. This statement covers the most difficult problem of the dynamics of an elastically deformable body. However the existing publications devoted to the study of flexible mechanisms do not mention the periodicity of elastic displacements of the links when the mechanisms move according to periodic laws. This article discusses the periodicity and pseudo-periodicity of the elastic displacements of the links using examples of calculations of the motion of a double pendulum and a slider–crank mechanism without taking into account dissipative forces.

Circularization versus eccentrification in intermediate mass ratio inspirals inside dark matter spikes

Inspirals of an intermediate mass black hole (IMBH) and a solar mass type object will be observable by space based gravitational wave detectors such as the Laser Interferometer Space Antenna. A dark matter overdensity around an IMBH---a dark matter spike---can affect the orbital evolution of the system. We consider here such intermediate mass ratio inspirals on eccentric orbits, experiencing dynamical friction of the dark matter spike. We find that by including the relative velocities of the dark matter particles, the dynamical friction tends to circularize the orbit, in contrast to previous inquiries. We derive a general condition for circularization or eccentrification for any given dissipative force. In addition to the dephasing, we suggest using the circularization rate as another probe of the dark matter spike. Observing these effects would be an indicator for the particle nature of dark matter.

Significance of Lorentz Force and Viscous Dissipation on the Dynamics of Propylene Glycol: Water Subject to Joule Heating Conveying Paraffin Wax and Sand Nanoparticles Over an Object with a Variable Thickness

Significance of Lorentz Force and Viscous Dissipation on the Dynamics of Propylene Glycol: Water Subject to Joule Heating Conveying Paraffin Wax and Sand Nanoparticles Over an Object with a Variable Thickness

Full‐scale shaking table test and numerical modeling of a 3000‐liter legged storage tank isolated with a vertical rocking isolation system

AbstractThis paper presents the numerical and experimental evaluation of a vertical‐rocking isolation (VRI). This evaluation is done by 1‐D shaking table tests performed on a full‐scale legged storage tank of 3000‐liters capacity and its representation through a simple yet representative rigid lumped‐mass model approach. The isolation system setup consisted of four ISO3D‐2G devices, each one placed on each leg of the tank, which uses high‐damping natural rubber to generate the restoring and dissipative forces. The ISO3D‐2G device is vertically flexible and laterally rigid, enabling the isolation mechanism of the rocking motion of the tank. The experiments were carried out using three white noise for the system identification and 17 ground motions inputs for the system validation. The measured variables included the lateral acceleration and displacement of the tank, and the vertical and rotational behavior of the isolation interface. The identification results showed a vertical‐rotational coupled fundamental mode that is highly dependent on the amplitude of deformation, with a period varying from 0.5 to more than 1 s, depending on the intensity of the motion. The maximum displacement of the tank at the top remained below 13 cm with total accelerations of nearly 0.3 g, both for motions with Peak Ground Acceleration (PGA) values ranging from 0.3 to 0.8 g. The mean maximum values were predicted with the simplified model with errors of less than 10% and 21% for displacements and accelerations, respectively. Finally, the results show that the behavior of vertical‐rocking isolated structures can be predicted by simplified models with reasonable errors and that the development of simple design guidelines and equations for VRI systems is possible.

Roll–Yaw Lock: Aerodynamic Motion Instabilities of Floating Offshore Wind Turbines

Abstract This article presents an investigation of a newly discovered motion instability phenomenon for floating wind turbines, first observed in numerical aero-hydro-servo-elastic simulations. The source of instability is identified as antisymmetric aerodynamic stiffness coupling terms in roll and yaw caused by the turbine thrust force. Analytical expressions for the roll–yaw and yaw–roll stiffness coupling terms are derived, using the actuator disk analogy of the rotor plane. It is demonstrated that a two degrees-of-freedom linear equation of motion without explicit external forcing qualitatively captures the instability. Based on this model, an analytical stability criteria is derived. An intuitive physical explanation of the phenomena is provided, considering the energy flow of the system. An important finding is that dissipative forces, in the form of aerodynamic and hydrodynamic damping, are needed to fully explain the observed instability. It is demonstrated, counterintuitively, that increased damping in yaw reduces the stability margin. This is explained by the fact that dissipative forces result in a phase difference between the harmonic roll and yaw motion in the coupled roll–yaw modes.

An amperometric glucose biosensor based on electrostatic force induced layer-by-layer GOD/chitosan/pyrite on a glassy carbon electrode.

Pyrite (PR), as a representative sulfide mineral, possesses the advantages of abundancy, thermodynamic stability, non-toxicity and semi-conductivity. In this study, an amperometric glucose biosensor (GOD/CS/PR/GCE) based on layer-by-layer of glucose oxidase (GOD), chitosan (CS) and pyrite (PR) on a glassy carbon electrode (GCE) was fabricated through electrostatic force. In this research, PR suspension prepared in phosphate buffer (pH 5.5) was first immobilized on the GCE surface, which exhibits a negative charge. Then, positively charged CS was adsorbed on the PR/GCE by electrostatic force. Finally, negatively charged GOD was further modified on the CS/PR/GCE surface through electrostatic force again. The surface morphology and adsorbance mechanism were supported by field emission scanning electron microscopy, quartz crystal microbalance with dissipation and atomic force microscope. The step-by-step procedure gives both strong adhesion ability and good bioelectrocatalytic activity of GOD on the CS- and PR-modified electrode surface. The linear range of this GOD/CS/PR/GCE biosensor was achieved from 0.5 to 60mM with the linear regression equation of y = 0.897x - 0.3016 (R2 = 0.9996) and a limit of detection value of 50µM. This approach of using pyrite and chitosan as physically modified GOD to serve as electrostatic glues could be useful for designing better enzyme-based biosensors for a wide variety of practical applications.

Dynamical forces and the influence of an equation of state on gravitational collapse

We investigate the equation of state (EoS) parameter on the collapse of a star undergoing dissipative collapse. The collapse starts from an initial static configuration described by the anisotropic generalisation of the Vaidya–Tikekar superdense model. The initial matter profile obeys a linear EoS and starts to radiate energy in the form of a radial heat flux as it leaves hydrostatic equilibrium. We study the evolution of the hydrostatic, gravitational, anisotropic and dissipative forces at play within the collapsing body via the dynamic Tolman–Oppenheimer–Volkoff equation. We show that the EoS parameter has a significant impact on the various forces which influences the outcome of gravitational collapse. The effect of the EoS parameter on the temperature profiles is also studied by employing a causal heat transport equation of Maxwell–Cattaneo form. Our investigation shows that the stiffness of the fluid which is related to its compressibility, is compromised in the presence of pressure anisotropy and heat flow.

Formation mechanism of surfactant-free microemulsion and a judgment on whether it can be formed in one ternary system

What is the formation and stability mechanism of surfactant-free microemulsion (SFME)? What is the inherent relationship between three components to form SFME? These problems restrict the understanding, popularization and application of SFME. In this work, a new methyl salicylate/ethanol/water SFME is constructed as a representative for experimental and theoretical research. Results show that: the dynamic equilibrium of conservative, dissipative and random forces leads to the decrease of free energy of ternary system and promotes the formation of SFME. In oil in water (O/W) and water in oil (W/O) droplets, directional arrangement and charge redistribution of ethanol molecules in the interface layer can be induced by water. The induced charges on the O/W and W/O droplets are –48.999 and 2.697 a.u., which is conducive to the dispersion of droplets and improves the stability of SFME. When O/W droplets collide, an “electron trap” can be formed by water molecules, so that charge transfer can be carried out spontaneously. In addition, a novel parameter “ ƍ ” is defined representing the interaction between amphi-solvent, oil and water. The relationship of S (the proportion of single-phase area in ternary phase diagram) and ƍ is: S = 67.8 – 97.2 ƍ. ƍ less than 0.7 is the requirement for SFME to be formed and the maximum of S is 70%. The proposed regulation is verified by other 44 ternary systems. Hope this work would lay a theoretical foundation for explaining the stability mechanism, and provide guidance for developing more SFMEs.

Inspiraling corrugation-induced quantum effects on neutron star binary plane

We use the path-integral formula and investigate some dynamical quantum effects induced by the inspiraling lateral corrugation of orbital plane in gravitationally bound neutron star (NS) binaries, with orbital separation of 109 m. Based on Dewitt's approach, we calculate the gravitational Casimir energy cost of the binary plane, which consists of statically gravitational effects and deformation-induced effects. It is found that the static effects include a term coming from the self-gravity of the orbital plane and the contribution of Newtonian gravitational potential of the binary system. While the deformation-induced effect also results from two parts, i.e. the instability of orbital binding energy, scaling as 1(R−r)2, and the dynamically Casimir energy cost of the orbital binding energy, decaying as 1(R−r)4. The dynamically gravitational Casimir phenomena and the corresponding energy cost modify the spiral-in orbital motion of the binary and thus the frequency of released gravitational waves (GWs). We consider the mechanical response of two NS components and qualitatively study the corrections to the orbital motion of the system and the GW frequencies. It is found that the dynamical Casimir effects exert a dissipative force on the binary plane, depending on the frequency of GWs. The resultant dissipation may enhance with the decaying separation and increasing GW frequencies, which subsequently accelerates the orbital decay of the binary. However, the dissipation rate just has an order of 10−70 eV/s. So the corrections to the dynamics of NS binaries are very marginal, by considering the wide separation, the cosmological coalescence time, and low-frequency GWs of the system.

Nonlinear atomic force microscopy: Squeezing and skewness of micromechanical oscillators interacting with a surface

We propose a two-frequency driving scheme in dynamic atomic force microscopy that maximizes the interaction time between tip and sample. Using a stochastic description of the cantilever dynamics, we predict large classical squeezing and a small amount of skewness of the tip's phase-space probability distribution. Strong position squeezing will require close contact between tip and surface, while momentum squeezing would also be possible in the van der Waals region of the tip-surface force. Employing a generalized Caldeira-Leggett model, we predict that surface-dependent dissipative forces may be the dominant source of quantum effects and propose a procedure to isolate quantum effects from thermal fluctuations.

Mechanisms of energy conversion in induction magnetohydrodynamic pumps for transporting conducting liquids

Efficiency of energy conversion in magnetohydrodynamic (MHD) pumps is relatively lower compared with conventional mechanical pumps. The processes of energy conversion in an induction MHD pump are identified and the energy efficiencies of the processes are evaluated based on the numerical simulations. Two numerical models with different geometrical dimensions are built to simulate all involved processes. The results illustrate that vortices suddenly occur in the pump channel when the flow rate reduces below a critical value. The size and scale of the vortices are dependent on the modeling dimension. By analyzing the energy conversion among different forms of energy, it is demonstrated that the energy conversion is strongly correlated with the vortex flow. The appearing vortices at low flow rates result in both large Ohmic dissipation and negative power of Lorentz force, which are the main obstructions for energy transfer from the input power to the fluid pressure energy. In addition, the overall efficiency of this machine is estimated using the model containing external components (e.g., coils, stators and ducts). It is found that the energy dissipation in the external components plays an increasing role of reducing the energy efficiency with the increasing flow rate.

Impact of nonlinear radiation on magnetohydrodynamic flow of hybrid nanofluid with heat source effect

This investigation is performed to deliberate the novel significance of nonlinear thermal radiation effect on magnetohydrodynamic flow of Casson hybrid nanoliquid caused by a curved stretching sheet. The flow and thermal transport nature of three different hybrid nanoliquids in the stimulus of viscous dissipation, nonlinear radiation and magnetic force is discussed numerically. The novelty of this work is to obtain the simultaneous solutions for three different types of hybrid nanoliquids, they are obtained by suspending titanium alloy (Ti6Al4vs.) is composed of titanium, aluminum and vanadium in the ratio of 90:6:4 respectively and aluminium alloy (AA7075) is compossed of Aluminum, Zinc, Magnesium and Copper nanoparticles in the ratio of 90:6:3:1 respectives with added metals Silicon, Ferrous and Magnesium. in three various working liquids viz. methanol, ethylene glycol and engine oil. The flow governing PDE's are transmuted into ODE's with suitable similarity transformation and solved by using Runge-Kutta and Newton's approach. Numerical outcomes of flow and temperature profiles are presented via graphical trends, also skin friction coefficient and rate of thermal transfer are illustrated via tabulated values. Major outcomes reveals that, inclusion of hybrid nanometer sized particles in pedestal liquid lead to an large hike in thermal transfer performance. Importantly, thermal transport rate and temperature profiles of the hybrid nanoliquid rises with improving nonlinear radiation values and these results are significant in nonlinear radiation case as compared with linear radiation case.

Integration of a dissipative contact force model into vehicle–track dynamics for analysing wheel–rail dynamic interaction under short-wavelength irregularity

Wheel–rail dynamic interaction under short-wavelength irregularity which has a detrimental effect on the service life of vehicle and track components, is of crucial importance to be estimated accurately. Aiming at this, dissipative contact force models are integrated into a validated vehicle–track coupled dynamics model, which enables to consider the energy dissipation at the wheel–rail interface. Wheel–rail interactions for different dissipative contact force models are evaluated, and the Hu–Guo model is selected as the most suitable one for wheel–rail interaction analysis. The wheel–rail interactions for the Hu–Guo model and Hertz theory are analysed under different track irregularities including sinusoidal rail corrugation and rail welded joints. The simulation results indicate that the Hu–Guo model has little effect on the normal interaction at low frequencies, but reduces the contact force fluctuation amplitude obviously at high frequencies above 600 Hz, with a more significant reduction at the resonance peak of high frequency range. The Hu–Guo model has an obvious contact force phase lead compared with the Hertz theory at higher frequencies above 1250 Hz. The Hu–Guo dissipative contact force model is needed for the wheel–rail interaction analysis at high frequencies above 600 Hz.

Seismic Performance Evaluation of RC Columns Retrofitted by 3D Textile Reinforced Mortars.

The paper investigates the seismic performance of rectangular RC columns retrofitted by a newly developed 3D Textile Reinforced Mortar (TRM) panel. The 3D-TRM used in this study consists of two components: self-leveling mortar and 3D textiles. Firstly, the flexural capacity of the 3D-TRM panel was investigated through the four-point flexural test. Secondly, a total of five specimens were constructed and experimentally investigated through static cyclic loading tests with constant axial load. One specimen was a non-seismically designed column without any retrofit, while the others were strengthened with either the 3D-TRM panel or conventional Fiber Reinforced Polymer (FRP) sheets. Experimental results in terms of hysteretic behavior, ductility ratio, and energy dissipation are investigated and compared with the cases of specimens with conventional retrofitting methods and without any retrofit. The maximum lateral force, ductility, stiffness degradation, and energy dissipation of RC columns with 3D-TRM panels were significantly improved compared with the conventional RC column. Therefore, it is concluded that the proposed retrofitting method can improve the seismic performance of non-conforming RC columns.

The effect of new generation polyurethane wall block on single span steel frame behavior

In building production industry, infill walls which are brittle elements are generally used. Nowadays, researches for alternatives to these brittle structural elements are still ongoing. In this study, low density two different polyurethane wall block (Polyurethane wall block and interlacing polyurethane wall block) are used as infill wall. In the experimental part of the study, single spanned, one frame and two infill wall frame system are prepared. Lateral loading tests of the frame systems have been performed in the laboratory. Macro and simplified micro models of the frame system has been prepared using finite element modelling (FEM) as the numerical part of the study. Incremental pushover analysis is performed for the created finite element models. From the FEM analysis results; capacities of load-displacement, stress, separation, ductility, energy dissipation and local buckling conditions of the frame systems are evaluated comparatively. It is seen that the finite element analysis results and the test results are compatible. The polyurethane wall added to the steel frame system increased the base shear force, system rigidity and energy dissipation capacity by approximately 64–68%, 25–40% and 50–62%, respectively. In addition, a macro model proposal is presented to simplify the modelling of the polyurethane wall block in the computer environment.

Nonstandard Null Lagrangians and Gauge Functions and Dissipative Forces in Dynamics

Nonstandard Null Lagrangians and Gauge Functions and Dissipative Forces in Dynamics

Mathematical Model of Satellite Rotation near Spin-Orbit Resonance 3:2

This paper considers the rotational motion of a satellite equipped with flexible viscoelastic rods in an elliptic orbit. The satellite is modeled as a symmetric rigid body with a pair of flexible viscoelastic rods rigidly attached to it along the axis of symmetry. A planar case is studied, i. e., it is assumed that the satellite’s center of mass moves in a Keplerian elliptic orbit lying in a stationary plane and the satellite’s axis of rotation is orthogonal to this plane. When the rods are not deformed, the satellite’s principal central moments of inertia are equal to each other. The linear bending theory for thin inextensible rods is used to describe the deformations. The functionals of elastic and dissipative forces are introduced according to this model. The asymptotic method of motions separation is used to derive the equations of rotational motion reflecting the influence of the fluctuations, caused by the deformations of the rods. The method of motion separation is based on the assumption that the period of the autonomous oscillations of a point belonging to the rod is much smaller than the characteristic time of these oscillations’ decay, which, in its turn, is much smaller than the characteristic time of the system’s motion as a whole. That is why only the oscillations induced by the external and inertial forces are taken into account when deriving the equations of the rotational motion. The perturbed equations are described by a third-order system of ordinary differential equations in the dimensionless variable equal to the ratio of the satellite’s absolute value of angular velocity to the mean motion of the satellite’s center of mass, the angle between the satellite’s axis of symmetry and a fixed axis and the mean anomaly. The right-hand sides of the equation depend on the mean anomaly implicitly through the true anomaly. A new slow angular variable is introduced in order to perform the averaging for the perturbed system near the 3:2 resonance, and the averaging is

Nanomechanics of self-assembled surfactants revealed by frequency-modulation atomic force microscopy.

Surfactants play a critical role in bottom-up nanotechnologies due to their peculiar nature of controlling the interfacial energy. Since their operational mechanism originates from the molecular-scale formation and disruption processes of molecular assemblies (i.e., micelles), conventional static-mode atomic force microscopy has made a significant contribution to unravel the detailed molecular pictures. Recently, we have successfully developed a local solvation measurement technique based on three-dimensional frequency-modulation atomic force microscopy, whose spatial resolution is not limited by jump-to-contact. Here, using this novel technique, we investigate molecular nanomechanics in the formation and disruption processes of micelles formed on a hydrophobic surface. Furthermore, an experiment employing a hetero-nanostructure reveals that the nanomechanics depends on the form of the molecular assembly. Namely, the hemifusion and disruption processes are peculiar to the micellar surface and cause a higher energy dissipation than the monolayer surface. The technique established in this study will be used as a generic technology for further development of bottom-up nanotechnologies.

On Ziegler Effect with Arbitrary Large Viscous Friction

We study a mechanical system with two degrees of freedom simulating the motion of rotor blades on an elastic bushing of a medium-sized helicopter. For small values of some problem parameters, the destabilizing effect due to small linear viscous friction forces has been studied earlier. Here we study the problem with arbitrary large friction forces for arbitrary values of the problem parameters. In the plane of parameters, the regions of asymptotic stability and instability are calculated. As a result, necessary and sufficient conditions for the existence of a destabilizing effect under the action of potential, follower forces and arbitrary friction forces have been obtained. It is shown that, if some critical friction coefficient $k_{*}$ tends to infinity, then there exists a Ziegler area with arbitrarily large dissipative forces.