Elastic Suspensions Research Articles

Finite Element Mode-ling of Damping of a Squeeze Gas Film in High-Frequency Microelectromechanical Switches with Capacitive Contact

The damping effects of a squeeze gas film are one of the main components of damping and naturally arise in the designs of dynamic micromechanical devices, in particular, in high-frequency micromechanical switches with an electrostatic activation mechanism, in which the electrostatic drive consists of a fixed electrode in the form of a plate and a movable electrode in the form of a movable plate suspended on elastic suspensions for the case of capacitive contact. In the static mode of the device, a thin film of gas consisting of air molecules or other inert gas surrounding the device is located and held between the electrodes of the electrostatic drive. This article presents a mathematical model based on the obtained linear inhomogeneous Reynolds differential equation and performs finite element modeling of the pressure distribution in the plate of a suspended movable electrode during compression of a gas film during electrostatic activation of micromechanical switches with a capacitive contact and parallel arrangement of the electrodes of an electrostatic drive depending on the magnitude of the coefficient of this component of damping in a three-dimensional coordinate system, the dependences between the damping force and the elastic force of the compressible gas film on the value of the damping coefficient are also presented. The presented results are applicable to assess the effect of isothermal damping of a squeeze gas film on the dynamics of micromechanical devices, in particular, on the dynamic characteristics of high-frequency micromechanical switches with an electrostatic activation mechanism and a capacitive contact.

Determination of rational parameters of the membrane suspension of the gyroscope rotor

Research is presented to determine the rational design parameters of elastic membrane suspensions of mechanical gyroscope rotors. The results obtained make it possible to significantly reduce the labor intensity and cost of predesign research when developing precision instruments. Keywords:gyroscopes, elastic suspension, gyroscope rotor, membrane elastic suspensions, angular stiffness, rotation angle antonvladim@mail.ru

Order–disorder transitions within deformable particle suspensions in planar Poiseuille flow

Three-dimensional simulations of the ordering of elastic capsule suspensions within planar Poiseuille flow channels are reported. The simulations utilize the immersed boundary method coupled with the lattice Boltzmann method to capture the complex flow-induced capsule deformations and hydrodynamic interactions within the suspensions. A parametric study is presented whereby the confinement ratio and the particle deformability are varied independently within a two-dimensional range relevant to this ordering phenomenon. The initial distribution of capsules is random, and the simulations evolve the system from a disordered state to an ordered one, while an order parameter that quantifies the fraction of capsules belonging to one-dimensional train assemblies is computed throughout time. A monotonic increase in ordering is observed with increasing deformability. However, an optimal confinement ratio is identified corresponding to a peak in the order parameter. This peak is attributed to the competition between increasing long-range capsule attractions and decreasing in-plane capsule density (with fixed volume fraction) as the confinement ratio increases. Simulations are also performed to understand how dispersity in capsule size and deformability impact the degree of ordering. It is shown that ordering is quite sensitive to dispersity in capsule size, and much less sensitive to dispersity in deformability. Overall, the results provide important insights for the design of microfluidic devices.

Integrated data-driven modeling and experimental optimization of granular hydrogel matrices

Integrated data-driven modeling and experimental optimization of granular hydrogel matrices

Rheology and structure of elastic capsule suspensions within rectangular channels.

Three-dimensional simulations of the pressure-driven flow dynamics of elastic capsule suspensions within both slit and rectangular cross-section channels are presented. The simulations utilize the Immersed Boundary Method and the Lattice-Boltzmann Method models. The capsule volume fraction is fixed at 0.1 (i.e., a semi-dilute suspension), while the channel Reynolds number (Re), the capillary number (Ca), and the cross-sectional channel dimensions are systematically varied. Comparing results for slit and rectangular channels, it is found that multi-directional confinement hinders inertial focusing due to the capsule-free layers that develop in the two transverse directions. Furthermore, the thicknesses of the capsule-free layers in the two transverse directions differ when the height and width of the channel are not equal. Both the size and aspect ratio of the channel impact the apparent viscosity. It is found that square channels exhibit maximal viscosity and that holding one dimension fixed while increasing or decreasing the other results in a decrease in viscosity. The results therefore represent an expansion of the Fahraeus-Lindqvist effect from 1D cylindrical channels to 2D rectangular channels.

Corrigendum to “The Oldroyd-B fluid in elastic instabilities, turbulence and particle suspensions”;

Corrigendum to “The Oldroyd-B fluid in elastic instabilities, turbulence and particle suspensions”;

Investigation of the Effect of Vibration on the Bearing Capacity of Composite Materials

Polymer coatings are increasingly used in mechanical engineering. In particular, sheet composite elements are created on their basis. But the question of the influence of vibration loads on the bearing capacity of composite structures remains relevant. This work presents the results of an experimental study of the operation of composite structures when exposed to vibration loads. The choice of the parameters of the test bench is due to the frequencies of natural vibrations of the specimens under study. The frequencies were determined using generally accepted approximations. A test bench was developed for carrying out measurements. A vibration-absorbing foundation was used, a support frame with the element was attached on elastic suspensions to the outer frame. A scheme for cutting sheet elements for tensile testing was developed. Nine sheet elements made of reinforced polymer material were tested. The influence of the number of loading cycles on the material ultimate strength is investigated. It was established that the presence of a reinforced polymer coating leads to a decrease in the vibration amplitude when approaching the resonance frequencies. This is due to the internal deformation of the polymer coating. After removing the vibration load, no cracks were found on the specimens.

Mediated interactions between rigid inclusions in two-dimensional elastic or fluid films.

Interactions between rigid inclusions in continuous three-dimensional linearly elastic solids and low-Reynolds-number viscous fluids have largely been quantified in the past. Prime example systems are given by functionalized elastic composite materials or fluid colloidal suspensions. Here, we address the significantly less frequently studied situation of rigid inclusions in two-dimensional elastic or low-Reynolds-number fluid films. We concentrate on the situation in which disklike inclusions remain well separated from each other and do not get into contact. Specifically, we demonstrate and explain that the logarithmic divergence of the associated Green's function is removed in the absence of net external forces on the inclusions, in line with physical intuition. For instance, this situation applies when only pairwise mutual interactions between the inclusions prevail. Our results will support, for example, investigations on membranes functionalized by appropriate inclusions, both of technical or biological origin, or the dynamics of active microswimmers in appropriately prepared thin films.

Circumferentially rotatable inspection robot with elastic suspensions for bridge cables

PurposePeriodic inspection of bridge cables is essential, and cable-climbing robots can replace human workers to perform risky tasks and improve inspection efficiency. However, cable inspection robots often fail to surmount large obstacles and cable clamps. The purpose of this paper is to develop a practical cable inspection robot with stronger obstacle-surmounting performance and circumferential rotation capability.Design/methodology/approa/chA cable inspection robot with novel elastic suspension mechanisms and circumferential rotation mechanisms is designed and proposed in this study. The supporting force and spring deformation of the elastic suspension are investigated and calculated. Dynamic analysis of obstacle surmounting and circumferential rotation is performed. Experiments are conducted on vertical and inclined cables to test the obstacle-surmounting performance and cable-clamp passing of the robot. The practicality of the robot is then verified in field tests.FindingsWith its elastic suspension mechanisms, the cable inspection robot can carry a 12.4 kg payload and stably climb a vertical cable. The maximum heights of obstacles surmounted by the driving wheels and the passive wheels of the robot are 15 mm and 13 mm, respectively. Equipped with circumferential rotation mechanisms, the robot can flexibly rotate and successfully pass cable clamps.Originality/valueThe novel elastic suspension mechanism and circumferential rotation mechanism improve the performance of the cable inspection robot and solve the problem of surmounting obstacles and cable clamps. Application of the robot can promote the automation of bridge cable inspection.

Модифицирование спортивных подвесных систем для использования в реабилитационном процессе

В работе представлен обзор литературы, посвященной использованию спортивных подвесных систем в реабилитационном процессе. Подвесная терапия, или cлинг-терапия, — это метод физической реабилитации с использованием разнообразных систем подвеса всего тела или конечностей. Эти системы в настоящее время широко используются как в восстановительном лечении, так и в тренировочном процессе. Обсуждается возможное модифицирование спортивных подвесных систем путем использования эластичных подвесов. Применение эластичных подвесов в спортивных вариантах подвесных систем позволяет не только выявить слабое звено в скелетно-мышечной цепи, но и откорректировать его, используя разнообразные динамические упражнения. Так, использование эластичных подвесов дает возможность активизировать более слабые мышечные группы, чередуя выполнение динамических и статических упражнений. При этом врач имеет возможность проследить за тем, чтобы в выполнении движения не участвовали другие, более сильные мышечные группы. Включение в выполнение движения компенсаторных мышц является сигналом к завершению или изменению условий выполнения упражнений. Таким способом возможно сформировать и натренировать правильный двигательный паттерн у пациента, не прилагая больших усилий. Применение эластичных подвесов дает возможность увеличивать или уменьшать нагрузку, не изменяя количество повторений упражнения и, соответственно, не изменяя длительность занятия.

Synthesis of a fuzzy regulator for a vibration protective platform

The problem solution of a fuzzy logic controller (FLC) synthesis for a combined vibration isolation system with an electromagnetic motor is considered. An analysis of the passive system characteristics is carried out and its key disadvantages, the presence of a pronounced resonance peak and the ineffectiveness of vibration isolation in the low-frequency range, are identified on the basis of a mathematical model of a vibration-protective platform on elastic suspensions. The structure of the FLC is proposed, a system of production rules is drawn up, a parametric synthesis of the FLC is carried out by finding the optimal centers location of the accessory functions terms for input and output quantities. Using mathematical modeling in the MATLAB Simulink software package, the advantages of a synthesized combined system over a passive installation are demonstrated. Keywords vibration, active vibration protection, fuzzy control, mathematical model, optimal control, electromagnetic system, mathematical modeling

The Oldroyd-B fluid in elastic instabilities, turbulence and particle suspensions

The Oldroyd-B fluid has become the starting point for almost all complex flow calculations and analysis involving the behavior of dilute polymer solutions. The reasons for this are clear: based on the kinetic theory of high molecular weight “phantom” chains near equilibrium, the resulting model, in its simplest form, produces a single mode description of the solution constitutive equation in terms of a single symmetric dyad order parameter. The physical connection to the individual chains is therefore unambiguous through the end-to-end configuration tensor. The flow of the fluid resulting from the mathematical solution of the constitutive equation coupled to Cauchy’s equation of motion and continuity has been examined for decades and its strengths and weaknesses in predicting the features of non-linear viscometric and non-viscometric polymer solution flows are well known. Moreover, “simple” extensions (e.g. the FENE-P model) can ameliorate the most serious of these shortcomings. For example, the multi-mode Oldroyd-B model can provide quantitative predictions of the linear viscoelasticity of a wide range of polymer solutions. Remarkably, even with all its shortcomings, the Oldroyd-B fluid has been invaluable in predicting at least qualitatively, features as complex as purely elastic instabilities, turbulent drag modification, and even the effective rheology of particles suspended in polymer solutions. While remaining mindful of the model’s shortcomings, any student of these diverse fields may find the Oldroyd-B fluid an important starting point.

INFLUENCE OF CURRENT IMBALANCES AND CENTER POSITION HARDNESS ON VIBROACTIVITY OF HORIZONTAL DRUM MACHINES

The issues of reducing the vibration caused by rotating rotors at the frequency of the first rotor harmonic (so-called rotor vibration) are among the most important in the design, manufacture and operation of almost all types of modern rotary machines. The washing machine as an object of study of the dynamics and reduction of vibration and noise is of particular interest due to the constant presence of randomly located and wandering imbalance of laundry in the drum and low requirements for accuracy of its manufacture and assembly of parts and assemblies. A mathematical model of oscillations of a multiconnected tank-drum system on elastic suspensions for the main types of machines and spin centrifuges with a horizontal axis of rotation is created. The model is developed in a linear formulation based on the Lagrange equation of the II kind for a washing machine. The accuracy and adequacy of the mathematical model was tested directly on the field object by measuring noise, vibration, forces in the supports and stress distribution in the individual elements and components of the machine in the entire range of drum speeds. Studies of the nature of system oscillations depending on the change in position and attachment points of elastic and damping elements were performed using simulation in the Simulink environment. As a result of research, the basic requirements for the layout of horizontal rotary machines of the drum type were experimentally confirmed: the center of mass of the tank must lie on the axis of rotation of the drum; the axis of rotation of the drum should be the main central axis of inertia of the tank; the center of mass of the tank must coincide with the center of mass of the loaded drum; the center of rigidity of the system of elastic supports must coincide with the center of gravity of the tank, and the main axes of rigidity – with the main central axes of inertia of the tank; the main axes of the constant viscous friction must coincide with the main central axes of inertia of the tank. The results of the theoretical study were applied to the problem of evaluating the efficiency of a liquid auto-balancing device for a proper squeezing machine depending on its dynamics.

Comparative Analysis for the Anti-Vibration Isolation of a Foundation in the Case of an Elevating Mechanism

To study the vibrations of a Multiparker lift lift model, use various models for the lifting mechanism. In order to increase the number of parking spaces in the center of the Romanian capital, it is intended to design a parking lot on several levels above the Dâmbovița river, which would include two elevators for lifting and lowering cars. One of the elevators works as a system of translating cam and roller translating follower and thus, due to transmitting the torque from the electric drive motor to the cam, respectively changing the travel direction at the end of the route, upon starting and stopping, vibrations may occur within the elevator. This system must be supported on a foundation in order to achieve anti-vibration isolation. There are several possibilities to achieve this anti-vibration isolation, among which one can mention the elastic suspensions mounted on springs, rubber mats or standardized elastic rubber elements

ВПЛИВ МОМЕНТНОЇ НЕЗРІВНОВАЖЕНОСТІ ТА ПОЛОЖЕННЯ ЦЕНТРУ ЖОРСТКОСТІ НА ВІБРОАКТИВНІСТЬ ГОРИЗОНТАЛЬНЫХ БАРАБАННИХ МАШИН

The issues of reducing the vibration caused by rotating rotors at the frequency of the first rotor harmonic (so-called rotor vibration) are among the most important in the design, manufacture and operation of almost all types of modern rotary machines. The washing machine as an object of study of the dynamics and reduction of vibration and noise is of particular interest due to the constant presence of randomly located and wandering imbalance of laundry in the drum and low requirements for accuracy of its manufacture and assembly of parts and assemblies. A mathematical model of oscillations of a multiconnected tank-drum system on elastic suspensions for the main types of machines and spin centrifuges with a horizontal axis of rotation is created. The model is developed in a linear formulation based on the Lagrange equation of the II kind for a washing machine. The accuracy and adequacy of the mathematical model was tested directly on the field object by measuring noise, vibration, forces in the supports and stress distribution in the individual elements and components of the machine in the entire range of drum speeds. Studies of the nature of system oscillations depending on the change in position and attachment points of elastic and damping elements were performed using simulation in the Simulink environment. As a result of research, the basic requirements for the layout of horizontal rotary machines of the drum type were experimentally confirmed: the center of mass of the tank must lie on the axis of rotation of the drum; the axis of rotation of the drum should be the main central axis of inertia of the tank; the center of mass of the tank must coincide with the center of mass of the loaded drum; the center of rigidity of the system of elastic supports must coincide with the center of gravity of the tank, and the main axes of rigidity – with the main central axes of inertia of the tank; the main axes of the constant viscous friction must coincide with the main central axes of inertia of the tank. The results of the theoretical study were applied to the problem of evaluating the efficiency of a liquid auto-balancing device for a proper squeezing machine depending on its dynamics.

Compliance, mass distribution and contact forces in cursorial and scansorial locomotion with biorobotic physical models

Locomotion in unstructured and irregular environments is an enduring challenge in robotics. This is particularly true at the small scale, where relative obstacle size increases, often to the point that a robot is required to climb and transition both over obstacles and between locomotion modes. In this paper, we explore the efficacy of different design features, using ‘morphological intelligence’, for mobile robots operating in rugged terrain, focusing on the use of active and passive tails and changes in mass distribution, as well as elastic suspensions of mass. We develop an initial prototype whegged robot with a compliant neck and test its obstacle traversal performance in rapid locomotion with varying its mass distribution. Then we examine a second iteration of the prototype with a flexible tail to explore the effect of the tail and mass distribution in ascending a slope and traversing obstacles. Based on observations from these tests, we develop a new platform with increased performance and a fin ray wheel-leg design and present experiments on traversing large obstacles, which are larger than the robot's body, of this platform with tails of varying compliance. This biorobotic platform can assist with generating and testing hypotheses in robotics-inspired biomechanics of animal locomotion.

Some problems of increasing reliability and safe operation of heavy mining machines

Abstract. In the work, the following rubber parts were subject to research: rubber-metal blocks (BMR) of a prismatic shape, rubber vibration isolators (VR) with a complex free surface shape, rubber-metal vibration isolators (VRM), as well as layered vibration isolators (VRMS). Their use in the design of vibration protection systems for heavy mining vibration machines (vibrating feeders, vibrating conveyors, mixers, etc.) is very relevant. To determine the parameters of rigidity, temperature of dissipative heating and durability of these parts of different configurations, the universally constructive-deformation parameter ( was used. On the basis of the energy criterion, the basic relationships were obtained, which make it possible to determine the indicators of the durability of the designed rubber parts. To determine quantitative indicators of reliability of the vibration isolators under the study, a set of actions was planned to register their failure parameters. The Weibull’s law was adopted as the main distribution law. The goal was to determine such reliability indicators as the probability of no-failure operation for time t, the value of ninety percent MTBF and the boundaries of the confidence interval, in which the actual value of the ninety percent MTBF of the tested rubber parts is located with a 90 % probability. The results of the registration of parameters during testing for the reliability of a batch of vibration isolators of the VRM type for about 16 years are given; received an array of data on failures and their operating time. The results of measurements of the values of the main physical and mechanical characteristics of vibration isolators are presented. The failure criterion of vibration isolators was taken as their main parameters exceeded the permissible values. The results showed that the hypothesis of using the Weibull’s distribution law as a theoretical description of the occurrence of failures is confirmed. The obtained values of the quantitative indicators of the reliability of rubber vibration isolators of elastic suspensions of heavy mining machines are confirmed by theoretical calculations and experimental studies.

Технологии групповой микрообработки для производства чувствительных элементов инерциальных МЭМС датчиков

The paper presents various variants of inertial MEMS sensors of tactical and navigation accuracy class used in the Russian aerospace industry. Currently, the microelectronics center of Joint Stock Company “Russian Space Systems” is carrying out a number of works on the development of technologies for group microprocessing of quartz and silicon sensitive elements for such sensors and their introduction into mass production. In this case, the main task of the study is to increase the accuracy and repeatability of the geometry of elastic suspensions of MEMS sensors. The developed technologies made it possible to ensure the formation of silicon elastic elements of MEMS accelerometers and gyroscopes with an accuracy of volumetric dimensions up to 1 micron; to increase the precision of micromachining of quartz sensitive elements by a factor of 5 in comparison with traditional technology. Currently, most of the mastered technologies are implemented in the serial production of sensitive elements of inertial MEMS sensors and are used in onboard systems of aerospace devices and vehicles.

Development of a plasma electroacoustic actuator for active noise control applications

Conventional loudspeakers generate sound through the vibration of a diaphragm, attached to a rigid frame through elastic suspensions. Although such construction is satisfactory for sound diffusion in steady environments, it is likely to fail in harsh conditions, which is often the case for active noise control applications. Plasma-based actuators appear to be a promising alternative since they do not involve any fragile moving parts. In this paper, a positive corona discharge actuator in a wire-to-mesh geometry is proposed in the perspective of active noise control applications, as it is capable of generating sufficient sound pressure levels with limited signal distortion. The study introduces analytical and numerical models aiming at characterizing the sound field generated by the corona discharge actuator. The numerical simulation can facilitate the designing of such transducers. The acoustic power of the experimental prototype is increased through the optimization of emitter wires arrangement. The comparison of analytical model and numerical simulation with the experiment is presented. The analytical model successively describes the low frequency sound pressure field, while the numerical simulation is valid in the broader frequency range.

The hybrid action tool for operations of cleaning of turbine units cavities

The paper deals with the hybrid action tool for cleaning of cavities and elements of turbine units whose operation is based on a combination of action of a water-ice flow with mechanical shock influence of the small concentrated masses mounted on elastic suspensions. Receiving energy from the flow, the masses, performing self-oscillating motion, come into contact with the treated surface having a layer of strong contamination, and create a multipoint shock-cyclic loading of the surface, which results in active development of initial defects of the contamination film, due to which the following action of the water-ice stream produces better and more productive cleaning. It is shown that the generated local stresses, determined on the basis of Hertz contact problems, reach 15-20 MPa, do not have a significant effect on the surface of the base, which is a thin curves shell, do not change the state of its surface in the plane of adhesion, but result in defects in surface film in the form of cracks and delaminations . In this case the film is eliminated by water-ice flow more dynamically. The use of water-ice jet, formed by the original tubeless device, enables the formation of a wide flow (with the top angle of p/12… p/6) and the work of its ice particles is spent on grinding the surface film. The jet stream cleans the surface and removes the products of destruction beyond the impact.The use of a hybrid tool has increased the productivity of treatment with the wetting angles of the jet flow, different from p/2, by more than 30%, while the consumption of cryogenic liquid (liquid nitrogen) is reduced by 20-25%.The process modeling is performed, the conditions of the destruction of the adhesive bond of the contaminant film with the surface are estimated, the conditions of its rational execution are determined.