Vibration Protection Research Articles

The Concept of Vibration Protection and an Overview of the Global Market of Vibration Protection Materials

Due to the development of modern technologies, the number of sources initiating vibrations and noises has significantly increased. A variety of techniques are used to eliminate the negative impact of extraneous noise and vibrations. The article presents the concept of vibration protection, the options and mechanism for selecting coatings, and an overview of the global market for vibration-proof materials. The most common methods of vibration protection are vibration isolation and vibration damping, implemented by using materials with appropriate properties. Vibration isolation of vehicles is carried out by surface treatment with special mastics or coating with substrates as well as with the usage of hydraulic vibration supports. To minimize the impact of vibrations on buildings and structures, special fastenings and suspensions, vibration isolators, supports, soft rolled and sheet materials are used. For vibration isolation of machine tools and precision equipment, separate supports, a layer of elastic material placed between the machine and the foundation, a floating floor on an elastic base are used. The article presents a brief analysis of metal, rubber and rubber-metal vibration isolation supports in the budget, medium and premium price segments. Vibration damping is performed using special plates, which are available on the market in the form of rolled materials and multilayer plates. Vibration-absorbing composite polymer coatings based on thermosetting polymers have become widespread. The industry of Russia and foreign countries has established the production of vibration-absorbing reinforced sheet materials. Russian scientists are also actively developing new types of coatings: gradient polymer composite materials, thermoplastic extrusion films, laminated fiberglass polymers, etc.

Quasi-zero rigidity condition for static force characteristic of parallelogram mechanism for seat vibration protection system

Introduction. Reducing vibration effects on machine operators is an urgent task; it allows to minimize the impact of vibrations on health, increase efficiency and attention. Accuracy and productivity can be improved. The problem of vibration protection is relevant for all types of machines, the working bodies of which interact with the soil and road surface. One of the impact reduction directions, along with vibration protection of cabs, is the development of vibration protection systems for operator seats. It is promising to use the effect of quasi-zero rigidity, which makes it possible to effectively damp low-frequency oscillations. For the proposed design based on a parallelogram mechanism, it is necessary to determine the condition for the horizontalness of the middle section of the static power characteristic.Materials and Methods. For the developed design scheme, using well-known power static and geometric relationships, novel analytical relationships between the parameters of the initial data and the vertical lifting force of the mechanism were derived. The initial parameters include the linear dimensions of the mechanism, the size of the quasi-zero rigidity zone, the weight of the chair with the operator, and the spring stiffness. When deriving analytical dependencies, the coordinates of the points of the mechanism moving and stationary relative to their own base were used.Results. The use of the developed analytical dependencies allows, for the given parameters of the initial data, to build a static power characteristic of the mechanism. The middle section of the characteristic is close to horizontal, but in general it is not horizontal. As an example, a static characteristic is given for a set of initial data values, the middle part of which is not horizontal. Equating the values of the vertical force of the mechanism at the left and right boundary points of the middle part of the characteristic made it possible to determine analytical dependences for ensuring quasi-zero rigidity.Discussion and conclusions. The obtained analytical expressions for ensuring the horizontalness of the middle section of the static power characteristic were verified. Applying the derived conditions decreases the number of parameters in the original data by one. An increase in the two dimensional parameters of the mechanism significantly reduces the required rigidity of the mechanism spring, which reduces the metal consumption.

Численно-аналитический метод преобразований для анализа нелинейных математических моделей полиномиальной структуры

The article considers a scientific problem of investigating mathematical models with polynomial nonlinearity, which are represented by systems of nonlinear differential equations. There is presented a numericall-analytical transformation method for investigating nonlinear dynamical systems with many degrees of freedom of polynomial structure. As opposed to the analogues, this method allows solving a wide range of problems for nonlinear systems 
 of general polynomial structure while reducing the computational resource intensity. An algorithm of the method 
 of transformations for investigating the nonlinear dynamic systems with m degrees of freedom is given. The research of stability of solutions of nonlinear dynamic systems with m degrees of freedom is carried out. Algorithmic formulas of transformation method for the solution of systems with nonlinearity of the fourth degree are given. Computational experiments on solving systems of differential equations with a small nonlinear part in the form of a multinomial 
 of the sixth degree using the transformation method show fourth order accuracy in computation. A nonlinear mathematical model of the vibration protection system is investigated by the presented method of transformations. The theorem on determination of the stationary state for systems of differential equations of polynomial structure by transformation method is proved. Algorithmic formulas for computation are presented. A general matrix form for vector indices is presented. Formulas for economical computation of right-hand sides of polynomial structure are presented and it is proposed to apply Pan's scheme with coefficient preprocessing. This method allows studying the different modes 
 of nonlinear models dynamics, for example, to determine such extreme modes as resonance, sub-harmonic, and polyharmonic modes. As an example of the method application, the vibration protection problem of the tower from external periodic influences was solved. The transformed solution takes into account all nonlinear polynomial components. The method allows to investigate the dynamics of a wide range of nonlinear systems with the necessary accuracy

Use of the Belleville spring package in the vibration protection mechanism of the operator’s seat

Reducing the vibration effects on the operator of a construction, road and other machines is a relevant objective, since its accomplishing improves the efficiency and accuracy of the work performed by machines and reduces the risk of operators’ occupational diseases. Vibration protection systems with the effect of quasi-zero stiffness are promising. To produce this effect, Belleville springs packages can be used. They are a way to create a simple, reliable and inexpensive passive mechanism of the vibration protection system of the operator’s seat. The influence of the static characteristic center slope of two Belleville springs packages on the maximum acceleration of the load under the sinusoidal kinematic excitation of the seat base movements is investigated. The static characteristic center slope of the spring packages was characterized by the coefficient that affects the type of the static characteristic according to the known analytical expressions for the separate spring force. To obtain the chair acceleration values in a fixed coordinate system, we used a simulation mathematical model developed in the Simscape Multibody package for modeling mechanical systems of the MATLAB mathematical system. The model used blocks of a fixed coordinate system, a sliding joint and a rigid body forming a chain. The maximum acceleration of the chair in a fixed coordinate system was defined during a predetermined period of time at the end of the transition process under the steady state oscillations. When conducting the computational experiment, the specified oscillations amplitude of the chair base and the angular frequency of these oscillations varied. For a proper comparison of the experimental results in the form of graphical dependencies of the maximum acceleration on the amplitude and frequency, the ranges of acceptable and unacceptable arguments combinations were selected for the two spring packages. The combinations of amplitude and frequency were considered unacceptable when the maximum deformation of the spring package went beyond the static characteristic maximum. For the two packages of springs, the acceptable regions were different, therefore their intersection used for the comparative analysis, was obtained. The springs package with a relatively high stiffness in the center of the static characteristic is found out to generally provide better vibration protection of the chair in the entire acceptable range of arguments. Simultaneously, a package with lower stiffness in the center of the characteristic dampens vibrations better in the small amplitudes area, i.e. when operating in the quasi-zero stiffness area.

Study on the influence of structural form and parameters on vibration characteristics of typical ship structures

Abstract For the plate or multicabin structure of ships, the vibration transmission characteristics have a great correlation with the structural mode. When the excitation force frequency get close to the natural frequency of the structure, strong vibration and sound radiation will occur. Therefore, it is very important and meaningful to study the vibration characteristics and protection methods of ship structures. Based on the classic finite element method, this article studies the influence of structural forms and parameters on the vibration characteristics of typical ship structures. Taking the multicabin structure as a benchmark structure model, the influence of the structural form on vibration mode and transmission characteristics of the target deck and other cabin decks in the multicabin structure was analyzed. Then, without changing the original structural layout, the effects of different structural parameters on the vibration mode and transmission characteristics were analyzed. Finally, the vibration protection process of the ship structure was formed. The results of this study can provide methodological basis and data reference for relevant research in future.

Estimation of Dynamic Characteristics of Vibration Protection Systems of a New Type for Water Transport Vessels

The use of traditional means of vibration isolation of ship power plants does not always give the desired effect, which predetermines the need to search for and use fundamentally new devices to improve the efficiency of vibration isolation of a ship engine. This can be achieved by installing active-passive vibration isolators in the elastic mounts of the engine, such as electromagnetic hydraulic vibration isolators (EHVO) for auxiliary engines and other marine equipment. Despite the seeming simplicity of the design and principle of operation, the calculation of EHVO is a rather complex problem, the solution of which is associated with a number of difficulties due to the specific features of electromagnetic devices, since their calculation is associated with a large number of factors and limitations. The known functions of time obtained by solving the equations were used to calculate the dynamic parameters of the EHVO: vibration energy, periodicity, overheating of the coils and efficiency

Dynamics of the Rolling Stock and the Choice of Parameters of Vibration Dampers

Modern railway rolling stock should meet requirements regarding comfort (maximum travel speed with minimum vibrations of wagons, noiselessness of movement, etc.).To eliminate the influence of dynamic loads, rolling stock is equipped with vibration dampers. The objective of the work is to select the parameters of the vibration dampers of rolling stock, depending on its characteristics, to ensure the due indicators of comfort and safety of transportation of passengers and goods by rail. To achieve this objective, applied methods of mathematical modelling were based on numerical programming of operation of dynamic systems. The indicators of vibration dampers are evaluated according to the results of studies of the dynamics of the rolling stock (in particular, of vibration protection rates).Assessment of dynamic state of the rolling stock implies application of methods of mathematical and physical modelling, which include the development of a physical and mathematical model, a calculation algorithm, and computer programming. The study of the mathematical model by numerical methods makes it possible to carry out a multifactorial experiment using a large number of input parameters (factors) and to select the characteristics of vibration dampers that are optimal for the conditions under consideration.To solve dynamic problems, the harmonic perturbation model, which is the most widespread, was specified in the form of a sinusoid with a period corresponding to the rail length.A quantitative assessment of the vibration process (frequency, amplitude) makes it possible to identify the main processes occurring in the system under consideration under various types of external load. The introduced assumptions related to rigidity, mobility and geometric immutability of the system allow determining the methods for obtaining a mathematical model and considering the vibrations as flat ones.The equations were solved in MathCad Prime 4.0 package using the Runge–Kutta method with automatic step selection. The subsequent study of the properties of the dynamic system was carried out by changing the resistance parameter of dampers of the first stage of spring suspension, while recording the values of the amplitude of the vibrations of the system and the period.The analysis of the results has shown that the vibration period of the body and bogies under any changes in the resistance parameter of the damper remains unchanged, while rational parameters of resistance of axle box dampers have been revealed for specified indicators. Hydraulic vibration dampers with the revealed parameters used on rolling stock help to reduce wear and damageability of running gears, improve ride comfort and traffic safety, as well as to reduce repair and maintenance costs.

Methodology of ensuring the efficiency of mechanical processing due to the application of vibration monitoring and vibration protection means

The article describes the main causes and sources of impulse - vibration effects on the elements of the "machine tool - device - tool - detail" system. The paper deals with the development of methods for increasing the efficiency of machining due to the rational choice of technical solutions for vibration protection by design and technological methods with the use of vibration monitoring. A criterion for the efficiency of machining is given, which is determined by a matrix using scalar parameters, which are traditionally used for vibration diagnostics. A complex criterion for the quality of machining has been determined, which describes the indicators of the geometric accuracy of the machined surface. The block diagram of algorithms for selection and rational use of structural and technological methods of vibration protection of technological system elements is presented. Vibration and technological criteria for choosing solutions for vibration protection and monitoring are proposed. The implementation of the developed algorithms is considered on examples of machining and numerical estimates are given, confirming the high quality of the developed solutions.

Introduction of technologies, methods and methods of protection against vibration effects of rolling stock

The article discusses the causes of vibration from urban rail transport, as well as the ways of its propagation. The assessment of the health risk of the population of urban agglomerations living near the transport infrastructure, when exposed to vibration and traffic noise, has been carried out. The analysis made it possible to identify factors that pose a potential danger to human life and health, as well as the possibility of causing harm to health when exposed to noise. A forecast of changes in the sanitary and hygienic situation in conditions of stabilization or changes in the levels of exposure to noise on the population has been made. The substantiations of the effectiveness of vibration and noise protection preventive measures are formulated.The article contains calculations of the health risk of the population exposed to excess exposure from transport facilities in order to predict and calculate the vibro-acoustic situation for a long period, as well as assess the effectiveness of vibration and noise protection measures aimed at implementing methods to ensure sanitary-epidemiological and social well-being of the population.According to the results of the calculation, it was found that the risk indicator on railway sections using sub-ballast mats with vibration-absorbing properties was determined as acceptable from the point of view of fulfilling sanitary and epidemiological requirements to ensure the social well-being of the population of urban agglomerations.

Минимизация виброактивности малошумных вентиляторов

Reducing the vibration activity of low-noise fans is becoming the most important direction in the creation of their new modifications. It is analytically shown that the efficiency of vibration damping of a mechanical system depends not only on the ratio of natural frequencies, vibration frequencies and damping coefficient, but also on technical solutions for installing dampers, for example, on an elastic or rigid foundation. The article proposes an algorithm for minimizing the vibration activity of a mechanical system which is an axial low-noise fan. To solve the problem of minimizing noise in the operating mode of the fan, an innovative technical solution for the construction of the case is being considered - the walls are made in the form of a "sandwich" consisting of layers of structural materials that provide strength characteristics, as well as noise and vibration protection. Contribution of the authors: the authors contributed equally to this article. The authors declare no conflicts of interests.

Algorithm for fatigue degree determination of the human operator under the influence of vibration

The issue of selecting methods for studying human muscle fatigue in the operator-joystick system is considered. Methods for removing potentials from human muscles are given. The applicability of the chosen method for evaluating the work of the research object is considered. A review of methods for diagnosing muscle fatigue parameters in the operator-joystick system is given. Keywords model, algorithm, vibration protection, control system, microcontroller

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

МОДЕЛИРОВАНИЕ РАБОТЫ ВИБРОЗАЩИТНЫХ СИСТЕМ ТРАНСПОРТНЫХ СРЕДСТВ С УПРАВЛЯЕМЫМ ДЕМПФИРОВАНИЕМ

The article discusses approaches and methods for mathematical and information modeling of oscillatory processes that occur during the operation of vehicle vibration protection devices. A schematic diagram of a lever relaxation vibration protection system is proposed. The main operational advantages of the proposed scheme are indicated. Both the theoretical foundations of mathematical modeling and their application in modern computer modeling systems are outlined.

Improvement of Machine Protection against Vibration

The need to improve the methods of vibration protection for power plants and technological equipment is substantiated in the article. When using the traditional elastic suspension for the vibration isolation efficiency, the stiffness of the suspension should be minimal, but to limit the mobility of the object protected from vibration, it should be, in contrast, maximum. In order to eliminate this contradiction and increase the efficiency of the vibration isolation mechanisms, the use of additional special devices in the form of stiffness compensators is proposed. A theoretical substantiation of the advantages of stiffness compensators based on the analysis of the vibration isolation mechanisms force characteristics is given. It is proved that the vibration-isolating mechanisms with stiffness compensators significantly change the function of the force transmitted to the base of the mechanism protected from vibration. An expression for evaluating the efficiency of using vibration isolators with stiffness compensators as compared with conventional spring-loaded elastic mechanisms is presented. Design of the vibration isolator with stiffness compensators on the basis of spherical rolling bodies is proposed. Theoretical materials confirming the effectiveness of the proposed technical solution are given. Vibration isolating mechanisms with stiffness compensators provide stable equilibrium of the vibration system, as well as allow to change the total stiffness of the vibration isolator and set the shape of the force characteristic. As a result, it is possible to change the frequency of natural vibrations of the system without changing its carrying capacity.

Determining the structure and parameters of the human model subjected to vibration

This article presents results from an experimental study of the frequency properties of a sitting person. This analysis shows that in order to define the structure and parameters of a human body model, it is necessary to find the only solution to the problem of determining the model parameters. Otherwise, this model cannot be used to build vibration protection systems, which is its main purpose. This problem was solved for a two-mass human model. To do this, the total model mass and although the amplitude-frequency response and input frequency impedance for both solids in the model structure are needed to be known. In addition to this, the influence of multi-articular muscles on the frequency characteristics of a human body is found using mechanical models with an arbitrary number of degrees of freedom. In particular, the possibility of the existence additional antiresonance frequencies on the upper mass is shown.

УПРАВЛЯЕМЫЕ ВИБРОЗАЩИТНЫЕ СИСТЕМЫ: ДИНАМИЧЕСКОЕ ПРОГРАММИРОВАНИЕ И ОПТИМИЗАЦИЯ

The article presents new scientific results of research in the field of the theory of optimal control of oscillatory processes related to the manifestation of a local effect in the dynamic programming method, the implementation of a step-by-step strategy for optimizing a dynamic system for control and finding algorithms for optimal positional control. Examples are given of finding positional control in vibration protection systems with an additional controlled elastic and damping link, as well as with a potential energy recuperator.

Energy analysis of transfer processes and their main characteristics in thermo mechanical damping systems

The article discusses the energy analysis of transfer processes in the damping system. The basic theoretical foundations based on the equations of the energy balance of the hydraulic shock absorber and the law of conservation of energy are presented. The proposed approach is associated with the development of a methodology and scheme for calculating the technical system of vibration damping. The schemes of interaction of the system through the phenomena of transfer and functioning of the vibration protection system with the environment are presented. It is shown that damper systems are based on the physical process of transformation of mechanical energy into thermal energy with subsequent dissipation into the environment. The total energy distribution in damping problems takes the following form the mechanical energy of motion is absorbed due to the hydraulic resistance of the liquid and turns into a dissipative component, which can reach 80% of the total energy. A mathematical model of the law of conservation of energy is presented which includes a dissipative function. The analysis of how it is possible to design work processes in a shock absorber due to energy dissipation and similarity criteria: Euler, Froude, Reynolds, etc. As a result of physical experiments, it was found that the movement of a fluid in hydraulic calibrated throttles gives rise to cavitation and various physical phenomena and accompanying processes, in which there is a significant change in the energy balance and energy dissipation in non-stationary modes of fluid movement.
 The dependence of the total power loss of the shock absorber under changing operating conditions, and the diagram of physical processes and energy transformations in the problems of damping, which are in dissipative processes, are given. The article describes the principles that can be used for the design of devices and modules of damper systems of a wide class with the possibility of energy recovery and accumulation by introducing a damper into the system, for example, a motor generator, an inductor with permanent magnets or a peso element in the design of a traditional telescopic shock absorber.

Protection of precision spacecraft equipment from internal sources of vibration

The work is devoted to the protection of a spacecraft from the influence of unacceptable internal vibration sources. The urgency of reducing the vibration activity on board the spacecraft to improve the accuracy of the target equipment is indicated. A particular problem of vibration protection of the spacecraft platform from a vibration source – an electric pump unit of a liquid thermal control system – is being solved. The basic requirements for electric pump unit vibration protection have been determined. Possible ways to reduce the level of vibration excited by the electric pump unit on the surface of the spacecraft fixation are considered. Particular attention is paid to such vibration protection methods as damping and vibration isolation, implemented by installing special vibration protection devices between the source (electric pump unit) and the object (spacecraft) – vibration isolators and vibration dampers. The principles of operation of vibration dampers and vibration isolators, the most common materials for vibration dampers are described. Examples of constructive solutions for linear single-axial vibration isolators are considered, recommendations for the use of promising products are developed. Particularemphasis is placed on the use of metal rubber as a material for vibration isolators. With regard to a specific design of electric pump unit, a diagram of the spatial structure of vibration isolation is proposed. Formulas for calculation are given in detail, a mathematical model of the vibration isolation system is developed. The procedure for calculating the parameters of the system has been formed. Based on the model, the maximum possible level of vibration suppression in the mid-frequency region was determined. Minimum required number of operable pixels was identified for monitoring the water surface with sufficient accuracy and reliability.

Method for predicting the technical appearance of grain and forage harvesters of new generations with a substantiation of the structure of their vibration protection system

The work is devoted to the development of a method for predicting the technical progress of self-propelled grain and forage harvesters and the substantiation of systems for their implementation. The necessity of improving the existing and developing new methods for predicting the properties of machinery, taking into account the existing features of the agro-industrial enterprises operation, were substantiated. A new technique for the synthesis of the technical appearance of products is proposed with the possibility of identifying the nomenclature of defining parameters based on the actual change in their values, ranking indicators with highlighting the most important of them for each category of business entities, forecasting using fuzzy logic methods, as well as justification of required machine systems of new generations using object-oriented design methods. A description of each of the stages of the forecasting process is given. On the basis of mass-produced grain and forage harvesters in Russia, an analysis of their constructive evolution with the allocation of stable and inherited development criteria has been carried out. A comparative analysis of the actual change in the defining parameters for machinery of the current and previous generations is shown. The technique and the results of forecasting the selected defining parameters are presented. It is shown that the predicted level of properties forms multidirectional requirements, which, from the point of view of implementation on the basis of existing design approaches, are contradictory. Taking into account the existing problems of motion dynamics and vibration loading of the workplace of operators of machinery of the current generation, it is stated that those multidirectional requirements are unattainable. Using the methods of object-oriented analysis, an object-target diagram of classes of possible options for constructing a vibration protection system for machinery of a new generation has been compiled. The relations of inheritance, which established the hierarchical decomposition of goals, were determined. It is shown that it is more expedient to control the selected vibration processes of combines without significant changes in their design and layout by means of systems for dynamic stabilization of the body and vibration isolation of the operator's workplace.

Experimental studies of vibroacoustic characteristics of the basic structure parts of the traction rolling stock and transportation technological vehicles

The paper presents the obtained results of the vibration studies, particularly, the structural elements of the railway rolling stock, created at the driver workplaces, structures of the internal combustion engines, hoods, frames while moving and a stationary machine, which determine the vibration spectral composition and propose the specific engineering solutions for the noise and vibration protection system.