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The diagnosis of structural damage usually belongs to a mathematical inverse problem. This work presents a novel frequency-shift flexibility sensitivity algorithm for structural damage assessment using only the first-order vibration mode to achieve the goal of successfully identifying structural damage with fewer modal parameters. The core idea of the proposed method is to make the first-order vibration mode contribute the most to a structural flexibility matrix through the frequency-shift operation. A high-precision flexibility matrix can be obtained after the frequency-shift operation, which only needs the first mode of structural free vibration. Through this special advantage, structural damage coefficients can be accurately calculated by the frequency-shift flexibility sensitivity equation. Thus, a reliable identification result can be obtained according to the values of the calculated damage coefficients. In some engineering applications, another advantage of the proposed method is that it does not require a complete finite element modeling process, as long as a few lower-frequency vibration modes of the intact structure are measured. A truss structure and a beam structure are used as two numerical examples to demonstrate the proposed approach. The results show that the proposed method has higher calculation accuracy than the ordinary flexibility sensitivity method by using only the first-order vibration mode. The proposed method can overcome possible misdiagnosis of the ordinary flexibility sensitivity method. It also has been shown that the proposed method may have the potential to identify minor damage in a structure. Using the experimental data of a steel frame structure, the effectiveness and reliability of the proposed method have been further verified. The proposed method provides a simple way for structural damage identification with only a few vibration modal data.

This paper attempts to solve the turbine failures reported by a hydropower station, namely, the violent vibration in the runner region under a special working condition and the blade cracking on the outlet edge near the lower ring. For this purpose, the entire flow channel of the turbine was simulated by computational fluid dynamics (CFD) on ANSYS, and the runner strength and mode of shaft assembly system (SAS) were computed by the liquid-solid coupling algorithm. The calculation results show that severe low (negative) pressure appeared on the outlet edge near the lower ring, excess stress was observed in that area, and the resonance occurred as the fifth and sixth order natural frequencies of the SAS were the same with the rotation frequencies of the blade. On this basis, the original blade was modified repeatedly. Through the modification, the flow field distribution in the runner region and the blade strength were both greatly improved, and the SAS natural frequencies were kept away from the various external excitation frequencies, laying a solid basis for the safe and stable operation of the turbine.

Identifying relatively weak areas is of great significance for improving the seismic reliability of structures. In this paper, a modal strain energy decomposition method is proposed, which can realize the decoupling of the comprehensive modal strain energy of a planar structure into three basic modal strain energies. According to the decomposition results, the modal strain energy decomposition diagram and the modal strain energy cloud diagram can be drawn so as to realize the quantitative and visual analysis of the vibration modes. The method is independent of load cases and can identify relatively weak areas of a structure from the perspective of inherent characteristics. The comparison with the shaking table test results of the two-story shear wall shows that the modal strain energy decomposition method can effectively identify the type of the relatively weak area of a structure and locate the position of the relatively weak area. Finally, the 6-story shear wall is analyzed by the modal strain energy decomposition method, and the relatively weak areas under the first two vibration modes are identified.

The aim of the study is to propose a diagnostics method based on blade’s vibration model in frequency domain. Amplitude spectrum A(ω) and phase spectrum φ(ω) have been experimentally identified which define transfer function G(jω) = P(ω) + jQ(ω) and their real P(ω) and imaginary Q(ω) parts. Transfer function G(jω) and resulting frequency, amplitude, phase characteristics and real P(ω) and imaginary Q(ω) parts are parts of blade’s diagnostics model. Changes in those characteristics are directly related to changes in the technical condition of the blades. It has been noticed that small changes in the technical condition cause large changes in frequency characteristics, which proves their usefulness in the diagnosis process.

Dynamic mesh atomizers have been widely used in various fields because of their compact structure, low energy consumption, and low production costs. The finite element method is an important technique to analyze the factors affecting the atomization performance of dynamic mesh atomizers. However, at present, there is a lack of decisive solutions to the basic problems of boundary setting in terms of the simulation and vibration displacement characteristics of atomizers under different vibration modes. In this paper, two errors were found in the Vibration Analysis of a Piezoelectric Ultrasonic Atomizer to Control Atomization Rate paper written by Esteban Guerra-Bravo et al. in 2021. First, in the finite element analysis, the boundary condition of the atomizing sheet was set to be fixed, which is inconsistent with the actual support situation and seriously affects the vibration of the atomizing sheet. Second, in the simulation result, from the first mode to the third mode, the growth rate of the maximum displacement at the center of the atomizing sheet was as high as 77.12%, even up to 221.05%, which is inconsistent with the existing vibration theory. In view of these errors, in this paper, the working principle of dynamic mesh atomizers is analyzed and the vibration equation of the atomizing sheet under peripheral simple support is derived. Through comparison with the literature, it was proven that the boundary setting and vibration displacement of the atomizing sheet in the original paper are unreasonable. By measuring the atomizing rate of the atomizing sheet under different boundary conditions, it was proven that the peripheral freedom of the atomizing sheet should be greater than or equal to 1, namely, peripheral freedom or peripheral simply supported. The vibration displacement theory was used for the simulation, and the relationship between the vibration displacement and resonant frequency of the atomizing sheet under peripheral simple support was measured. It was found that with the increase in the resonance frequency, the maximum displacement of vibration modes with only nodal circles was larger than that of the other vibration modes, and the maximum displacement increased slightly with the increase in the number of nodal circles by about 0.98%.

As deformations of the main reflector of a radio telescope directly affect the observations, the evaluation of the deformation is extremely important. Dynamic characteristics of the main reflector of the Nobeyama 45 m radio telescope, Japan, are measured under two conditions: The first is when the pointing observation is in operation, and the second is when the reflector is stationary and is subjected to wind loads when the observation is out of operation. Dynamic characteristics of the main reflector are measured using piezoelectric accelerometers. When the telescope is in operation, a vibration mode with one nodal line horizontally or vertically on the reflector is induced, depending on whether the reflector is moving in the azimuthal or elevational planes, whereas under windy conditions, vibration modes that have two to four nodal lines are simultaneously induced. The predominant mode is dependent on the direction of wind loads., Comment: Accepted for publication in Journal of Vibration Engineering & Technologies

When the design of a vibration system requires a broad bandwidth, the numbers and the ratios of energy peaks become major design factors. In particular, within a specific range of frequency, an increase in the number of peaks can widen the valid working bandwidth by decreasing the distances between peaks. In this paper, a planar symmetric dual-body vibration system is used to implement desired work ratios at six target frequencies. The geometrical relation between vibration modes and energy peaks is investigated to develop the design method and introduces geometrical representation of vibration modes of a symmetric dual-body system together. Six vibration modes of a symmetric dual-body system are divided into two groups with three vibration modes that represent the centers of vibration. It is shown that the orthocenters of two modal triangles of each of two rigid bodies coincide with its center of mass. The frequency responses to both direct and base excitations are derived in terms of vibration centers and target frequencies, and thus work ratios are obtained. Finally, the derived equation of work ratios is used to determine the modal matrix composed of the vibration modes when the desired mass, specific work ratios, and target resonant frequencies are given. Consequently, the corresponding stiffness matrix is found and realized. Numerical examples of four cases with different work ratios are presented to illustrate the proposed design method.

In this paper, a frequency-adjustable tuning fork electromagnetic energy harvester is introduced. The electromagnetic vibration energy harvester can adjust its natural frequency according to a change in the environmental excitation frequency without any change to the structure. In the frequency-adjustable range, it can make the energy harvester resonant with the environment excitation, and the output frequency stays the same. The frequency-adjustable tuning fork electromagnetic energy harvester significantly increases the range of frequencies used. The operating frequency of the centre can be easily switched from 9.2 to 20 Hz, enabling the application of multiple excitation frequencies. In addition, the output power and power density are significantly increased compared to a piezoelectric tuning fork energy harvester of the same size. The peak power is 23.59 mW at 9.2 Hz, the power increases by 14.85 mW, and the power density increases by 169.88%. The experimental results show that the electromagnetic tuning fork frequency-adjustable conversion energy harvester can make the LED lamp work.

raw data acquired during experiments carried out in the hydraulics laboratory of the Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy

[ES] La Universidad Politécnica de Valencia desarrolló un banco de pruebas para pantógrafos con el uso de catenarias virtuales. El mismo consiste en una estructura en forma de pórtico con un sistema de excitación vertical eléctrico. Este será mejorado ampliando su rango de frecuencias, e incluyendo dos movimientos adicionales para la simulación: descentrado y peralte de curva. La investigación presente tiene como objetivo el desarrollo de un modelo virtual en elementos finitos del banco, para caracterizar el comportamiento dinámico y posteriormente utilizar el mismo, para realizar modificaciones y ampliar su rango de frecuencias de ensayo. Se realizó un análisis modal experimental a través de un martillo instrumentado y un acelerómetro. Con las FRF obtenidas y el programa Matlab® se reconstruyó un modelo virtual del banco para determinar las frecuencias naturales e identificar los modos de vibración principales. Después, con ayuda de los planos, fichas técnicas y datos reales, se desarrolló un modelo de elementos finitos con ayuda del programa ANSYS®. Se utilizó técnicas de modelado para representar todos los elementos de la estructura, así como sus respectivos ensambles. Utilizando los resultados del análisis modal experimental y del análisis modal de elementos finitos, se ajustó el modelo de elementos finitos para alcanzar los valores reales. Una vez ajustado el modelo de elementos finitos, se logró reproducir con excelente precisión el modo vertical y el modo lateral del banco de pruebas y con una precisión aceptable el modo axial y torsional con eje de rotación en ¿y¿., [EN] The Polytechnic University of Valencia developed a test bench for pantographs with the use of virtual catenaries. It consists of a frame-shaped structure with a vertical electrical excitation system. This will be improved by expanding its frequency range, and including two additional movements for the simulation: offset and curve camber. The objective of this research is the development of a virtual model in finite elements of the bench, to characterize the dynamic behavior and later use it, to make modifications and expand its test frequency range. An experimental modal analysis was performed through an instrumented hammer and an accelerometer. With the FRF obtained and a Matlab® program, a virtual model of the bench was reconstructed to determine the natural frequencies and to identify the main vibration modes. Then, with the help of the plans, technical sheets and real data, a finite element model was developed with ANSYS® program. Modeling techniques were used to represent all the elements of the structure, as well as their respective assemblies. Using the results of the experimental modal analysis and the finite element modal analysis, the finite element model was adjusted to achieve the actual values. Once the finite element model was adjusted, it was possible to reproduce the vertical mode and the lateral mode of the test bench with excellent precision as well as the axial and torsional mode (axis of rotation in "y") with an acceptable precision.

In this paper, a novel tuning fork structure for self-frequency up-conversion is proposed. The structure has an in-phase vibration mode and an anti-phase vibration mode. The in-phase vibration mode is used to sense the environment vibration, and the anti-phase vibration mode is used for energy conversion and power generation. The low-frequency energy collection and the high-frequency energy conversion can be achieved simultaneously. Theoretical and experimental results show that the tuning fork frequency up-conversion energy harvester has excellent performance. This structure provides the energy harvester with excellent output power in a low-frequency vibration environment. At the resonant frequency of 7.3 Hz under 0.7 g acceleration, the peak voltage is 41.8 V and the peak power is 8.74 mW. The tuning fork frequency up-conversion energy harvester causes the humidity sensor to work stably. The structure has the potential to power wireless sensor nodes or to be used as a small portable vibration storage device, especially suitable for the monitoring of the environment related to human movement.

How to control deformation and avoid resonance is the key to ensuring the safety of the super-long pipeline when it is floating in the sea. Based on the deformation warning value of pipeline prototype composite material obtained from laboratory tests, the raw water pipeline project in Tong’an Xiamen adopts wireless communication equipment to transmit data, supplemented by aerial photography technology to monitor and feedback the strain and vibration during the dynamic construction of long-distance pipeline floating transportation. Combined with dynamic construction, this monitoring method avoids excessive deformation and resonance of the steel pipeline during floating transportation, and prevents the destruction of the anticorrosive coating. The airtightness test after completion shows that the whole pipeline meets the acceptance requirements. The monitoring results show that the strain at the bent position of the pipeline is large in the process of floating transportation, and the jacking speed and position of the tugboats have an important influence on the deformation of the pipeline. The same type of project should focus on these aspects and timely feedback monitoring data. At the same time, the study also provides detailed strain, modal analysis and effective monitoring technology for the safety of offshore steel pipeline floating transportation.

This paper provides an experimental study and computer modeling analysis of vibration performance of full-scale wood truss joist floors, related to the static deflection and vibration mode/frequency and single-person-induced vibration. The vibration behavior of full-scale truss joist floors was investigated and the influences of the strongbacks on the vibration behavior were assessed. The results showed that the simulated predictions agreed well with the measured results. Strongbacks do not significantly affect the fundamental frequency of the truss joist floors but influence the second and third modal frequencies. The use of strongback rows at mid-span effectively decreased the maximum deformation of point loading at floor center. The effect of adding strongbacks at one-third of each span on decreasing maximum deformation at the floor center was minimal. The case of walking parallel to the joist produced higher acceleration response at the floor center than that of walking perpendicular to the joist. The closer the placements of strongbacks were to the mid-span, the more significant reduction of the vibration at floor center was. Two strongback rows at mid-span performed the best effect on reduction of vibration response at floor center. However, the use of strongbacks had limits of reduction peak acceleration of the sheathing between the joists. The study provides a valuable guide for future vibration serviceability study and design optimization of wood truss joist floors.

In order to evaluate the impacts of parameter uncertainty and nonparametric uncertainty on the natural characteristics of a dual-rotor system, a nonparametric probabilistic method based on random matrix theory is proposed. In this paper, a nonparametric Riccati whole transfer model is derived based on the maximum entropy principle and the random matrix theory. It is used to model a dual-rotor system with nonparametric uncertainty, as well as to calculate the natural characteristics of the system. Furthermore, the impacts of parameter uncertainty and nonparametric uncertainty on the natural characteristics at the intermediate support element and at the disk-shaft element are discussed using numerical simulations, and the results are compared with related references. The results show that at the same level of uncertainties, the effect of nonparametric uncertainty is often more significant than that of parameter uncertainty. The effects of uncertainties also increase with the level of uncertainties. The results of this paper provide a theoretical basis for the design of uncertain dual-rotor and multi-rotor systems.

Many reptiles, known as ‘sand swimmers’, adapt to their specific environments by vibrating or rotating their body. To understand these type of interactions of active objects with granular media, we study a simplified model of a self-excited spherical object (SO) immersed in the granular bed, using three-dimensional discrete element method (DEM) simulations. Modelling the vibration by an oscillatory motion, we simulate the longitudinal locomotion of the SO in three modes: transverse vibration, rotation around different axes, and a combination of both. We find that the mode of oscillation in y direction coupled with rotation around x-axis is optimal in the sense that the SO rises fastest, with periodic oscillations, in the z direction while remaining stable at the initial x position. We analyze the physical mechanisms governing the meandering up or down and show that the large oscillations are caused by an asynchronous changes between the directions of oscillation and rotation. We also observed that the SO’s rising rate is sensitive to three parameters: the oscillation amplitude, the oscillation frequency, f, and the rotation angular velocity, Ω. We report the following results. 1. When the frequencies of the rotation and transverse motion are synchronised, SO rises when Ω&lt, 0 and sinks when Ω&gt, 0, the average rising/sinking rate is proportional to |Ω|. 2. The rising rate increases linearly with the oscillation amplitude. 3. There exists a critical oscillation frequency, above and below which the rising mechanisms are different. Our study reveals the range of parameters that idealized ‘swimmers’ need to use to optimize performance in granular environments.

A guitar is constructed essentially of wood. However, each wood brings with it some specific characteristics. Its acoustic behavior is related to the elastic properties of the materials that compose it. It is known that the elastic properties of materials interfere not only in their mechanical resistance, but also in their dynamic behavior; a structure can vibrate more or less intensely depending on the material that composes it and its elastic properties. The present work analyzes the dynamic behavior of a computational guitar model through modal analysis calculated by the finite element method (MEF) applying boundary conditions that simulate the stiffness of the lateral bands and the tension of the strings on the easel and neck, obtaining answers in terms of natural frequencies and the corresponding forms of vibration modes. And so, compare with frequency responses obtained experimentally through the method of pulse excitation. The results show that the responses in numerical natural frequencies are similar to the values ​​obtained experimentally, indicative of belonging to the same mode of vibration. Una guitarra está construida esencialmente de madera. Sin embargo, cada madera trae consigo algunas características específicas. Su comportamiento acústico está relacionado con las propiedades elásticas de los materiales que lo componen. Se sabe que las propiedades elásticas de los materiales interfieren no solo en su resistencia mecánica, sino también en su comportamiento dinámico; una estructura puede vibrar de forma más o menos intensa según el material que la componga y sus propiedades elásticas. El presente trabajo analiza el comportamiento dinámico de un modelo computacional de guitarra mediante análisis modal calculado por el método de elementos finitos (MEF) aplicando condiciones de contorno que simulan la rigidez de las bandas laterales y la tensión de las cuerdas en el caballete y el mástil, obteniendo respuestas en términos de frecuencias naturales y las correspondientes formas de modos de vibración. Y así, compare con las respuestas de frecuencia obtenidas experimentalmente mediante el método de excitación de pulsos. Los resultados muestran que las respuestas en frecuencias naturales numéricas son similares a los valores obtenidos experimentalmente, indicativos de pertenencia a un mismo modo de vibración. Um violão é construído essencialmente de madeira. Porém, cada madeira traz consigo algumas características específicas. O seu comportamento acústico está relacionado às propriedades elásticas dos materiais que o compõem. Sabe-se que as propriedades elásticas dos materiais interferem não apenas em sua resistência mecânica, mas também em seu comportamento dinâmico; uma estrutura pode vibrar de forma mais ou menos intensa dependendo do material que a compõe e de suas propriedades elásticas. O presente trabalho analisa o comportamento dinâmico de um modelo computacional de violão através de análises modais calculadas pelo método de elementos finitos (MEF) aplicando condições de contorno que simulam a rigidez das faixas laterais e a tensão das cordas no cavalete e braço obtendo respostas em termos de frequências naturais e as correspondentes formas dos modos de vibração. E assim, comparar com respostas em frequência obtidas experimentalmente através do método de excitação por impulso. Os resultados mostram que as respostas em frequências naturais numéricas se assemelham com os valores obtidos experimentalmente, indicativo de pertencerem a um mesmo modo de vibração.

Некрасов Сергей Геннадьевич, д-р техн. наук, профессор, профессор кафедры информационно-измерительной техники, Южно-Уральский государственный университет, г. Челябинск; nekrasovsg@susu.ru. S.G. Nekrasov, nekrasovsg@susu.ru. South Ural State University, Chelyabinsk, Russian Federation Важной тенденцией развития промышленности является разработка цифровых моделей промышленных объектов, работа которых основана на информации, поступающей с сенсоров. Это позволяет оптимизировать функциональные возможности, прогнозировать техническое состояние объектов, что особенно важно, например, в области металлургического производства, где вынужденные остановки сопровождаются огромными потерями. Сами сенсоры тоже являются объектами моделирования, так как нуждаются в адаптации к жестким условиям производства, в которых проявляются их собственные недостатки, при этом важную роль имеет корректное введение поправок на условия окружающей среды, диагностика и самодиагностика, которые невозможны без построения различного типа моделей сенсора. Целью работы является разработка универсальной дискретной модели акустического сенсора, пригодной для приема и излучения акустических сигналов. Методы. В работе использованы методы классической механики и математики, теории колебаний, обобщенных функций, распределенных систем, а для обеспечения вычислений использовались методы математического программирования. Результаты. Основным результатом является универсальная дискретная модель сенсора с рабочим элементом в виде круглой пластины, которую выбором параметров можно трансформировать в модель однонаправленного динамического микрофона с плоской мембраной или излучателя с фокусирующим сферическим элементом. Показано, что на основе модели можно синтезировать узконаправленные диаграммы излучения и получить тем самым необходимую пространственную избирательность и помехозащищенность измерений. Заключение. Расчеты, проведенные с использованием предложенной модели, соответствуют известным результатам в акустике. Верификация дискретной модели по натурному образцу показала высокою точность определения резонансных частот и форм колебаний сенсора. An important trend in the development of industry is the development of digital models of industrial facilities, the work of which is based on information coming from sensors. This allows you to optimize functionality, predict the technical condition of objects, which is especially important, for example, in the field of metallurgical production, where forced stops are accompanied by huge losses. The sensors themselves are also modeling objects, because they need to adapt to rigid production conditions in which their own shortcomings are manifested, while the correct introduction of corrections for environmental conditions, diagnostics and self-diagnostics, which are impossible without building various types of sensor models, is important. The purpose of the work is to develop a universal discrete model of an acoustic sensor suitable for receiving and emitting acoustic signals. Methods. The work used methods of classical mechanics and mathematics, vibration theory, generalized functions, distributed systems, and mathematical programming methods were used to provide calculations. Results. The main result is a universal discrete model of a sensor with a working element in the form of a round plate, which by choosing parameters can be transformed into a model of a unidirectional dynamic microphone with a flat membrane or a radiator with a focusing spherical element. It is shown that on the basis of the model it is possible to synthesize narrowdirectional radiation diagrams and thereby obtain the necessary spatial selectivity and noise immunity of measurements. Conclusion. Calculations made using the proposed model correspond to the known results of acoustics. Verification of the discrete model using a natural sample showed a high accuracy in determining the resonant frequencies and forms of oscillation of the sensor.

Одним з важливих завдань під час проектування насосного обладнання для атомних електростанцій є забезпечення його працездатності й жорсткості в умовах виникнення екстремальних динамічних впливів природного та техногенного характеру. Одним з найбільш небезпечних та інтенсивних природних впливів є сейсмічний вплив, а найбільшне безпечними техногенними впливами вважаються повітряна ударна хвиля (ПУХ) і падіння літака (ПЛ) на огороджувальні конструкції будівлі реактора. Уданий час для розрахункової оцінки працездатності обладнання для АЕС під час особливих динамічних впливів (ОДВ) використовуються математичні моделі й методи розрахунку, які дозволяють визначити напружено-деформований стан конструкції в цілому, оцінити локальні деформації в зонах з найбільш високим рівнем еквівалентних напружень та дослідити поведінку конструкції в інших екстремальних умовах, що впливають на безпеку АЕС. Розрахункова оцінка динамічного відклику конструкції на зовнішні впливи природного й техногенного характеру необхідна для уникнення помилкових конструктивних рішень на стадії проектування та виготовлення нового обладнання. One important part during designing of pumping equipment for nuclear power plants is to ensure pumping equipment oper-ability and stiffness under extreme dynamic loads of natural and anthropogenic nature. One of the most dangerous and intensive natural sources is seismic load, and the most dangerous anthropogenic impact are considered to be air shock wave (ASW) and aircraft crush (AC) on the enclosures of the reactor building. At the present time mathematic models and methods for calculation of NPP equipment operability under special dynamic loads (SDL) are applied to define stress-strain state of the design in whole, to assess local deformation in zones having the highest level of equivalent stresses and for studying the design state in other extreme conditions affecting the safety of NPP. Calculation estimation of the design dynamic response to external loads of natural and anthropogenic nature is necessary to avoid wrong decision solutions at the design stage and manufacturing of new equipment. Одной из важных задач при проектировании насосного оборудования для атомных электростанций являет ся обеспечение его работоспособности и жесткости в условиях возникновения экстремальных динамических воздействий природного и техногенного характера. Одним из наиболее опасных и интенсивных природных воздействий является сейсмическое воздействие, а наиболее опасными техногенными воздействиями считаются воздушная ударная волна (ВУВ) и падение самолета (ПС) на ограждающие конструкции здания реактора [1, 2]. В настоящее время для расчетной оценки работоспособности оборудования для АЭС при особых динамических воздействиях (ОДВ) используются математические модели и методы расчета, позволяющие определить напряженно-деформированное состояние (НДС) конструкции в целом, оценить локальные деформации в зонах с наиболее высоким уровнем эквивалентных напряжений и исследовать поведение конструкции в других экстремальных условиях, влияющих на безопасность АЭС [3, 4]. Расчетная оценка динамического отклика конструкции на внешние воздействия природного и техногенного характера необходима для того, чтобы избежать ошибочных конструктивных решений на стадии проектирования и изготовления нового оборудования.

In the present work, an innovative two-phases local/nonlocal constitutive mixture model based on the stress-driven model for free vibrations problems is presented. The above two-phases model has been formulated by defining a convex combination of local/nonlocal phases through a mixture parameter and the closed form solution for free vibrations problems is given. The proposed local/nonlocal model has been applied to compute the natural frequencies of four nanobeams study cases. The results are presented in terms of normalised natural frequency as function of both nonlocal and mixture parameters. First, the influence of the two parameters is studied. The effectiveness of the present model is discussed by comparing the results with those obtained by applying the Gradient Elasticity theory. Finally, the normalised natural frequencies for the second, third and fourth modes of vibrations are presented and discussed for each study case.

Object and purpose of research. This paper studies a large welded sidewall structure manufactured at Sevmash. The purpose of the study is to determine vibroacoustic efficiency criteria for low-frequency vibration treatment. Materials and methods. Dynamic parameters of the sidewall were studied by exciting it by impact during its low-frequency treatment, an intermediate operation prior to mechanical processing. Main results. This work identified vibroacoustic efficiency criteria for low-frequency vibration treatment of welded sidewall structures. Conclusion. This work shows that monitoring of amplitude-frequency parameters could be applied in assessment of efficiency (sufficiency) for low-frequency treatment.

[Objectives] In this paper, the influence of thrust bearing seating on the acoustic radiation of a submarine is studied. [Methods] By utilizing the Finite Element(FE)method and FE coupling fluid interface method, the structure vibration of the pressure hull is calculated with different distributions of longitudinal exciting forces. In this case, the symmetrical distribution of exciting forces and moments are beneficial for reducing vibration. According to the above conclusions, symmetrical thrust bearing seating is designed and the longitudinal stiffness of the system controlled through choosing the size of components. Two submarines are designed, one with conventional thrust bearing seating and the other one with symmetrical thrust bearing seating. The vibration response and radiation noise of the structures of the two submarines are forecasted. [Results] It can been seen that when the propeller longitudinal force is constant, symmetrical thrust bearing seating can significantly decrease the level of vibration and radiation noise. [Conclusions] The results can provide references for the acoustic optimization and design of the thrust bearing seating of submarines.

Accepted: 2018-03-02, 資料番号: SA1180094000

For large-scale offshore wind turbine blades, ANSYS and UG were respectively used to complete the solid modeling and the calculation of vibration modes, and the influences of the rotating speed on each order vibration mode and their main reasons were analyzed. Furthermore, the effects of material categories, the deviations of physical parameters in the process of material manufacture and structural parameters on the natural frequencies of rotating blades were respectively compared. Numerical results show that the dynamic stiffening effect of rotating blades is obvious, and the stress stiffness and the geometric stiffness play a dominant role on the natural frequencies from the first to the sixth order and from the seventh to the tenth order respectively. The influences of material categories on natural frequencies of the blades are significantly higher than those of physical parameter deviations and chord length changes. The effects of the equal amplitude increase of elasticity modulus or the chord length and the equal amplitude decrease of density on the tenth order frequency for the torsional vibration are less than those of them on the first nine orders' frequencies for the shimmy and flapping vibration, making that the increase amplitude of the blade natural frequencies first increases and then decreases with the increase of the order number. In addition, the results in this work can provide technical references for the optimization design and the further analysis of vibration characteristics of wind turbine blades.

Numerous papers deal with the Equivalent Plate Model (EPM) for corrugated panels. Comparison of published formulas for the four relevant equivalent bending stiffnesses D 11 eq , D 22 eq , D 66 eq , and D 12 eq revealed ambiguities: Three different formulas were found for D 22 eq , which describes the bending of the ridges and troughs; for D 66 eq two ‘competing’ formulas emerged. Expressions not converging to the flat-plate values in the limit of vanishing corrugation height were discarded. All discussed formulas are written in a uniform notation for general one-dimensionally periodic shapes. Formulas derived for isotropic panel materials were generalized to the orthotropic case. In order to resolve the ambiguities and assess the EPM with regard to its range of applicability, vibration modes of six rectangular corrugated panels were measured. While agreement with numerical results obtained with COMSOL was fair, the EPM predictions of natural frequencies were satisfactory only for low-order modes. Finally, equivalent bending stiffnesses were determined numerically from COMSOL results for a few low-order modes by inverse methods. Thus the ambiguities with regard to D 22 eq and D 66 eq could be resolved. However, the D 12 eq values determined numerically came out significantly larger than the EPM prediction, in particular for stronger corrugations. Even though this discrepancy had little effect on the natural frequencies tested in the present paper, it remains a theoretical challenge.

This study has presented a method to estimate the damage location in the concrete gravity dam monolith. The first four vibration mode of the highest monolith of the Koyna dam was estimated and analyzed by the combined discrete and continuous wavelet transform. The position of the damage scenarios was identified by using bior 3.9 wavelet in the spatial variation of the data response. The sensitivity of wavelet to random signal noise was investigated by using noise to displacement response of cracked monolith. Three noise levels were introduced in the model and the capacity of this method to detect damage from noisy data was discussed.

資料番号: SA1170277000

In this work, a model for the dynamical four-point bending test is present, with particular emphasis on application to an asphalt concrete (AC) composite, a viscoelastic material, based on the EulerBernoulli theory, which approaches an equation where the Young modulus E can be substituted by the operator (E + γ∂/∂t), where γ is an internal damping parameter associated to the binder viscoelasticity and t is the time. As course aggregate in the composition of the AC mixture, the sintered aggregate of calcined clay was used, interesting to be employed as an alternative to the lack of natural course aggregate in some regions of the planet, where the presence of sedimentary rocks prevails. The results indicated that γ decreases with the temperature and loading frequency and the apparent noise in the stiffness versus strain curve is resulted from the natural vibration mode of the beam.

The membrane dynamics of spinning solar sails have a special relevance when considering attitude control of the spacecraft. Because of being non-rigid structures, local deformation occurs, changing the overall effect of the Solar Radiation Pressure, which might lead to attitude disturbances and unexpected behavior. Thus, an accurate model and study of such dynamics is needed. Until this point, several researches on the topic have been conducted (Nakano, T., et al., 2005 - Takao, Y., 2018), modeling the membrane as a completely flexible body. However, the deformation observed in IKAROS (a spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to demonstrate solar sail technology) during its low-spin operation suggested a higher rigidity of the sail than the predicted one (Shirasawa, Y.,et al., 2012). The difference between the observed and the predicted deformation of IKAROS is believed to be caused by the bending stiffness present in the membrane. First, this study shows that the bending moment has strong effects on the attitude of the sail during its spin axis reorientation. Given the difficulty of measuring the actual bending stiffness of the membrane, it is neces Outgoing

Natural gas hydrates are ice-like crystalline materials formed from natural gas and clathrate ice under high pressure and low temperature. Ice XVI, the first S-II type clathrate ice produced in the lab, was simulated by first-principles density functional theory with the CASTEP code. A 34-molecule supercell was built to mimic the hydrogen-disordered structure. The vibrational spectra were calculated as a reference for inelastic neutron scattering (INS), infrared (IR) absorption, and Raman scattering experiments. Two kinds of H-bond vibration modes corresponding to two different bond strengths were found in our previous studies. In this paper, the statistics of distribution calculated by integrating these two kinds of modes was found to match the phonon density of states (PDOS) very well. We confirmed that the two basic types of H-bonds also appeared in clathrate ice XVI. The typical normal modes were analyzed to illustrate the dynamic process of lattice vibrations.

Using FE analysis, this work fully devoted to added masses determination of the plate in infinite liquid in the case of different movements. Various forms and sizes of the plate are considered. The problem consists of two parts: first is studying of the plate motion in liquid as rigid; second is studying of the plate vibrations in its own modes, fixed with a hard screen and contacting with liquid by one side. The condition observance of liquid environment continuity leads to the Laplace equation, which is solved by using numerical approach. Finite element analysis of steady state problem is performed for added masses determination using thermal analogy. A compact analytical solution of the two considered problems is presented. The results of finite element analysis and corresponding analytical results of the problems are compared for the case of infinite liquid environment. doi: 10.18720/MPM.4112019_19

Electrocatalysis provides a powerful means to selectively transform molecules, but a serious impediment in making rapid progress is the lack of a molecular-based understanding of the reactive mechanisms or intermediates at the electrode–electrolyte interface (EEI). Recent experimental techniques have been developed for operando identification of reaction intermediates using surface infrared (IR) and Raman spectroscopy. However, large noises in the experimental spectrum pose great challenges in resolving the atomistic structures of reactive intermediates. To provide an interpretation of these experimental studies and target for additional studies, we report the results from quantum mechanics molecular dynamics (QM-MD) with explicit consideration of solvent, electrode–electrolyte interface, and applied potential at 298 K, which conceptually resemble the operando experimental condition, leading to a prototype of operando QM-MD ([Formula: see text]-QM-MD). With [Formula: see text]-QM-MD, we characterize 22 possible reactive intermediates in carbon dioxide reduction reactions ([Formula: see text] RRs). Furthermore, we report the vibrational density of states ([Formula: see text]-DoSs) of these intermediates from two-phase thermodynamic (2PT) analysis. Accordingly, we identify important intermediates such as chemisorbed [Formula: see text] ([Formula: see text]), *HOC-COH, *C-CH, and *C-COH in our [Formula: see text]-QM-MD likely to explain the experimental spectrum. Indeed, we assign the experimental peak at 1,191 cm(−1) to the mode of C-O stretch in *HOC-COH predicted at 1,189 cm(−1) and the experimental peak at 1,584 cm(−1) to the mode of C-C stretch in *C-COD predicted at 1,581 cm(−1). Interestingly, we find that surface ketene (*C=C=O), arising from *HOC-COH dehydration, also shows signals at around 1,584 cm(−1), which indicates a nonelectrochemical pathway of hydrocarbon formation at low overpotential and high pH conditions.

An analytical translational-rotational-coupling dynamic model is developed to evaluate the natural characteristics of two teeth difference external compound planet transmission by adopting centralized parameters method. The governing differential equations are established by deriving relative displacement relationships between all motional components, and Matlab is used to calculate and obtain the natural frequencies and free vibration modes of the transmission system. The analysis results show that the vibration modes are classified into rotational mode of the central members, translational mode of the central members and complicate vibration mode of the planetary gears. The vibration modes are different from the NGW planetary transmission, and especially the planetary gears vibration mode are quite complex with several different vibration modes. The research can provide useful reference for preventing resonance, vibration and noise reduction, and structure optimization of the planet transmission mode used in polishing grinding.

For RV reducer widely used in Robots, this work develops a lumped parameter model to investigate free vibration properties of general description. The dynamic model admits three planar degrees of freedom for each component and includes key factors affecting vibration such as involute and cycloid gear mesh stiffness, crankshaft bending stiffness and bearing stiffness. For the linear case, examine of the associated eigenvalue problem reveals the specific structure of vibration modes. The modes are classified into three types: rotational, translational, and planetary component modes. All vibration modes fall into one of these three categories. The unique properties of each type is examined which is analytically verified with candidate mode method. Furthermore, the work investigates effects of parameters, which include stiffness, mass, moment of inertia and crankshaft eccentricity, on natural frequencies of three vibration modes and crankshaft eccentricity is in particular scrutinized. It is helpful for understanding the relationship between parameters and vibration modes.

In the work is presented the modeling of ultrasonic motor with three degrees of freedom. The basic and operating diagram of ultrasonic motor with piezoceramic active elements. The presentation of all vibration modes discovered by computer is make it and the possibility of being accomplished from practical viewpoint. From viewpoint all vibration modes presented are briefly described and as for the features of the useful are exhibited more to length.

Operational transfer path analysis (OTPA) calculates contributions of reference points to response point vibration by using only operational data. Through OTPA, effective interior noise and vibration reduction are achieved by applying intensive countermeasure to the high contributing part. However, it becomes difficult occasionally when many reference points have similar contributions by a vibration mode. In this case, obtaining high contributing vibration mode and considering how to reduce the mode become important information. In this study, we attempted to calculate the vibration mode contribution by modifying OTPA. Principal component calculated in OTPA procedure is composed of correlated vibration factors among reference points. We then considered the relationship between the principal component and the vibration mode, and associated the principal components with the vibration modes of a test structure. As a result, high contributing vibration modes to the response point could be found. In addition, information about which side of the structure (response or reference side) had better to be measured intensively was also obtained by evaluating the influence of each principal component to the response point (principal component transfer function). Finally, Several countermeasures were applied to the structure considering the principal component and vibration mode contributions. The result shows effective vibration reduction at the response point could be carried out. Through these procedures, the modified OTPA became more useful tool for applying effective countermeasure.

Vibration mode of piezoelectric ultrasonic microsensors was investigated on buckled diaphragm structures from the viewpoint of higher order vibration modes than the fundamental one. Several vibration modes were generated on the diaphragms as the response to an ultrasound pulse, and their natural frequencies changed with increasing the buckling deflection in different rates. The natural frequencies of some modes approached each other, and the modes were accordingly superposed and degraded into a single mode in the large buckling ranges. The large buckling of the diaphragms consequently improves their vibration and thus the output waveforms.

The resonator of a solid-state vibratory gyro is responsible for sensing angular motion. Frequency splitting of an axisymmetric-shell resonator is a common problem caused by manufacturing defects. The defect causes a frequency difference between two working modes which consist of two nodes and two antinodes. The difference leads to the loss of gyroscopic effect, and thus the resonator cannot sense angular motion. In this paper, the resonator based on an axisymmetric multi-curved surface shell structure is investigated and an approach to eliminate frequency splits is proposed. Since axisymmetric multi-curved surface shell resonators are too complex to be modeled, this paper proposes a simplified model by focusing on a common property of the axisymmetric shell. The resonator with stochastic imperfections is made equivalent to a perfect shell with an imperfect mass point. Rayleigh's energy method is used in the theoretical analysis. Finite element modeling is used to demonstrate the effectiveness of the elimination approach. In real cases, a resonator's frequency split is eliminated by the proposed approach. In this paper, errors in the theoretical analysis are discussed and steps to be taken when the deviation between assumptions and the real situation is large are figured out. The resonator has good performance after processing. The elimination approach can be applied to any kind of solid-state vibratory gyro resonators with an axisymmetric shell structure.

Chloride due to de-icing salt induced the corrosion of the guardrail post on the highway along the seashore of Hokuriku district. This study proposed the non-destructive method to estimate the structural integrity using the vibration mode obtained by the vibration test. Test guardrail posts which modeled the corrosion were produced. The vibration characteristics of those posts due to the impact and the resonance examination were observed. Also the stiffness and load carrying performance of those posts were investigated using FEM analysis. As the results of the examination and analysis, this study targeted the high-order vibration mode shapes to estimate the corrosion damage of the guardrail post at the basement. Moreover, the structural integrity of those posts was estimated using the relation of the MAC (Modal Assurance Criterion) and the ratio of the bending stiffness.

International audience; The aim of this paper is to investigate the design and the integration of a static force sensor based on a resonant bulk acoustic wave piezoelectric transducer. Experimental measurements of the electrical admittance spectrum show its dependence on the applied force. We noticed that the quality of the frequency response for a given vibration mode degrades with the increase of the applied force, which limits the force measuring range. The root cause of the response-stress dependence is investigated by means of the developed analytical model and a finite element analysis. The analysis results show that the selected operating vibration mode, the components of the structure on which the piezoelectric specimen is positioned and the boundary conditions at the contact interfaces between all the components have a direct effect on the electrical admittance spectrum. A modified structure was proposed to enhance the quality of the frequency response. The experimental tests show higher measuring range (up to 1500 N).

The paper proposes the first 18 vibration modes for plates, and the first 14 vibration modes for cylinders and cylindrical shells. All the edges of these structures are simply supported and the free frequencies are calculated using an exact three-dimensional shell model. A comparison is proposed using two different numerical models such as a classical two-dimensional finite element model and a refined two-dimensional generalized differential quadrature model. The 3D exact model gives all types of vibration modes, when the four edges are simply supported, changing the imposed half-wave numbers m and n in the two in-plane directions α and β . Some of these modes have one of the two half-wave numbers equals zero. When this condition is simultaneously combined with the condition of transverse displacement different from zero, the resulting vibration mode is defined as cylindrical bending mode. The cylindrical bending case has all the derivatives made in the direction where m =0 or n =0 equal zero. This feature means that the vibrational behavior does not change along this particular direction. The numerical models with the simply supported boundary conditions for all the edges do not achieve these results. These cylindrical bending numerical results are obtained modifying the boundary conditions. Proposed results will demonstrate the validity of this idea and how to modify the mathematical models in order to obtain and improve the cylindrical bending solutions.

A reliable procedure to identify the dynamic behaviour of existing masonry buildings is described in the paper, referring to a representative case study: a historical masonry palace located in Benevento (Italy). Since the building has been equipped with a permanent dynamic monitoring system by the Department of Civil Protection, some of the recorded data, acquired in various operating conditions, have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eigenfrequencies and vibration modes of the structure. The obtained experimental results have been compared to the numerical outcomes provided by three detailed Finite Element (FE) models of the building. The influence of Soil-Structure Interaction (SSI) has been also introduced in the FE model by a sub-structure approach where concentrated springs were placed at the base of the building to simulate the effect of soil and foundation on the global dynamic behaviour of the structure. The obtained results evidence that subsoil cannot a priori be disregarded in identifying the dynamic response of the building.

The main objective of the femur bone analysis is to know the natural frequencies, natural vibration modes and identify the fracture location of the bone through the computer simulation based on the FEA. Finite element Method or Finite Element Analysis is an approximation techniques used for the analysis of complex objects and geometries. The femur bone analysis is subjected to free- free and fixed-fixed boundary conditions. For these two different boundary conditions natural frequencies and natural vibration modes are identified. The mode shape shows that the natural frequency of free-free boundary condition varies from 0 Hz to 1381.1 Hz and for fixed-fixed boundary condition 1211 Hz to 7856.4 Hz. On the bases of these two boundary conditions mode shape is determined and fracture location can be easily notified. To prevent the fracture of femur bone external excitation frequency must be avoided to coincide with these natural frequencies. The results were compared with experimental results available in literature. For the design of femur bone model Solid Edge software is used and the model is imported in ANSYS R 14.5 (FEA based software) for the free vibration analysis.

International audience; The aim of this paper is to investigate the feasibility of a 1D tensile/compression force sensor for mechatronic systems. The main issue to address is the sensing of the static force component, dynamic force sensing is also required. Measurements on a test bench show that for a given vibration mode of the piezoelectric structure, the applied force (stress) has an effect on the material frequency response (electrical admittance). Furthermore, the sensitivity depends on the surrounding materials used in the resonant structure. Key elements are drawn based on the measurements to support modeling and optimal design activities.

The paper proposes a comparison between a three-dimensional (3D) exact solution and several two-dimensional (2D) numerical solutions. Numerical methods include classical 2D finite elements (FEs), and classical and refined 2D generalized differential quadrature (GDQ) solutions. The free vibration analysis of two different configurations of functionally graded material (FGM) plates and cylinders is proposed. The first configuration considers a one-layered FGM structure. The second one is a sandwich configuration with external classical skins and an internal FGM core. Low and high order frequencies are analyzed for thick and thin simply supported structures. Vibration modes are investigated to make a comparison between results obtained via the 2D numerical methods and those obtained by means of the 3D exact solution. The 3D exact solution is based on the differential equations of equilibrium written in general orthogonal curvilinear coordinates. This exact method is based on a layer-wise approach where the continuity of displacements and transverse shear/normal stresses is imposed at the interfaces between the layers of the structure. The 2D finite element results are obtained by means of a well-known commercial FE code. Classical and refined 2D GDQ models are based on a generalized unified approach which considers both equivalent single layer and layer-wise theories. The differences between 2D numerical solutions and 3D exact solutions depend on the considered mode, the order of frequency, the thickness ratio of the structure, the geometry, the embedded material and the lamination sequence.

International audience; Laser ultrasonics was applied to the manufacturing control of the integrity (no failure) of coated spherical particles designed for High Temperature Reactors (HTR). This control is of major importance, since the coating of the nuclear fuel kernel is designed to prevent from the diffusion of fission products outside the particle during reactor operation. The SiC layer composing the coating is particularly important, since this layer must be an impenetrable barrier for fission products. The integrity of the SiC shell (no crack within the shell) can be assessed by the ultrasonic vibration spectrum of the HTR particle, which is significantly changed, compared to the reference spectrum of a defect-free particle. Spheroidal vibration modes of defect-free dummy particles with a zirconium dioxide (ZrO2) core were observed in the 2–5 MHz range. A theoretical analysis is presented to account for the observed vibration spectra of defect-free or cracked HTR particles.

The development of tow-placement technology has made it possible to control fiber tows individually and place fibers in curvilinear distinct paths in each layer of a laminated plate. This paper presents an analytical method for determining natural frequencies and vibration modes of laminated plates having such curvilinear reinforcing fibers. Spline functions are employed to represent arbitrarily shaped fibers, and Ritz solutions are used to derive frequency equations using series type shape functions. The strain energy is evaluated by numerical integration involving the fiber orientation angle, and is calculated using the derivative of the spline function in minute intervals. The results show that the natural frequencies obtained by the present method agree well with results from finite element analyses. The vibration mode shape contour plots of the plates are seen to reflect clear influences of the fiber shapes.

Detection of persistent pollutants such as polychlorinated benzene in environment in trace amounts is challenging, but important. It is more difficult to distinguish homologues and isomers of organic pollutantd when present in trace amounts because of their similar physical and chemical properties. In this work we simulate the Raman spectra of hexachlorobenzene and benzene, and figure out the vibration mode of each main peak. The effect on the Raman spectrum of changing substituents from H to Cl is analyzed to reveal the relations between the Raman spectra of homologues and isomers of polychlorinated benzene, which should be helpful for distinguishing one kind of polychlorinated benzene from its homologues and isomers by surface enhanced Raman scattering.