Main Vibration Modes Research Articles

High-temperature Raman spectroscopic study of vanadoborate Na3VO2B6O11**Project supported by the National Natural Science Foundation of China (Grant Nos. 51302268 and 51102239) and the Natural Science Foundation of Anhui Province, China (Grant No. KJ2015A339).

Raman spectra of a vanadoborate (Na3VO2B6O11) crystal from room temperature up to the melting point have been recorded. The main internal vibrational modes of the crystal have been assigned. It was found that all the Raman bands exhibit decreases in frequency and the widths of the Raman bands increase with the increase of temperature. However, no phase transition was observed under 525 °C. The micro-structure of its melt was studied by quantum chemistry ab initio calculation. The continuous three-dimensional network of the crystal collapsed and transformed into VO4 and VBO6 clusters during the melting process with an isomerization reaction from four-coordinated boron to a three-coordinated species.

Uniform Damping Ratio For Non-Classically Damped Hybrid Steel Concrete Structures

Steel–concrete hybrid systems are used in buildings, in which a steel structure has been placed on a concrete structure to make a lighter structure and have a faster construction. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e., stiffness, mass and especially damping. Dynamic response of hybrid structures has some complications. One of the reasons is the different stiffness of the two parts of structure and another reason is non-uniform distribution of materials and their different features such as damping in main modes of vibration. The available software is not able to calculate damping matrices and analyze these structures because the damping matrix of these irregular structures is non-classical. Also an equivalent damping should be devoted to the whole structure and using the available software. In the hybrid structures, one or more transitional storeys are used for better transition of lateral and gravity forces. In this study, an equation has been proposed to determine the equivalent uniform damping ratio for hybrid steel–concrete buildings with transitional storey(s). In the proposed method, the hybrid structure containing concrete, steel and transitional storeys appropriately substituted with 3-DOF structure. A wide range of eigenfrequency and mass ratios is examined for each ratio pair, and given the characteristics of the primary system, the complete 3-DOF structure can be formed. Equivalent uniform damping ratio is derived by means of a semi-empirical error minimization procedure. The multiple nonlinear regressions are used for determination of equations of modal damping ratios of hybrid buildings.

Shaking table test and time-history analysis of high-rise diagrid tube structure

As a new type of high-rise building structure system, diagridtube in tube structure is increasingly applied in high-rise building.Guangzhou West tower is the first high-rise diagrid tube intube structure in China. To study seismic performance of thestructure, elastic time-history analysis and shaking table testwere conducted. The results of elastic time-history analysis andshaking table test were in a good agreement, which verified thevalidity of the elastic time-history analysis. Dynamic characteristicsand responses of the model structure’s acceleration,displacement and strain under different intensity earthquakeaction were obtained through analysis and test. Dynamicresponses of prototype structure were deduced based on similaritylaw and shaking table test results. Research shows thatdiagrid tube structure has a small deformation under earthquakeactions; the main vibration mode is translation, whiletorsional effect is not obvious; whiplash effect has less influenceon the structure; diagrid members, diagrid nodes andshear walls at the bottom of the structure are weak parts.

Free Modal Analysis for the Pinion of Logarithmic Spiral Bevel Gear with 20CrMnTi

In order to obtain the pinion's natural frequencies and mode shapes of a new kind of spiral bevel gear (SBG) which is logarithmic spiral bevel gear (LSBG) in the unconstrained state for the purpose of dynamic characteristics study, select the low carbon alloy steel 20CrMnTi (China specification) with good mechanical properties, which the carbon content is 0.17%-0.23%, the elastic modulus E=2.06675×1011Pa, the Poisson's ratio is 0.25, and the density is 7.85×103kg/m3, the finite element model of LSBG pinion which consist of 35100 nodes, 19889 Solid187 tetrahedron FEM elements is established by using free meshing method based on LSBG pinion's physical model in this paper. Solve the modal parameters of the first 6 orders, draw the main vibration mode shape according to the first 6 orders natural frequencies respectively. The first 6 orders critical revolution speeds are calculated by the first 6 orders corresponding natural frequencies, and the LSBG pinion allowable work revolution speeds are 117074.16 revolutions per minute. The free modal analysis of the conventional SBG pinion with the same parameters is done for comparison with LSBG pinion. The results show the LSBG pinion's nature frequency and the critical revolution speed are both lower than that of conventional SBG. The conclusions reflect the vibration response characteristics of LSBG pinion, and provide theoretical basis for dynamic response, structure design and optimization of LSBG pinion.

Free Modal Analysis for Spiral Bevel Gear Wheel Based on the Lanczos Method

In order to obtain the spiral bevel gear wheel natural frequencies and mode shapes in the unconstrained state for the purpose of dynamic characteristics study, the spiral bevel gear wheel three-dimensional solid model of a mini-bus main reducer is established in this paper. The finite element model of spiral bevel gear wheel which consists of 32351 nodes, 18436 solid187 tetrahedrons finite element method elements is established by using free grid meshing method in this paper. Extract the first 6 orders modals parameters such as natural frequencies and main vibration mode shapes by using the Lanczos method. The new 1st to 4th orders modals are formed by comparing and merging 2 orders repeated modals. In order to verify the effectiveness of the finite element analysis results, the experiment modal test based on the impulse force hammer percussion transient single-point excitation and multi-point response analysis method has been done. The maximum difference value of natural frequency between experimental modal test result and finite element modal analysis results is 29.86 Hz, the maximum error rate is 0.41%, which confirmed the result of finite element method is effective and reliable. The conclusions reflect the vibration response characteristics of spiral bevel gear wheel, and provide theoretical basis for dynamic response, structure design and optimization of spiral bevel gear wheel.

Vibration reduction and firing accuracy improvement by natural frequency optimization of a machine gun system

Structure vibration is known to influence the firing accuracy of a machine gun system. Studying the dynamic characteristics of the machine gun system and reducing its vibration response are crucial. Eigenfrequency optimization based on topology is an emerging vibration suppression technique that reduces structural vibration and stabilizes a machine gun system. This paper presents an effective and efficient method that accomplishes these tasks. The objective function is the frequency of the main vibration mode confirmed by modal and transient dynamic analyses. The frequency is maximized by subjecting topology optimization to mass constraints. Based on topology optimization results, the revised model addresses all structural and manufacturability concerns. Dynamic analysis, exterior ballistics calculation, and experimental test are conducted to verify the effectiveness of the proposed method. Results show that muzzle vibration and structure deformation are reduced and firing accuracy is remarkably improved.

New metalorgano-chalcogenide compounds based on polymeric frameworks constructed by Se–Hg intermolecular interactions: Preparation, structural characterization, and Raman evaluation

This study investigated the synthesis and structural characterization of two new polymeric frameworks based on metalorgano-chalcogenide materials. X-ray analyses revealed the frameworks of prepared compounds 1 and 2 to be polymeric chains achieved through Se–Hg intermolecular interactions. A detailed Raman evaluation of the compounds was performed, showing their synthetic precursors to constitute a safe and reproducible model for the assignment of the main vibrational modes of the molecules investigated. Complete characterization of 1 and 2 also included elemental analysis, IR spectroscopy, UV–Vis absorption data, and EDX analysis.

The City Hall of Mirandola Hardly Hit by the Earthquake of 2012: Damage Assessment and Approaches for the Seismic Improvement

damaged by Emilia-Romagna earthquake sequence of May 2012. The research suggests solutions for the rehabilitation of a masonry historic building that presents a serious damage pattern. The solutions includes the base isolation of the global structure. Through the historical analysis, the damage survey and the mechanisms analysis were defined the macro-structure of the palace. Subsequently, was generated different configurations based on the aggregation or separation of the five macro-structure identified. The separation of these proposed projects is done through the use of seismic isolators and dampers. It was carried out a simplified finite element model and the linear elastic dynamic modal analysis was performed to evaluate the main modes of vibration of each configuration, which correspond to the higher values of percentage of participating mass. Finally a response spectrum analysis was performed with the use of data of the earthquake of 29 May 2012. It going to evaluate the seismic behavior of all the configurations.

Modal Analysis on Working Equipment of Hydraulic Excavator

In the traditional design of the working equipment of the hydraulic excavator, its stress distribution was almost determined by adopting the static calculation method, and then its strength was ensured by selecting the safety factor, which is not fully considered because of the dynamic stresses resulting from shocks and vibrations in the operating process of the hydraulic excavator. Based on the finite element analysis software ANSYS, the 3D models of the main components (boom and bucket rod) of the working equipment for certain type of hydraulic excavator were analyzed. The inherent frequency and the main vibration mode were analyzed by extracting the first 6-th order modal. The research results show that with the increase of modal order, the vibrating mode form increased in complexity. The first and the second orders vibrating mode can be both a linear bending deformation or muster within a certain plane individually. From the beginning of the third order, the model deflection begins to become a mutual coupling complex vibrating type which showed multiple orders of bending and torsion deformation. The maximum deflection of boom is concentrated near the ear plate as well as the hinge point connected with boom and oil cylinder. On the other sides, the maximum deflection of bucket rod is concentrated on its middle part. i.e. between the hinge joints of rocker and the ear plate as well as near the rear supporting plate. Therefore, in order to ensure strength and working safety of the working equipment, it is necessary to improve the structure of the maximum deformation. The Modal analysis provides important modal parameters for the corresponding analysis of the boom and bucket rod of the working equipment in hydraulic excavator, and provides a basis for the optimization design of the analysis on total vibration and structural dynamic characteristics.

Gas-phase electronic spectrum of the indole radical cation

The visible and near-UV electronic spectrum of the indole radical cation is measured in the gas phase by photodissociation of indole+–Ar and indole+–He complexes in a tandem mass spectrometer. A series of resolved vibronic transitions extending from 610 to 460 nm are assigned to the D2 ← D0 band system, while weak transitions between 390 and 360 nm are assigned to the D3 ← D0 system, and a stronger, broad, unresolved absorption between 350 and 300 nm is attributed to the D4 ← D0 system. Time-dependent density functional theory calculations are used to assign vibronic structure of the D2 ← D0 band system, and show that the main active vibrational modes correspond to in-plane ring deformations. The strongest D2 ← D0 vibronic transitions of indole+–He do not correspond with any catalogued diffuse interstellar bands, even considering band displacements of up to 50 cm−1possibly caused by the attached He atom.

Hydroxyl radical initiated oxidation of formic acid on mineral aerosols surface: a mechanistic, kinetic and spectroscopic study

Environmental context The presence of air-borne mineral dust containing silicates in atmospheric aerosols should be considered in any exploration of volatile organic compound chemistry. This work reports the mechanisms, relative energies and kinetics of free-radical reactions with formic acid adsorbed on silicate surface models. We find that silicate surfaces are more likely to act as a trap for organic radicals than to have a catalytic effect on their reactions. Abstract Heterogeneous reactions of atmospheric volatile organic compounds on aerosol particles may play an important role in atmospheric chemistry. Silicate particles are present in air-borne mineral dust in atmospheric aerosols, and radical reactions can be different in the presence of these mineral particles. In this work, we use quantum-mechanical calculations and computational kinetics to explore the reaction of a hydroxyl free radical with a formic acid molecule previously adsorbed on several models of silicate surfaces. We find that the reaction is slower and takes place according to a mechanism that is different than the one in the gas phase. It is especially interesting to note that the reaction final products, which are the formyl radical attached to the cluster surface, and a water molecule, are much more stable than those formed in the gas phase, the overall reaction being highly exothermic in the presence of the surface model. This suggests that the silicate surface is a good trap for the formed formyl radical. In addition, we have noted that, if a second hydroxyl radical approaches the adsorbed formyl radical, the formation of carbonic acid on the silicate surface is a highly exothermic and exergonic process. The carbonic acid molecule remains strongly attached to the surface, thus blocking CO2 formation in the formic acid oxidation reaction. The spectroscopic properties of the systems involved in the reaction have been calculated, and interesting frequency shifts have been identified in the main vibration modes.

Complex Mode Analysis and Simulation Research of Automotive Driveline Based on Bending-torsional-axial Coupled Vibration Hybrid Model

The characteristics of torsional-bending-axial coupled vibration hybrid model for automotive driveline are introduced based on the combination of system dynamics and structural dynamics and the modelling methods of hybrid model for automotive driveline are also discussed from three aspects which are structural dynamic modelling of shaft, system dynamic modelling of helical gear pair, bearing and attaching mass(inertia), connections among components by coordinate transformation. Complex mode analysis of driveline is analyzed and it is found that the main vibration mode of first four order modal calculated by hybrid model are torsional vibration and they are similar to the first four order modal calculated by system dynamic branched torsional vibration model, the main vibration modes are two or three forms of coupled vibration after the fifth order modal. It is discovered that the shudder degree of hybrid model is slightly enhanced and the characteristic frequency is almost the same between hybrid model and branched torsional model from the simulation research of launch shudder. It is also concluded that bending and axial vibrations have little effect on launch shudder phenomenon.

Experimental study on vibration dephasing time varying with molecular surroundings

Measuring the vibration dephasing time in molecular vibration is the free-mark method for detecting molecules harmlessly. Since molecular vibration refund processes are associated with molecular environment change, molecular vibration dephasing time also may reflect the substance's molecular environment change, which can be used to study the interaction between a certain molecule and its neighboring molecules. The molecular vibration spectrum and vibration dephasing time are obtained from the time-resolved coherent anti-stokes Raman scattering (CARS) simultaneously. Benzonitrile and methanol are used as samples for studying, the vibration dephasing time changes for the main vibration spectra when the environment changes. With benzonitrile mixed with anhydrous alcohol, its vibration dephasing time changes with environment are measured in three typical benzonitrile molecular vibrations 1017 cm-1, 2247 cm-1 and 3085 cm-1. For adjoining methanol molecular vibrations 2851 cm-1, and 2960 cm-1, vibration dephasing time changes are measured under environmental conditions. Results show that significant changes of molecular vibration dephasing time will take place in different environments. For a unidirectional molecular environment change, the molecular vibration dephasing time of benzonitrile is a one-way change, while the methanol molecule is of non-unidirectional vibration dephasing time change. But methanol molecules with vibration intensity ratios between two unidirectional changes with environment for I2851/I2960 are of a one-way change. By experimental measurement the vibration dephasing time of the main vibration mode of benzonitrile and methanol molecules varies with the changes in the environment, further understanding of differences on vibration dephasing time of molecular vibration spectra of adjacent and non-adjacent variations can explain the variation of vibration dephasing time of benzonitrile molecules. This method has the ability of detecting molecular environment change and molecular interactions, and has an important application prospect in the field of life science, molecular biology, and material science etc..

Energy aspects and workpiece surface characteristics in ultrasonic-assisted cylindrical grinding of alumina–zirconia ceramics

Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina–zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the cylindrical plunge grinding process and axial ultrasonic vibrations provide a unique surface treatment conditions, which leads to reduced peak heights and increased valley depths of the surface topography. The main axial vibration mode provides the overlap of the adjacent cutting traces and consequently smoothens the surface topography in cylindrical plunge grinding. It has been analytically and experimentally shown that, applying ultrasonic vibrations, grinding energy can be reduced up to more than 35% depending on the process parameters. The surface characteristics of the ground workpieces have been investigated in terms of four surface roughness parameters and the roundness error.

SSI on the Dynamic Behaviour of a Historical Masonry Building: Experimental versus Numerical Results

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.

Thermal and spectroscopic study of the 3,4-(methylenedioxy)cinnamate compounds of transition metals in the solid state

In this study, the trans-3,4-(methylenedioxy)cinnamic acid was used as precursor for the synthesis of transition metal compounds, which were characterized by coupled TG-DTA/FT-IR system, elemental analysis, FT-IR spectroscopic study and titrimetric analysis with EDTA. The characterization by these techniques allowed to determine the hydration water content, number of ligand coordinated to the metal, thermal behavior and thermal stability, as well as monitor the main gaseous products released in each decomposition step. The elemental and titrimetric analyses were performed in order to support TG-DTA data. A theoretical FT-IR calculation was made using the Gauss View 5.0.2W program and the vibration frequencies obtained were compared with the experimental ones showing as a result a difference of around 30cm−1 between them. In these spectra were analyzed the main vibration modes as COO− (carboxylate group), CC (aromatic ring, alkene), CO and CH2 (methylenedioxy group) and CH (alkenes, aromatic).

Design and Calibration of a Six-Axis Force Sensor for Docking Mechanism

A six-axis force sensor for docking system is presented based on the piezoelectric force sensing element. The dynamic character of the six-axis force sensor is analyzed. The natural frequency and the main vibration mode are obtained. A calibration machine with three force sources is developed for calibration of the six-axis force sensor. A calibration arm is designed for loading of the torque. Static force analysis is conducted for the calibration arm. Result show that the deformation influence of the arm can be ignored.

Research on Main Drive System Vibration of Six-Roller Wide Strip Aluminum Cold Rolling Mill

Vibration appears in the main drive system of the six-roller cold rolling mill of one plant. The oscillation frequency is 2.5 Hz. The oscillation cycle is 0.4 second. The oscillation period has nothing to do with the speed. Using the finite element software ANSYS, the low natural frequency is got through the modal analysis and harmonic response analysis based on the measured vibration data from the field. Horizontal vibration is the main vibration mode and it is the electromechanical coupling vibration. Main motor is controlled by IEGT inverter of TEMIC and the low frequency harmonic component is difficult to eliminate. AC drive trap filter is designed to dodge the 2.5 Hz frequency. The solution has achieved the recognition by the TEMIC company. The problem was solved and good results were obtained.

Nonlinear dynamic modeling for a diesel engine propeller shafting used in large marines

Longitudinal vibration, torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system. However, these vibrations of the propeller-crankshaft-sliding bearing system generated by the fluid exciting force on the propeller are much more complex. Currently, the torsional and longitudinal vibrations have been studied separately while the research on their coupled vibration is few, and the influence of the propeller structure to dynamic characteristics of a crankshaft has not been studied yet. In order to describe the dynamic properties of a crankshaft accurately, a nonlinear dynamic model is proposed taking the effect of torsional-longitudinal coupling and the variable inertia of propeller, connecting rod and piston into account. Numerical simulation cases are carried out to calculate the response data of the system in time and frequency domains under the working speed and over-speed, respectively. Results of vibration analysis of the propeller and crankshaft system coupled in torsional and longitudinal direction indicate that the system dynamic behaviors are relatively complicated especially in the components of the frequency response. For example, the 4 times of an exciting frequency acting on the propeller by fluid appears at 130 r/min, while not yield at 105 r/min. While the possible abnormal vibration at over-speed just needs to be vigilant. So when designing the propeller shafting used in marine diesel engines, strength calculation and vibration analysis based only on linear model may cause great errors and the proposed research provides some references to design diesel engine propeller shafting used in large marines.

Modal Analysis of the Dynamic Disc of New-Type Plate-Rolling Crusher

The finite element analysis software Solidworks Simulation is used to the modal analysis of the dynamic disc of the new-type plate-rolling crusher, its natural frequency and main vibration modes of preceding five orders are obtained. The analysis results show that while the natural frequency of preceding two orders of the dynamic disc is closed to the engagement frequency of the gears of the reducer casing, resonance occurs. So corresponding measures of avoiding resonance are proposed, the study offers theoretical references for the dynamic design of the dynamic disc.