Analysis Of Vibrational Modes Research Articles

Effect of clearances in rolling element bearings on their dynamic performance, quality and operating life

The performance of rolling element bearings is one of the machine quality measures in industry. The fatigue life and performance of rolling element bearings depends mainly on the dynamic characteristics of those bearings. This paper studied the effect of the internal radial clearance on the damping characteristics, natural modes of vibration, and fatigue life of rolling element bearings. Vibration modal analysis was performed on rolling bearings of the same size and type to measure their dynamic characteristics. These dynamic characteristics include the natural frequency of the first mode of vibration, damping, and amplitude of frequency response function at resonance. The internal radial clearances of these bearings were measured. A statistical analysis was performed to study the correlation between the internal radial clearance and the dynamic characteristics of rolling bearings. It was found that the damping ratio of the bearing assembly increased by reducing the internal radial clearance of the bearing. Similarly, rolling bearings that have large internal clearances showed short predicted fatigue life. It is concluded that the dynamic characteristics, and consequently the dynamic performance, of rolling bearings are significantly affected by the internal radial clearance.

Methylamine Treated Mn3O4 Nanoparticles for Efficient Water Oxidation Catalyst at Neutral Condition

Developing alternatives to replace fossil fuels is an important issue for maintaining sustainable energy system in the future. Hydrogen fuel is an attractive alternative owing to its high energy density and environmentally friendly by-products. Electrical water splitting powered by a renewable energy source is a promising way to produce hydrogen fuel. However, anodic water oxidation is considered to be a bottleneck due to its high overpotential. Therefore, designing efficient catalyst for water splitting is regarded as an important issue. Previously, Ir and Ru-based catalysts have been shown to exhibit remarkable catalytic activity toward oxygen evolving reaction (OER) under acidic condition. Despite their high activity, it is difficult to use noble-metal-based catalysts for commercial applications because of the scarcity of precious metals and their costs. Therefore, non-precious transition metal oxide electrocatalysts were investigated for water oxidation reaction such as cobalt oxides, nickel oxides, iron oxides and manganese oxides.1,2 Their activities were only retained under basic conditions and advancement in electrocatalysts that show moderate activity at neutral pH has been relatively insufficient. Nature has highly efficient OER catalysts in photosystem II which is Mn4CaO5 cluster also called as oxygen evolving complex. Inspired by unique structure and catalytic mechanism of this cluster, Mn-based catalysts have been actively studied. Among various manganese oxide, nanoparticle system showed superior catalytic activity due to its totally different reaction mechanism compared to the bulk counterparts.3,4 However, after synthesis of manganese oxide nanoparticles, long alkyl organic ligands are attached on the surface of nanoparticles interrupting the approach of water molecules, which inhibits water oxidation. Previously, hydrophobic organic ligands were removed by thermal decomposition with sufficient annealing process. Alternative way to remove alkyl ligands is replacing it with different ligands through surface ligand treatment such as BF4 -, PF6 -, OH-, thiol, SCN- and PbCl3 -. Surface ligand exchange is beneficial in that it does not need high temperature annealing and possibility of fine surface control. We have successfully synthesized 6 nm Mn3O4 nanoparticles (NPs) and used for further surface treatments. Mn3O4 NPs were OH ligand exchanged as a first step and followed by methylamine treatment in aqueous solution. Identical TEM images and XRD patterns showed that the size of NPs was unchanged and the phase of NPs was maintained as Mn3O4. Electrokinetic study of the OER was analyzed by cyclic voltammetry (CV) at pH 7 and compared between OH ligand exchanged Mn3O4 NPs and further methylamine treated Mn3O4 NPs. Methylamine treatment reduced the overpotential for OER by nearly 100 mV at the current density 5 mA cm-2. Tafel slopes was also decreased after methylamine treatment to 83.1 mV dec-1. To understand the phenomenon of increased catalytic activity after methylamine treatment, further analysis of the surface of NPs were conducted using spectroscopic measurement. In the XPS O 1s spectra, surface hydroxyl group (Mn-OH) was increased up to 57.3 % after OH ligand exchange. Also, FTIR spectra showed increased ratio of Mn-OH to lattice oxygen (Mn-O-Mn) for OH ligand exchanged Mn3O4 NPs compared to Mn3O4 NPs which indicates successful OH ligand exchange on the surface of Mn3O4 NPs. After methylamine treatment of OH ligand exchanged Mn3O4 NPs, methylamine was not attached to the surface of NPs. XPS N 1s spectra did not show characteristic methylamine peak, FTIR did not show C-N vibration mode and elemental analysis indicates that N does not exist in the NPs. To figure out the role of methylamine on the surface of OH ligand exchanged Mn3O4 NPs, titration and zeta potential was measured. After methylamine treatment surface was more deprotonated. Deprotonation resulted in loss of positively charged proton which induced negative charge on the surface of Mn3O4 NPs and showed negative zeta potential. On the basis of nonexistence of methylamine on the surface and surface deprotonation after methylamine treatment, we hypothesized that methylamine work as Brønsted-Lowry base. Methylamine was replaced by ethylamine, ethylenediamine, dimethylamine, trimethylamine and ammonia water, then after reaction with different amines, overpotential was decreased for all cases. Interestingly, amines with larger pK a showed larger decrease in overpotential. Based on these results, we first proposed correlation between the surface charge and oxygen evolving activity. Deprotonating the surface of the catalyst through simple acid-base reaction induced a change in the surface state followed by catalytic activity improvement. This understanding can be applied for developing efficient nano-catalysts by deprotonating the nanoparticle surface to induce surface state change. [1] J. Am. Chem. Soc., 2014, 136, 4201-4211 [2] J. Am. Chem. Soc., 2014, 136, 7435-7443 [3] Sci. Rep., 2015, 5, 10279 [4] J. Am. Chem. Soc., 2017, 139, 2277-2285 Figure 1

A facilely one pot low temperature synthesis of novel Pt doped PbS nanopowders and their characterizations for optoelectronic applications

Different concentrations of Pt doped PbS nanostructures synthesis has been attained facilely by chemical route. X-ray diffraction (XRD) and FT-Raman spectroscopy analyses confirms the structure. After close inspection and indexing of diffraction peaks, the absence of additional peak owing to any contamination or free Pt in final products was confirmed. XRD data was further used to evaluate the lattice constants, crystallite size, density and strain to see the effect of Pt on these. Calculated lattice parameters confirm the single cubic phase, which was in correlation with vibrational modes analysis. The crystallite size was calculated in range from 9 to 11 nm. For further confirmation of Pt doping and its homogeneity in final product the EDX/SEM mapping was carried out and approved the homogeneous presence of Pt in PbS. SEM study revealed that the morphology is changing from nanoparticles (NPs) to nanosheets (NSs). Diffused reflectance spectra (DRS) were measured for powdered samples and energy gap was estimated up to 1.32 eV. Photoluminescence spectra was recorded and shows an intense green and broad red emission bands at 518 and 700 nm, correspondingly. The values of dielectric constant are found in range of 18–28. Total ac electrical conductivity is rising with applied frequency. The energy gap value suggest the application of synthesized Pt:PbS NPs and NSs in solar cell.

Modal analysis using camera-based heterodyne interferometry and acoustic excitation

Abstract Vibration modal analysis is a significant technique in dynamic analysis that has been widely used for structural damage detection and health monitoring. To accurately identify the modal parameters of a structure, a non-destructive method using camera-based heterodyne interferometry and acoustic excitation is proposed in this paper for modal analysis. Based on a high-speed complementary metal oxide semiconductor (CMOS) camera, full-field images of a vibrating structure with a high-density spatial resolution can be rapidly collected and processed to extract adequate vibration response data for modal analysis using heterodyne interferometry. Combined with an acoustic wave as an excitation source to trigger the vibration response of the structure, impairment can be avoided. To verify the validity of the proposed method, an experiment for extracting the modal parameters of a steel cantilever beam is introduced. During the test, the vibration response of a beam under the excitation of random white noise is detected using heterodyne interferometry to extract the natural frequencies. The mode shapes are retrieved from the full-field vibration response determined via heterodyne interferometry using an acoustic wave at natural frequencies. The results show significant consistency with those from finite element analysis (FEA) and laser Doppler vibrometry (LDV), demonstrating that the proposed method is an effective technique for vibration modal analysis.

Modal analysis of micro wind turbine blade using COSMOSWorks

In this paper, vibration modal analysis of a horizontal axis micro wind turbine blade of different rotational speeds was carried out by using the finite element analysis software COSMOSWorks. The dynamic stiffening phenomenon and its effect on the vibration mode of the wind turbine blade were taken into account. Numerical results were analyzed and compared. The analysis can help not only to ensure the reliability of system operation but also to improve the structural performance.

First-principles analysis of vibrational modes of calcite, magnesite and dolomite

Calcite, magnesite and dolomite are important in Earth's evolutionary history, so they are significant in sediments and biominerals. As we know, the experimental investigations of calcite, dolomite, magnesite with Raman spectra are widespread. In order to show microprocess about Raman spectra, the first-principles vibration calculations deserve further discussion. So, the first-principles density functional perturbation theory is employed to calculate the phonon dispersion, IR spectrum, Raman spectrum, thermodynamic properties and dielectric permittivity. The vibration modes of phonon dispersion curves are investigated through symmetry system. The vibration type from group theory is used to discuss the IR activity and Raman activity, where the minerals space group are R3¯c, R3¯c and R3¯ for clacite, magnesite and dolomite, respectively. The calculated phonon dispersions show that minerals with ionic and covalent bonds are dynamically stable. The vibration analysis of IR modes and Raman modes reveals the strongest covalent bond in (001) plane, and it can produce bigger shear modulus. In addition, the differently cationic masses have a little effect on thermodynamic and dielectric properties for minerals. The investigated results in this paper can promote the analysis of minerals at microscopic level, where the information of vibration can expound the stably combinative direction of electron cloud of minerals. So it can present the macroscopically mechanical property, which would help researchers to research earth mantle.

Organically-modified silica aerogels: A density functional theory study

The primary particles of silica aerogels resulting from three different mixtures of precursors – 50% tetramethylorthosilicate (TMOS)/50% vinyltrimethoxysilane (VMTS); 50% tetraethylorthosilicate (TEOS)/50% aminopropyltriethoxysilane and 50% TEOS/50% glycidylpropoxi – as well as aerogels of pure TMOS and VTMS, have been studied by quantum mechanics density functional theory calculations (DFT), at the B3LYP/6-311+G(d,p) level of theory). Thermo-chemical calculations have indicated that cage structures are the most favored for all materials, followed by other species (linear and cyclic) with high degrees of condensation. A vibration mode analysis based on a numerical model fitted to experimental infrared spectra, has allowed the identification of the most representative silica clusters for all the materials studied. The resulting theoretical spectra were close to their experimental counterparts. Analysis of calculated and experimental 29Si-NMR spectral data generally corroborated the derived model.

In Situ Measure of Intrinsic Bond Strength in Crystalline Structures: Local Vibrational Mode Theory for Periodic Systems.

The local vibrational mode analysis developed by Konkoli and Cremer has been successfully applied to characterize the intrinsic bond strength via local bond stretching force constants in molecular systems. A wealth of new insights into covalent bonding and weak chemical interactions ranging from hydrogen, halogen, pnicogen, and chalcogen to tetrel bonding has been obtained. In this work we extend the local vibrational mode analysis to periodic systems, i.e. crystals, allowing for the first time a quantitative in situ measure of bond strength in the extended systems of one, two, and three dimensions. We present the study of one-dimensional polyacetylene and hydrogen fluoride chains and two-dimensional layers of graphene, water, and melamine-cyanurate as well as three-dimensional ice I h and crystalline acetone. Besides serving as a new powerful tool for the analysis of bonding in crystals, a systematic comparison of the intrinsic bond strength in periodic systems and that in isolated molecules becomes possible, providing new details into structure and bonding changes upon crystallization. The potential application for the analysis of solid-state vibrational spectra will be discussed.

Finite element analysis of resonant properties of silicon nanowires

This paper presents a 3D nanostructure modal vibration analysis by using finite element models. The modal frequencies and corresponding modal shapes of silicon nanowires of various thickness against length ratios are determined by solving a linear structural eigenvalue problem for the 3D solid finite element model, where surface stress effects are taken into account by using the stress stiffness matrix. The cases of fixed/fixed and fixed/free boundary conditions at the nanowire ends are investigated. The results obtained by 3D solid models and models based on the beam bending theory have been compared with each other, as well as with the results obtained elsewhere in the literature computationally and experimentally. It has been shown that the effects caused by surface stresses are insignificant for wires with length-to-width ratio less than 10.

Computational analysis of vibrational modes in tetra-sulfur using dimensionally reduced potential energy surface

ABSTRACTElectronic structure calculations are carried out for the S4 molecule at the CCSD(T)-F12a/VTZ-F12 level of theory to map out its potential energy surface, which possesses a double-well shape with a low-energy barrier. Two degrees of freedom are considered: the distance R and the gearing motion angle between the two weakly-perturbed S2 dimers, which form S4. Vibrational states are computed on this 2D-surface and assigned quantum numbers based on their energies and the shapes of their wave functions. Two progressions of vibrational states are identified: a long progression of easily assignable states that develop nodes along the ‘channels’ on the surface, and a shorter progression of states that develop nodes across the ‘channels’ and are much harder to assign, due to the double-well effect. Normal mode analysis indicates that these two modes in S4 represent a significant mixture of conventional bending and stretching motions. When the angle is increased, the lower frequency mode corresponds to stretching of the distance R, while the higher frequency mode corresponds to compression of R. Frequencies of the modes, ∼180 and ∼420 cm−1, are in a qualitative agreement with earlier ab initio studies of tetra-sulfur, and with sparse experimental data.

Optical properties of Sm3+ doped strontium bismuth borosilicate glasses for laser applications

Stupendous progress in realizing optical materials is due to extreme strides which were adapted so far in understanding optical properties of materials. Keeping this in view a series of Bismuth Borosilicate glasses modified with strontium and doped with various concentrations of Sm3+ (SrOBi2O3B2O3SiO2Sm2O3) have been prepared by classical melt quench technique. These glasses were structurally characterized by XRD to confirm amorphous nature. Vibration mode analysis of samples has been analyzed by infrared transmission spectroscopy. This paper show cases various optical phenomena such as absorption and luminescence which plays a key role in design of engineered optical materials. To understand absorption, optical excitation, emission and time decay process optical spectroscopy measurements were done. Judd-Ofelt (JO) theory was employed to determine intensity parameters Ωλ=2,4,6 for symmetry of ligand environment existing among Sm3+ ions. From emission spectra various radiative parameters like transition probability (Ar), branching ratios (βr) and radiative time were determined. Emission bands of 4G5/2 → 6H5/2 (560 nm), 4G5/2 → 6H7/2 (599 nm) 4G5/2 → 6H9/2 (636 nm) and 4G5/2 → 6H11/2 (708 nm) have been recorded with excitation at 401 nm. Above all emission wavelengths 599 nm is more intense and has shown a bright orange emission. Among four emission bands corresponding to 4G5/2 → 6H7/2 transition in emission spectra shows high (σE) peak stimulated emission (22.85 × 10−22 cm2) and optical gain (O.G) is (28.33 × 10−25 cm2s) assure optoelectronic applications. The life time τ exp of excited level 4G5/2 was determined through decay and non-exponential decay curves. Inokuti-Hirayama model was used to fit non exponential curve for the analysis of luminescence quenching, quantum efficiency (96%), transfer mechanism of energy among Sm3+ ions to ensure Laser applications. CIE colour chromaticity coordinates of present Sm3+ doped glasses also suggest the synthesized glasses are suitable improvement of orange-red lasers.

A third order nonlinear model to study the dynamic behaviour of composite laminated structures under thermal effect with experimental verification

The present article includes the modal analysis of laminated composite structures under thermal effect. Experiments are conducted to study the influence of temperature change on natural frequencies of glass fibre reinforced polymer (GFRP) composites. GFRP laminated plates are prepared in the laboratory using vacuum bagging by resin infusion. The specimens are thermally conditioned to obtain temperature variation ranging from −10 °C to 120 °C. A Green–Lagrange nonlinear finite element (FE) model based on third order shear deformation theory (TSDT) has been developed for the analysis. The FE solutions in terms of natural frequencies are compared with experimental data and an extensive parametric study is carried out. The free vibration modal analysis of a hollow stiffened laminated panel is also carried out to identify the effect of temperature change with proper temperature distribution within the stiffened structures using 1D heat conduction model and the solutions may be used as benchmark.

UV Resonance Raman Spectroscopy as a Tool to Probe Membrane Protein Structure and Dynamics.

Ultraviolet resonance Raman (UVRR) spectroscopy is a vibrational technique that reveals structures and dynamics of biological macromolecules without the use of extrinsic labels. By tuning the Raman excitation wavelength to the deep UV region (e.g., 228nm), Raman signal from tryptophan and tyrosine residues are selectively enhanced, allowing for the study of these functionally relevant amino acids in lipid and aqueous environments. In this chapter, we present methods on the UVRR data acquisition and analysis of the tryptophan vibrational modes of a model β-barrel membrane protein, OmpA, in folded and unfolded conformations.

Energy Flow Method for Analysis of Vibrational Modes in Motorcycle

Energy Flow Method for Analysis of Vibrational Modes in Motorcycle

Vibration mode analysis of multi-degree-of-freedom permanent magnet synchronous motor

Multi-degree-of-freedom motors have attracted more and more attentions, and the liquid suspension multi-degree-of-freedom PM motor is regarded as one of the research hotspots of new kind of electrical machine. In order to further optimize the structure of liquid suspension permanent magnet synchronous multi-degree-of-freedom motor and improve the stability of the operation, the mode force analysis of the motor's component is carried out. The characteristics and basic structure of the motor are introduced, and the principle and rules of the motor resonance are expounded in detail. Based on the theory of mechanics, the mode of the motor spherical shell is studied and calculated. By finite element analysis, the modal changes of stator shell under static and energized conditions are calculated and the comparison is made. Then, the 2nd order modal deformation of the spherical shell is monitored by hammering and sensor with the measured data obtained and compared with the finite element simulation. The solid mechanical structure of the claw stator core is analyzed so that the stress distribution and deformation displacement distribution are obtained. The results of the simulation and analysis provide the reference for the optimal design of this kind of motors or actuators.

The Study on Bridge Damage Identification Based on Vibration Mode Analysis and Hadoop Platform

The methods of damage identification of bridge structures are developing rapidly and various. With the development of science and technology, especially the development of cloud computing technology in recent years, which has brought great convenience to human life, at the same time, it may also provide a new technical way to solve the problem of bridge damage identification. As an open source and distributed system architecture, the Hadoop is the most extensive research and applied data processing platform at home and abroad. Hadoop platform processes the data collected by tests aisles objectively and properly, makes the bridge damage identification more accurate and credible.

ANÁLISE COMPARATIVA DOS MODOS E FREQUENCIAS NATURAIS DE VIBRAÇÃO DE VIGAS ENGASTADA LIVRE E BI-ENGASTADA SUJEITAS À OSCILAÇÕES LIVRES

The objective of this work was the theoretical and computational modeling of free-form and bi-set beams, objectively showing their ways of vibrations and their natural frequencies. The study of the dynamics of rigid or flexible structures, under the action of external forces, such as regular marine waves, winds, external mechanical vibrations of any order, is of extreme importance for the prevention of possible structural problems, for example, displacements, partial or total ruptures of these structures. All the study was carried out Recebido em: 10/08/2018Revisado em: 28/08/2018Aprovado em: 20/09/2018 19Colloquium Exactarum, v. 10, n.4,Out-Dez. 2018, p.18–27. DOI: 10.5747/ce.2018.v10.n4.e252using the methods of Computational Analysis of the Natural Vibration Modes and Frequencies of a Free Beam of Forms for Free Frequencies and Computational Calculation of Lies and Natural Vibration Frequencies of a Beam Without Free Sets of Free Oscillations and the Computational Computation of Lies and Natural Frequencies of Vibration of a Bi Beam established by the Method ofAssumed Modalities. The computational resources used to do the theoretical remodeling of the beams and their functions were Matlab®and Maple®. Employees to implement three-dimensional vibration modes and development of new studies with different bundles and physical properties. This comparative work of the beams provided the mathematical and dynamic knowledge of modeling of the structures, being they, modeling skills through programming.

Temperature Induced Nonlinear Effect on Free Vibration Characteristics of Fibre Reinforced Polymer Bridge Deck

The present paper deals with free vibration analysis of fibre reinforced polymer (FRP) bridge deck considering temperature induced nonlinear behaviour of composite materials. The finite element formulation based on the third-order shear deformation theory using Green–Lagrange approach of nonlinearity by considering large deformation and large rotation is developed to model the FRP bridge deck panel. The bridge deck is modelled by using a laminated plate with closely spaced box stiffeners. The plate and the stiffeners elements are formulated separately and merged thereafter. The eight-noded isoparametric plate bending elements and the three-noded isoparametric beam elements are used to formulate deck plate and stiffeners, respectively. Compatibility between plate and stiffener elements is maintained by considering identical degrees of freedom per node for both. The effect of temperature rise on natural frequencies of a laminated composite plate is studied in the present paper. The free vibration modal analysis is carried out to identify the effect of temperature change with proper temperature distribution within the stiffened structures using 1D heat conduction model, and the solutions may be used as benchmark.

Diamond film growth by HFCVD on Q-carbon seeded substrate

While hot-filament assisted chemical vapor deposition (HFCVD) is a well-established technique to synthesize diamond thin films using microdiamond seeds, the quality of grown diamond thin films is often compromised due to the presence of contaminants, i.e. graphitic entities and the eroded tungsten filament remnants, at the film-substrate interface. Here, we present a novel approach to form high-quality, contamination-free diamond thin films with HFCVD using Q-carbon precursor. The Q-carbon is a metastable phase which is formed by nanosecond laser melting of amorphous carbon and rapid quenching from the superundercooled state and consists of ∼75% sp3 and rest sp2 hybridized carbon. Using Q-carbon seeds in HFCVD, we demonstrate the growth of polycrystalline diamond film with a clean interface without any tungsten filament impurities. With large-area vibrational Raman mode analysis, we also observe a significant reduction in the presence of overall graphitic entities in the diamond film. With the realization of such a high-quality interface, we present a pathway to fabricate significantly improved diamond coatings and solid-state devices.

Selection measure of energy propagation in vibration diagnostic and modal analysis methods

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