Vibration Method Research Articles

Application of the lumped-parameter method for modeling nonlinear vibrations of drill strings with stabilizers in a supersonic gas flow

In this paper, we study the nonlinear dynamics of a drill string under the effect of external loads in a supersonic gas flow, taking into account supporting stabilizers. The case of the drill string spatial lateral vibrations, which are the main cause of the drilling equipment failures, is considered. To account for nonlinear effects, a mathematical model based on the general relations of Novozhilov's nonlinear theory of elasticity is developed. The discretization of the model is conducted using the lumped-parameter method. The explicit fourth order Runge-Kutta method is utilized for obtaining a numerical solution for the studied system. The effect of damping elements (supporting stabilizers) on the drill string lateral vibrations is analyzed. Numerical illustrations are presented, and the corresponding recommendations for deep and shallow drilling are given.

INCREASING THE RADIATION SAFETY OF NUCLEAR POWER PLANTS USING THE METHOD OF CONTROLLING THE TIGHTNESS OF FUEL ELEMENTS

The problem of monitoring the tightness of fuel elements at the stage of their manufacture to improve the radiation safety of nuclear power plants is considered. A vibration method is proposed for non-destructive testing of the tightness of cylindrical fuel rods. The method makes it possible to perform accelerated testing of a batch of fuel rods and remove samples with gross leakage under conditions of mass production. A description of the method is given, a mathematical model of free vibrations of a fuel element is developed. The time dependences of the pressure and the period of free oscillations of the fuel element were obtained by calculation. The assessment of the influence of the inhomogeneity of the fuel element structure on the test result is carried out. Inhomogeneity causes an error in measuring the oscillation period up to 1%, which can lead to a false result. Three-dimensional plots were constructed, reflecting the main form of free vibrations of a homogeneous and inhomogeneous section of a fuel element. On the basis of the performed assessment, recommendations were given for conducting fuel rod tightness control, excluding a false result.

Investigation of Ship Vibration Effects on the Gas Distribution and Output Voltage of a Proton Exchange Membrane Fuel Cell.

The effects of ship vibrations on the mass transfer and performance of proton exchange membrane fuel cells (PEMFCs) have many vague aspects. Hence, the method of loading ship vibrations with the sliding mesh is first proposed in this paper. Furthermore, this method is adopted to form the solution of the simulation study of PEMFC performance under ship vibrations. In the framework of computational fluid dynamics, the ship vibration is loaded into the three-dimensional PEMFC model and successfully solved. Then, a series of special cases are performed to explore the gas distribution and output features of PEMFCs in ship environments with different vibrations. Finally, the results show that the ship vibrations have vectorial effects on the gas transfer in the PEMFC. Additionally, vibrations perpendicular to the channel evidently affect the gas transfer. Moreover, while the vibrations are parallel to the channel, they remain nearly normal. Relatively, a more significant influence on the output voltage of the PEMFC will occur under smaller frequencies and/or greater amplitudes of ship vibrations.

Temperature measurement of cloud or haze layers based on Raman rotational and vibrational spectra.

Pure rotational Raman lidar is often used for atmospheric temperature profile measurements. However, high elastic scattering suppression ratios (>107) are required for temperature measurement in clouds and haze, which imposes stringent requirements on spectral separation techniques. To solve this problem, a lidar measurement technique based on vibrational and rotational Raman spectra is proposed. Using nitrogen vibrational and rotational Raman scattering to obtain temperature profiles under strong elastic scattering, combined with the dual-rotational Raman temperature measurements under weak elastic scattering, a vertical distribution of atmospheric temperature including cloud and haze layers, can be obtained. The feasibility of the method was verified by numerical simulation. The Raman lidar for temperature measurements was established in Xi'an University of Technology, and the obtained temperature results show good agreement with the radiosonde measurements. The proposed method combines the high sensitivity of the dual-rotational Raman method and the high Mie-scattering suppression of the vibrational Raman method, thus further improving the adaptability of Raman lidar to cloudy and hazy air conditions and supporting atmospheric and cloud physics research.

A Material Substitute for Column A-Pole of LCV by Using Composite Reinforced Aluminium

Automobile industry is always in search to find an alternative methodology to implement the continuous changes in passenger car norms and customer expectations. Weight is main factor of the vehicle which has dominant effect on emission, performance and efficiency of the vehicle. Now day’s use of Mild Steel is reduced with lightweight materials like Aluminium and its alloys, Glass fiber, Plastic and others. The work has been carried out to decrease the weight of the A-Pole reinforcement of the passenger car SUV class and to fulfill the vibration requirement. A traditional material Mild Steel is replaced by composite of Glass fiber with Aluminium reinforced. Project executed in three stages. At initial stage present geometry details are reverse engineered like its dimensions and thickness. Continued by setting base line targets for new material by FEA method for vibration and linear static analysis. Correlation of light weight structure is achieved with different iterations with help of tools like ANSA, Hypergraph Metapost, Hypermesh, Optistruct and Nastran. Results comparison shows that the Aluminium with reinforced glass fiber reduces the mass of A-Pole by 30% by mechanical strength.

Thermodynamic properties of geikielite (MgTiO3) and ilmenite (FeTiO3) derived from vibrational methods combined with Raman and infrared spectroscopic data

We present a model for the lattice vibrational density of states of MgTiO3 (geikielite) and FeTiO3 (ilmenite) that predicts thermodynamic properties, in agreement with observational data. The model is based on Kieffer’s method combined with spectroscopic data. For both substances experimental data sets are influenced by non-stoichiometry. For geikielite that affects the volume, whereas for ilmenite volume and bulk modulus are affected. We show that Kieffer’s method enables predicting bulk moduli in pressure–temperature space. We demonstrate that intrinsic anharmonicity or electronic effects significantly affect the heat capacity of ilmenite, whereas that is not the case for geikielite. We use Kieffer’s method to derive multiple-Einstein models, from which we demonstrate that thermodynamic properties are insignificantly influenced by dispersion in Grüneisen, mode-q and anharmonicity parameters for both substances. We show that our results enable predicting thermodynamic properties and shear modulus of the solid solution formed from geikielite and ilmenite. Geikielite and ilmenite are added to our thermodynamic database for the system MgO–SiO2–FeO, to enable modeling phase stability and physical properties of titanium-rich reservoirs in the Earth’s Moon.

Intermolecular interaction study of Ag-amino acid biomolecular complex using vibrational spectroscopic techniques and density functional theory method

Nowadays, people are more healthy skin conscious which leads to a healthy and beneficial lifestyle. There are different skin products in the market and many are coming up according to consumer demand. In the present study, we have chosen three molecules D-Proline, TCA and Ag metal that are very much beneficial for the skin and synthesize their biomolecular complex. The study of their biomolecular complex at the atomic level shall help to produce potential drugs having high efficacy and fewer side effects. The present paper emphasizes the interaction study of silver (Ag) metal ions with amino acid D-Proline and the solute-solvent mixture of D-Proline and Trichloroacetic acid (TCA) under the Raman, FTIR and UV-Vis experimental techniques. The favourable binding sites of D-Proline, (D-Proline)Ag, (D-Proline)Ag2, D-Proline-TCA, (D-Proline-TCA)Ag and (D-Proline-TCA)Ag2 complexes are studied using the B3LYP method with a LANL2DZ basis set. The study includes electronic and molecular behaviour examined under MEP surface study, frontier molecular orbital analysis, NBO analysis, and AIM analysis to investigate the type of interactions between the metal and the ligand. The IEFPCM solvation model is undertaken to execute the UV-Vis simulation using methanol as solvent. BSSE method is carried out to provide an appropriate interacting environment. The complexes' drug-likeness properties and bioactivity score are studied to understand their bioactivity and pharmacokinetics. The Autodock tool is implemented to execute the molecular docking study of the complexes with the preferable binding sites of 1QCY collagen receptor.

Exploration and Comparison of the Effects of Vibration and Backwashing Methods on the Process of the Sulfur-Based Autotrophic Denitrification

Both the vibration and backwashing methods are efficient pathway to improve the denitrification ability in reactors. However, the comparison of the effects of vibration and backwashing on the sulfur-based autotrophic denitrification (SAD) reactor is still lacking. In this study, two SAD reactors were compared under various conditions, and the results showed that the use of the oyster shell powder could lower the sulfate productivity with better denitrification ability, and the denitrifiers could be more enriched due to the use of the oyster shell powder. In addition, vibration method performs better than backwashing in improving SAD denitrification ability, reasonable vibration intensity can not only help to reduce energy consumption, but also improve the ability of denitrification of the SAD reactors to a greater extent. Overall, the results of the experiments in this study are helpful for improving the ability of SAD reactors at low temperature and could provide the possibility for wider application of SAD technology.

Experimental and numerical study of the thermal-frictional behavior of a horizontal heated tube equipped with a vibrating oscillator turbulator

This study investigates a novel heat transfer enhancement method named electromagnetic vibration (EMV) method. For the first time a stretched oscillator with geometries of string and strip was placed coaxially inside a heated copper tube and induced to vibrate at the natural frequencies. Longitudinal vibration of the stretched oscillators creates harsh turbulence, radial flow and vortexes inside the heated tube. Tests were conducted for various vibrational frequencies ranging 0 to 1 KHz in different mass flow rates. The experimental results indicated that oscillator with the geometry of strip has the better thermal performance; also the heat transfer coefficient can be increased with increasing vibration frequency from 2.18 to 2.50 folds. For comprehensive analyze at high frequency vibrations, a numerical model was conducted for the vibrating strip geometry to evaluate this new method capability in heat transfer performance enhancement. The numerical study shows that at 1 KHz frequency, heat transfer coefficient and thermal enhancement factor (TEF) can reach up to 32.2 and 14.2 fold compare to the plain tube, respectively. This magnificent increment shows the high potential of the EMV method as a new heat transfer augmentation technique.

Study on the Material Removal Mechanism of Ultrasonic Elliptical Vibration Cutting of Medical β Titanium Alloy.

For new medical β titanium implants, the surface micro texture processing technology is a difficult problem. To solve this problem, a new method of ultrasonic elliptical vibration cutting (UEVC) is adopted in this paper. The mechanism of material removal in ultrasonic elliptical vibration cutting is explored for different cutting paths. By means of simulation and experimentation, the material removal mechanism of ultrasonic elliptical vibration cutting medical β titanium alloy is revealed with respect to the aspects of cutting deformation, stress distribution, force and thermal variation, and chip formation mechanism. The results show that: (1) The cutting temperature and cutting force in the UEVC process obey the law of periodic change, and the maximum point of cutting force appears ahead of the maximum point of cutting temperature. (2) The material removal process of UEVC is a “press–shear–pull” composite cutting process. The tool squeezes the material to form the chips. Under the action of high temperature, the material is removed by adiabatic shear. (3) The difference of UEVC paths will affect the removal mode of materials and form different surface morphology. (4) For different cutting paths, compressive stress is distributed at the lowest point of the machining pit, and tensile stress is distributed at the protrusion position.

Effect of Vibration and Noise Measuring Points Distribution on the Sensitivity of Pump Cavitation Diagnosis

Cavitation is an essential factor in the deterioration of the hydraulic performance of centrifugal pumps. The study of cavitation fault diagnosis can help avoid or reduce the damage it causes. The vibration and noise analysis method can predict the incipient cavitation more accurately. In order to improve the accuracy of cavitation fault diagnosis, this paper studies the distribution of vibration and noise measuring points for centrifugal pump cavitation diagnosis. The research object is a centrifugal pump with an inducer and splitter blades. Vibration acceleration sensors and hydrophones were used to collect structural vibration and liquid-borne noise signals at different positions of the pump unit. Root-mean-square (RMS) and fast Fourier transform (FFT) methods were used to construct spectrums of vibration and noise signals with different NPSH and compare the sensitivity of different measuring points to the inception and development of cavitation. In addition, the SST k-ω turbulence model and Zwart cavitation model were used to study the cavitation volume distribution in the pump under different cavitation stages. By setting monitoring points at the impeller outlet, the frequency domain signal distribution of pressure pulsation was studied. The results show that the vibration acceleration measuring points at the pump inlet flange and pump axial position, and liquid-borne noise measuring point at the inlet position, are more sensitive to the diagnosis of cavitation fault. Motor current is also the basis for judging the inception of cavitation. Moreover, as the cavitation intensifies, the dominant frequency signal of the pressure pulsation in the pump is partially shifted.

Comparison between Synthetic and Biodegradable Polymer Matrices on the Development of Quartzite Waste-Based Artificial Stone

The development of artificial stone from the agglutination of polymeric resin using industrial wastes can be a viable alternative from a technical, economic, and sustainable point of view. The main objective of the present work was to evaluate the physical, mechanical, and structural properties of artificial stones based on quartzite waste added into a synthetic, epoxy, or biodegradable polyurethane polymer matrix. Artificial stone plates were produced through the vacuum vibration and compression method, using 85 wt% of quartzite waste. The material was manufactured under the following conditions: 3 MPa compaction pressure and 90 and 80 °C curing temperature. The samples were characterized to evaluate physical and mechanical parameters and microstructure properties. As a result, the artificial stone plates developed obtained ≤0.16% water absorption, ≤0.38% porosity, and 26.96 and 10.7 MPa flexural strength (epoxy and polyurethane resin, respectively). A wear test established both artificial quartzite stone with epoxy resin (AS-EP) and vegetable polyurethane resin (AS-PU) high traffic materials. Hard body impact resistance classified AS-EP as a low height material and AS-PU as a very high height material. The petrographic slides analysis revealed that AS-EP has the best load distribution. We concluded the feasibility of manufacturing artificial stone, which would minimize the environmental impacts that would be caused by this waste disposal. We concluded that the production of artificial rock shows the potential and that it also helps to reduce environmental impacts.

Denoising Raman spectra using fully convolutional encoder–decoder network

AbstractRaman spectroscopy is a vibrational method that gives molecular information rapidly and non‐invasively. Despite its advantages, the weak intensity of Raman spectroscopy leads to low‐quality signals, particularly with tissue samples. The requirement of high exposure times makes Raman a time‐consuming process and diminishes its non‐invasive property while studying living tissues. Novel denoising techniques using convolutional neural networks (CNN) have achieved remarkable results in image processing. Here, we propose a similar approach for noise reduction for the Raman spectra acquired with 10 lower exposure times. In this work, we developed fully convolutional encoder‐decoder architecture (FCED) and trained them with noisy Raman signals. The results demonstrate that our model is superior (p value < 0.0001) to the conventional denoising techniques such as the Savitzky‐Golay filter and wavelet denoising. Improvement in the signal‐to‐noise ratio values ranges from 20% to 80%, depending on the initial signal‐to‐noise ratio. Thus, we proved that tissue analysis could be done in a shorter time without any need for instrumental enhancement.

Measurement of Bridge Vibration by UAVs Combined with CNN and KLT Optical-Flow Method

A measurement method of bridge vibration by unmanned aerial vehicles (UAVs) combined with convolutional neural networks (CNNs) and Kanade–Lucas–Tomasi (KLT) optical-flow method is proposed. In this method, the stationary reference points in the structural background are required, a UAV is used to shoot the structure video, and the KLT optical-flow method is used to track the target points on the structure and the background reference points in the video to obtain the coordinates of these points on each frame. Then, the characteristic relationship between the reference points and the target points can be learned by a CNN according to the coordinates of the reference points and the target points, so as to correct the displacement time–history curves of target points containing the false displacement caused by the UAV’s egomotion. Finally, operational modal analysis (OMA) is used to extract the natural frequency of the structure from the displacement signal. In addition, the reliability of UAV measurement combined with CNN is proved by comparing the measurement results of the fixed camera and those of UAV combined with CNN, and the reliability of the KLT optical-flow method is proved by comparing the tracking results of the digital image correlation (DIC) and KLT optical-flow method in the experiment of this paper.

Highly sensitive and reproducible SERS substrates with binary colloidal crystals (bCCs) based on MIM structures

Surface-enhanced Raman scattering (SERS) is a powerful molecular vibrational spectrum characterization method, and has shown promising applications in surface science, life science, environmental monitoring, etc. Developing new simple processes to fabricate low-cost substrates is an essential prerequisite to promote and strengthen the practical application of the SERS technique. For this purpose, the present work reports on the development of a metal/insulator/metal (MIM) structure combined with polystyrene (PS) binary colloidal crystals (bCCs) based on nanosphere self-assembly and electron-beam evaporation technologies. The PS bCCs are used to form a dielectric layer sandwiched between a bottom Ag reflection layer and an upper Ag shell layer. Compared with single-sized colloidal spheres, the PS bCCs exhibit considerably richer morphologies and structures. In addition, the closely packed Ag shell arrays enhance the density of electromagnetic field “hot spots” thus increasing the SERS activity. The PS bCCs-based MIM substrate could achieve an enhancement factor (EF) of 1.10 × 108 and an ultralow detection limit for the Rhodamine 6G (R6G) molecule of about 10−14 M. The results demonstrate that the proposed substrates with a facile fabrication strategy, low cost, large area and high sensitivity have high potential applications of SERS sensors for bio- and chemical molecular analysis.

A semi-analytical method for free vibration of semi-closed shells of revolution with variable curvature

This study is concerned with the free vibration analysis of semi-closed shells of revolution with variable curvature, with a focus on the analytical solution to the natural frequency of such shells. A semi-closed shell of revolution with variable curvature is firstly divided into some narrow small shell segments, then the first small shell segment with a closed shell apex is approximated with a semi-closed conical shell, while the remaining small shell segments are approximated with a series of progressively larger truncated conical shells. Since each small conical shell is part of the large semi-closed shell of revolution with variable curvature and has to vibrate in sync with the large shell, the analytical solution to the axisymmetric free vibration of the large shell can be transformed into the analytical solutions to the synchronous free vibration of these small conical shells. The general solutions for the natural frequencies of all small conical shells are analytically derived under the condition that conical shells have zero meridional curvature. The undetermined constants in the general solutions are determined by letting all natural frequencies of these small conical shells be equal. Finally, the analytical solution for the axisymmetric free vibration of semi-closed shells of revolution with variable curvature is presented and is proved to be basically reliable by conducting a confirmatory experiment based on polymer 3D-printing technique.

Nonsynchronous Rotor Blade Vibrations in Last Stage of 380 MW LP Steam Turbine at Various Condenser Pressures

This paper presents an analysis of nonsynchronous rotor blade vibrations in the last stage of an LP steam turbine at various condenser pressures. The nonlinear least squares Levenberg–Marquardt method is used in a tip-timing analysis to determine nonsynchronous multimode rotor blade vibrations, which is a novelty. This is done with two sensors in the casing and a once-per-revolution sensor. The accuracy of the nonlinear least squares Levenberg–Marquardt multimode method is compared with the one-mode linear method. The algorithm is verified by comparing it with one-mode tip-timing methods for synchronous and nonsynchronous vibrations. The analysis shows that the rotor blades vibrate simultaneously with two modes in non-nominal conditions, which is also a novelty. The rotor frequencies are unchanged, although the blade vibration amplitudes vary, depending on the pressure in the condenser. Flutter does not appear in the last stage for the various condenser pressures and powers that were tested.

A novel eddy current damper system for multi-mode high-order vibration control of ultra-long stay cables

Recently, the multi-mode high-order wind-induced vibration of the ultra-long stay cables has been observed on several cable-stayed bridges, which may result in a visual panic of the users and the fatigue of the stay cables at anchorage ends. In order to investigate the multi-mode high-order wind-induced vibration characteristics of ultra-long stay cables, a vibration monitoring system (VMS) of the stay cables is established on the Sutong Bridge (STB). Furthermore, to suppress the in-plane and out-of-plane vibration responses of the stay cables simultaneously, a novel eddy current damper system (ECDS) is proposed in this study. The damping coefficients of the ECDS for multi-mode high-order vibration of the stay cables are determined via a modified method. Moreover, laboratory tests are conducted to evaluate the performance of the developed dampers. Furthermore, the field tests of seven stay cables of the STB are carried out to identify the modal damping ratios of the cable-damper system via the free vibration method. The results show that it is feasible to provide sufficient additional modal damping ratios for multi-mode high-order vibration of ultra-long stay cables applying the ECDS proposed in this study. Finally, the one-year field measurements of the wind-induced vibration responses of the seven stay cables of the STB are carried out to validate the ECDS suppress effects on multi-mode high-order vibration control of ultra-long stay cables. The measurement results show that the multi-mode high-order vibration responses of the monitored stay cables of the STB are effectively suppressed.

A relative torsional vibration monitoring method for intelligent ships and associated error analysis

In this era of rapidly developing transport technology, shipping accounts for two thirds of the total international trade and transport industry. Nowadays, 'ship intelligence' is an important avenue to pursue in the development of the shipping industry and it requires ships and their working machinery to undergo real-time and high-precision inspection and diagnoses of their operational state. This paper develops a simple method for monitoring relative torsional vibration using multiple measuring points, which is suitable for the monitoring of intelligent ship rotating machinery. A proof-ofprinciple prototype is also designed to verify whether this calculational method can achieve clearer and more accurate physical significance and engineering practicability compared with the traditional single-point measuring method. According to the test results, under the condition of 100 pulses per revolution and at a speed of less than 3000 r/min, the relative error of speed measurement of the proof-of-principle prototype is within ±0.011%, which is close to the theoretical maximum accuracy of a 54 MHz sampling rate. The measurement result for the relative torsional angle shows that the maximum error is less than 0.17 mrad, the relative error is less than 1.75% and the maximum error in the amplitudes of the first and third harmonics is 9 mdeg. These accuracies are higher than those of the traditional method, which are 2.62% and 12 mdeg, respectively, in this study. Under the condition of speed fluctuations and rolling vibration, distortion occurs in the time-domain and frequency-domain torsional angle curves when the single-point measuring method is adopted. With the multi-point measuring method, much more accurate measurement values of the torsional angle are acquired compared with the single-point measuring method and accurate time-domain and frequency-domain curves are also obtained. Finally, the health status of the torsional angle is evaluated using an intelligent dynamic alarm system with a torsional vibration threshold, which has a better evaluation effect in line with the engineering practice and specification requirements. Therefore, this simple multi-point relative torsional vibration inspection method has universal applicability and wide application value.

Finite element explicit dynamics simulation of motion and shedding of jujube fruits under forced vibration

Current fruit motion response simulations during vibration harvesting mainly adopt linear theoretical calculation methods for the fruit motion patterns analysis, which cannot reflect some nonlinear vibration features of fruits under real conditions and cannot simulate the fruit-branch vibration separation process. In this paper, the finite element (FEM) explicit dynamic simulations technique was combined with experimental and modal analysis to investigate and simulate the dynamic responses of the Jun jujube fruit-stem system under various forced vibration conditions. According to the obtained results, the greater the fruit vibration amplitude, the greater the maximum stress on the stem during vibration, while the maximum stress position depends on the vibration direction. The fruit-stem system resonance can be triggered at a specific mode depending on the vibration method and mode shape. Due to its nonlinearity, the fruit-stem system has primary resonance with an excitation frequency close to the natural frequency and a sub-harmonic resonance with an excitation frequency close to an integer multiple of the natural frequency. The stress failures can be employed as criteria for material failures at the connection between the branch and the fruit. Accordingly, the fruit shedding process from the branch can be accurately simulated during vibratory harvesting, and the fruit shedding movement can be effectively predicted under complex excitation conditions.