Vibrational Study Research Articles

Assessment of Traffic-Induced Ground Vibrations and Effects on Masonry Monuments in Ayutthaya Historical Park, Thailand

ABSTRACT This paper presents an assessment study of traffic-induced ground vibrations and their effects on masonry-type historic structures in Ayutthaya Historical Park, a UNESCO World Heritage Site in Thailand. The first objective is to propose a practical prediction of the attenuation rate of vibration for risk management of the monuments located along roadsides in the city. The attenuation of vibration waves traveling from traffic sources and the intensity of ground vibrations were determined by in situ vibration measurement. The results from the investigations in the Ayutthaya area were compared with those obtained from other sites having different characteristics of subsoil classified by the average shear wave velocity (Vs). It was found that the attenuation rates at a long distance from the source tend to be dependent on soil property in terms of Vs of subsoils. The attenuation curves derived from the regression analysis are proposed for risk management from the vibration of the heritage site. The second objective is to assess the effects of traffic vibrations on historic structures. The highest amplitude observed in Ayutthaya was within the recommended vibration criteria for historic buildings. In addition, finite element analysis of a 3D stupa model revealed that the stresses resulting from the ground vibration records induced by traffic was lower than the strength of ancient brick and mortar.

Synthesis, single crystal X-ray analysis and vibrational spectral studies of 2-(pyrrolidin-1-yl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine

2-(Pyrrolidin-1-yl)-5-(4,4,5,5-tetramethyl-1, 3, 2-dioxaborolan-2-yl)pyridine is a synthetic intermediate containing nitrogen-containing heterocycle and borate ester group. The title compound was obtained through nucleophilic substitution reaction and Suzuki reaction. The structure of the compound was determined by MS, 1H NMR, 13C NMR and infrared spectrum. The single crystal of the title compound was also measured by X-ray diffraction, and the optimized crystal structure was determined by DFT calculation using the B3LYP/6-311 + G(2d, p) basis set, followed by crystallographic and conformational analysis. Finally, the geometric parameters, MEP, FMO, Hirshfeld analysis, and infrared characteristic vibrational absorption bands of the title compound were also analyzed.

An experimental study of forced vibration on natural convection between closed ended concentric and eccentric annular of horizontal cylinder

An experimental study of forced vibration on natural convection between closed ended concentric and eccentric annular of horizontal cylinder

Flow-induced vibration of a cantilevered cylinder in the wake of another

This work presents an experimental study of the flow-induced vibration of a cantilevered circular cylinder in the wake of another cylinder, fix-supported at both ends. The diameter and spacing ratios, d/D and L/d are 0.24 – 1.0 and 1.0 – 5.5, respectively, where d and D are the diameters of the upstream and downstream cylinders, respectively, and L is the separation from the upstream cylinder center to the front stagnation point of the downstream cylinder. Measurements are performed over the reduced velocity Ur=3.8 – 68.3 (based on D and freestream velocity), with the downstream cylinder vibration, vortex shedding frequency, surface pressure distribution and flow structures simultaneously captured. The downstream cylinder accompanied by a smaller d/D and/or L/d is more susceptible to galloping vibration and hysteresis in the galloping response. The mechanism behind initiation and sustenance of galloping is unveiled. It has been found that the effective mass and damping play a key role in initiating and sustaining the vibrations. The variation in the flow structure is discussed in detail in both streamwise and spanwise directions, along with the fluid–structure interactions.

Теоретическое исследование стабилизатора вибрации с обратной связью по интегралу смещения для энергетического оборудования

Reducing the vessel hull vibration caused by the power equipment is usually obtained by the effective vibration-isolating fastening. Vibration impact on the mechanisms and automation tools greatly reduces their reliability, affects the health of passengers and crew members. Despite the modern vibration-insulating materials and compensators, the problems of eliminating the variable forces transmitted from the vibration source have not been fully solved. Increasing the operational requirements for the vibration safety of water transport requires the scientifically based and technical solutions, improving the designs of vibration isolation supports for mounting the marine power plants. Vibration reduction problems must be solved both at the design stage and at the stage of construction, repair and modernization. The conducted studies of vibrations under the influence of the harmonic force, step load and gradually increasing load have shown high efficiency of the support in all cases of load application under different simulation modes. At stabilization of the position the support was controlled by the integral of the displacement. The results of the studies conducted on the test model for the vibration protection of marine power equipment showed the effectiveness of the stabilizer. There is presented a theoretical study of a stabilizer with feedback on the displacement integral in the MathCAD software package. The numerical experiment is based on the Newton equation. The parameters of the stabilizer are determined, on the basis of which it is possible to design the actuator. It can be an electric motor, the direction of rotation of which depends on the direction of displacement of the protected object. The motor rotates a screw pair that compresses the spring. The spring acts on the clutch, the torque changes and maintains the vibration source. The simulation results helped to infer that it is necessary to stabilize the position of the unit for all load application modes.

Case study of vibration in a mobile milling machine

Many industries rely on heavy-duty machinery such as cranes, pipelines, motors, which are subject to wear and tear. Milling of such parts using conventional machine tools presents many drawbacks and is impossible in some cases. In such situations, mobile machine tools can be used to machine directly on site. However, mobile machines are flexible, and are prone to detrimental vibrations during cutting operations. Vibrational stability in the surfacing process has been extensively studied in conventional milling. However, the focus of this article is an original study on a mobile milling machine used for on-site surfacing operations. An experimental investigation into the vibrational behavior of the machine is carried out and a sensorless method is used to detect the onset of chatter. Machine flexibility is discussed using a tool-point frequency response function and references from the literature. Milling operations are carried out over a range machining parameter to determine an experimental stability limit. Internal sensors for spindle motor consumption and spindle motor encoder are monitored during the machining process. A threshold is established for determining the appearance of chatter using only the machine’s internal sensors.

A study of Stall-Induced Vibrations using Surrogate-Based Optimization

Stall-Induced Vibrations (SIV) are an important design consideration for wind turbine blade design, especially for large, modern, wind turbines with highly flexible blades. Their severity depends on both the inflow and the structural characteristics of the blades. Studying SIV has a high computational cost, because it requires high-fidelity aeroelastic simulations, and potentially a large number of input variables. In an effort to reduce the computational cost of the domain exploration, in this work we have adopted a Surrogate-Based Optimization (SBO) framework. This way, the combination of input variables that lead to SIV can be explored with the minimum number of aeroelastic simulations. The proposed SBO framework can use any type of surrogate model, and leverages Delaunay triangulation to iteratively select samples to refine the surrogate model. The occurrence and severity of SIV on the IEA 10MW turbine is studied in a five variables space consisting of: wind speed, yaw angle, vertical wind shear, wind veer, and atmospheric temperature. A well-trained surrogate model is developed and used to predict the damping ratio of the first blade edgewise mode in the entire inflow space at a reduced computational cost. Sensitivity analysis of the predicted damping ratio shows that yaw angle is the most influential variable, while temperature is the least influential variable in terms of inflow conditions that can lead to the occurrence of SIV. Inflow conditions with a moderate yaw angle (around 10–25 deg), high wind speeds, and moderate to high negative veer are found to lead to severe SIV. This study should serve as a guiding tool to decide the scope of the more computationally expensive simulations such as high-fidelity CFD-based aeroelastic simulations which can provide a more accurate description of SIV.

Optimization of Brake Disc Profile Based on the Thermal Performance for Electric Vehicles

The brake disc market has reached the value of USD 20.9 billion in 2021 at a CAGR of 4.9% and it is expected to grow to USD 26.5 billion by 2026. However, the difficulties associated with the brake discs are significant rise in the temperature which results in, early wear, thermal cracks and brake fade leading to uneven braking and premature replacement. In this context many researchers have been studying the parameters like brake disc material and type of ventilation. The objective of the work was to study of the effect of ventilation types on thermal responses and optimize the brake disc profile for better thermal performances. Center of gravity and dynamic load transfer were calculated for two wheeler electric vehicle experimentally which was followed by computing the force required for braking process and heat flux on the brake disc analytically. Ventilation of type cross drilled holes (CD) was adopted in brake disc modelling, and was carried out in SOLIDWORKS 2022 and finite element model for the brake disc was created in ANSYS 17.2 with mesh size of 2 mm for lamellar graphite iron (LGI) with temperature dependent material properties. The transient thermal analysis for three braking cycles were carried out with the considerations such as: initial velocity of the vehicle of 96 km/h, ambient temperature of 22°C, conduction and convection modes of heat transfer and 5 s of deceleration and acceleration time. Transient thermal analysis was carried out by applying the heat flux on the frictional surface of the brake disc. For the solid disc without ventilation, it was found that the maximum temperature at the end of first braking cycle (0 to 5 s) was 157.72°C, at end of second braking cycle (10 to 15 s) was 256.95°C and at the end of third braking cycle (20 to 25s) was 349.73°C. As the wear rate for lamellar graphite iron grows exponentially beyond 300°C, ventilations were provided on the brake disc to reduce the temperature on the disc. For the optimized brake disc with ventilation type VT-12, it was found that maximum temperature at the end of first braking cycle (0 to 5 s) was 139.43°C, at end of second braking cycle (10 to 15 s) was 222.68°C and at the end of third braking cycle (20 to 25s) was 299°C. The overall character of these shows a quick rise in temperature at the start of the process, followed by the achievement of the maximum value and, eventually there is a drop in temperature. In this research the future work can be carried out by implementing the noise, vibration and harness studies which would benefit the industry with better braking system.

Experimental Study Results Processing Method for the Marine Diesel Engines Vibration Activity Caused by the Cylinder-Piston Group Operations

The article discusses the method and results of processing statistical data from an experimental study of vibrations in marine diesel engines caused by the operation of cylinder-piston groups. The results of the application of a ranking method for identifying factors that influence vibration in marine diesel engines are presented to determine the most significant ones. A series of experiments were conducted according to special plans to actively implement the random balance method. This helped to establish the correctness of selecting the most significant factors from a variety of factors that influence the process under study. The article presents a mathematical model that enables the calculation of current values and prediction of changes in the most significant indicators, with the clearance between the piston and the cylinder liner being the most important.

A Novel Finite Element Model for the Study of Harmful Vibrations on the Aging Spine

The human spine is susceptible to a wide variety of adverse consequences from vibrations, including lower back discomfort. These effects are often seen in the drivers of vehicles, earth-moving equipment, and trucks, and also in those who drive for long hours in general. The human spine is composed of vertebrae, discs, and tissues that work together to provide it with a wide range of movements and significant load-carrying capability needed for daily physical exercise. However, there is a limited understanding of vibration characteristics in different age groups and the effect of vibration transmission in the spinal column, which may be harmful to the different sections. In this work, a novel finite element model (FEM) was developed to study the variation of vibration absorption capacity due to the aging effect of the different sections of the human spine. These variations were observed from the first three natural frequencies of the human spine structure, which were obtained by solving the eigenvalue problem of the novel finite element model for different ages. From the results, aging was observed to lead to an increase in the natural frequencies of all three spinal segments. As the age increased beyond 30 years, the natural frequency significantly increased for the thoracic segment, compared to lumber and cervical segments. A range of such novel findings indicated the harmful frequencies at which resonance may occur, causing spinal pain and possible injuries. This information would be indispensable for spinal surgeons for the prognosis of spinal column injury (SCI) patients affected by harmful vibrations from workplaces, as well as manufacturers of automotive and aerospace equipment for designing effective dampers for better whole-body vibration mitigation.

Study of vibrations in micro-scale piezothermoelastic beam resonator utilising modified couple stress theory

Study of vibrations in micro-scale piezothermoelastic beam resonator utilising modified couple stress theory

Modification and development in the microstructure of PVA/CMC-GO/Fe3O4 nanocomposites films as an application in energy storage devices and magnetic electronics industry

We used casting method to create nanocomposites films from carboxymethylcellulose (CMC)/polyvinyl alcohol (PVA) and GO/Fe3O4 as nanofiller. Various analyses such as structural, vibrational, optical, conductivity, dielectric and magnetic studies reveal promising properties of the prepared polymer nanocomposites (PNCs) films. The amorphous phase of the polymer blend increased with increasing GO/Fe3O4 concentration up to samples containing 0.05%GO/1%Fe3O4 nanofiller, according to X-ray diffraction. The complexation of the nanofiller with the polymer blend's –OH, –COO, CO, and –CH groups through a coordinate bond/hydrogen bond was confirmed by Fourier-transform infrared analysis. While the Urbach energy showed a trend in the opposite direction, the optical bandgap gradually turned red as the nanofiller concentration increased. The interaction of GO/Fe3O4 ions with the CMC/PVA matrix is attributed to the changes in optical properties of CMC/PVA. The Jonscher's power law (JPL) is observed in all samples' ac conductivity spectra. To comprehend the charge storage competences, research of dielectric permittivity was also conducted. A study of dielectric permittivity was also conducted to comprehend the charge storage competences. While AC conductivity increases with frequency, dielectric characteristics decrease with frequency. With the addition of nanofiller, AC conductivity and dielectric characteristics increase. For 0.05%GO/1%Fe3O4 nanofiller loaded sample, the highest AC conductivity and dielectric constant were attained. The results of vibrating sample magnetometer (VSM) revealed that synthesized nanocomposite films exhibit superparamagnetic features. The unique features of CMC/PVA-GO/Fe3O4 films enable their employment in a variety of industries, including magnetic electronics, energy storage devices, and optoelectronics.

Phase transitions of L-histidinium hydrogen oxalate crystal under high pressures investigated by Raman spectroscopy

L-histidinium hydrogen oxalate (L-HisH)(HC2O4) crystal is formed from amino acid. L-histidine with oxalic acid whose vibrational high pressures behavior have not yet been investigated in the literature. Here we synthesized (L-HisH)(HC2O4) crystal by slow solvent evaporation method in a 1:1 ratio of L-histidine and oxalic acid. In addition, a vibrational study of (L-HisH)(HC2O4) crystal as a function of pressure was performed via Raman spectroscopy in the pressure range of 0.0–7.3 GPa. From analysis of the behavior of the bands within 1.5–2.8 GPa, characterized by the disappearance of lattice modes, the occurrence of a conformational phase transition was noted. A second phase transition, now from structural type, close to 5.1 GPa was observed due to the incidence of considerable changes in lattice and internal modes, mainly in vibrational modes related to imidazole ring motions.

Case study: Analysis and research on pipeline vibration of liquid oxygen kerosene of rocket engine and vibration reduction measures Measures

Abnormal vibration often occurs in the liquid oxygen kerosene transmission pipe- line of rocket engines, seriously threatening the safety of rocket engines. Improper handling will result in rocket launch failure and enormous economic losses. Therefore, the vibration of the transmission pipeline must be studied. In this paper, a three-dimensional high-pressure transmission pipeline model comprising a corrugated pipe, a multi-section bending pipe, and other auxiliary structures is established. Using the two-way fluid–solid coupling method, vibration analysis is performed on the pipeline under external pressure pulse excitation. The accuracy of the computation results is verified by a thermal test. Two vibration reduction strategies are presented and validated by simulation in accordance with the findings of the vibration study. The main conclusions are as follows: (1) At the same frequency, the amplitude distribution of vibration acceleration significantly correlates with the flow field pressure, indicating that fluid pressure fluctuation is the root cause of the abnormal vibration of the pipeline, and the vibration of the pipeline increases with the average pressure. (2) The time-average value and fluctuation amplitude of the larger stress and strain are mainly concentrated in the two supports, namely, the inside of the elbow and the bellows, which is different from the distribution of vibration acceleration. Such places are prone to structural failure and should be given attention. (3) The guide plate and the support enhancement method can reduce the vibration, but the support enhancement method has a better effect, reducing the vibration velocity and acceleration by 86.4% and 93%, respectively.

Applications of Fourier series and Fourier Transform in Electrical and Electronics Devices

Abstract: Fourier series are of great importance in both theoretical and ap­ plied mathematics. For orthonormal families of complex­valued functions Fourier Series are sums of the φn that can approximate periodic, complex­valued functions with arbitrary precision. This paper will focus on the Fourier Series of the complex exponentials. Of the many possi­ ble methods of estimating complex­valued functions, Fourier series are especially attractive because uniform convergence of the Fourier series (as more terms are added) is guaranteed for continuous, bounded functions. Furthermore, the Fourier coefficients are designed to minimize the square of the error from the actual function. Finally, complex exponentials are relatively simple to deal with and ubiquitous in physical phenomena. This paper first defines generalized Fourier series, with an emphasis on the se­ ries with complex exponentials. Then, important properties of Fourier series are described and proved, and their relevance is explained. A com­plete example is then given, and the paper concludes by briefly mentioning some of the applications of Fourier series and the generalization of Fourier series, Fourier transforms. In the mid­eighteenth century, physical problems such as the conduction pat­ terns of heat and the study of vibrations and oscillations led to the study of Fourier series. Of central interest was the problem of how arbitrary real­valued functions could be represented by sums of simpler functions. As we shall see later, a Fourier series is an infinite sum of trigonometric functions that can be used to model real­valued, periodic functions. We shall begin by giving a brief description of the trigonometric polynomials,and especially of their relation to the complex exponentials. The Fourier series, the founding principle behind the field of Fourier analysis, is an infinite expansion of function in terms sine’s and cosines. Fourier transform provides a continuous complex frequency of a function. It is useful in the study of frequency response of a filter, solution PDE, Discrete Fourier transform and FFT in the signals analysis. The advent of Fourier transformation method has greatly extended our ability to implement Fourier methods on digital multimedia visualization system. It covers the mathematical foundations of Digital signal processing (DSP), classical sound, synthesis algorithms and multi-time frequency domain analysis associated musical sound. In this paper, we are analysis of square wave in terms of Fourier component, may occur in electric circuits designed to handle sharply rising pulses and how to convert analog to digital system by using Fourier transform and its applications in electronics and digital multimedia visualization signal process of communication system.

Vibrational Solvatochromism Study of the C-H···O Improper Hydrogen Bond.

The improper C-H···O hydrogen bond is an important weak interaction, with broad implications for protein and nucleic acid structure, molecular recognition, enzyme catalysis, and drug interaction. Despite its wide identification in crystal structures, the general existence of C-H···O hydrogen bonds remains elusive especially for natural C-H groups in bulk aqueous solutions at room temperature. Vibrational spectroscopy is a promising methodology to tackle this challenge, as formation of C-H···O hydrogen bonds usually causes shifts of the C-H stretch frequency. Yet, prior observations are inconclusive, as they are all based on a simple blue-shift in aqueous solution and cannot distinguish if it is an effect caused by solvent reorganization or a specific hydrogen-bonding interaction. In this work, we used vibrational solvatochromism as a calibration of the solvent reorganization effect and identified a specific H-bonding interaction. We performed vibrational solvatochromism study of C-H(D) of multiple alcohol molecules including the CH mode of CD3CH(OH)CD3 and the CD3 modes of CD3OH, CD3CH2OH, and CD3CH(OH)CD3 in a series of solvents. We found an abnormal blue-shift of the Raman frequency of the C-H and C-D bonds at both the Cα and Cβ positions of alcohols in water, which lies in an opposite direction to the expected trend due to vibrational solvatochromism. This experimental evidence supports that the improper C-H···O hydrogen bonds might generally exist between nonpolarized C-H and water in liquid solutions at room temperature.

Crystal growth and vibrational spectroscopic studies on the novel nlo active piperazine-1,4-diium 3-phenyl-2-propenoate single crystal by experimental and computational technique

An organic nonlinear optical (NLO) single crystal of piperazine-1,4-diium 3-phenyl-2-propenoate (PAPP) is synthesized and delineated by spectroscopic techniques in association with quantum chemical computation. The quantum chemical calculation is performed utilizing density functional theory (DFT) with B3LYP/6-311 G(d,p) basis set. The FT-IR and FT-Raman techniques are adopted to point out the presence of various functional groups in PAPP molecule. The natural bond orbital (NBO), natural charge, molecular electrostatic potential (MEP) and HOMO-LUMO analyses are performed to spot hydrogen bonds and charge transfer interaction present in the molecule. Hole-electron analysis is performed to identify the types of interaction present in the molecule. Interaction region indicator analysis is performed to identify the steric effect, van der Waals force and hydrogen bonds. The optical quality of PAPP single crystal and the band gap energy is found out using UV–visible analysis. The nonlinear optical behaviour of the PAPP molecule is established by evaluating dipole moment, polarizability and hyperpolarizability. The third-order NLO parameters of PAPP crystal are estimated by employing the Z-scan technique.

An Application of the Melnikov Method to a Piecewise Oscillator

In this paper we present a new application of the Melnikov method to a class of periodically perturbed Duffing equations where the nonlinearity is non-smooth as otherwise required in the classical applications. Extensions of the Melnikov method to these situations is a topic with growing interests from the researchers in the past decade. Our model, motivated by the study of mechanical vibrations for systems with ''stops'', considers a case of a nonlinear equation with piecewise linear components. This allows us to provide a precise analytical representation of the homoclinic orbit for the associated autonomous planar system and thus obtain simply computable conditions for the zeros of the associated Melnikov function.

Vibrational and ultrasonic relaxation spectroscopic study of keto-to-enol tautomerism: The case of acetylacetone

We report on a concentration-dependent Raman and ultrasonic relaxation study of the binary acetylacetone solutions in a wide mole fraction range. We combined vibrational and ultrasonic relaxation spectroscopies with DFT theoretical calculations for the systematic examination of the keto-to-enol tautomerism taking place in acetylacetone solutions with polar and non-polar solvent. Two sets of solutions were prepared with different solvents in terms of polarity. Raman spectra revealed that the keto and enol tautomers of acetylacetone coexist in solution and the keto tautomer is favored as the solvent polarity increases. A single Debye-type relaxation process is detected in the acoustic spectra, which is assigned to the interconversion process between ACAC tautomers. The isentropic volume change associated with the isomerization reaction was estimated from the acoustic data and found to decrease up to x∼0.2, while above this mole fraction reaches an almost constant value of ∼13.6 ml/mol, close to the theoretically estimated value of ΔVtheor,CCl4=12.955 ml/mol in CCl4 solvent environment. The keto-to-enol isomerization in the dilute region was found to be strongly affected by the presence of the non-polar solvent molecules, while for mole fractions higher than x∼0.3 the process is not considerably altered. Several physical properties of the system including density and acoustic properties, as well as the intermolecular free length and polarizability exhibited an inflection point at a specific mole fraction signifying the cross-over of two different regimes related with different tautomerization rates analogous to that observed in the Raman spectra. The results are analyzed and discussed in the framework of the current phenomenological status of the field.

Productivity analysis focusing on internal combustion engine vibration when using local fuels and additives

The purpose of this article is to analyze the vibrations and behavior of an internal combustion engine of three vehicles: A1, J1, K1 which are exposed to both the geography, relief and road conditions of the Metropolitan District of Quito. To implement the quantitative methodology in the research it is important to perform a complete analysis of the vehicle based on its technical data sheet: A1, J1, K1, in order to identify both fuel consumption and the use of additives to reduce the friction that cause vibrations in the engine, especially the condition of the road. In addition, it is important to check how the level of vibrations can be reduced, the percentage of fuel when using additives and to verify the data provided by the vibration study of each vehicle. The results show that the tests carried out at 3500 RPM in vehicle A1 show a value of 27%, in vehicle J1 a value of 17% and vehicle K1 a value of 15%, these values are related to the use of additives. The results of the research are linked to field tests, individual tests, comparison of results and discussion of the feasibility of each of the tests performed on each vehicle to find similarities or marked differences.