Excessive Vibration Research Articles

Influence of sodium bicarbonate treatment on the free vibration characteristics of Phoenix sp. fiber loaded polyester composites

Natural fiber-based polymeric composites have become increasingly popular in machine tool and automobile applications in recent years. While, using the composite in such applications, it may fail due to excessive vibrations caused by dynamic loads. Therefore, it is necessary to understand the free vibration behavior of composites before employing it to such applications. The purpose of this work is to compare the free vibration characteristics of untreated and sodium bicarbonate treated Phoenix sp. fiber reinforced polyester composites fabricated through compression molding technique with different fiber content (0, 10, 20, 30 and 40 wt.%) and constant fiber length (20 mm). The chemical treatment was carried out for different time periods (24, 120 and 240 h) with 10 wt.% concentration of sodium bicarbonate solution. The results revealed that the natural frequency of treated fiber composites was greater than the untreated fiber composites which maybe ascribed to the increased stiffness of the fibers and interfacial bonding after the treatment. In addition to this single fiber pull-out test was also performed to assess the interfacial strength among the composite constituents. Especially, the composites loaded with 120 h treated fiber showed better results and it can be suggested for various engineering applications.

Influence of structural parameters on the modal characteristics of a Francis runner

The modal characteristics are important issues of a Francis turbine runner. It is prone to cause excessive vibration even resonance of turbine if the natural frequency is close to the excitation frequency. Thus, in the runner design and optimization processes, not only hydraulic characteristics but also dynamic characteristics should be considered to ensure the safe and stable operation of the unit. The modal analysis of hydrofoil NACA0009 is calculated by means of coupled acoustic fluid–structure model to verify the feasibility of the method and the results show good agreement with the experimental results. Then the effect of gap and structure parameters are discussed. Results show that the effect of fluid in the crown gap and seal on natural frequency and added mass is small, but the effect of fluid in the band gap and seal is considerable. The mode shapes are similar under different structural parameters, but the natural frequency and added mass factor are different. The effect of root rounding radius is more obvious than that of blade thickness and band thickness. Besides, the effect mechanism of band thickness on modal characteristics is quite complex, the lower-order frequency decreases while the higher-order frequency increases with the increase of the band thickness. The results in this paper are helpful to avoid the typical resonance frequency such as rotor–stator interaction frequency in the design and optimization processes.

Data-Driven Railway Crosstie Support Condition Prediction Using Deep Residual Neural Network: Algorithm and Application

Ballasted track substructure is designed and constructed to provide uniform crosstie support and serve the functions of drainage and load distribution over trackbed. Poor and nonuniform support conditions can cause excessive crosstie vibration which will negatively affect the crosstie flexural bending behavior. Furthermore, ballast–tie gaps and large contact forces at the crosstie–ballast interface will result in accelerated ballast layer degradation and settlement accumulation. Inspection of crosstie support condition is therefore necessary while very challenging to implement using current methods and technologies. Based on deep learning artificial intelligence techniques and a developed residual neural network (ResNet), this paper introduces an innovative data-driven prediction approach for crosstie support conditions as demonstrated from a full-scale ballasted track laboratory experiment. The discrete element method (DEM) is leveraged to provide training and testing data sets for the proposed prediction model. K-means clustering is applied to establish ballast layer subsections with representative ballast particles and provide additional insights on layer zoning for dynamic behavior trends. When provided with DEM simulated particle vertical accelerations, the proposed deep learning ResNet could achieve 100% training and 95.8% testing accuracy. Fed with vertical acceleration measurements captured by advanced “SmartRock” sensors from a full-scale ballasted track laboratory experiment, the trained model could successfully reach a high accuracy of 92.0%. Based on the developed deep learning approach and the research findings presented in this paper, the innovative crosstie support condition prediction system is envisioned to provide railroaders accurate, timely, and repeatable inspection and monitoring opportunities without disrupting railway network operations.

Vibration damping capacity of a rotating shaft heat treated by various procedures

Abstract Many of today’s rotating shaft systems require the superior stability characteristics of a rotating shaft to prevent system instability. Rotating shaft material properties play a crucial role in the vibration behavior of rotating shaft systems. It is important to control vibrations in the systems because excessive vibration amplitudes can cause inefficiency and system failure. The objective of this study is to investigate the vibration damping capacity of a rotating shaft treated by various procedures (deep cryogenic treatment, induction hardening, hot forging, and conventional heat treatment) in order to see the effects of the treatment procedures. An AISI 4140 steel material for the rotating shaft was selected because it is the most widely used material in industry. The rotating shaft is supported on oil lubricated journal bearings rather than rolling element bearings as used in prior studies by the authors. The results showed that rotating shaft material damping capacity due to treatment processes plays a major role for the rotating shaft systems stability. It is observed that the vibration damping ability of the rotating shaft with induction hardening to dissipate mechanical vibration was superior to deep cryogenic treatment, especially to hot forging and conventional heat treatment processes. Also, the results indicate that the dynamics characteristics of the rotating shafts supported by oil lubricated journal bearings are different to those supported by rolling element bearings.

Dynamic Vehicle and Rigid Road Interaction Analysis and Vibration Control of the Quarter Car Model Using Adaptive Neuro Fuzzy Algorithm

In this study 3-DOF quarter car model with the three bumps on the rigid road, the assumption has been modeled with the non-random irregularity. To reduce the excessive vibrations occurred on the vehicle body, an active suspension system with the linear actuator has been considered. Moreover, to control this actuator, an adaptive neuro-fuzzy algorithm is designed. The training and testing data of the ANFIS has been obtained from Proportional Integral Derivative (PID) control algorithm. After that the successful training process, a testing procedure has been applied to ANFIS for the measure of the adaptive neuro-fuzzy system with data that are not considered in the training process. Then, the performance of the ANFIS is compared by the PID algorithm and passive suspension system in terms of vehicle body vertical acceleration, vehicle body vertical displacement, and control force. The road model used in the study has been modeled according to non-random road profile mathematical formulation considering periodical and discrete road profile cases. In this formulation, one can easily determine the height, width, and number of the road defect with the series mathematical formulation. Consequently, with the results obtained from the presented study, it is proven that ANFIS is a very effective controlling algorithm to suppress vibration occurred on the vehicle body due to vehicle road interaction. Furthermore, the performance of the ANFIS has been tested with different parameters, for example, different number membership functions (MF), which used the fuzzification of the input parameters.

Flow Past a Fixed and Freely Vibrating Drilling Riser System with Auxiliaries in Laminar Flow

Drilling risers used in oil and gas operations are subjected to external loads such as wave and current. One of the phenomena that arise from the external loads is the Vortex-Induced Vibration (VIV), which affects the performance of the riser due to excessive vibration from the vortex shedding. A significant factor influencing the VIV is the design of the drilling riser and its auxiliary lines. Until now, the optimum geometrical size and gap between the auxiliary and the main riser are still very scarcely studied. In this paper, the main objective is to study the effects of the gap ratio (G/D) on the vortex shedding phenomenon on a fixed and freely vibrating riser. The riser system was modelled with a main drilling riser and six auxiliary lines with a constant diameter ratio (d/D) of 0.45 and gap ratio (G/D) = 0 to 2.0 in the laminar flow regime with Reynold Number, Re = 200. The simulations were conducted for Single Degree of Freedom (SDOF) using Computational Fluid Dynamics (CFD) software, Altair AcuSolve. It was found that the freely vibrating riser experienced higher lift and drag forces as compared to the fixed riser due to the synchronization (lock-in) of the shedding vibration and the natural frequencies. The lock-in phenomenon is normally observed on the drilling riser at different current directions. The forces are reduced when G/D is higher. The vortex shedding was significantly reduced for auxiliaries between 0.3 to 1.4. It is confirmed that by modifying the interaction of the vortices in the wake region with auxiliary lines, the hydrodynamic forces will be decreased. Finally, this fundamental study could potentially be used in the designing stage of an optimum drilling riser system by considering significant governing factors.

Analysis, optimization and control of an adaptive tuned vibration absorber featuring magnetoactive materials

Excessive vibration may cause premature fatigue failure on structural components if it is not properly controlled. One effective way to attenuate vibration is to attach a tuned vibration absorber to the main structural component. Passive tuned vibration absorbers are mainly effective to attenuate vibration at a specific range of frequencies and thus they become infective under varied environmental conditions which can significantly alter the tuning frequencies. The present study aims at development of a wide-bandwidth and light-weight adaptive tuned vibration absorber (ATVA) featuring a magnetorheological elastomer (MRE) which is tuned to absorb the vibrations of a flexible beam. The accelerance transfer function is derived for both beam with and without ATVA. The effectiveness of the ATVA to control vibration of the flexible beam caused by external excitation under wide range of frequencies is demonstrated. The proposed ATVA consists of C-Shape frame with winding coils, two isometric MRE specimens with 40% volume fraction, and active mass. An empirical model for the MRE has been developed through an experimental identification method in order to predict the MRE's elastic modulus under various levels of excitation frequencies and applied magnetic fields. Using MRE models and magneto-circuit analysis, the frequency bandwidth of the ATVA is analytically obtained. The analytical model is then used to develop a multidisciplinary design optimization formulation to minimize the mass and maximize the frequency bandwidth of an ATVA featuring MRE given several geometrical and physical constraints. Finally, a tuning algorithm has been presented to determine the required applied magnetic flux density to the MRE layers based on the identified phase difference between the absolute acceleration of the host and relative acceleration of the host and ATVA's resonator.

Study on Modal and Harmonic Response Analysis by Modifying Motorcycle Chassis using Finite Element Method

Motorcycle chassis is one of the most important structures in the design of a motorcycle. Excessive vibration occurs in chassis is undesirable as it may lead to structural failure and discomfort among riders. This study aims to model the motorcycle chassis and carry out dynamic analysis to understand the behaviour of the chassis under vibration. Modelling of chassis was conducted based on Seri Perlis motorcycle, which is characterised by double cradle frame. In dynamic analysis, the modal and harmonic response analysis were employed in this study of the motorcycle chassis and the material used is low carbon steel. Both modal and harmonic response analysis were conducted using Ansys. The results show natural frequencies for six mode shapes and the steady-state response of the chassis under the engine weight excitation revealed that the deformation under z-axis orientation was more prevalent. From this study, the dynamic behaviour of the chassis was understood and improvement of the chassis can be made in the future.

Instrumentation used for vibration monitoring on the supports of the tank scales of the port transshipment complex

The main thing for rotating equipment is to measure vibration, since, in the process of irreversible state change, a chain of defects always occurs and at least one of them significantly changes the vibration of the equipment. Using tank scales for static equipment, the vibration measuring makes it possible to determine the actual values of the levels and compare them with the maximum permissible values set by the manufacturer or regulatory documents. Also, the measurement of vibration levels in the time signal allows determining resonant frequencies at which vibration levels significantly increase due to the coincidence of the natural frequencies of the equipment with external workers, which can lead to increased loads on the supporting metal structures, suspended equipment and subsequently to fatigue destruction of the latter. Results of the work: the excess of the measured vibration levels on the supports of the hopper scales No. 28.1 was recorded by vibration acceleration in pt.11 (longitudinal direction) from twelve measurements; the excess of the measured vibration levels on the supports of the hopper scales No. 28.2 was not recorded, but increased levels of vibration speed were observed in pt. 11 and pt. 12; excessive vibration levels at the same measurement points on different scales may indicate that it is necessary to conduct a survey of the operation of the valve mechanism for smooth running and to monitor the condition of the metal structure under the fourth supports; it is recommended to perform a repeated measurement of the vibration of the hopper scales after inspection and repair of the structures of the scales.

Towards devising a vibration based machinery health monitoring system

Excessive vibration is one of the main causes of damaging the vulnerable parts of the machines. However, a low-cost vibration monitoring system is yet to be proposed in the literature to the best of our knowledge. In this paper, we propose a low-cost wireless vibration monitoring system that can be used to monitor the machine vibration remotely at any time. It will help the maintenance department to decide on the maintenance required for a particular machine and improving the lifetime of the machine as well. By using our device, we find which machine in the textile factory needs more maintenance. Besides, by analyzing our data, we establish a relationship between machine vibration, machine age, and machine quality.

Force and vibration analysis in biomechanical preparation of root canals using reciprocating endodontic file system: In vitro study.

The shaping and cleaning of the root canal are very important in root canal treatment. The excessive force and vibration during biomechanical preparation of the root canal may result in failure of the endodontic file. In this study, force and vibration analysis was carried out during root canal preparation. The samples of human extracted (premolar) teeth were provided by the College of Dental Science and Hospital. Endodontic instruments for reciprocating motion, such as the WaveOne Gold file system, had been used for root canal preparation. Force and vibration signals were recorded by dynamometer and accelerometer, respectively. The acquired signals were denoised using the db4 (SWT denoising 1-D) wavelet. Four levels of decomposition were carried out for each signal. The signal denoising technique was used to remove unwanted noise from the acquired signal. FESEM analysis was used to visualize the levels of severity of endodontic files during the cleaning and shaping of the root canal. In most of the cases, the failure occurred due to the improper use of the root canal instrumentation. The optimum amount of force was used to avoid the file failure and provided the proper instrumentation. The curve fitting regression model was used to find the interdependency between force and vibration.

Reducing Vibrations Generated in a Gas Turbine Model MS9001E Used in South Baghdad Power Plant Station by Improving the Design of Bearings with Damper

Gas turbines are engines an energy plant makes use of for generating the rotary motion to show power generators. The gas turbine is largely a combustion engine for changing natural gas or different liquid fuels to rotational mechanical energy. Often, the gas turbine generates excessive noise or vibrations. In this work, the problem of vibrations occurrence in the gas turbine model MS9001E used in the south Baghdad power station is solved. This is done by making a groove in the bearing pad to increase the oil flow, replacing the bearing type with a tilt-pad bearing type with damper. The finite element method was used in the analysis process by ANSYS program. The results showed a decrease in the values of vibration amplitude, total deformation, stress, and strain.

Stability testing of the Pfizer-BioNTech BNT162b2 COVID-19 vaccine: a translational study in UK vaccination centres

ObjectiveThe roll-out of the Pfizer-BioNTech BNT162b2 COVID-19 vaccine has brought many logistical challenges, such as the absence of comprehensive stability data leading to strict handling instructions during dilution and administration....

Research and Solution of Vibration Problem of an Air-cooled heat exchanger of Reciprocating Compressor

Excessive vibration of complex structures in a multi-excitation environment is an arduous problem. Especially in a reciprocating compressor, how to quickly and accurately position the vibration sources, analyze the excitation features and take effective solutions is of great significance to the safe and stable operation of the compressor. In this paper, the problem of excessive vibration of an air-cooled heat exchanger used in a variable speed CH4 compressor was studied. The air-cooled heat exchanger is composed of tubes, tube boxes and support frame. Its vibration is evoked by complex periodic gas pulsation in the tubes. The vibration model of the heat exchanger was simplifies as a multi-freedom model with periodic excitations using the lumped parameter method. The model has advantages of clear physical concept, easy solution and high accuracy of result. In the model, the air-cooled heat exchanger was simplified as three mass blocks connected by six springs. And then, modal test of the heat exchanger was carried out on site. The vibration modes and natural frequencies of the exchanger were obtained according to the test results. After that, above mentioned multi-freedom model was further simplified as a single freedom vibration model, so that it was convenient to propose the vibration control measures. The practical application results proved that these measures were effective. This research provided a practical and fast analytical method for solutions of compressor vibration problems.

Modelling of Flow Patterns over Spillway with CFD (Case Study: Haditha Dam in Iraq)

Spillways are designing to release surplus water over a volume of storage. The excess water flows from the top of the reservoir and is carried back to the river by a spillway. Many radial gates were destroyed under hydrodynamic load. Radial gate connectors are susceptible to fatigue failure due to excessive vibration; therefore, gate vibration during operation must be investigated to confirm safe operation at the design water pressure. Several studies were carried out to analyse and simulation of flow over the spillway. In this article, the flow pattern over the Haditha dam spillway has been simulated using computational fluid dynamics (CFD). The numerical model was performed using Ansys Fluent 2020 R1 to simulate the flow properties; determination of cavitation damage at three discharges corresponding in the design of Haditha dam are 4700, 7140, and 7900 m3/s. In addition to finding the effect of gate vibration under dynamic water loads. The Realisable k-ɛ turbulence model was utilised with the volume of fluid (VOF) model to simulate the interaction between air and water phases. The validation of the numerical model was achieved by comparing it with a physical model. The physical model of the Haditha Dam spillway was made from iron with a scale of 1:110. It has been designed and constructed in a hydraulic laboratory according to the modelling principle of the hydraulic structure. The results showed that a high agreement between the physical and numerical model and the k-ɛ turbulence model could simulate the Haditha dam spillway with low cost and few times. The cavitation damage may occur at the region start at the end of the arching spillway to stretches downstream, and there is no damage of gate vibration under dynamic water load.

Optimum placement and design of multiple tuned mass dampers for vibration control of asymmetric buildings

This study proposed a design procedure to determine the optimal location, moving direction, and system parameters of multiple tuned mass dampers systematically for vibration control of asymmetric buildings under dynamic loadings such as earthquake or wind excitations. A piece of computer software was developed as a postprocessor of any commercial structural analysis programs, such as ETABS, SAP2000, and so on. First, the modal parameters of target building structure were extracted from its finite element model. The optimum location and moving direction of the multiple tuned mass dampers system are determined based on the controlled mode shapes and both modal participating mass ratio and modal direction factor. Then, the optimal parameters of the multiple tuned mass dampers system were calculated by minimizing the mean square modal displacement response ratio of the controlled mode for the target building with and without multiple tuned mass dampers system. To evaluate control effectiveness, the responses of the building with and without multiple tuned mass dampers system were compared in both frequency and time domains. The analysis results from a 5-story building with different torsion-coupling degrees and a 46-story real building show that the proposed multiple tuned mass dampers system is quite effective in mitigating excessive floor vibration, base shear, and elapsed time of vibration due to earthquake excitations to enhance both structural safety and resident comfort. It is also concluded that the torsion-coupling effect should be considered in determining the optimum planar location of multiple tuned mass dampers system which is equivalent to mass increase of the multiple tuned mass dampers system and thus improves the control efficacy for asymmetric buildings.

Wave flume tests of a semi-submersible platform controlled by a novel rotational inertia damper

Semi-submersible platforms (SSPs) may subject to excessive wave-induced vibrations, which should be effectively suppressed. In the past decades, some vibration control methods have been proposed and developed, such as the fixed heave plate (FHP) and tuned heave plate (THP). Recently, the authors proposed using inerter-based control device, i.e. rotational inertia dampers (RIDs), to control the vibrations of SSPs, and the control effectiveness has been demonstrated through analytical studies. To further investigate the feasibility and effectiveness of the proposed method, wave flume tests are conducted and reported in the present study. In particular, a 1:70 scaled SSP model was manufactured, and the vibration characteristics of the platform were determined firstly through free vibration tests. After that, the bare and RID equipped SSPs were tested under the regular and irregular waves. For comparison, the SSP equipped with the commonly used FHP was also tested. The experimental results demonstrate that both the RID and FHP systems are effective in reducing the heave motion of SSP. However, compared to the FHP, the RID system showed a much better control performance with a very small physical mass. The wave flume tests demonstrated the superior vibration control performances of RID on SSP.

Vibration control of stress ribbon bridges subjected to moving vehicles

Stress ribbon bridges experience excessive vibration when subjected to moving vehicles due to flexibility and low damping, affecting the running safety and ride comfort of the vehicles. It is of great challenge to suppress the vibration of a vehicle-stress ribbon bridge (VSRB) system because of the strong geometric nonlinearity of the stress ribbon bridge, which might also lead to the inapplicability of the conventional optimal design of tuned mass dampers (TMD). This paper proposes an eddy-current tuned mass damper (ECTMD) and its parameter optimization method for suppressing the excessive vibration of stress ribbon bridges subjected to moving vehicles. A dynamic analysis method of the VSRB system is first presented for evaluating the control performance of the ECTMD. Then, a response surface method is proposed to optimize the parameters of the ECTMD for improving control performance. The control performance of the ECTMD optimized by the proposed procedure is validated using a numerical study of a real stress ribbon bridge. Numerical results demonstrate that the conventional design methodology of the TMD based on the linear theory is not the optimal design for the VSRB system due to its nonlinear vibration feature, whereas the proposed response surface method well optimizes the ECTMD's parameters, thus achieving the optimal control performance. This study provides an effective passive control approach for reducing the dynamic responses of stress ribbon bridges excited by moving vehicles.

More Efficient Wind Energy Conversion System Using Shunt Active Power Filter

Wind energy takes first place in many countries among other renewable energy. However, the power quality problems such as nonlinear and unbalanced loads, unbalanced grid, can increase the mechanical vibrations as well as the risk of overheating in Wind Energy Conversion System (WECS). Therefore, the objective of this work is the use of robust flying capacitor converter in order to enhance the WECS efficiency by minimizing mechanical vibrations and reducing thermal stress with minimum voltage stress of power switches. To this end, this paper proposes a WECS based on doubly fed induction generator (DFIG) with the stator connected directly to non-ideal power grid, grid side converter (GSC) with flying capacitor topology and robust input output linearization control used to regulate the dc side capacitor voltage and also compensate the current harmonics in power grid in order to avoid excessive heating and mechanical vibrations in WECS. Simulation using MATLAB demonstrate that the proposed approach improves the power quality by reducing the total harmonic distortion (THD) of grid current to a value which satisfies the limits of IEEE standard, and allows the 8 KW DFIG to operate with reduced mechanical vibration and minimum heating stress in addition to the generation of power.

High torque and excessive vibration on the induction motors under special voltage fluctuation conditions

Purpose Voltage fluctuation (flicker) is a power quality disturbance that can produce several undesirable effects on industrial equipment. This paper aims to present the methodology and results of investigations undertaken to examine the speed and torque of an induction motor (IM) under voltage fluctuation conditions. Design/methodology/approach The IM response to different characteristics of voltage fluctuations is presented. It will be shown that under a special condition the IM torque can even reach two times the rated torque. To show how this occurs, a qualitative discussion is given on the motor response by linearized equations. Findings The small-signal analysis was used to determine the frequency which leads to maximum speed fluctuations. It was shown that, if the motor is excited with a modulation frequency (resonant frequency) which is one of its natural frequencies (modes), the mode will act as a fluctuating amplifier and greatly increase the amplitude of torque and speed fluctuations. Sensitivity analysis is also carried out to evaluate the influence of motor parameters on the resonance frequency. The results show that the resonance frequency is not affected at all by the changes in magnetizing reactance. This has been shown that magnetic saturation does not have any impact on the resonance frequency. The most effective parameters are rotor and stator resistances. Originality/value With the increasing popularity and use of arc furnace loads in the metallurgy industry and due to the wide application of large IMs in the industry, it is possible that the frequency of torque pulsation locates near a natural frequency and then will create an oscillation with a large magnitude, potentially leading to accelerated fatigue or severe damage of shaft. However, if this phenomenon occurs in industries, the resonance frequency must be filtered from the input voltage. Experimental results on a 1.1 kW, 380 V, 50 Hz, 2 pole IM are used to validate the accuracy of simulation results.