Vibration Speed Research Articles

Improved motorised spindle control using a biogeography-based optimisation algorithm

The BBO algorithm is introduced to estimate the equivalent stator resistance in the classical DTC method. BBO algorithm achieves the purpose of suppressing current harmonics and reducing torque by improving the online identification accuracy of the stator resistance of the motorised spindle, thus improving the performance of the motorised spindle control system. The vibrational speed of the electric spindle is significantly reduced at each operating frequency after using the BBO-DTC algorithm. The torque ripple of the electric spindle is obviously reduced, especially at 150 Hz and from 450~600 Hz. Analyses of the electromagnetic vibration speed of the electric spindle and the experimental input torque data indicate that the control performance of the BBO-DTC algorithm is improved. Not only is the dynamic performance of the system improved, but variations in the electromagnetic flux and the electromagnetic torque are also reduced. The control performance of motorised spindle is effectively improved.

Improved motorised spindle control using a biogeography-based optimisation algorithm

The BBO algorithm is introduced to estimate the equivalent stator resistance in the classical DTC method. BBO algorithm achieves the purpose of suppressing current harmonics and reducing torque by improving the online identification accuracy of the stator resistance of the motorised spindle, thus improving the performance of the motorised spindle control system. The vibrational speed of the electric spindle is significantly reduced at each operating frequency after using the BBO-DTC algorithm. The torque ripple of the electric spindle is obviously reduced, especially at 150 Hz and from 450~600 Hz. Analyses of the electromagnetic vibration speed of the electric spindle and the experimental input torque data indicate that the control performance of the BBO-DTC algorithm is improved. Not only is the dynamic performance of the system improved, but variations in the electromagnetic flux and the electromagnetic torque are also reduced. The control performance of motorised spindle is effectively improved.

Numerical Simulation of Hole Distribution Blasting with Different Distribution Forms

According to the vibration of cut blasting, the number of holes and the location of holes are reasonably designed by using finite element software LS-DYNA. The rectangular holes and hollow holes in straight cut are simulated respectively. Of the hole in the straight-cut undercut blasting vibration law. The analysis shows that the larger the diameter of the hole is, the better the vibration reduction is. The more the number of holes is, the more obvious the damping effect is. The best blasting effect of the large diameter hollow hole and the large diameter rectangular hole is 0.93cm/s Reduce the blasting vibration speed, buffered the blasting time; get both a good blasting effect and effective rapid damping effect.

Analysis of vibration monitoring data of an onshore wind turbine under different operational conditions

A wind turbine structure works under the complicated environment and its operational state is complex. In this study, the operational state of a 1.5 MW wind turbine and the vibration response of the tower have been monitored for a long time. The vibration characteristic of the wind turbine under different operational conditions is discussed in detail, and it was observed that the rated rotation speed condition has the highest vibration level. The Campbell diagrams of wind turbine both in the FA direction and SS direction are drawn based on the natural frequencies results, which are identified by data-driven stochastic subspace identification method. It was observed from the Campbell diagrams that when the rotation speed is close to the grid-connected rotation speed, the blade-passing frequency 3f (0.43 Hz) is equal to the fundamental frequency of wind turbine which will easily lead to the resonance. This phenomenon is confirmed by the time history diagrams of the operational condition and vibration speed of a certain startup process. Lastly, the relationship between first-order, second-order modal parameters and operational conditions of the wind turbine are discussed in detail respectively. The mean value of first-order natural frequency is affected slightly by the different operational conditions while the value of second-order natural frequency increases significantly with the increase of rotation speed. The work in this paper can help us to better understand the response of the wind turbine under different operational conditions, which can also lay the foundation for the structure design, modal validation and damage diagnosis of wind turbine.

A Study on a Mechanism of Lateral Pedestrian-Footbridge Interaction

Based on the pedestrian lateral force hybrid Van der Pol/Rayleigh model, this study investigates the interaction dynamic model of a pedestrian-flexible footbridge lateral coupling system. A multi scale method is adopted to decouple the equation. The paper also studies the nonlinear dynamic response of the pedestrian-footbridge coupling system as well as the relationship between the lateral displacement of pedestrians and flexible footbridges, and the lateral interaction of the two variables. The results show that with the same frequency tuning parameters, when the mass ratio of pedestrians and footbridges is very small, the larger the mass ratio is, the larger the lateral response amplitude of pedestrians becomes. Conversely, when the mass ratio of pedestrians and footbridges is much larger, the larger the mass ratio is, the smaller the response amplitude becomes. When the natural frequency of a footbridge is larger, its Phase Angle becomes larger. As the lateral amplitude of pedestrians increases, the Phase Angle approaches zero. Moreover, regarding the variation of the Phase Angle between the interaction force and footbridge lateral vibration speed based on the lateral relative displacement of pedestrians, of which the variation range is (0, π ), as the pedestrians’ lateral amplitude increases, the Phase Angle approaches − π / 2 . The dynamic load coefficient varies linearly with the lateral amplitude of pedestrian vibrations.

Experimental study of the accuracy of balancing an axial fan by adjusting the masses and by passive auto-balancers

The paper reports determining and comparison of the quality of dynamic balancing of rotating parts in the assembly (impeller) by correction mass and applying passive auto-balancers using the axial fan VO 06-300-4 as an example. The impeller is balanced in two planes of correction – from the side of a fairing and from the side of an electric motor’s shank.It was established that prior to balancing the magnitudes of root-mean-square values (RMS) of vibration speed at the casing of the fan correspond with a margin to the balance quality grade: 1x vibration components (1x) ‒ G2.5; total – G6.3. The main source of vibrations is the dynamic residual imbalance of the impeller. The basic component of vibration speeds is the 1x one (at a frequency of 25 Hz), that is, it can be reduced by balancing. The non-1x vibration components occur at subharmonic frequencies, 25/2 and 25/3 Hz, and are smaller by the order of magnitude.When the impeller is balanced by correction mass, the initial imbalances from the side of a fairing and a shank are, respectively, 81.4 and 115.2 g∙mm, and the residual ones are 7.4 and 7.2 g∙mm. The magnitudes of RMS of vibration speed can be reduced at the fan’s casing to the magnitudes corresponding to the balance quality grade (with a margin): 1x – G0.4; total – G2.5. The main contribution to the residual vibrations is made by the non-1x vibration components occurring at subharmonic frequencies.At dynamic balancing of the impeller by two ball auto-balancers, in the presence of any imbalances (in two planes of correction) that can balance the auto-balancers, the RMS of vibration speed at the fan’s casing correspond to the balance quality grade: 1x – G1; total – G2.5. Ball auto-balancers react to imbalances constituting not less than 3 % of their balancing capacity. The residual imbalances are not stable, but are not larger from the side of a fairing and a shank than, respectively, 22.2 g∙mm and 21.6 g∙mm.Research results are applicable for low-pressure axial fans, specifically VO 06-300/VO-12-300; VOG/VO-15-320; VO 2,3-130/VO 46-130. They make it possible to decide on the expediency of balancing fans by passive auto-balancers

Adaptive fuzzy optimal control for a class of active suspension systems with full‐state constraints

In this study, an adaptive fuzzy inverse optimal control problem is investigated for a class of vehicle active suspension systems. Since active suspension systems have dynamic characteristics of complexities and spring non-linearities, the fuzzy logic systems are utilised to learn the unknown non-linear dynamics. In addition, there exist the constraints of the displacements of the sprung and unsprung masses, vertical vibration speeds, and current intensity in the considered suspension system, therefore, the Barrier Lyapunov functions are introduced into the control design to ensure that the full-state constraints are not overstepped. The inverse optimal control method is adopted by constructing an auxiliary system, which circumvents the assignment of solving a Hamilton–Jacobi–Bellman equation and brings about an inverse optimal controller associated with a meaningful objective functional. Based on Lyapunov stability theory and backstepping recursive design algorithm, a fuzzy adaptive optimal control scheme is developed. It is proved that the proposed control scheme not only guarantees that the vertical vibration of the vehicle is stabilised by the electromagnetic actuator but also achieves the goal of inverse optimality with regard to the cost functional. Finally, the simulation studies check the validity of the presented control strategy.

Creation of zinc oxide based nanomaterials by repetitively pulsed laser treatment

By repetitively pulsed laser treatment with a frequency of 500 Hz was metal/semiconductor nanocomposite on a basis of zinc oxide nanowires created. An analysis of results made it possible to find that with described laser-induced vibroexcitation of samples, vibration speed increases for frequencies multiple to frequency of the initial oscillation, and when frequency is increasing the amplitude is decreasing. Samples heating particularities in consequence of laser irradiation were determined. Analysis of X-ray diffraction images showed that the zinc oxide creation on the porous copper-zinc alloy substrate occurs as a result thermal oxidation by the repetitively pulsed laser treatment. It is shown that intensification condition of mass transfer in a solid state of a metal material is a local non-stationary deformation that is produced by a highly-powered outer action. Using of synergies of thermal action and vibrations in a sound frequency range caused by laser irradiation, provides opportunity of a new approach realization for the structures creation of composite nanomaterials on a basis of zinc oxide in metal/semiconductor Cu/ZnO nanocomposite.

Experimental Investigation on Micro-Groove Manufacturing of Ti-6Al-4V Alloy by Using Ultrasonic Elliptical Vibration Assisted Cutting.

The micro-groove structure on the planar surface has been widely used in the tribology field for improving the lubrication performance, thereby reducing the friction coefficient and wear. However, in the conventional cutting (CC) process, the high-quality, high-precision machining of the micro-groove on titanium alloy has always been a challenge, because considerable problems including poor surface integrity and a high level of the material swelling and springback remain unresolved. In this study, the ultrasonic elliptical vibration assisted cutting (UEVC) technology was employed, which aimed to minimize the level of the material swelling and springback and improve the machining quality. A series of comparative investigations on the surface defect, surface roughness, and material swelling and springback under the CC and UEVC processes were performed. The experimental results certified that the material swelling and springback significantly reduced and the surface integrity obviously improved in the UEVC process in comparison to that in the CC process. Furthermore, for all the predetermined depths of the cut, when the TSR (the ratio of the nominal cutting speed to the peak horizontal vibration speed) was equal to one of twenty four or one of forty eight, the accuracy of the machined micro-groove depth, width and the profile radius reached satisfactorily to 98%, and the roughness values were approximately 0.1 μm. The experimental results demonstrate that the UEVC technology is a feasible method for the high-quality and high-precision processing of the micro-groove on Ti-6Al-4V alloy.

Finite element modeling of ultrasonic-assisted turning: cutting force and heat generation

Adding ultrasonic vibrations to conventional turning can improve the process in terms of cutting force, surface finish and so on. One of the most important factors in machining is the heat generation during the cutting process. In ultrasonic-assisted turning (UAT) the tool tip also vibrates at very high frequency and this sinusoidal motion causes complexity in heat modeling of the cutting system. Modeling and simulation of cutting processes can help to understand the nature of process and provides information to select optimum conditions and machining parameters. In this article, a finite element model has been developed for predicting tool tip temperature in UAT. The effect of machining parameters including cutting speed, feed rate and amplitude of vibration on the tool tip temperature has been investigated. In order to simplify the machining process, the cutting experiment has been carried out in dry condition. The results showed that by applying ultrasonic vibration to the cutting tool, the tool tip flash temperature increases but in some condition its average value could be less than the conventional machining.

Vibration Control for a Rotor Supported by Oil-Film Bearings Using a Bearingless Motor

Rotors of large turbomachinery are usually supported by oil-film bearings, because an oil-film bearing has a simple structure, high load capacity, and large damping. However, an oil-film bearing induces self-excited vibration at high rotational speeds. Therefore, a suppression method for the self-excited vibration is needed. This study proposes the application of a bearingless motor (BELM) for a rotor supported by oil-film bearings. To realize the proposed rotor system, an experimental rotor, supported by the oil-film bearings and equipped with a BELM, is designed and fabricated. This study illustrates the winding configuration and the controller design of the BELM for a stable suspension system. The test rotor with the oil-film bearings and the BELM exhibited stable rotation at rotational speeds higher than the onset speed of the self-excited vibration. Furthermore, the radial force required to suppress the self-excited vibration is discussed. Because it is desirable for the radial force of the BELM to be small in the actual machine, we realized a stable and high-speed rotation with a small radial force. Thus, we demonstrate the feasibility of a compact, stable, and high-speed rotor–oil-film bearing system.

Russian stationary vibration control and mechanical displacement systems for electric power pumps of thermal power plants

The article discusses the possibility of using Russian stationary vibration and mechanical quantities control systems for electric power boilers of thermal power plants, in particular, the implementation of automated control of absolute vibration bearing, axial shear and speed with the requirements of regulatory documents. A review and analysis of the market of stationary systems for monitoring vibration and mechanical quantities, their technical and metrological characteristics was carried out. The possibility of integrating Russian stationary systems for monitoring vibration and mechanical quantities into automated process control systems of thermal power plants, their application in various subsystems, including the subsystem of technological protection and safety locks, is considered. An assessment was made of compliance with regulatory documents governing the construction of such systems, taking into account the requirements of supervisory authorities.

Numerical investigation of elastohydrodynamic contacts subjected to harmonic load variation

PurposeThe purpose of this paper is to study the behavior of elastohydrodynamic contacts subjected to forced harmonic vibrations including the effect of changing various working parameters such as frequency, load amplitude and entrainment speed.Design/methodology/approachThe time-dependent Reynolds equation is solved using the Newton–Raphson technique. The film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds equation and film thickness equation including elastic deformation.FindingsThe frequency of vibration, load amplitude and entrainment speed are directly related to the film thickness perturbation, which is formed during load increasing phase of the cycle. The film thickness formed during load increasing phase is larger than that formed during load decreasing phase with larger deviation at a higher frequency or load amplitude and vice versa for lower frequency or load amplitude. The entrainment speed of the contact has an opposite effect to that of the frequency of vibration or load amplitude.Originality/valuePhysical explanations for the behavior of elastohydrodynamic contact subjected to forced harmonic vibration are presented in this paper for various working parameters of frequency, load amplitude and entrainment speed.

Variable frequency drive harmonics and interharmonics exciting axle torsional vibration resulting in railway wheel polygonisation

ABSTRACTSevere vibrations and an increase in structural component fatigue failures have been observed on a freight locomotive class operating on a heavy haul route within South Africa. The root cause of these severe vibrations were investigated experimentally and it was found that polygonised wheels were cuasing these severe vibrations. A coupled mode of vibration exists in the traction system that is a combination of traction motor pitching and wheelset axle torsion. Harmonics and interharmonics are features of an AC motor controlled by a variable frequency drive (VFD) and were confirmed to cause resonance of the coupled vibration mode. Interharmonics are a function of the fundamental frequency () of the VFD and the input AC frequency ( supplied to the VFD. It was found by experimentation that the interharmonic caused resonance of the coupled mode while the locomotive operated at 40 km/h. This running speed and frequency of vibration was found to fix the wavelength of a 20th order polygon on the wheels during approximately 11% of the locomotive’s load hauling time.

Analysis of In-Plane Vibration and Critical Speeds of the Functionally Graded Rotating Disks

In this paper, the in-plane free vibration analysis of the functionally graded rotating disks with variable thickness is presented utilizing DQM. It is assumed that the rotational velocity of the disk is constant and the thickness and material properties including modulus of elasticity and density vary along the radial coordinate. The distribution of the forward and backward traveling waves versus the angular velocity is demonstrated for several modal circles and nodal diameters with respect to the fixed and rotating coordinate systems. After presenting the accuracy and convergence of the numerical method, the derived formulation and the solution method are validated by comparing the results with those obtained in the literature for simple rotating disks. Furthermore, the critical speed of the rotating disk is introduced and obtained for different modes. Finally, the effects of the functionally graded index (describes the distribution of material properties) and geometric shape of the disks (thickness profile and radius ratio) on the natural frequencies and critical speed of the disk are presented. It is observed that as the number of nodal diameter increases, the critical speed of the disk consequently decreases and reaches to an asymptotic value. This value is independent of the geometric characteristics of the disk.

Heat effect on the material removal in the machining of fibre-reinforced polymer composites

Abstract This paper aims to investigate the heat effect on the material removal mechanisms in the machining of fibre-reinforced polymer (FRP) composites. A coupled thermal-mechanical microstructured-model was established to investigate the cutting processes both with and without ultrasonic tool vibration. A systematic cutting experiment was also conducted to assess the reliability of the theoretical predictions. It was found that the cutting temperature influences significantly the material removal process, but has a little effect on the cutting forces. The fibres and matrix deform and fracture in brittle modes when the temperature is below the glass transition point of the matrix material, Tg. The matrix material becomes softer and its deformation turns to be ductile when the temperature exceeds the glass transition point. This consequently brings about significant deformation and fracture of fibres in the subsurface. During cutting, with increasing the cutting time, the cutting-induced heating zone spreads quite ahead of the cutting edge. However, with the assist of ultrasonic vibration, the high-frequency motion of the cutting tip dramatically reduces the tool-work interaction time at each vibration cycle; thereby slows down the heat generation and temperature rise. The high-frequency motion also leads to rapid chip removal and reduces temperature rising rate and heat accumulation. As a result, both the tool and workpiece temperature can be maintained to be below the Tg of the matrix material. Nevertheless, the advantage of the vibration-assisted process becomes trivial once the feed rate is larger than its maximum vibration speed.

A novel high temperature eddy current damper with enhanced performance by means of impedance matching

When an electrically conductive material is exposed to time-varying magnetic fields, eddy currents are generated inside the conductor which oppose the change in the magnetic field. When eddy currents circulate through the conductor they are dissipated in form of heat due to the resistivity of the material. For low frequency vibrations, eddy current damping force is proportional to the vibration speed. Therefore, damping of vibrations at low frequencies or displacement amplitudes becomes increasingly difficult using this technology. Typical damping densities of eddy current dampers range between 0.1 for most devices and 2 MN s m−4 for best-in-class prototypes. Those values are relatively low compared with, for examples, hydraulic dampers that can reach up to 4 MN s m−4. This low density limits potential applications of the technology. In addition, certain applications like vibration isolation of aircraft engines may require the damper to operate at high temperatures. However, most of current damping solutions are rarely effective at temperature higher than 100 °C because they frequently use NdFe magnets. In this paper, a passive eddy current damper with enhanced performance for use in high temperatures is presented. The Z-Damper takes advantage from impedance matching inside a magnetic linear gear to amplify the input vibration motion, maximizing the effectiveness of an integrated eddy current damper. SmCo magnets and high temperature components are used in the Z-Damper, potentially enabling operation in a wide temperature range. A theoretical model describing the dynamic behavior of the Z-Damper is presented and a set of experiments were conducted to evaluate its performance. A prototype of the Z-Damper has been designed, manufactured and experimentally demonstrated in a temperature range from 25 °C to 200 °C under low frequency (up to 60 Hz) harmonic excitations. A maximum equivalent viscous damping coefficient of 35 Ns mm−1, measured at 200 °C, has been achieved. A damping density of 8.4 MN s m−4 is calculated.

Dynamic characteristics and experimental study on a wind turbine gearbox

A gearbox is part of the transmission chain of wind turbine, which can increase rotational speed and reduce torque. Dynamic characteristics of the gearbox directly influence the vibration and the service life of the wind turbine system. In this paper, dynamic behaviors of a megawatt level wind turbine gearbox are studied theoretically and experimentally by dividing the gearbox into a transmission sub-system and a body sub-system. The transmission sub-system, i.e., the gear-shaft-bearing sub-system, is coupled with the gearbox body using bearings which are simulated as mass-less springs. The theoretical study applies a finite element model for the gearbox, where the internal excitations are caused by time-varying stiffness, transmission errors and mesh impacts. The time-varying wind load is considered as the external excitation, collected by a remote real-time online test and transformed into load spectrums through the rain-flow counting method. With boundary conditions and working conditions being defined in the finite element model, the natural characteristic analysis and the dynamic response analysis are conducted. Results show that the operating frequencies of the gearbox are far away from the main natural frequencies of the system, thus avoiding resonances. The main vibration components of the gearbox are with meshing frequencies of the second and third gear stage and their multiplication counterparts. Moreover, the greatest vibration occurs at the bearing housing of the high-speed shaft with the root-mean-square value of its vibration speed less than 3.5 mm/s. A test rig is developed and the experimental vibration conditions are monitored by acceleration sensors. The experimental results are in accordance well with the theoretical results. In this way, the theoretical model is validated. The methodology reported in this paper can provide valuable guidance for practical industrial engineers.

Research on Cooling Technology of Shredder Cutting Tool With Ultrasonic Vibration-Assisted Cutting

To improve service life of shredder cutters, new technologies such as ultrasonic vibrationassisted cutting and cooling technology (jet and spray) are introduced into the design of the cutter for a two-axis horizontal shredder. Ultrasonic vibration-assisted cutting technology is theoretical analyzed, and result shows that the effect of friction reduction only happens when the speed of cutting is less than vibration speed. Therefore, the vibration-assisted cutting get a friction reduction of 52.5% and a cutting temperature reduction of 10.5% when the vibration-assisted cutting with an amplitude of 25 μm and a frequency of 20 kHz is performed on the shredder with the rotational speed of 60 r/min. Three cooling methods are proposed to lower the temperature of shredder tools such as air jet cooling, water jet cooling, and spray cooling. They are all simulated with Ansys-fluent software on the basis of the Lagrangian model. Simulation results show that water jet cooling can realize better cooling effect, whereas its cooling effect will not improve obviously until the jet diameter increases to around 4 mm. In addition, the cooling effect of the spray with vibration cutting which has less coolant consumption is very close to that of the water jet without vibration cutting. Therefore, the mode of spray cooling with vibration cutting can be used instead of the mode of water jet cooling for higher coolant utilization. By comparing with the traditional cutting of shredder, the spray cooling with vibration cutting has a cutting temperature reduction of 65%.

Model Test Study on the Influence of Train Speed on the Dynamic Response of an X‐Section Pile‐Net Composite Foundation

Based on a large‐scale X‐section pile‐net composite foundation model, we experimentally studied the dynamic characteristics of the pile‐net composite foundation under a high‐speed railway train load; analyzed the distribution characteristics of the dynamic stress, dynamic displacement, speed, and acceleration of the foundation soil under different train speeds; and investigated the vibration response of the track subgrade foundation system, as well as the distribution characteristics and attenuation pattern of the dynamic stress inside the subgrade foundation under cyclic train loading. The following results are obtained. The peak vertical vibration speed and the peak acceleration attenuate by 90% and 62.5%, respectively, after passing through the embankment. The vibration velocity increases linearly with the train speed; the ratio of the peak dynamic soil stresses at the top of the piles and between the piles is approximately 3.4. The change in train speed does not have a large influence on the peak dynamic displacement or peak dynamic soil stress. The peak spectral vibration acceleration caused by the train loading is located within the range of medium‐to‐low‐frequency vibrations, and the characteristic frequency corresponds to the passing frequency of the bogies and carriages; as the train speed increases, the peak spectral vibration acceleration increases, and the high‐frequency components increase significantly.