High Frequency Vibration Research Articles

An investigation into vibration-induced fatigue failure of metro vehicle cowcatcher and its structural improvement design

Cowcatchers are used in metro vehicles to remove obstacles on the track. The failure of the cowcatcher will seriously affect the safety and reliability of the train. This paper investigated the fatigue failure of cowcatchers of metro vehicles induced by the high frequency vibration through both field tests and numerical simulations. The dynamic stress, acceleration, and eigenmode of a cowcatcher as well as the wheel out-of-roundness (OOR) were measured to identify the primary factor of the fatigue failure of cowcatchers. The investigation results indicate that the main cause of the premature fatigue fracture of cowcatchers is the first-order bending eigenmode of the cowcatcher (95.4 Hz) excited by rail corrugation with the passing frequency of approximately 95 Hz. A modal differential frequency design method was proposed to improve the design of cowcatcher. The first-order natural mode frequency of the re-designed cowcatcher increases from 95.4 Hz to 160 Hz, which can effectively avoid the serious vibration excited by rail corrugation. Subsequently, a random vibration model was proposed to evaluate the effects of the improved cowcatcher. The acceleration measured in the field was used as the input of the model to reproduce the vibration environment of the cowcatcher. The model was validated by the measurement result of dynamic stress of the original cowcatcher. The fatigue life of the improved cowcatcher was calculated by the model. Compared with the original cowcatcher, the service life of the improved cowcatcher is greatly improved.

Compensation for High-Frequency Vibration of SAR Imaging in the Terahertz Band Based on Linear Chirplet Transform and Empirical Mode Decomposition

SAR in THz band is very important and valuable in the field of radar signal processing, and it is much sensitive to the high-frequency vibration of the platform due to the short wavelength. In this article, the high-frequency vibration is characterized as a multicomponent SFM signal, and the parameters estimation method based on the linear chirplet transform and empirical mode decomposition is proposed to compensate for the high-frequency vibration errors. This method can extract the instantaneous frequency of the received signal with high precision, and the focused SAR image can be obtained consequently. Results of simulated and real measured data are provided to illustrate the effectiveness of the novel algorithm proposed in this article.

Experimental study on influence of forced vibration of cooling channel on heat transfer instability at atmospheric and quasi-critical pressure

Hydrocarbon fuel is used as coolant to cool scramjet by flowing through cooling channels at atmospheric pressure and quasi-critical pressure conditions. The instability of the heat transfer will occur in this process. However, the effect of scramjet vibration on the heat transfer instability is unclear. In order to study the effect of cooling channel forced vibration on the unstable heat transfer performance at trans-crtical pressure, cooling channel heat transfer characteristics under different vibration condition are analyzed. Experimental results show that at atmospheric pressure, cooling channel vibration causes a drastic change in the temperature of the inner wall during unstable heat transfer process, but vibration will not change the fuel bulk temperature oscillation process. As a result, forced vibration can lead to heat transfer deterioration in the gas-liquid two-phase flow. Under the condition of quasi-critical pressure, cooling channel vibration not only change the inner wall temperature, but also influence the fuel bulk temperature. The forced vibration can lead to heat transfer enhancement. High frequency vibration can effectively suppress heat transfer instability and reduces heat transfer fluctuations.

Analysis and Compensation of Vibration Induced Beat Frequency Shift in OFDR Based Fiber-Optic Distributed Acoustic Sensor

Optical frequency domain reflectometry (OFDR) is an attractive locating technology for distributed acoustic sensor (DAS) due to its high spatial resolution, but the detectable bandwidth of vibration is very limited up to date, because high frequency vibration will induce time-variant beat frequency shift within the probe, which can deteriorate or even invalidate the demodulation algorithm. In this work, the influence of vibration induced beat frequency shift in OFDR is analyzed and assessed by the crosstalk power spectral density (PSD). Then an adaptive two-dimensional cross-correlation algorithm is proposed for beat frequency shift compensation, in which the instantaneous beat frequency shift within the probe is estimated and compensated for precise strain demodulation. In the experiment, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$18 \text{-}kHz$</tex-math></inline-formula> vibration signal is successfully detected with spatial resolution of 12 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm cm$</tex-math></inline-formula> and strain resolution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$594\;\rm p\varepsilon/\sqrt{Hz}$</tex-math></inline-formula> , whose frequency is an order of magnitude higher than previous works. The proposed beat frequency shift compensation algorithm is evaluated in different conditions, and a suppression of crosstalk PSD up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$40.5\rm \ dB$</tex-math></inline-formula> is proved.

Mu-Synthesis PID Control of Full-Car With Parallel Active Link Suspension Under Variable Payload

This article presents a combined <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> -synthesis PID control scheme, employing a frequency separation paradigm, for a recently proposed novel active suspension, the Parallel Active Link Suspension (PALS). The developed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> -synthesis control scheme is superior to the conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> control, previously designed for the PALS, in terms of ride comfort and road holding (higher frequency dynamics), with important realistic uncertainties, such as in vehicle payload, taken into account. The developed PID control method is applied to guarantee good chassis attitude control capabilities and minimization of pitch and roll motions (low frequency dynamics). A multi-objective control method, which merges the aforementioned PID and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> -synthesis-based controls is further introduced to achieve simultaneously the low frequency mitigation of attitude motions and the high frequency vibration suppression of the vehicle. A seven-degree-of-freedom Sport Utility Vehicle (SUV) full car model with PALS, is employed in this work to test the synthesized controller by nonlinear simulations with different ISO-defined road events and variable vehicle payload. The results demonstrate the control scheme's significant robustness and performance, as compared to the conventional passive suspension as well as the actively controlled PALS by conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> control, achieved for a wide range of vehicle payload considered in the investigation.

Perceptual Discrimination of High Frequency Vibrations about Measurement-based Tactile Texture

Perceptual Discrimination of High Frequency Vibrations about Measurement-based Tactile Texture

一种高频振动除尘设备的结构设计

一种高频振动除尘设备的结构设计

Laboratory Prediction of Tire Tread Wear and Associated High Frequency Vibrations

Laboratory Prediction of Tire Tread Wear and Associated High Frequency Vibrations

High-precision and high-efficiency fabrication of blazed grating by ultrasonic-assisted ultraprecision planing

Blazed gratings are optical components typically employed in modern optical engineering. To realize high-precision and high-efficiency fabrication of blazed gratings on reliable materials, an ultrasonic-assisted ultraprecision planing (UAUP) method using a round-nose diamond tool under elliptical vibration mode is proposed in this paper. High-phosphorus electroless nickel-phosphorus plating was adopted as the grating blank. The generation mechanism of the blazed grating texture was studied, and the relationship between the processing parameters and blazed grating characteristic dimensions was established. Through a combination of simulation and experiment, the theoretical and experimental results of the morphologies and optical performances of the blazed gratings were systematically compared and analyzed. The results show that the blazed grating configuration is an envelope of the diamond tool profile under ultrasonic vibration; the UAUP method has an extremely high machining efficiency owing to the high vibration frequency; and the blazed gratings fabricated using smaller vibration amplitudes exhibit high machining quality, good shape consistency, and favorable optical performance, thus verifying the feasibility of the UAUP method. • An ultrasonic-assisted ultraprecision planing (UAUP) method is proposed. • The grating configuration is precisely controlled by the processing parameters. • The machining efficiency of blazed gratings is extremely improved. • The fabricated blazed gratings exhibit favorable optical performance.

О вибрационной неустойчивости Кельвина-Гельмгольца для жидкостей сравнимых вязкостей

We study the behavior of a two-dimensional system of immiscible incompressible viscous liquids in a rectangular cavity under horizontal harmonic high-frequency vibrations. In this system, influ-ence of pulsating motions of the liquids causes the development of Kelvin-Helmholtz instability leading to the formation of a quasi-stationary relief on the interfacial surface in the form of a frozen wave. A direct numerical modeling of the relief formation was carried out with the use of AN-SYS Fluent software; the influence of the viscosity ratio on the parameters of the frozen wave and the flow generated by vibrations near the interface was investigated. The dependencies of the char-acteristics of the wave relief on supercriticality and vibration frequency are plotted for different ra-tios of liquid viscosities. In the cases of vibrations with sufficiently high frequency, the obtained numerical results are consistent with analytical theory developed for ideal liquids. For lower fre-quencies, the observed relief wavelength turns out to be noticeably longer than the theoretical pre-dictions. For high vibration frequencies, with increasing supercriticality the wavelength increases monotonically, while for low frequencies it decreases monotonically. The relief height increases as the intensity of vibration influence increases; with significant supercriticality, it exceeds the theo-retical values obtained in the ideal fluid approximation. The generation of reverse averaged flow by vibrations near the interface is found when viscosity of the upper fluid is low. In this case, the flows in the upper and lower liquids are directed opposite to each other and a noticeable decrease in the average flow generation intensity is observed.

Study on High-frequency Vibration Characteristics of High-speed Railway Fastener System

Study on High-frequency Vibration Characteristics of High-speed Railway Fastener System

NONLINEAR DYNAMIC RESPONSES OF LOCOMOTIVE EXCITED BY RAIL CORRUGATION AND GEAR TIME-VARYING MESH STIFFNESS

Rail corrugation is usually generated in modern railway transportations, such as high-speed railway, urban railway, and heavy-haul railway. It is one of the major excitations to the wheel–rail dynamic interaction, which will cause extra vibration and noise, failures, or even risk of derailment to the vehicle and its components. A dynamics model of a heavy-haul locomotive considering the traction power from the electric motor to the wheelset through gear transmission is employed to investigate the nonlinear dynamic responses of the locomotive. This dynamics model couples the motions of the vehicle, the track, and the gear transmission together. In this dynamics model, excitations from the rail corrugation, the nonlinear wheel–rail contact, the time-varying mesh stiffness, and the nonlinear gear backlash are considered. Then, numerical simulations are performed to reveal the dynamic responses of the locomotive. The calculated results indicate that different nonlinear phenomenon can be observed under the excitation of the rail corrugation with different amplitude and wavelength. The high frequency vibrations excited by the time-varying mesh stiffness are usually modulated by the low frequency vibrations caused by the rail corrugation. However, this is likely to vanish under the chaotic conditions with some corrugation wavelength. The vibration level of the vehicle and the gear transmission increases generally with the corrugation amplitude. However, some corrugation lengths have been found to be more responsible for the vibration of the dynamics system, which should be concerned greatly during the locomotive operation. Meanwhile, involvement of gear transmission systems will cause different dynamic responses between the wheelsets under rail corrugation and gear mesh excitations.

White Layer in M76 High Carbon Rail Steel: Formation Mechanism and Properties

High-frequency vibrations resulting from many factors under loads existing in the wheel-rail system have a huge impact on the structure and properties of rail steel: there are signifi contact stresses in the surface layer that affect strength characteristics and overall fatigue of the railway track structure. Such an impact results, in particular, in the formation of the so-called White Layer (WL): a hardened layer on the surface of the base material, resistant to chemical etching, and having high hardness (above 1000 HV) and brittleness.The objective of the research was to study the features of the formation mechanism, as well as the properties of the white layer formed on the metal surface using an integrated approach, namely, of destructive testing methods, electron microscopy, XRD, metallography, and microhardness measurements.The reliability of experimental studies is due to the use of standardised test methods, developed methods of destructive and non-destructive testing in the main areas, the involvement of an accredited and certified laboratory, which makes it possible to fulfill in full the tasks set with appropriate quality.The results of the research allowed to present an analysis of the white layer, the formation of which took place in high-carbon M76 rail steel after cyclic tests with a 20 kHz frequency. The morphology, phase composition, and microhardness of these inclusions have been studied in detail in comparison with the base metal. It is shown that the white layer is highly dispersed, pearlitelike, featureless inclusions of a ferrite-cementite structure, while their microhardness is 3–4 times higher than the original steel and is of 1000–1200 HV. A possible explication of a mechanism of the formation of a white layer is suggested: crushing of ferrite and cementite, which are part of pearlite, without intermediate phase transformations.

Microstructures and corrosion resistance enhancement of ultrasonic vibration-assisted medium entropy alloy base laser multi-phase coating

The CoCrNi medium entropy alloy base coating (MEABC) was fabricated on the TC4 titanium alloy by the laser cladding (LC) technology, the effects of the ultrasonic vibration (UV) on the microstructures and the corrosion resistance of the coatings were studied. The MEABC was consisted primarily of BCC and (Ni,Co)Ti2, Cu could be precipitated at the grain boundary, producing the AlCu2Ti nanocrystals. The micro-forming quality of the coating was enhanced due to the UV effect. The temperature gradient/heat flux density of the UV assisted laser induced pool (LIP) were varied under an action of the high frequency vibration, refining the microstructure. The corrosion resistance and micro-hardness of the coating were enhanced due to the UV effects and the slow diffusion effect of the medium entropy alloy system, producing the multi-phase, such as the amorphous phases (APs) and the nanocrystalline phases (NPs), etc. This study provides the theoretical/experimental basis for the multi principal component coating by UV assisted LC process.

Modelling of a shear-type piezoelectric actuator for AFM-based vibration-assisted nanomachining

Recent research investigations have reported the benefit of enhancing conventional AFM-based nanoscale machining operations by the introduction of high frequency vibrations between the AFM tip and the processed material. The technique relies on piezoelectric actuation and is relatively straight forward to implement in practice. However, the non-linearity of piezoelectric actuators when operated under high electric field and frequency conditions can affect the dimensional accuracy of the fabricated nanostructures. To address these issues, the paper reports a method based on coupled mechanical-electrical Finite Element (FE) modelling to predict the relative motion between an AFM tip and a workpiece for vibration-assisted AFM-based nanomachining applications. In particular, the novelty of the proposed method is that it combines two classical approaches for modelling the nonlinear behaviour of piezoelectric materials. More specifically, two sources of non-linearity are considered simultaneously by combining the field-dependant model from Muller and Zhang with the frequency-dependant model from Damjanovic. The resulting combined model is employed to establish the piezoelectric constitutive equations implemented in the developed coupled field FE model. A further distinguishing characteristic of the work is that the proposed approach was subsequently validated by comparing the predicted widths of nanoscale grooves against those machined with a custom AFM-based vibration-assisted nanomachining configuration.

Investigation of mixed hBN/Al2O3 nanoparticles as additives on grease performance in rolling bearing under limited lubricant supply

Grease plays an important role in reducing friction and wear of rolling bearings and improving their service life and reliability. However, increasing attention is being paid to the environmental pollution caused by discarded grease. In this paper, calcium sulfonate complex grease (CSCG) was prepared by using green raw materials, namely poly-alpha-olefin oil as the base oil and complex calcium sulfonate soap as thickener. In order to improve the lubrication and damping performance of the grease, hexagonal boron nitride (hBN) and nano-Al2O3, which have the potential to replace toxic additives, are mixed into the grease in different mass proportions. The thickener structure of each grease was characterized and analyzed. According to the bearing vibration and life of the two key performance indicators, four-ball tests and bearing vibration tests under limited lubricant supply (LLS) were performed. The results show that CSCG with 0.75 wt% hBN and 0.25 wt% Al2O3 (BN75AL25) has the best tribological and vibration suppression performance. The mean friction coefficient decreased by 11.3%, the wear scar diameter decreased by 6.1%, and the worn surface morphology improved significantly compared with CSCG. The frequency domain analysis showed that high, medium and low frequency vibrations were suppressed by 19%, 11.7% and 16.4%, respectively. In conclusion, BN75AL25 has the potential to become a green high-performance grease under LLS, which is worth further research and exploration.

The Effect of Low Magnitude High Frequency Vibration on Bone Healing by Clamp Method in Nonunion Tibial Fractures

Introduction: This study aimed to investigate the clinical effect of Low Magnitude High Frequency Vibration (LMHFV) on nonunion tibial fractures, noninvasively.&#x0D; Methods: The Experimental (n=5) and control (n=5) groups were age-matched and pooled based on the Nonunion Tibia Score System (NUSS) (p&gt;0.05). LMHFV (0.35g, 50 Hz, 20 minutes x 4/day) was applied to the experimental group for three months by a mechanical stimulator that we developed using a ‘clamp method’. The control group was followed during three months without any application other than routine treatment. The results were evaluated using the Radiographic Union Score for Tibial Fractures (RUST) and American Orthopedics Foot and Ankle Score (AOFAS). No statistically significant difference was observed between the groups at the beginning and in the end of the 3- month application for RUST and AOFAS scores (p&gt;0.05).&#x0D; Results: Pain and function assessment, at the beginning and end of the study, as a part of The AOFAS scorewere not statistically different (p&gt;0.05) in the control group. However, increases in pain and function AOFAS scores were statistically significant in the experimental group at the end of the 3- month application (p

A fast sparsity-free compressive sensing approach for vibration data reconstruction using deep convolutional GAN

Vibration data from physical systems, such as civil structures and machinery, often carries important information about the dynamic characteristics, but streaming acquisition of higher-frequency vibration often accrue large volumes of data, resulting in data transmission and storage challenges. Compressive sensing (CS) is a relatively newly-developed technique for efficient data representation, capable of reconstructing the target signal using only a few random measurements through sparse optimization. However, the real-world application of CS is hindered by the strong assumption of signal sparsity and a costly reconstruction process. In this work, we propose a novel deep learning method for vibration data reconstruction by using deep convolutional generative adversarial networks (DCGAN), which is composed of a generator G and a discriminator D. A modified 1D symmetric U-net architecture with shortcuts is presented for G to flexibly deal with different inputs, while a typical 1D classifier is used as D. A composite adversarial loss function is proposed considering errors in both time and frequency domains. The proposed DCGAN approach has several appealing properties. First, it directly learns the end-to-end mapping between the compressed and original signals without employing the sparsity assumption or random sampling, which fundamentally differs from existing sparsity-based CS methods. Second, the reconstruction process is highly computationally efficient as the network is fully feed-forward and no optimization is needed during data reconstruction. The proposed DCGAN approach is evaluated using the simulation data from a numerical 9-floor frame as well as experimental data collected from a large test steel grandstand. The results demonstrate the superiority of the proposed DCGAN in computational accuracy and efficiency compared to the tested sparsity-based algorithms. Furthermore, the influences of network configurations (network depth, down-sampling strategy, and shortcuts) are comprehensively explored.

Field experimental tests and analyses of suspension frame vibration of low-medium speed maglev train

Pushed by social demands, China has continuously developed its low-medium speed maglev transportation systems in recent decades. However, with the increase of the running mileage of the train, high frequency vibration of suspension frame gradually appears. In this paper, a method to analyze the high frequency vibration of suspension frame by detecting the current of traction motor is proposed. Field measurements of suspension frame vibration and traction motor current of low-medium maglev train were conducted on a maglev line that has been commercially put into operation. The test results show that the speed of the measured maglev train was closely correlated with vibration accelerations of the suspension frame in three directions, but as the speed increased, the influence it imposed on the suspension frame vibration waned. The dominant frequency of traction motor resultant current was consistent with the dominant frequency of the suspension frame vibration acceleration. The switching frequency of traction inverter was the main cause of high frequency vibration of suspension frame.

Mechanical property enhancement of sintered Nd-Fe-B magnets by dual-scale regulation of microstructure

The brittleness of sintered Nd-Fe-B magnet limits its applications in high frequency and high vibration environments. In this study, rod-like Ti particles were applied for dual-scale microstructure regulation to improve the mechanical properties of sintered Nd-Fe-B magnets. The bending strength of Ti-added magnets increased from 403.47 to 631.98 MPa, which shows an increase of 56.6%. The intrinsic coercivity of the Ti-added magnet increased from 15.20 kOe to 17.52 kOe. The mechanical properties and intrinsic coercivity are significantly improved without reducing the remanence. The Ti particles reduced the grain size and favorably altered the alignment of the grains, and hence effectively reduced the stress concentration effect. Furthermore, Ti particles promoted the formation of nano amorphous phase in the grain boundary phase, which greatly improved the strength of the grain boundary phase. This study provides a theoretical basis for the preparation of sintered Nd-Fe-B magnets with excellent mechanical properties.