Effect of integral squeeze film damper on vibration and noise of spur gear with center-distance error

When the actual installation center distance between a pair of spur gears is greater than the theoretical center distance,backlash increases,leading to increased vibration and noise.The structural parameters of an integral squeeze film damper(ISFD)were designed with the stiffness of rigid support as reference to investigate the effect of an ISFD on the dynamic characteristics of a spur gear transmission system with center-distance installation error.A spur gear test bench with center distance-error was built to investigate the vibration and noise reduction characteristics of ISFD.The experimental results indicate that,compared with a rigid support,the ISFD can reduce vibration by approximately 40%and noise by approximately 5 d B.ISFD can effectively absorb the impact energy caused by an increase of in backlash,which is conducive to the stable operation of the spur gear transmission system.

State Estimation for Sound and Vibration Emitted from a Machine Based on Sound Measurement Under Existenceof Background Noise

Many studies on the diagnosis for machines have become important recently because of increased use of various complex industrial systems.The correlation information between sound and vibration is very important for machine diagnosis.Usually,vibration pickups are attached directly to the machine in order to measure vibration data.However,in some cases,the sensors can not be attached directly on highly precise devices.In this study,a method to estimate the fluctuation of sound and vibration is proposed based on the measurement data of sound emitted from the machine under existence of background noise.The effectiveness of the proposed theory is experimentally confirmed by applying it to the observed data emitted from a rotational machine driven by an electric motor.

Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers

We theoretically investigate the application of the fringe-locking method(FLM) in the dual-species quantum test of the weak equivalence principle(WEP).With the FLM,the measurement is performed invariably at the midfringe,and the extraction of the phase shift for atom interferometers is linearized.For the simultaneous interferometers,this linearization enables a good common-mode rejection of vibration noise,which is usually the main limit for high precision WEP tests of the dual-species kind.We note that this method also allows for an unbiased determination of the gravity accelerations difference,which meanwhile is ready to be implemented.

Railway ground vibration and mitigation measures: benchmarking of best practices

Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their resi-dents.Among the different sources,the one coming from the rail transit system will play a central concern in the following years due to its sustainability.Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry.This paper aims to describe and compare the different mitigation systems existing and reported in liter-ature through a comprehensive state of the art analysis providing the performance of each measure.First,an introduction to the ground-borne vibration and noise gen-erated from the wheel-rail contact and its propagation through the transmission path is presented.Then,the impact and the different ways of evaluating and assessing these effects are presented,and the insertion loss indicator is introduced.Next,the different mitigation measures at different levels(vehicle,track,transmission path and receiver)are discussed by describing their possible appli-cation and their efficiency in terms of insertion loss.Finally,a summary with inputs of how it is possible to address the future of mitigation systems is reported.

A new mechanism for friction-induced vibration and noise

For years,friction-induced vibration and noise(FIVN)has puzzled many researchers in academia and industry.Several mechanisms have been proposed for explaining its occurrence and quantifying its frequencies,notably for automotive brake squeal,clutch squeal,and even rail corrugation.However,due to the complex and complicated nature of FIVN,there is not yet one fundamental mechanism that can explain all phenomena of FIVN.Based on experimental results obtained on a simple test structure and corresponding numerical validation using both complex eigenvalue analysis(CEA)and transient dynamic analysis(TDA),this study attempts to propose a new fundamental mechanism for FIVN,which is the repeated cycles of partial detachment and then reattachment of the contact surfaces.Since friction is ubiquitous and FIVN is very common,the insight into FIVN reported in this paper is highly significant and will help establish effective means to control FIVN in engineering and daily life.

Vibration and Noise Optimization of New Asymmetric Modular PMaSynRM

An optimized structure to weaken the vibration and noise of a new asymmetric permanent magnet-assisted synchronous reluctance motor(PMaSynRM)is proposed.The new asymmetric PMaSynRM has the advantages of a low torque ripple and high fault tolerance.However,the asymmetric structure generates an unbalanced magnetic force(UMF),which results in vibration and noise problems.In this study,the vibration and noise of the motor are analyzed and optimized.First,the radial pressure is analyzed,and an optimized structure is proposed.The electromagnetic performance of the motor before and after optimization is analyzed using the finite element method.Second,a three-dimensional model is established,and modal analysis is conducted considering the orthotropy of the stator and effective windings.Finally,the vibration and noise are simulated and analyzed,and the validity of the analysis results is verified experimentally.The analysis results indicate that the optimized motor realizes a reduction in the motor vibration and noise.

车内噪声主动控制发展综述及其在实车上的应用

本文对小型轿车车内噪声分布及其声源进行了分析,对国内外研究者对噪声主动控制研究成果的发展历程作了综述,并介绍了噪声主动控制理论及模型,最后结合具体实车,介绍了目前应用在实车上的车内噪声主动控制范例。

Fast Calculation of Electromagnetic Forces in IPMSMs Under PWM VSI Supply Based on Small-Signal Time-Harmonic Finite Element Method

This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.

Research on Influence of Damping Material on Structure Performance of Torpedo

Reducing the self-noise and radiated noise of torpedo is an effective way to enhance its detection and concealment capabilities.After discussing the basic principle on noise and vibration control and main noise sources in torpedo,the application of damping treatment for noise and vibration absorption was proposed in this paper.Compared composite materials(damping and metal materials)used as segment joint,their different contributions to the damping performance of base structure were investigated.The results show that the damping material can be used as segment joint effectively in vibration control.Taking cantilever beam as an example,four different damping treatments were compared in natural frequency and damping loss factor,the results show the influences of different damping layer layouts on the structure damping performance,and offer a reference for the torpedo shell design.

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection,quantification,and prediction of damages.Early detection of faults may allow the downtime of maintenance to be rescheduled,thus preventing sudden shutdown of machines.In cylinder pressure developed,vibrations and noise emissions data provide a rich source of information about condition of engines.Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue.The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines.The effects of changing various fuel injection parameters was analyzed.Scope of using non-intrusive technique has been analyzed by changing locations of microphone.Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up.Various frequency ranges of contributing noise and vibration sources were identified.Time-Frequency analysis showed the onset of various cyclic.Based on the identification of various frequency bands,it is possible to device suitable filters in order to extract more information.

Characterization of Automotive Brake Discs with Laser-Machined Surfaces

In the automotive and transport industry,braking noise and vibrations are persisting issues and difficult to control.Automo-tive engineers and researchers are putting considerable effort into overcoming these problems,and significant breakthroughs have been made in this area.In this study,M-shaped grooves were bionically designed and manufactured on the frictional surfaces of four automotive brake discs using a laser machine.Various tests were conducted to characterize the physical and mechanical performance of the modified discs along with their noise and vibration responses.The experimental results demonstrate that discs with laser-machined grooved surfaces have better surface hardness and residual stress reduction than discs with un-grooved surfaces.Significant improvement in the braking performance was observed in terms of disc thickness variation,friction and wear,noise,and vibration reduction.It is concluded that the reduction in braking noise and vibrations is mainly caused by the reduction in the coefficient of friction and wear,increase in damping ratio,and improvement of disc thickness variation of the brake disc by laser surface grooving.

Overview on Amorphous Alloy Electrical Machines and Their Key Technologies

Amorphous alloy(AA)is attracting more and more attention in electrical machines due to its excellent low loss characteristics.This paper overviews advances on AA electrical machines over the last 30 years,with particular reference to new and novel topologies and processing techniques of AA electrical machines and their key technologies.These include current states and trends for radial-flux AA electrical machines,axial-flux AA electrical machines,influences of processing techniques on electrical performance of AA iron cores,the characteristics of loss and vibration and noise of AA core and AA machines,optimum design of AA electrical machines,etc.The paper highlights the application prospects of the AA electrical machines.