Research on the Influence of Raceway Waviness on the Vibration Characteristics of Deep Groove Ball Bearings

The dynamics model of a 2-degree-of-freedom deep groove ball bearing is established by incorporating the raceway surface waviness model comprising multiple sinusoidal functions superposition.The model is solved using the fourth-order Runge-Kutta method to obtain the vibration characteristics including displacement,velocity,acceleration,and frequency of the bearing.Validation of the model is accomplished through comparison with theoretical vibration frequencies.The influence of the amplitude of waviness of the inner and outer ring raceway surfaces of deep groove ball bearings on the vibration displacement,peak-to-peak vibration displacement and root-mean-square vibration acceleration is analyzed,and the results show that as the amplitude of the inner and outer ring raceway surfaces waviness increases,all the vibration characteristic indexes increase,indicating that the vibration amplitude of the bearings as well as the energy of the waviness-induced shock waveforms increase with the increase of the amplitude of the waviness.

Application of Improved Hybrid Interface Substructural Component Modal Synthesis Method in Vibration Characteristics of Mistuned Blisk

The large and complex structures are divided into hundreds of thousands or millions degrees of freedom（DOF） when they are calculated which will spend a lot of time and the efficiency will be extremely low. The classical component modal synthesis method （CMSM） are used extensively, but for many structures in the engineering of high-rise buildings, aerospace systemic engineerings, marine oil platforms etc, a large amount of calculation is still needed. An improved hybrid interface substructural component modal synthesis method（HISCMSM） is proposed. The parametric model of the mistuned blisk is built by the improved HISCMSM. The double coordinating conditions of the displacement and the force are introduced to ensure the computational accuracy. Compared with the overall structure finite element model method（FEMM）, the computational time is shortened by23.86%–31.56%and the modal deviation is 0.002%–0.157% which meets the requirement of the computational accuracy. It is faster 4.46%–10.57% than the classical HISCMSM. So the improved HISCMSM is better than the classical HISCMSM and the overall structure FEMM. Meanwhile, the frequency and the modal shape are researched, considering the factors including rotational speed, gas temperature and geometry size. The strong localization phenomenon of the modal shape’s the maximum displacement and the maximum stress is observed in the second frequency band and it is the most sensitive in the frequency veering. But the localization phenomenon is relatively weak in 1st and the 3d frequency band. The localization of the modal shape is more serious under the condition of the geometric dimensioning mistuned. An improved HISCMSM is proposed, the computational efficiency of the mistuned blisk can be increased observably by this method.

Transfer matrix method for determination of the natural vibration characteristics of elastically coupled launch vehicle boosters

The analysis of natural vibration characteristics has become one of important steps of the manufacture and dynamic design in the aerospace industry. This paper presents a new scenario called virtual cutting in the context of the transfer matrix method of linear multibody systems closed- loop topology for computing the free vibration characteristics of elastically coupled flexible launch vehicle boosters. In this approach, the coupled system is idealized as a triple-beam system-like structure coupled by linear translational springs, where a non-uniform free-free Euler-Bemoulli beam is used. A large thrust-to-weight ratio leads to large axial accelera- tions that result in an axial inertia load distribution from nose to tail. Consequently, it causes the development of significant compressive forces along the length of the launch vehicle. Therefore, it is important to take into account this effect in the transverse vibration model. This scenario does not need the global dynamics equations of a system, and it has high computational efficiency and low memory requirements. The validity of the presented scenario is achieved through com- parison to other approaches published in the literature.

Non-linear Torsional Vibration Characteristics of an Internal Combustion Engine Crankshaft Assembly

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.

Effects of Vibration Characteristics on the Atomization Performance in the Medical Piezoelectric Atomization Device Induced by Intra-Hole Fluctuation

Oral inhalation of aerosolized drugs has be widely applied in healing the affected body organs including lesions of the throat and lungs and it is more effiicient than those conventional therapies,such as intravenous drip,intramuscular injection and external topical administration in the aspects of the dosage reduction and side effects of drugs.Never-theless,the traditional atomization devices always exhibit many drawbacks.For example,non-uniformed atomization particle distribution,the instability of transient atomization quantity and difficulties in precise energy control would seriously restrict an extensive use of atomization inhalation therapy.In this study,the principle of intra-hole fluctua-tion phenomenon occurred in the hole is fully explained,and the produced volume change is also estimated.Addi-tionally,the mathematical expression of the atomization rate of the atomizing device is well established.The mecha-nism of the micro-pump is further clarified,and the influence of the vibration characteristics of the atomizing film on the atomization behavior is analyzed theoretically.The curves of sweep frequency against the velocity and amplitude of the piezoelectric vibrator are obtained by the Doppler laser vibrometer,and the corresponding mode shapes of the resonance point are achieved.The influence of vibration characteristics on atomization rate,atomization height and atomization particle size are also verified by experiments,respectively.Both the experimental results and theoretical calculation are expected to provide a guidance for the design of this kind of atomization device in the future.

Experimental investigation on vibration characteristics of the medium-low-speed maglev vehicle-turnout coupled system

The steel turnout is one of the key components in the medium–low-speed maglev line system.However,the vehicle under active control is prone to vehicle–turnout coupled vibration,and thus,it is necessary to identify the vibration characteristics of this coupled system through field tests.To this end,dynamic performance tests were conducted on a vehicle–turnout coupled system in a medium–low-speed maglev test line.Firstly,the dynamic response data of the coupled system under various operating conditions were obtained.Then,the natural vibration characteristics of the turnout were analysed using the free attenuation method and the finite element method,indicating a good agreement between the simulation results and the measured results;the acceleration response characteristics of the coupled system were analysed in detail,and the ride quality of the vehicle was assessed by Sperling index.Finally,the frequency distribution characteristics of the coupled system were discussed.All these test results could provide references for model validation and optimized design of medium–low-speed maglev transport systems.

Structure vibration characteristics of two stage double helical tooth planetary gear trains with unequally spaced planets and stars

A computational model of two stage double helical tooth planetary gear set is employed to built the lateraltorsional coupling dynamic governing equations. Base on the dynamic equation, the free vibration properties of the system with unequally spaced planets and stars are analyzed. The vibration modes are classified into three types: star mode, planet mode, and coupling mode. For each of the modes, the relation between inherent frequency and vibration amplitude is investigated in detail by the eigenvalue and mode characteristics.

Prediction of Vibration Characteristics in Beam Structure Using Sub-Scale Modeling with Experimental Validation

Geometric or sub-scale modeling techniques are used for the evaluation of large and complex dynamic structures to ensure accurate reproduction of load path and thus leading to true dynamic characteristics of such structures. The sub-scale modeling technique is very effective in the prediction of vibration characteristics of original large structure when the experimental testing is not feasible due to the absence of a large testing facility. Previous researches were more focused on free and harmonic vibration case with little or no consideration for readily encountered random vibration. A sub-scale modeling technique is proposed for estimating the vibration characteristics of any large scale structure such as Launch vehicles, Mega structures, etc., under various vibration load cases by utilizing precise scaled-down model of that dynamic structure. In order to establish an analytical correlation between the original structure and its scaled models, different scale models of isotropic cantilever beam are selected and analyzed under various vibration conditions（ i.e. free, harmonic and random） using finite element package ANSYS. The developed correlations are also validated through experimental testing The prediction made from the vibratory response of the scaled-down beam through the established sets of correlation are found similar to the response measured from the testing of original beam structure. The established correlations are equally applicable in the prediction of dynamic characteristics of any complex structure through its scaled-down models. This paper presents modified sub-scale modeling technique that enables accurate prediction of vibration characteristics of large and complex structure under not only sinusoidal but also for random vibrations.

Simplified Method and Influence Factors of Vibration Characteristics of Isolated Curved Girder Bridge

The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.

Vibration characteristics of a multi-block high-temperature superconducting maglev system

The multi-block high-temperature superconducting （HTS） maglev system has more complicated dynamic characteristics than the single-block HTS maglev system. To study its vibration characteristics, we designed a maglev measurement system. The system responses at the excitation frequencies of 2, 3 and 15 Hz were examined. Results show that the responses under excitation frequencies of 2 and 3 Hz include a 6 Hz component, which means that the maglev system is a critical nonlinear system. Moreover, the 6 Hz component is much stronger than the 2 Hz or 3 Hz components in the response spectra. There is the interaction between excitation and response. Under an excitation frequency of 15 Hz, intensified low-frequency perturbations were observed.

Numerical modeling and experimental investigation of a two-phase sink vortex and its fluid-solid vibration characteristics

A sink vortex is a common physical phenomenon in continuous casting,chemical extraction,water conservancy,and other industrial processes,and often causes damage and loss in production.Therefore,the real-time monitoring of the sink vortex state is important for improving industrial production efficiency.However,its suction-extraction phenomenon and shock vibration characteristics in the course of its formation are complex mechanical dynamic factors for flow field state monitoring.To address this issue,we set up a multi-physics model using the level set method(LSM)for a free sink vortex to study the two-phase interaction mechanism.Then,a fluid–solid coupling dynamic model was deduced to investigate the shock vibration characteristics and reveal the transition mechanism of the critical flow state.The numerical results show that the coupling energy shock induces a pressure oscillation phenomenon,which appears to be a transient enhancement of vibration at the vortex penetration state.The central part of the transient enhancement signal is a high-frequency signal.Based on the dynamic coupling model,an experimental observation platform was established to verify the accuracy of the numerical results.The water-model experiment results were accordant with the numerical results.The above results provide a reference for fluid state recognition and active vortex control for industrial monitoring systems,such as those in aerospace pipe transport,hydropower generation,and microfluidic devices.

Vibration characteristics and machining performance of a novel perforated ultrasonic vibration platform in the grinding of particulate-reinforced titanium matrix composites

Ultrasonic vibration-assisted grinding(UVAG)is an advanced hybrid process for the precision machining of difficult-to-cut materials.The resonator is a critical part of the UVAG system.Its performance considerably influences the vibration amplitude and resonant frequency.In this work,a novel perforated ultrasonic vibration platform resonator was developed for UVAG.The holes were evenly arranged at the top and side surfaces of the vibration platform to improve the vibration characteristics.A modified apparent elasticity method(AEM)was proposed to reveal the influence of holes on the vibration mode.The performance of the vibration platform was evaluated by the vibration tests and UVAG experiments of particulate-reinforced titanium matrix composites.Results indicate that the reasonable distribution of holes helps improve the resonant frequency and vibration mode.The modified AEM,the finite element method,and the vibration tests show a high degree of consistency for developing the perforated ultrasonic vibration platform with a maximum frequency error of 3%.The employment of ultrasonic vibration reduces the grinding force by 36%at most,thereby decreasing the machined surface defects,such as voids,cracks,and burnout.

VIBRATION CHARACTERISTICS OF FLUID-STRUCTURE INTERACTION OF CONICAL SPIRAL TUBE BUNDLE

Heat transfer enhancement is achieved by flow-induced vibration in elastic tube bundles heat exchangers. For a further understanding of heat transfer enhancement mechanism and tube structure optimization, it is of importance to study the vibration characteristics of fluid-structure interaction of tube bundles. The finite element method is applied in the study of fluid-structure interaction of a new type elastic heat transfer element, i.e., the dimensional conical spiral tube bundle. The vibration equation and element matrix for the tube are set up by the regulation of different helical angles and coordinate transformation, together with the simplification of the joint body of the two pipes. The vibration characteristics of conical spiral tube bundle are analyzed at different velocities of the tube-side flow, and the critical velocity of vibration buckling is obtained. The results show that the natural frequency of the tube bundle decreases as the flow speed increases, especially for the first order frequency, and the critical velocity of vibration buckling is between 1.2665 m/s-1.2669 m/s. The vibration mode of conical spiral tube bundle is mainly z-axial, which is feasible to be induced and controlled.

Analysis of vibration reduction characteristics and applicability of steel-spring floating-slab track

A coupled dynamics computation model for metro vehicles, along with a steel-spring floating-slab track, is developed based on the theory of vehicle-track coupled dynamics. Using the developed model, the influences of the thickness, length and mass of floating-slab, spring rate and its arrangement space, running speed, etc. on the time and frequency domain characteristics of steel-spring fulcrum force are analyzed. The applicability of steel-spring floatingslab track is discussed through two integrated example cases of metro and buildings possessing distinct natural vibra- tion characteristics. It is concluded that, it is quite significant, in the optimization modular design of the parameters of steel-spring floating-slab track, to take the matching relationship of both the amplitude-frequency characteristics of steel-spring fulcrum force and natural vibration characteristics of integrated structures into comprehensive consideration. In this way the expensive steel-spring floating-slab track can be economically and efficiently utilized according to the site condition, and at the same time, the economic losses and bad social impact resulted from the resonance during usage of steel-spring floating-slab track can be avoided.

Study of the natural vibration characteristics of water motion in the moon pool by the semi-analytical method

The three-dimensional natural vibration characteristics of water inside a moon pool of an ocean structures are studied. The governing equations are derived based on the linear potential flow theory, and the boundary condition of the total opening bottom suggested by Molin is adopted. A semi-analytical method is used to solve the governing equations, and the natural frequencies and the motion modes are obtained. Two types of motions are studied： （1） the piston motion in the vertical direction, and （2） the sloshing motion of the free surface. The influences of moon pool＇s structural parameters on the natural frequencies, and the modal shapes are analyzed.

Experimental study on driver seat vibration characteristics of crawler-type combine harvester

To improve the driving comfort of combine harvesters,driver seat low-frequency vibration and related driver ride-comfort problems were investigated on a Chinese CFFL-850 crawler-type full-feed combine harvester based on ISO2631.Driver vibration and driving seat transmission characteristics were measured under the following conditions:no-load idling,driving on the road,driving in the field,and simulated harvesting.The root mean square values composite vibration under four conditions were 3.63 m/s^(2),2.35 m/s^(2),3.34 m/s^(2),and 2.67 m/s^(2),respectively.For the same condition,the maximum root mean square scores of vibration component on driver whole-body occurred in the seat support surface(test point 1)and vertical direction(Z direction),which were 3.56 m/s^(2),2.05 m/s^(2),3.15 m/s^(2),and 2.43 m/s^(2),respectively.The test point 2 to test point 1 vertical-transfer function curve trends were nearly identical.Nearly all of the transfer coefficients were greater than 1 in the range of 1-50 Hz,therefore,the seat vibration attenuation performance was poor.Based on the analysis results,the driver seat structure was altered and a verification test was performed.The test results indicated that after an X-damping mechanism was installed,vibration acceleration,on the surface of the seat support under the road-driving conditions,decreased from 2.35 m/s^(2) to 1.68 m/s^(2).Under the simulated harvesting condition,the vibration acceleration decreased from 2.56 m/s^(2) to 1.46 m/s^(2).Nearly all of the seat vertical transfer coefficients were less than 1 within the frequency range of 1-80 Hz,therefore the dynamic comfort of the seat was ameliorated after structural improvement.

Analysis and evaluation of vibration characteristics of a new type of electric mini-tiller based on vibration test

Now the internal combustion engine mini-tiller has become the main and indispensable agricultural machinery in vast hilly and mountainous areas of Southwest China.However,its intense vibration may pose a big threat to operators.As a countermeasure to the tiller vibration,a new type of electric mini-tiller powered with a group of lithium battery and a brushless DC motor was developed.The vibration signals at the handle of the tiller were tested under 6 conditions as follows:the tiller was under states of static and working in the field,at slow,medium and rapid speed,respectively.The signals were processed by means of the time domain eigenvalue analysis and the frequency spectrum analysis.The results show that with the electric motor rated speed increased from 95 to 140 r/min under static conditions,the RMS values increased 122.54%,and with the forward speed increased from 0.30 to 0.80 m/s under working conditions,the RMS values increased 201.78%.When the tiller was working,the first order vibration frequencies were 25.99 Hz,26.99 Hz and 28.99 Hz at slow,medium and rapid speed respectively,all not within 37.50-65.00 Hz,the sensitive range of human hands to the vibration frequency.In addition,according to the results of hand transmitted vibration analysis,it can be found that compared with operating the internal combustion engine mini-tiller under the same working condition,the onset of vibration-induced white finger can be delayed for 3.70 years to 10.20 years by operation of the new electric tiller.

Vibration Characteristics of Framed SUV Cab Based on Coupled Transfer Path Analysis

The vibration transmission paths in a sport-utility vehicle with a frame structure were used to evaluate the coupled vibra-tion of each vibration transmission link.This method was based on the transmission path of an“engine-powertrain mount system-frame-vehicle body suspension-body-driver seat rail,”and the research objective was to improve the vibration char-acteristics of the cab.This coupled transfer path analysis combined analysis and experiment to establish the vehicle vibration transmission path model and a finite element simulation model.With this method,the vibration level of the driver’s seat rail was reduced and engineering practice was effectively used to improve the vibration characteristics of the cab.This method was applied to a framed SUV cabin.

Intrinsic dielectric properties and vibration characteristics of La(Mg_(1/2)Sn_(1/2))O_(3) ceramic

La(Mg_(1/2)Sn_(1/2))O_(3)(LMS)ceramic was synthesized via the conventional solid-state reaction method.The main phase of the sample is LMS with a double perovskite structure(monoclinic P121/n1 symmetry),which is confirmed by X-ray diffraction.Scanning electron microscopy shows the sample is wellcrystallized with dense and uniform grains as well as clear grain boundaries.The Raman scattering and Fourier transform far-infrared reflection spectroscopies were employed to analyze the lattice vibrational modes of the sample.The Raman active modes were fitted by the Lorentz function,and the lattice vibrational modes were assigned and illustrated accurately.The four-parameter semiquantum model was applied to simulate the intrinsic dielectric properties,which agree well with the data calculated from the microscopic polarizability&damping angles.The A1g(La)Raman mode in A-site has a great impact on the dielectric loss,and F^(2)_(3u)mode makes the largest contribution to the dielectric constant and the dielectric loss.

Vibration characteristics simulation and comparison of traditional cab system model and seat–cab coupled model for trucks

To define the application fields of the traditional cab system model and the seat–cab coupled model,this paper mainly aims to investigate the differences of the vibration characteristics of the two models.First,the two models and their motion equations were introduced.Then,based on the mechanical parameters of the seat and cab system for a truck,the transmissibility characteristics of the two models were analyzed.The results show that the traditional model can relatively accurately predict the pitch and roll vibration characteristics of the real seat–cab system.However,it overvalues the vertical vibration transmitted from the front suspensions of the cab.Third,the typical excitation conditions and the measuring points were selected.Finally,under the typical excitation conditions,the dynamic responses of the measuring points were calculated.The results show that under the vertical excitation condition,the dynamic responses of the two models have obvious differences.Under the roll excitation condition and the pitch excitation condition,the roll responses and the pitch responses of the cab between the two models show almost no obvious difference.Under the random excitation condition,the vertical acceleration responses have relatively larger deviations between the two models,however,the angular acceleration responses are almost the same.For the preliminary design of the cab system,the traditional cab system model can be used.However,for the accurate design and the optimization of the seat–cab system,the seat–cab coupled model is recommended.