Study of Axial Vibration of a Motor-Compressor System Using Operational Modal Analysis

A case study of excessive vibration on a motor-compressor system is presented in this paper.After barely two months of operation,the reciprocating compressor motor’s routine monitoring revealed excessive axial vibration amplitude.For this reason,the Operational Modal Analysis(OMA)was carried out in order to identify the pri-mary cause.According to the investigation,one of the harmonic components which was 18 times the motor’s running speed matched with a resonance frequency of 112 Hz.According to OMA study,the motor was vibrating in torsional motion because the compressor’s load had stimulated the entire motor-compressor unit at this reso-nance frequency.The analysis also demonstrates the bulging effect of the motor shaft’s axial vibration on the motor’s endplate.

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.

Vibration Modal Analysis of Compressor Blade based on ANSYS

Compressor is an important part of aero engine. In the environment of high temperature and high pressure,compressor blade will suffer from several physical and chemical processes,such as centrifugal force,aerodynamic force vibration and oxidation. These processes will lead compressor blade to fatigue fracture,and at the same time,make negative effects on the engine’ s overall performance. Based on the software ANSYS15. 0,we made strength analysis and modal analysis of compressor blade in this paper. As a result,we got its natural frequencies,relevant modal parameters and vibration mode cloud pictures. After analyzing the influence that centrifugal force made on modal parameters,we predicted the expected damage of the blade. Eventually the analysis results will provide the basis for overall performance evaluation,structural crack detection,fatigue life estimation and strength calculation of aircraft engine compressor.

Numerical Simulation Study of Vibration Characteristics of Cantilever Traffic Signal Support Structure under Wind Environment

Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model with the same scale as the actual structure and performing modal analysis,a preliminary understanding of the dynamic properties of the structure is obtained.Based on the two-way fluid-structure coupling calculation method,the wind vibration response of the structure under different incoming flow conditions is calculated,and the vibration characteristics of the structure are analyzed through the displacement time course data of the structure in the crosswind direction and along-wind direction.The results show that the maximum response of the structure increases gradually with the increase of wind speed under 90°wind direction angle,showing a vibration dispersion state,and the vibration response characteristics are following the vibration phenomenon of galloping;under 270°wind direction angle,the maximum displacement response of the structure occurs at the lower wind speed of 5 and 6m/s,and the vibration generated by the structure is vortex vibration at this time;the displacement response of the structure in along-wind direction increaseswith the increase of wind speed.The along-wind displacement response of the structure will increase with increasing wind speed,and the effective wind area and shape characteristics of the structurewill also affect the vibration response of the structure.

Vibration Characteristics Analysis and Structure Optimization of Catenary Portal Structure on Four-Wire Bridge

The portal structure is the support equipment in the catenary,which bears the load of contact suspension and support equipment.In practical work,with the change of external forces,the support equipment bears complex and changeable loads,so it has higher requirements for its reliability and safety.In order to study the dynamic characteristics of catenary portal structure on continuous beam of four-way bridge,taking the catenary portal structure on Dshaping four-way bridge as the research object,the portal structure simulation model of bridgenetwork integration was established in Midas Civil.The maximum point of deformation and stress was determined by finite element analysis of catenary hard span equipment,and the frequency and mode of natural vibration of hard span were obtained by modal analysis.Secondly,through the field dynamic stress acquisition test,combined with the results of finite element analysis,the fault location is determined,and the vibration characteristics are analyzed.Finally,based on the results of modal analysis and vibration analysis,the method that the vibration of portal structure beam is affected by structural stiffness and vibration frequency amplitude is proposed.The torsional vibration of the portal structure beam was suppressed by increasing the stiffness of the beam and reducing the vibration conduction between the trolley and the beam,and the hard cross beam was optimized by strengthening the hanging column and the connecting beam and adding diagonal support between the pillar and the portal structure beam.By comparing the values of shear,bending moment,displacement and dynamic stress on the hard span before and after optimization,the amplitude peak after structural optimization is reduced by about 25%,and the application of oblique support and reinforcement of the beam can significantly improve the portal structure vibration.

Vibration measurement and modal analysis for tunneller

In this paper, the method of vibration measurement and modal analysis for AM50 Tunneller machine is presented. When the machine was used for cutting man made coal bed and real coal bed, the vibration of the machine was measured and the results of signal analysis show that the vibration characteristics under the two kinds of working situations are similar. The modal model of the machine is established, and then, the intrinsic vibration characteristics of AM50 tunneller are investigated by means of the method of experimental modal analysis. The vibration response simulation under a set of loading spectra measured is carried out by force response simulation software.

STUDY ON THE VIBRATION CHARACTERISTIC OF THE METAL PUSHING BELT CONTINUOUSLY VARIABLE TRANSMISSION

The solid and finite element model of metal pushing type continuously variable transmission are established at speed ratio of i =0 5 and i=2 0. In order to solve the problem of the complicated of structure,the node node rod discrete finite element model is put forward and the whole system is simplified and established.The natural frequency and mode shape of system are solved by iterative Lanczos reduce method for sensitivity analysis in finite element model.The new method and the result can be used to improve the smoothness of the variable transmission system and to propose the theory for reducing noise at operation.

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.

Application of experimental modal analysis technique to structural design of linear vibrating screen

A large model of the screen was mounted in the laboratory for studying its modal performance. The model is suspended with steel ropes. Modal test was carried out with artificially exciting by 500 g impacting hammer and 100 kg exciting force shaker respectively. Synthesis and correction of the modal parameters are obtained from both testing methods. Design faults of vibrating screen were determined based on the analy-sis and dynamic correction of structure approaches about the screen was put forward finally.

Studies on vibration characteristics of a pear using finite element method

The variation of the vibration characteristics of a Huanghua pear was investigated using finite element simulations. A new image processing technique was used to obtain the unsymmetrical and un-spherical geometrical model of a pear. The vibra-tion characteristics of this type of pear with the correlation of its behavior with geometrical configurations and material charac-teristics were investigated using numerical modal analysis. The results showed that the eigenfrequency increased with the in-creasing pear Young’s modulus, while decreased with increasing pear density, and decreased with increasing pear volume. The results of this study provided foundation for further investigations of the physical characteristics of fruits and vegetables by using finite element simulations.

Experimental and Numerical Investigations on Vibration Characteristics of a Loaded Ship Model

In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method （FEM） by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain.

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.

Research on Breeze Vibration Law and Modal Identification Method of Conductor Considering Anti-Vibration Hammer Damage

In the harsh environment,the structural health of the anti-vibration hammer,which suffers from the coupled effects of corrosion and fatigue damage,is significantly reduced.As part of the conductor structure,the anti-vibration hammer is rigidly attached to the conductor,effectively suppressing conductor vibration.The conductor’s breeze vibration law and natural modal frequency are altered damage to the anti-vibration hammer structure.Through built a vibration experiment platform to simulate multiple faults such as anti-vibration hammer head drop off and position slippage,which to obtained the vibration acceleration signal of the conductor.The acceleration vibration signal is processed and analyzed in the time and frequency domains.The results are used to derive the breeze vibration law of the conductor under multiple faults and propose an anti-vibration hammer damage online monitoring technology.The results show that the vibration acceleration value and vibration intensity of the conductor are significantly increased after the anti-vibration hammer damage.The natural frequency increases for each order,with an absolute change ranging from 0.15 to 6.49 Hz.The anti-vibration hammer slipped due to a loose connection,the 1st natural frequency increases from 8.18 to 16.62 Hz.Therefore,in engineering applications,there can be no contact to determine the anti-vibration hammer damage situation by monitoring the modal natural frequency of the conductor.This is even a tiny damage that cannot be seen.This method will prevent the further expansion of the damage that can cause accidents.

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.

Modal analysis on transverse vibration of axially moving roller chain coupled with lumped mass

The modal characteristics of the transverse vibration of an axially moving roller chain coupled with lumped mass were analyzed.The chain system was modeled by using the multi-body dynamics theory and the governing equations were derived by means of Lagrange's equations.The effects of the parameters,such as the axially moving velocity of the chain,the tension force,the weight of lumped mass and its time-variable assign position in chain span,on the modal characteristics of transverse vibration for roller chain were investigated.The numerical examples were given.It is found that the natural frequencies and the corresponding mode shapes of the transverse vibration for roller chain coupled with lumped mass change significantly when the variations of above parameters are considered.With the movement of the chain strand,the natural frequencies present a fluctuating phenomenon,which is different from the uniform chain.The higher the order of mode is,the greater the fluctuating magnitude and frequency are.

Dynamic Characteristics Analysis and Vibration Experiment of Upper-time of Flight Counter (U-ToFC)

The dynamic characteristic parameters of Up-time of Flight Counter （U-ToFC） are important for research of structure optimization and reliability. However, the current simulation is performed based on homogenous material and simplified constraint model, the correct and reliability of results are difficult to be guaranteed. The finite element method based on identification of material parameters is proposed for this investigation on dynamic analysis, simulation and vibration experiment of the U-ToFC. The structure of the U-ToFC is complicated. Its＇ outside is made of aluminum alloy and inside contains electronic components such as capacitors, resistors, inductors, and integrated circuits. The accurate material parameters of model are identified difficultly. Hence, the parameters identification tests are performed to obtain the material parameters of this structure. On the basis of the above parameters, the experiment and FEA are conducted to the U-ToFC. In terms of the flight acceptance test level, and two kinds of joints condition between the U-ToFC and fixture are considered. The natural frequencies, vibration shapes and the response of the power spectral density of the U-ToFC are obtained. The results show simulation which is based on parameters identification is similar with vibration experiment in natural frequencies and responses. The errors are less than 10%. The vibration modes of simulation and experiment are consistent. The paper provides a more reliable computing method for the dynamic characteristic analysis of large complicated structure.

Modal analysis of coupled vibration of belt drive systems

The modal method is applied to analyze coupled vibration of belt drive systems. A belt drive system is a hybrid system consisting of continuous belts modeled as strings as well as discrete pulleys and a tensioner arm. The characteristic equation of the system is derived from the governing equation. Numerical results demenstrate the effects of the transport speed and the initial tension on natural frequencies.

Influence of structure and material on the vibration modal characteristics of novel combined flexible road wheel

Aiming at the independent development of tracked vehicles,it is urgent to improve its mobility,passability and ride comfort,a new type of flexible road wheel with a“wheel-hinge-hub”combined structure is proposed in this study.The vibration model characteristics of the flexible road wheel were studied by the combination of numerical simulation and experiments.The superelasticity of rubber is obtained through uniaxial tensile experiment of the material and a detail three-dimensional nolinear finite element model of the flexible road wheel is established through finite element software ABAQUS.The free vibration equation of the flexible road wheel is solved by Lanczos vector direct superposition method,and its predicted modes and natural frequencies are compared with experimental results,which verifies the accuracy and reliability of the established finite element model.On this basis,the effects of various key structural or material factors on the natural frequencies of the flexible road wheel are studied using orthogonal experimental design method.Besides,the vibration modal characteristics of the flexible road wheel are also compared with those of the rigid road wheel.The research results provide a theoretical basis for the vibration and noise reduction of flexible road wheel.

Research on vibration reduction test and frame modal analysis of rice transplanter based on vibration evaluation

The chassis of rice transplanter tends to vibrate severely in the severe working environment,causing a severe effect on the operational performance and driving comfort.In order to avoid this situation,this paper constructs a vibration evaluation system of the rice transplanter and carries out experimental analysis.According to the optimal acceleration sensor placement scheme,a test platform system was designed.Taking the high-speed transplanter chassis as the research object,this study carried out the experiments modal analysis and optimization on the chassis.The three-dimensional model of the transplanting machine chassis established by SolidWorks was imported into ANSYS Workbench for finite element modal simulation analysis.Comparing the two modal analyses,it is found that the results data of the two analysis methods were very close.After optimization,the length x1,the section width x2 and the thickness of the hollow beam x3 of the main load-bearing beam of the frame were as follows:x1=1641.5 mm,x2=26.7 mm,x3=5 mm,respectively.The maximum overshoot of the low-level system was reduced by 28.57%.It has been verified that the vibration of the whole machine has been effectively reduced.

Vibration Control of the Rail Grinding Vehicle with Abrasive Belt Based on Structural Optimization and Lightweight Design

As a new grinding and maintenance technology,rail belt grinding shows significant advantages in many applications The dynamic characteristics of the rail belt grinding vehicle largely determines its grinding performance and service life.In order to explore the vibration control method of the rail grinding vehicle with abrasive belt,the vibration response changes in structural optimization and lightweight design are respectively analyzed through transient response and random vibration simulations in this paper.Firstly,the transient response simulation analysis of the rail grinding vehicle with abrasive belt is carried out under operating conditions and non-operating conditions.Secondly,the vibration control of the grinding vehicle is implemented by setting vibration isolation elements,optimizing the structure,and increasing damping.Thirdly,in order to further explore the dynamic characteristics of the rail grinding vehicle,the random vibration simulation analysis of the grinding vehicle is carried out under the condition of the horizontal irregularity of the American AAR6 track.Finally,by replacing the Q235 steel frame material with 7075 aluminum alloy and LA43M magnesium alloy,both vibration control and lightweight design can be achieved simultaneously.The results of transient dynamic response analysis show that the acceleration of most positions in the two working conditions exceeds the standard value in GB/T 17426-1998 standard.By optimizing the structure of the grinding vehicle in three ways,the average vibration acceleration of the whole car is reduced by about 55.1%from 15.6 m/s^(2) to 7.0 m/s^(2).The results of random vibration analysis show that the grinding vehicle with Q235 steel frame does not meet the safety conditions of 3σ.By changing frame material,the maximum vibration stress of the vehicle can be reduced from 240.7 MPa to 160.0 MPa and the weight of the grinding vehicle is reduced by about 21.7%from 1500 kg to 1175 kg.The modal analysis results indicate that the vibration control of the grinding vehicle can be realized by optimizing the structure and replacing the materials with lower stiffness under the premise of ensuring the overall strength.The study provides the basis for the development of lightweight,diversified and efficient rail grinding equipment.