Journal of Vibroengineering
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Experimental research and optimal control of vibration screed system (VSS) based on fuzzy control
Get PDFTo enhance the compression performance and improve the paving quality of the VSS of the pavers, the experimental research of the VSS is performed to assess the VSS’s vibration stability under various excitations of the tampers and vibrator screed. A VSS’s dynamic model is also established to simulate and evaluate the VSS’s working performance. The root-mean-square (RMS) acceleration responses of the vertical and pitching motions at centre of gravity of the screed floor are chosen as the objective functions. In order to increase the VSS’s working performance, the dynamic parameters of the angular deviations of tampers are then controlled based on Fuzzy control. The research results indicate that the RMS value of the vertical screed motion is remarkably increased, concurrently the RMS value of the pitching screed angle is significantly reduced by controlling the angular deviations of tampers under different excitation frequencies of the VSS. Therefore, the VSS’s working performance is significantly improved in comparison without the control of the angular deviations
Effects of foundation mass on dynamic responses of beams subjected to moving oscillators
Get PDFThis paper aims at the effects of foundation mass on the dynamic responses of beams subjected to moving oscillators. To achieve this aim, experiments were performed for a beam resting on the foundation considering effects of the foundation model including linear elastic spring, shear layer, viscous damping. In addition, special effects of mass density of foundation during vibration were established to obtain the characteristic parameter of the influence of foundation mass based on natural circular frequency of the structure system determined from FFT plots of the time history of acceleration data. Furthermore, the experimental parameters were used to analyze the influence of the foundation mass on the dynamic response of the beam subjected to moving oscillator. Comparisons between experimental and simulated results showed that the foundation mass showed significant effects on the dynamic characteristic response of the beam system. It increased the general vibrating mass of the structure system. Hence, it decreased of the natural frequency of the structural system and caused a significant increase on the dynamic response of the beam when compared with the case without considering the foundation mass. Finally, the relationships between the foundation properties and the parameters of foundation mass were derived and discussed
Effect of annulus drilling fluid on lateral vibration of drillstring
Get PDFAnnular drilling fluid between the drillstring and borehole wall has a great influence on lateral vibration of drillstring and the influence involves the added mass. Assuming the drilling fluid is incompressible, we derive the added mass coefficient that annular drilling fluid influences on lateral vibration of drillstring in the case of axial flow of drilling fluid. When the axial flow of drilling fluid is considered, the added mass coefficient is difficult to solve. We apply CFD method and dynamic mesh technique to establish the calculation model for the flow in the annulus caused by the vibration of drillstring in the annulus. The pressure distribution and velocity distribution of annular drilling fluid are obtained. The added mass force of the drilling fluid acting on the drillstring along the direction of the drillstring is obtained from the pressure distribution, and the added mass coefficient of the lateral vibration of the drillstring is obtained. This paper provides the basis to solve the added mass coefficient of the lateral vibration of drillstring considering axial flow of drilling fluid
Erratum: Numerical investigation and experimental test on aerodynamic noises of the bionic rear view mirror in vehicles
Get PDFRemote vibrometry recognition of nonlinear eigen-states for object coverage of randomly large size
Get PDFFor objects of “large” vibration size such as waves on the sea surface, the choice of measurement method can create different understandings of system behavior. In one case, laser vibrometry measurements of a vibrating bar in a controlled laboratory setting, variation in probe spot size can omit or uncover crucial structural vibration mode coupling data. In another case, a finite element simulation of laser vibrometry measures a nonlinearly clattering armor plate system of a ground vehicle. The simulation shows that sensing the system dynamics simultaneously over the entire structure reveals more vibration data than point measurements using a small diameter laser beam spot, regardless of the variation of footprint (coverage) boundaries. Furthermore, a simulation method described herein allows calculation of transition probabilities between modes (change-of-state). Wideband results of both cases demonstrate the 1/f trend explained within – that the energy of discrete structural vibration modes tends to decrease with increasing mode number (and frequency), and why. These results quantify the use of less expensive non-imaging classification systems for vehicle identification using the remote sensing of surface vibrations while mitigating spectral response distortion due to coverage variation on the order of the structural wavelength (spectral reduction or elimination)
Multiple root resonance of tandem mill
Get PDFThe multiple-root resonance theory is introduced. The multiple-root resonance region is defined, and it includes the sub-multiple-root resonance region and complete-multiple-root resonance region. It is proved that the vibration mode shapes are identical if the natural frequencies are similar in size. The dynamic analysis of the 3-DOF model is investigated, and the results show that the variations of the mass ratio and stiffness ratio induce the natural frequencies approaching and forming a multiple-root resonance. The dynamic analysis of the tandem mill is made to study the multiple-root vibration, and the results show that with the increase in mass ratio, the 6th and 7th-order natural frequencies continue approaching one another and converge at the 5th-order natural frequency. The finite element analysis of the rolling mill shows that there are two similar natural frequencies in the rolling mill, and the vibration modes are not identical but have large vertical-component vibrations. The field test shows that the multiple-root resonance occurs in the tandem mill; after the foundation reconstruction, the multiple-root resonance is replaced by resonance with one dominant frequency, and the vibration is reduced
New structural seismic protection for high-rise building structures
Get PDFPresented Structural Seismic Isolation Method (SSIM) aims to provide high safety for Highly Reliable Structures (HRS) against strong earthquakes including near-fault and long-period ground motions. The examined structure is converted to Structural Seismic Isolation System (SSIS) by the SSIM method which exhibited inverse pendulum behaviour. For this purpose, structure foot base and foundation contact surfaces have been designed as any curved surfaces (spherical, elliptical, etc.) depending on the earthquake-soil-superstructure parameters and this contact surfaces have been separated by elastomeric (lead core rubber or laminated rubber bearings) seismic isolation devices. It would allow the structure foot base to turn around gyration centre through rubber bearing contact and maintains similar behaviour to the super-structure. SSIS system provides the possibility of keeping the natural-period of the structure in a larger interval, which is greater than the predominant-period of the majority of possible earthquakes (including near-fault pulse) using currently existing conventional elastomeric isolators with up to 4 second period. Thus, the structure can sustain its serviceability after strong and long-period earthquakes. In this study SSIS system’s performance is presented for high-rise building structures, for this aim, the finite element model of the building (Bg) structure with SSIS system (SSIS-Bg) has been prepared and the nonlinear dynamic analysis of the model has been conducted using strong and long-period ground motions. Results indicate that the base and top accelerations, base shear and base moment responses of the SSIS-Bg structure is 23.21 %, 75.47 % and 85.74 % in average lower than the Conventional Application Method of Seismic Base Isolation Devices for Building (CAMSBID-Bg) structures respectively and it is not prone to resonant vibrations under long-period earthquakes related with the excessive deformation in the isolation layers in case of using CAMSBID-Bg structures. It should be noted that in this study with the presented SSIM method and SSIS system, it is aimed to protect only the Highly Reliable Structures(HRS) from the effects of strong and long-period ground motions and these structures (HRS) are classified as follows: 1) Nuclear Containment Structures; 2) High-rise buildings that contain information, operating systems, sensitive instruments, communication systems, routing systems, bank operating systems, databases, management systems and other similar facilities that are linked to the security and economy of a country; 3) High-rise hospitals etc
Impact compression properties of artificial cemented sand material under active confining pressure
Get PDFIn order to explore the mechanical properties of rock with deep in-situ stress under explosive impact, cemented sand material (artificial material) instead of rock was used to carry out impact dynamics test under the condition of confining pressure. The experimental results show that the stress-strain curve of cemented sand specimens tested by triaxial impact compression changes significantly compared with those tested by uniaxial impact compression. The dynamic failure mode of cemented sand specimens placed under confining pressure constraints is one of axial tensile failure, while the dynamic compressive growth factor, peak strain, dynamic elastic modulus, and specific energy absorption of cemented sand specimens all have the characteristics correlated with confining pressure. The research results in this study can be as an important basis for the mechanism analysis of rock breaking by blasting in deep rock mass
Research on modeling and optimization simulation analysis of micro electric vehicle suspension
Get PDFSuspension system is one of the key parts of vehicle, the performance of suspension system has great influence on vehicle handling stability and safety. In order to improve the performance of suspension system, the Macpherson suspension of a vehicle is taken as the research object, the suspension model is established by ADAMS/Car, and carried out parallel wheel travel simulation to analyze the key parameters variation of camber angle, toe angle, caster angle, kingpin inclination angle and scrub radius. Simulation results show that camber angle and scrub radius are beyond normal design range and require optimization. Wheel alignment parameters are determined by sensitivity analysis, and optimized by ADAMS/Insight. Then carried out simulation to analyze the performance of optimized suspension system. Results show that optimized suspension system satisfies the requirements of vehicle stability and safety
Computer simulation and investigation vibration parameters of a centrifugal submersible pump
Get PDFThe dynamic characteristics of one of the centrifugal pump critical parts such as the rotor shaft are studied in the article whilst the highest level NASTRAN CAD PATRAN module was used to carry out the dynamic analysis. During the analysis a computational mechanical scheme has been compiled as well as force factors generating rotor vibrations have been determined. The axial, radial and hydrodynamic forces affecting the impeller and pump shaft have been calculated according to the analytical formula. Under the given boundary conditions in the FE model and the chosen method for determining the natural vibrations, a numerical solution of the equations of free and forced vibrations has been found using the algorithms of the NASTRAN program. The natural vibrations of the rotor have been determined using the Lanczos method. The dynamic stability of the shaft, the stress-strain state of the shaft and its displacement under static loads, the frequency and shape of the natural vibrations of the rotor necessary for the calculations have been determined. The amplitude-frequency characteristics of the system have been determined and analyzed for affection by external forces at the reverse and blade frequencies. Using the amplitude parameters of the forced oscillations, the dynamic gain of the rotor has been determined. Based on the amplitude-frequency parameters, the option of the number of blades for the working centrifugal impeller of the pump has been justified. The technique of computer simulation and determination of the vibroactivity parameters of a submersible centrifugal pump rotor shaft is given in the article