Journal of Engineering and Thermal Sciences
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The effect of lubricant inertia on fluid cavitation for high-speed squeeze film dampers
Get PDFThis work studies the effect of lubricant inertia on the fluid cavitation for partially sealed high-speed squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs). The lubricant cavitation is modeled by both the Elrod algorithm and the Gumbel’s cavitation boundary condition to provide the comparison between the most common lubricant cavitation models. Additionally, the fluid inertia is integrated by adapting a finite-length SFD model for partially sealed dampers. The integrated SFD model is incorporated into a numerical simulation model and the results are validated by comparison with experimental data. The results of the analysis demonstrate that the fluid inertia effects significantly extend the cavitation region and influence the cavitation onset and the film reformation
Axisymmetric scattering of a fluid spheroid illuminated by an acoustical Bessel beam
Get PDFDepending on the partial wave series expression, the scattering of a fluid spheroid illuminated by a zeroth-order Bessel beam is calculated in the spherical coordinate. For a fluid spheroid, the scattering is associated with the host medium, and the immersed spheroid medium. Although spherical and cylinder fluid objects has been discussed a lot before, a prolate and oblate fluid spheroid has not been investigated deeply. In the paper, two limited boundary conditions (Neumann and Dirichlet) are presented and discussed about far-field scattering form functions. By comparing these two limited conditions, the analysis could be applied into underwater detection and acoustic tweezers, or other fields. For other fluid materials, this method could also be utilized to calculate and analyze
Analysis of corn ears movement within the threshing crescent using high-speed recording method
Get PDFThe main objective of the research was to establish movement of corn ears within the threshing crescent between the cylinder and the concave using high-speed recording method. Tangential threshing unit was used in the experimental trials. Cylinder rotation and linear velocity of rasp bars (11.00 m s-1, 14.14 m s-1 and 17.28 m s-1) were determined by using threshing cylinder covered with filler plates having 4 different shapes. During the trials, speed of corn ears within threshing crescent, number of impacts received by the corn ear, rising height of the corn ear after impact of rasp bar and time between two impacts of rasp bar to the corn ear, depending on the shape of filler plates of threshing cylinder were found. Video analysis of corn ear movement showed that the speed of corn ears movement in the threshing crescent highly depends on linear velocity of rasp bars. The average speed of corn ear within threshing crescent and number of impacts received by the corn ear were increased with increase of linear velocity of rasp bars irrespective of cylinder filler plates are used. Moreover, both above-mentioned parameters were larger in the second part of concave length than in the first one. A tendency of increase of the corn ear moving over the surface of the concave and decrease of number of impacts received by the corn ear was observable by reduction in the threshing crescent. Following reduction of linear velocity of rasp bars to 14.14 m s-1, it would be reasonable to cover the threshing cylinder with filler plates that can reduce the cross-section area between rasp bars and concave (to 94.26 cm2 in view of one gap between adjacent rasp bar). In this case, filler plates showed a substantial effect on behaviour of corn ears: they restrict a rising height of the corn ear, may be subject to additional rotational motion, deflect the corn ear to the clearance between the rasp bar and the concave bar as well as deflect threshed kernels towards concave grates
Free vibration of square plate with temperature effect
Get PDFIn modern engineering, researchers/scientists are very keen to know first few modes of vibration because it provides how system/structure behaves under vibration. In this paper, author computed the natural vibration of non homogeneous tapered square plate. Here tapered means that plate’s thickness varies linearly along x-axis. Here non homogeneity arises in the plate’s material due to simultaneous variation in density (circular variation) and Poisson’s ratio (exponential variation). Temperature variation on the plate is viewed bi-parabolic along the axes. Rayleigh-Ritz technique is applied to obtain the frequency equation and vibrational frequency modes under different combination of parameters. The findings of the papers are presented in tabular form
Manufacturing and characterization of CNT based polymer composites
Get PDFCarbon nanotubes have been the concentration of all-encompassing research due to the excellent mechanical, thermal, electrical and magnetic properties. In the present work fifteen specimens of polymer composites is manufactured, multi walled carbon nanotubes (MWCNT’s) are considered as filler material for proposed volume based amount and for three unique direction of E glass fiber. The effect of different percent loadings of MWCNTs on the morphology and thermal behavior of the composites had been inspected. Thermal analysis investigation showed that a clear improvement of thermal stability of composites increased with increasing MWCNTs content. The experimental results are compared with statistical results and found to be in good agreement
Incremental dynamic analysis of SDOF by using nonlinear earthquake accelerograms based on modified inverse Fourier transform
Get PDFIn evaluation of structures, performing nonlinear response of model over a time analysis or incremental dynamic analysis needs more time. Hence, it can be beneficial if the event history report is carried out with long time steps without loss of accuracy. This study includes a method to simplify of accelerograms meant on the change of their Fourier reports. So, the Fourier Spectrum of the accelerogram is initially determined. Next applying a PC code generation, the similar Inverse Fourier Convert is computed utilizing a comparatively large time stage, depending on the structure’s times; that is ordinarily five to ten times bigger than primary accelerogram’s duration stage to generate the visible accelerogram. This application from the simplified accelerogram apparently takes much less time. Results indicates that the analysis time can be reduced up to 80 % by using the proposed method. While the maximum response shows an error of merely five to ten percent, about the sort of structure and the characteristics of the records used
Application of deterministic resampling particle filter to fatigue prognosis
Get PDFThe method based on a particle filter for a fatigue crack growth prognosis has proved to be a powerful and effective tool for developing prognostics and health management (PHM) technology. However, the widely used basic particle filter have the unavoidable particle impoverishment problem, which will make particles unable to approximate the true posterior probability density function of the system state and lead to a prognosis result with a large error. This paper proposes a fatigue crack growth prognosis method based on a deterministic resampling particle filter. The active structural health monitoring based on the Lamb wave is used for on-line crack length monitoring with piezoelectric transducers. With the on-line crack measurement, the crack state and crack growth model parameters are estimated for a fatigue crack growth prognosis. In addition, the deterministic resampling procedure is employed to overcome the particle impoverishment problem. The result shows the proposed crack growth prognosis method based on deterministic resampling particle filter can provide more satisfactory results than the basic particle filter
Seismic behavior of bifurcated concrete filled steel tube columns with a multi-cavity structure
Get PDFIn order to meet the architecture and construction needs of high rise buildings, the special-shaped columns are becoming more and more widely used. In this study, cyclic tests on seven special-shaped bifurcated Concrete Filled Steel Tube (CFST) columns are carried out. Test variables are the column cross section types and the loading directions. The strength, ductility, hysteretic behavior, energy dissipation ability, failure modes and seismic mechanisms are analyzed. Test results show that: the cross-section type of the column is the main factor influencing the seismic behavior of the specimens. Compared with the basic cross section type, the strength, ductility and energy dissipation capacity of the strengthened cross section type all significantly increased. The cross sections with the inserted angle steel or circular steel tube have the best comprehensive seismic behavior. Also, the loading direction has a considerable influence on the seismic behavior. Compares with the short axis loading specimen C1-Y, the strength of the long axis specimen C1-X and 45° axis C1-Z increase by 92.5 % and 44.0 %, respectively, indicating that the differences in loading direction should be taken into consideration in the seismic design. Based on the test results, the FEM analysis are also carried out. The FEM results show a satisfactory agreement with experimental results. The concrete constitutive relationship and modelling method proposed is suitable for the simulation of special-shaped bifurcated CFST columns with multiple cavities
Active vibration isolation using a six-axis orthogonal vibration isolation platform with piezoelectric actuators
Get PDFPiezoelectric actuators (PEA) act an important role in active vibration control area due to the advantages of fast response, high output force, small size and light weight. A 6-axis orthogonal vibration isolation platform based on PEAs is designed, which satisfies the demands of heavy payload, small installation space and multi degree of freedom vibration isolation. The dynamic model of the six-axis orthogonal vibration isolation platform with PEAs is established using Newton-Euler method. With the layout of six PEAs around the axis of symmetry, the dynamic equations could be decoupled into two single-input-single-output (SISO) subsystems and two multi-input-multi-output (MIMO) subsystems. Based on the modal superposition method, the two MIMO subsystems are further decoupled. The control strategy for each SISO system is developed with LQR control method. To evaluate the effectiveness of the control method, the simulation and verification experiment are conducted. The simulation result and experimental data indicate that the decoupling control of the proposed six-axis orthogonal vibration isolation platform with piezoelectric actuators effectively reduces the vibration response of payload within the target frequency range of 20 Hz to 200 Hz
Roller spinning forming regularity
Get PDFIn this paper we use ABAQUS finite element analysis software to design the 3D model. We observed the forming rule of grooved V-shaped pulley during the spinning process, and the impact of rotary working angle and processing temperature on V-belt forming is calculated. The results of this study provide us some theoretical information and pragmatics value for spinning pulley in veritable production