Journal of Engineering and Thermal Sciences
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Analysis on the dynamic characteristics of the dual-rotor structures of a certain aero-engine
Get PDFA finite element model was constructed for a dual-rotor structure based on a certain aero-engine in this paper. Its dynamic characteristics was calculated and analyzed with the finite element software ANSYS. The characteristics were contrasted and analyzed for the dual-rotor structure with four bearings or five bearings. The influence was discussed and analyzed about the change of bearing’s stiffness to dynamic characteristics. The main conclusion was concluded as following: the low-pressure rotor vibrated in the first bending mode for the first and second modal shape; the critical speed gradually increased as the stiffness, it behaved obviously during a certain range of the stiffness, and meanwhile some modal shape would disappeared
Correction of max-min approach for analyzing shock response of strongly nonlinear system
Get PDFA novel method combining max-min approach (MMA) with energy method is proposed for the derivation of the approximate analytical solution for shock response of the strong nonlinear system. MMA is used to evaluate the governing differential equation with nonlinearity terms and to obtain the approximate solution. The maximum shock response displacement of the system is obtained by energy method, and then the approximation solution by MMA is corrected. Three examples are given to illustrate the validity of the method. It is shown that the corrected MMA method always lead to a better approximate solution for different kinds of nonlinear problems. The results provides a new simple but effective method for the analysis of shock response of strong nonlinear problems
Numerical prediction of temperature effect on propagation of rubbing acoustic emission waves in a thin-walled cylinder structure
Get PDFTemperature field has serious effects on the accuracy of rubbing acoustic emission (AE) source localization in a thin-walled cylinder structure, but it is difficult to explore the functioning mechanism through experiments. This paper aims to propose a thermos-elastic coupling simulation procedure to reveal the effect of the uniform temperature and non-uniform temperature field on the propagation characteristics of AE waves. To obtain the behaviors of guiding wave in the thin-walled cylinder, an efficient numerical simulation tool for AE wave propagation modeling is explored. The numerical results of AE propagation in a plate are compared with the experimental data. Then the semi-analytical finite element method is introduced to calculate the characteristics of multi-modal and dispersion. To remove the unwanted reflections from boundaries generated by the numerical simulation, a methodology combined with the infinite element and Rayleigh damping is presented. Consequently, several AE wave propagation simulations are carried out respectively, including the model with the uniform temperature in a range of 20-700 °C, and the non-uniform temperature field with the temperature of the central region, 649 °C. On the basis of the modeling and evaluation results, both the peak-to-peak amplitude and arrival time versus temperatures are summarized and analyzed. The validation results demonstrate that the proposed approach could be used efficiently to research rubbing AE source localization applications with a high degree of accuracy
The sensitivity analysis of the translation and the rotation angle of the first-order mode shape of the joints in frame structures
Get PDFWhen damage occurs, there are changes in the structural stiffness. This causes changes in the vibrational information, such as translation and rotation angle of the joints in the structure. This paper presents a sensitivity study of translation and slope of the first-order mode shape of the joints in the frame structure, and which will contribute to structural damage identification further. Starting from the equation of natural vibration of frame structure, and according to the characteristics of the stiffness matrix, derive sensitivity coefficient expression of translation and slope of first-order mode shape of the joints in the structure, and obtain the first-order relative sensitivity coefficient of the first story is always smaller than zero when single column of the first story damage occurs. The numerical analysis of the four stories three spans frame shows consistent results with the formula derivation
Carrying capacity analysis and optimizing of hydrostatic slider bearings under inertial force and vibration impact using finite difference method (FDM)
Get PDFAccuracy of machine tool with a gantry frame is reduced due to the vibration caused by inertial force impact. Hydrostatic slider bearings are considered as key structures of machine tools, which play an important role in improving impact and vibration resistance ability as dynamic performance. In this work, an incline model which combines bending deformation with linear displacement is simulated using working conditions of the straddle carrier under inertial force impact as an imitation of vibration amplitude. Using finite difference method (FDM), numerical solution of pressure distribution in oil pad can be determined by solving the Reynolds equation. Relationship between carrying capability and incline extent can be determined by analyzing the resolution of the Reynolds equation. A new type of oil pad size optimizing process is propose in this work, which is carried out based on the analysis of the analyzing result to enhance the inertial force resistance ability. Finally, impact resistance capacity of machine tool can be improved by sacrificing oil film thickness
The untrenched pipe’s stability analysis on the seabed under wave loadings using dynamic method
Get PDFThe on-bottom stability of submarine pipeline is a key problem of submarine pipeline design. The key issue is to simulate the interaction among wave, pipe and soil. The factors such as contact effect, frictional coefficient between pipe and soil, pipe’s penetration, the impact of yield stress are considered. Also, the results show that the computation of the pipe/soil interaction may provide a helpful tool for the engineering practice of pipeline on-bottom stability design
Identification of moving vehicular parameters based on glowworm swarm optimization algorithm
Get PDFThis paper presents an indirect method for the identification of parameters of moving vehicle based on Glowworm Swarm Optimization (GSO) algorithm. And a local search method is introduced in the movement phase of GSO to enhance the accuracy and convergence rate. The moving vehicle is modeled as 2-DOF systems with five parameters. And Newmark direct integration method is used to calculate the dynamic response of the system. Acceleration measurements at selected stations on the vehicle are used only to identify the parameters of the moving vehicle. Several test cases are carried out to illustrate the efficiency of the method and the results show that the vehicle parameters can be identified precisely with the proposed method and it is not sensitive to measurement noise
The empirical analysis on the portfolio optimization’s effective border
Get PDFThis paper discusses the portfolio optimization problem in an effective boundaries were drawn based on the efficient frontier portfolios which is analyzed using mean-variance model empirical method and simulated annealing algorithm. The conclusions show that drawing the efficient frontier based on simulated annealing algorithm is relatively accurate
Aerodynamic performance analysis of wind-sand flow on suspension bridge suspender cables
Get PDFWith the deterioration of global climate and environment, the phenomenon of wind-sand flow frequently occurs in many regions. Suspension bridge suspender cables suffer corrosion and impact from wind-sand flow. The riding-type suspender cable with four strands which is commonly used in suspender cables of long-span suspension bridges is taken as an example to investigate the influence of wind-sand flow on the suspender cables. The wind-sand flow field around the suspender cables of a long-span suspension bridge is simulated within the FLUENT software on the basis of the numerical simulation of computational fluid dynamics. The forces produced by the wind-sand flow on the suspender cables are analyzed from the simulation, and then the numerical results and the calculated results based on a theoretical equation which was used to obtain the pressure on a building in a wind-sand area are compared together. Results show there are big differences between them. The reasons will be investigated in future research, and finally a new suitable theoretical equation for the pressure of wind-sand flow on suspender cables will be proposed
Effect of dynamic regime of rollers of pocket folding machine to quality of printing products
Get PDFMeasurements of dynamics of rollers and their segments in the direction of transverse axis of rotation of eight cassettes of folding machines were carried out in this work. Measurements were carried out in pre-selected positions of rollers and their segments for two different rotating velocities of the rollers. In the first case the roller was rotated at 9 m/min velocity and in the second – at 90 m/min. It was determined that before renewal some rotating rollers for the investigated velocity of rotation of the roller 90 m/min experienced the displacements up to 80 μm. The displacements (beatings) of the rollers and their segments originating during the process of rotation in the direction of transverse axis of rotation have substantial effect to the quality of folding of printing products. Numerical investigation of the rollers was performed by using the axisymmetric model. Supplementary stiffness from the static loading caused by centrifugal forces is taken into account. The eigenmodes are calculated. The standing waves on the surface of the roller are investigated