Concrete pavement slab may get a significant built-in curling for dry shrinkage and built in temperature gradient during early age. Effection of built-in curling of slab on dynamic load and riding comfort were analyzed based on quarter vehicle vibration model and road-vehicle dynamic interaction analysis method.The results show that built-in curling has more effects on roughness and random dynamic load of higher-grade pavement, and the main effects on road roughness and vehicle random dynamic load parameters relative to frequency of (slab length/speed). Built-in curling and environmental temperature gradient overlay will produce upward or downward curling, slab upward curling have a larger influence on the pavement roughness and random dynamic load, down warping has little effect. sensitivity analysis show the riding comfort, pavement grade, vehicle parameters and speed have more significant effectiton than curling. three roll shaft constuction built-in curling shape have a higher effect than built in curling. Effective built-in temperature difference keep below -10 ℃ may lead to a good performance of pavement slab.
Dynamic analysis method of anisotropic asymmetric rotor-bearing system based on 3D finite element method was presented. The system mass, stiffness and coriolis force matrices expressed in the rotating coordinate system were generated by ANSYS. Time-varying bearing stiffness in the rotating coordinate was then obtained by coordinate transform. The differential equations of motion of the system were generated by applying constraints and time-varying bearing stiffness to the system matrices using the corresponding relationship between node number and column index of the matrices. Floquet theory and Hill infinite determinant method were adopted to solve the differential equations and frequency characteristics and stability of the system were obtained. The proposed method was validated based on a literature model, and the proposed method was applied to the dynamic analysis of an industrial rotor considering the anisotropic asymmetric characters.
The common batch manifold learning algorithms can’t achieve dimensionality reduction rapidly of additional samples with the learned manifold structure, the incremental orthogonal neighborhood preserving embedding (IONPE) manifold learning algorithm was proposed. It achieves dynamic incremental learning for the additional samples with the block processing idea based on orthogonal neighborhood preserving embedding. Firstly, select some overlapping points from the original samples and add them to the additional samples; Secondly, get the subset of low-dimensional embedding coordinates of additional samples by ONPE not depending on the original samples; Finally, based on the principle of minimizing the differences of the overlapping point coordinates, the low-dimensional embedding coordinates of the additional samples were integrated into the original samples by rotating, shifting and scaling transformation. The fault diagnosis case of the gearbox confirmed that the IONPE algorithm has good incremental learning ability. It improves the processing efficiency of the additional samples while inheriting the superior clustering performance of ONPE.
Vibrations on grinding machines are primarily caused by the unbalance in the grinding wheel. A new type of liquid-transfer active balancing device is proposed to adjust the balancing state of grinding wheel and increase grinding accuracy. In the balancing system, compressed air is used for driving balancing liquid to transfer between two opposite chambers. The distribution of liquid in balancing disk is changed and the grinding wheel is balanced. Balancing performance of the device is analysed .The experiment result demonstrates that the unbalance response is reduced from 10.2um to 0.37um at 5500 r/min and the decrease in amplitude is more than 95%.
In order to ensure the glass deformation coordinated with cable net, the structure model which included glass panel, cable net, sealant, and spider was established to study the influence of glass panel to the static performance and dynamic characters of cable net. The flow field was simulated considering the buildings around the glass facades. Based on those, fluid-structure interaction analysis was carried out to study the spectrum characteristics, dynamic response of glass facades. Under the average wind load, cable net reaching new equilibrium position, Wind-induced response of structure was researched with frequency domain method. Comparison of two methods results show that under wind load, the structure vibration forced by wind was a narrow band process; the glass stiffness effectively reduced the average displacement and pulse response of the cable net.
In order to investigate the effect of the splitter blades on the unsteady flow and structural dynamic characteristics on the molten salt centrifugal pump, the directly coupled method, considering the interaction of fluid and structural fields, was applied to compare the unsteadiness and structural dynamic characteristics of the pump with and without splitter blades by using the ANSYS CFX 12.1 and ANSYS Workbench. By comparing the results of the unsteady flow and the structural characteristics, some conclusion are drawn: the results of pressure fluctuation and the radical trust are changed greatly, which indicate that the effect of FSI is quite obvious which cannot be ignored; the pressure fluctuation, the radical trust, the maximum equivalent stress fluctuations, the maximum deformation fluctuations, and the equivalent stress distribution and deformation of the pump are decreasing by adding splitter blades, which can prove that the splitter blades can improve the impeller blade loads and the capability of anti-fatigue.
Multi-DOFs structural modal parameters identification turns into several SDF structural modal parameters identifications through treating structural output data by Continuous Wavelet Transform. An optimization issue with the objection function of the difference between theoretical formula of wavelet skeleton and the wavelet skeleton calculated from structural output-only data is carried out. The optimal objective value can be gained through searching reasonable modal parameters included in the theoretical formula of wavelet skeleton. And the optimization turns into structural modal parameters identification. Quantum-behaved Particle Swarm Optimization, as a swarm intelligence optimization algorithm, is used in the structural modal parameters identification above to identify the structural modal parameters (frequencies, damp ratios and modal shapes) under ambient excitation just one time. Finally, the modal parameters identification method based on Quantum-behaved Particle Swarm Optimization combined with Continuous Wavelet Transform presented herein is verified by a numerical simulation of a simple-support beam. The results show that methodology herein can effectively identify structural modal parameters under ambient excitation.
A circular wire-cable vibration isolator is designed by adopting independent wire rope loops as elastic damping elements. Owing to its unique structure, the isolator exhibits nonlinear elastic stiffness and asymmetric hysteresis dynamic behavior in the tension–compression mode. In the present study, a modified normalized Bouc-Wen model is proposed to describe the hysteretic behaviour of a circular wire-cable vibration isolator. A two-stage identification method is developed for identifying the model parameters. Periodic loading experiments were carried out to validate the proposed model and identification method. The results verify that the proposed model and identification method are effective for accurate description of asymmetric hysteresis dynamic behavior in the tension–compression mode of circular wire-cable vibration isolator. It establishes the foundation for dynamic design method of circular wire-cable vibration isolator.
For the effective prevention or reducing the loss of the rock burst in coal mine, a mine thin-walled component with square folds for rock burst prevention was put forward, the rock burst prevention are embodied in the fracturing process in which the component absorbs the impact energy and space to provide the energy release space for the coal rock .The ABAQUS finite element software was used to simulate the energy absorption properties of different wall thickness and number of modules in axial and compare with the conventional rectangular thin-walled analysis. The Result Indicates that (1)the thin-walled component with square folds have the lower crushing peak load and the higher total energy absorption and specific energy-absorption capability, the rock burst prevention effect is remarkable.(2) reducing the wall thickness of the thin-walled component with square folds and reducing the length to increase the module number of the component in axial all could effectively reduce the crushing peak load , but reduce the total energy absorption and specific energy-absorption capability at the same time. According to the simulation results to select the size of the mine thin-walled component with square folds for rock burst prevention, the experimental study was carried out to prove the accuracy of the simulation. The mine thin-walled component with square folds for rock burst prevention was combined with the existing supporting , which can make it act as hydraulic prop and the bumper bracket of top beam 、mudsill and the two sides etc.
With the improving requirements of the dynamic quality of transmission system, only the eigensensitivities analysis could not satisfying the requirements of dynamic characteristics about transmission system of vehicle. It’s need to turn to response sensitivity research to find guideline for reduce vibration of vehicle transmission system in designing stage. This paper studies the sensitivities of dynamic response with respect to design parameters (such as shaft torsional stiffness, moment of inertia, transmission errors of gear pairs, et al.) The lateral-torsional coupling dynamic model which adopting engine as input source is built up by lumped parameter method. The sensitivity equations are derived from dynamic equations which containing nonlinear terms (such as time-varying mesh stiffness, backlash of gear pairs, mass eccentricity, transmission error et al.). The relative sensitivity of dynamic response with respect to design parameters which then turning into relative sensitivity of force/torque with respect to design parameters are acquired from numerical simulation method. The results of the relative response sensitivities give the theoretical basis of next works which containing dynamic modification, model updating, parameter optimization and so on.
Classical thin shell theories and modal superposition principle are used to investigate the dynamic response of isotropic circular cylindrical shells with both ends shear diaphragms supported. The contribution of non-radial vibration components and responses of sinusoidal and cosine modes are taken into account. The force, moment and coupling mobility functions of a circular cylindrical shell which simultaneously subjected to harmonic point force and moment excitations are derived. It is shown that non-radial vibration components have remarkable effects on the prediction accuracy for modes and mobility frequency spectrum, and the real parts of coupling mobility functions may be negative. It can provide a theoretical guidance for the vibration and noise reduction of cylindrical shell structures and for designing active and passive vibration isolation systems with circular cylindrical shell foundations.
A dynamic model for the over-hang part of the micro-endmill is proposed, which comprehensively considered the shear deformations and rotary inertia effect arising from the nature of the micro-endmill by using the theory of Timoshenko beam. The convergence behavior of the built model is analysed, and its accuracy is verified by experiment, and the applicability of the model is proved by comparing with the calculated results from finite element method and the Euler beam theory. Based on the developed model, the effect of the tool tip diameter, tip section aspect ratio and semi-taper angle on the natural frequencies of micro-endmill are studied. The proposed model enables better parametric design and optimization of micro-endmill for excellent dynamic performance.
A relative wave crest detecting algorithm base on all the tenses is proposed aiming at how to detect the number of medium layer on multilayer penetration. The algorithm mainly uses time information as a basis for the layer number recognition, then utilizes the polarity of the difference between the wave peak apex and the data points before and after it to preliminary identify the number of the wave peak, then bases on pulse width and fengfeng interval information for number of peaks for further confirmation in order to improve the correction of recognition the number of medium layer. The algorithm is feasible and correct in data processing through simulation and shooting range test. The algorithm provides a new design thought for the penetration layer recognition, does not rely solely on peak, makes full use of time and amplitude information of the signal comparing with the existing absolute threshold comparison method.
In this paper, the effects on dynamic characteristics of a mechanism with clearance driven by harmonic drive, considering the flexibility of harmonic gear, were investigated. Firstly, the contact model of a mechanism with clearance driven by harmonic drive was established by using the nonlinear spring-damp model. Then, a slider-crank mechanism with clearance was simulated. The result showed that harmonic drive and flexibility of mechanical parts had cushioning effect of collisions for clearance. The cushioning effect was not obvious when the stiffness of mechanical parts was high, while the reduction of stiffness of mechanical parts would result in large deformation during the run which would influence the mechanical properties of the mechanism. It set a theoretical foundation for the use of harmonic drive in mechanisms with clearance.
Rotary cranes are widely used to transport heavy loads and hazardous materials in various environments, such as shipyards, factories, nuclear installations, and construction sites. Because horizontal motion of booms in rotary cranes typically generates undesirable two dimensional load sway, a trajectory generation method is proposed for achieving boom positioning and residual load sway suppression. Firstly, a partial linearized dynamic model of a rotary crane that includes a centrifugal force term responsible for two dimensional load sway is derived. Next, an S-shaped curve trajectory that can suppress residual load sway is generated by numerical calculation. The parameters of the trajectory can be obtained only by solving algebraic equations. This trajectory may be applied to conventional industrial controllers for reducing their system construction cost. Finally, comparative simulations and experimental results demonstrate the effectiveness of the proposed method. Therefore, the crane can be precisely operated without sensor systems for measuring load sway, consequently, the structure of the crane can be simplified and implementation cost can be reduced.
Many ground motion intensity indexes were used to the structure seismic analysis, but there were no unified final conclusion and lack of systematically analysis on the applicability for these index. The correlation between the ground motion intensity and the structure seismic response was investigated by inputting 100 typical ground motion records to the SDOF system and the seismic-isolation-and-reduction continuous-beam bridge which have different period. The results show that the intensity index can be separated into four groups. The group I index represented by Sa(T1) has a high correlation with different period structure. The group II index represented by PGA has a high correlation with short period structure. The group III index represented by PGD has a high correlation with middle period structure. The group IV index represented by PGV has a stable correlation. The group I index is suggested to used as the ground motion intensity. A practical engineering analysis shows that different intensity indexes have different correlation with the known natural vibration period structure.