Papers by Keyword: Natural Vibration

Abstract: A method of thermal structure analysis is developed for supersonic missile rudder. The method calculates the aerodynamic heat based on Eckert reference enthalpy method, and calculates the temperature field by finite element method. The temperature field is taken as the volume load while calculating the thermal stress gradient and time history. Considering the influence of thermal stress, the natural vibration characteristics such as the mode and vibration frequency with time are obtained. The numerical computation results show that the aerodynamic heat is distributed unevenly across the rudder, such as stagnation point, laminar flow, transition and turbulence. The solid blocks of rudder shaft, longitudinal and transverse wall plates cause local low temperature, and large temperature gradient leads to higher thermal stress. Due to the change of material properties and thermal stress, the natural vibration frequency of the rudder has a significant decrease at sometime. The software of ANSYS was used to calculate and output cloud diagrams. The software of Microsoft Office was used to make curve graphics. The developed APDL command flow is very efficient and portable, which is convenient for complex structural model, and can provide technical support for supersonic missile rudder.

Abstract: It is a wll-recognized fact that effective damping of vibrations in the structure containing piezo-electrical elements strongly depends on their distribution throughout the structure. In this paper, we consider the possibilities of applying the problem on natural vibrations of elecro-elastic and electro-viscoelastic deformable bodies for identification of optimal location of piezo elements. The results of numerical simulation of the optimal piezo element arrangement in the structure, providing generation of the maximal electric potential at the prescribed resonance frequencies, are presented. The investigation has been carried out for the prototype of the plane wing, representing cantilevered symmetrical and nonsymmetrical trapezoidal plates. The possibilities of applying the problem of natural vibrations for the purpose of optimal performance of piezo elements as sensors and actuators are analyzed.

Abstract: The rung-shape long-span tensile cable-membrane structure in Foshan Century Lotus Stadium was analyzed. The effects of different pre-stressing degree and membrane tensile rigidity were discussed on structure natural vibration, static wind loads response and wind-induced dynamic analysis. Dynamic wind equivalent coefficient which can be used in structural design was also preliminary analyzed.

Abstract: This paper established the theoretical equations of transfer matrix method for frame shear wall structures to solve natural vibration and elastic response under earthquakes. Columns at each storey are combined into an equivalent shear member and shear walls are combined into an equivalent bending member. The structure is simplified as a double member system with the two members being coordinated by the in-plane infinite rigid floors. Transfer matrix of the structure was derived according to the fluctuated equations of equivalent members and the equilibrium and displacement compatibility conditions. After considering the boundary conditions at the bottom and top of structure, it presented the equations and method to solve seismic response, natural frequencies and modes of vibration of the structure. In comparison with FEM, it is a more convenient and universal method and is recommended for preliminary design of frame shear wall structures.

Abstract: Based on present research, there is a big difference between the estimation of the fundamental frequency of Girder Bridge obtained by the design code of bridge, issued by ministry of transport of the P.R. China in 2004, and the theoretical value in some cases. To overcome above issue, theoretical analysis combined with numerical simulation was applied to estimate the fundamental frequency of Girder Bridge with variable cross-section. The effect of the height ratio between mid-span cross-section and support cross-section on the fundamental frequency was discussed in detail. Finally, an improved formula was proposed to estimate the fundamental frequency of Girder Bridge, and the effectiveness of the proposed formula was verified.

Abstract: Through the ansys software, we analysised the space truss structures for its dynamic response and observed its formation of frequency diagram . Based on the analysis of the observation ,natural vibration rules of the space truss structure are discussed. In the process of analysis, We got the conclusions of the support conditions of the change and support amount of adjustment to the influence of the space truss structure vibration frequency.

Abstract: Based on present research, there is a big difference between the estimation of the first frequency of Girder Bridge obtained by the design code of bridges, issued by department of transportation of China in 2004, and the theoretical value in some cases. To overcome above issue, theoretical analysis combined with numerical simulation was applied to estimate the fundamental frequency of Girder Bridge with uniform cross-section. The effect of the ratio between side span and central span on the estimating fundamental frequency was discussed in detail. Finally, an improved method was proposed to estimate the first frequency of Girder Bridge, and the effectiveness of the proposed method was verified.

Abstract: In order to improve the vibration problem arise when rotational speed of a ball screw is increased, an analytical model is proposed to study the nonlinear dynamic behavior of the ball screw with preload considered. The contact force of each rolling element described according to nonlinear Hertzian contact deformation and the re-circulating mechanism has been taken in to account. A end-type ball screw is selected as an example, the methods of Runge-Kutta-fehlberg is used to solve the equations of motions numerically. It was found that the preload can be useful in controlling the vibration of the system,but the inhibit effect is not proportional to it,in the light of different type of ball screw, corresponding prevention preload is recommended.

Abstract: In this paper a sluice project is taken as an example. Dynamic finite element method is used to analyze dynamic response of sluice structure under the action of seismic acceleration (0.157g). The subspace iterative method is used in the modal analysis of the sluice structure after the finite element model is established, the natural vibration frequencies, and mode shapes are obtained. And then the response spectrum method is employed to implement dynamic response of the structures. The results show that the dynamic stress concentrations take place on some regions

Abstract: The natural frequencies and mode shapes of 2, 3 and 4 spans continuous beam with universal cross section are calculated, and these dynamic parameters of 2 spans continuous beam model are measured. From the analysis and the model test, the locations of the maximum curvatures of the mode shapes are determined, and comparing that with the maximum bending moment of the beam under the action of uniformly distributed load, the selection of the natural frequency of the beam is discussed with the General Code for Design of Highway Bridges and Culverts as the impact factors of the beam is calculated. It is shown from the results of the analysis and the test that, for the impact factor, when the effect of positive bending moment caused by impact force is calculated, the fundamental frequency must be used as shown in the General Code, and the 2^nd or 3^rd frequency must be used when the effect of negative bending moment caused by impact force is calculated. The selection of the frequency should be combined with the mode shape into account for the specific circumstances.