Vibration model of a multi-supported guide bar and analysis on the effect of supports location

Two methods (equivalent force method and segmental mode assuming method) of calculating the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load is found, considering the structure characteristic of the guide bar, which has long length but small section, and supported by many bearings. The calculation shows that these two methods are convenient for computer programing and have the same results in obtaining the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load, solving the problem that the vibration function of this kind of beam is hard to deal with because it cannot be simplified with the boundary condition of two ends. Then the segmental mode assuming method is used to analyze the impact of the support location on the natural frequencies and mode shapes of the guide bar. The relation graphs of the natural frequencies with support location, as well as the support locations where the natural frequencies reached the maximum and the minimum are found, providing a reference for the support location selection for the guide bar. The changing curves of the mode shapes with support location are plotted, which show that the bending deformation is homogeneous when the length of each segment is approximately equal, avoiding the phenomenon that bending stresses concentrates at the large-amplitude segments and cause breakage while less stress exists in small-amplitude segments and hinder the exploiting of their performance, providing a reference for the structure design of the guide bar

Numerical analysis and optimization of wheel vibrations and radiation noises of the high-speed train

Finite element and boundary element models of the standard wheel, damping wheels and S-type damping wheels were established and compared. The radial vibration and axial vibration of the standard wheel could be reduced to decrease the vibro-acoustic radiation. Regarding damping wheels and S-type damping wheels, the coupling between the radial vibration and axial vibrations of 1 pitch circle could be reduced to decrease the radiation noise. The vibration acceleration in the tread, rim and web plate was significantly improved after applying damping in the standard wheel. If the web plate was changed into S-type structure, the vibration acceleration of the wheel at three positions was further reduced. The radiation noise of S-type damping wheels was significantly improved. The radiation noise of the web plate was significantly greater than that of the tread, which was caused by the larger radiation area of the web plate

Numerical optimization of vehicle noises in multi-peak frequency points based on hybrid genetic algorithm and simulated annealing

The finite element model of Body in White was built, and the corresponding modes were computed in this paper. These computational modes were then compared with experimental results. The small errors showed that the accuracy of the finite element model can satisfy the computational requirements. Based on the verified finite element model, acoustic cavities in the vehicle were extracted to build a boundary element model. Sound pressure levels at all passengers in the vehicle were then computed, compared and analyzed. Results indicated that the sound pressure curve had 6 peak noises. Using the characteristic frequency weight coefficient and field point weight coefficient, the body panels which made large acoustic contributions to the comprehensive sound field under multi-characteristic frequencies were determined. Finally, the improved genetic algorithm based on simulated annealing was used to optimize the key body panels, and peak noises at researched field points after the optimization were further computed. The computational results were compared with those of the original structure, which presented that the noise was improved at most frequency points in the spectrum and peak noises were suppressed obviously

Experiment and simulation research of the ground-borne vibration for a high-speed train

In order to study the effect of the operational loads on the ground-borne vibration of the high-speed train, a train-track coupling model with considering the vertical and horizontal effects is established and applied to calculate the impact of different operational speeds on vibration acceleration. As shown in the results, the vibration acceleration is largely affected by different frequencies generated from different train speeds. By means of an indoor dynamic triaxial test, the impact of different vibration frequencies of a train on soil body is simulated. And a large number of medium- and low-frequency vibration tests are conducted according to the settings of load form, drainage requirement and vibration number of train vibration loads. The experimental results are analyzed to study the effect of different frequencies on dynamic characteristics, and a dynamic strain-time calculation formula, that takes the frequency factor into consideration, is proposed. Meanwhile, the improved formula that considered frequency is substituted into the finite element model (FEM) of the train, so as to analyze the impact of different vibration frequencies on the settlement, is applied. As shown in the results, the proposed improved formula, that considered the frequency, is good at prediction. The effect of vibration efficiency on the engineering can be reflected by a simulated high-speed train model. Based on the simulation model, a reinforcement measure is conducted for the ground-borne, and it is calculated that the settlement is obviously reduced and the service time of the train ground-borne is increased. This paper can provide a reference for a theoretical research and engineering practice