Papers by Keyword: Modal Parameter Identification

Abstract: In this paper the feasibility of natural excitation method which uses cross-correlation function instead of impulse response function of the response to identify the modal parameter of 500kV SF₆ current transformer was discussed .Four different algorithms were used to extract the modal parameter of 500kV SF₆ current transformer with the measured cross-correlation function obtained by natural excitation method. The results of modal parameter identification using natural excitation method and experimental modal analysis were compared in the experimental way.

Abstract: Due to the interference of strong vibration signal, a big error exists in modal parameter identification based on traditional ARMA model. In order to solve this problem, a new method for modal parameter identification based on natural excitation technique (NExT) and ARMA model is presented. Firstly, NExT is used to obtain cross-correlation function of different response sequences. Then, ARMA model of cross-correlation function is established, and the parameters of ARMA model are estimated by least squares method. Finally, the modal parameter identification is achieved using the relationship between the ARMA parameters and structural modal parameters. Experiment shows that the identification results of our method are more accurate than the traditional ARMA model.

Abstract: Modal parameter identification of civil engineering structures under seismic excitations has important implications for health diagnosis, plastic analysis and optimization design of structure. A numerical simulation model of frame construction was carried out. Apply two types of seismic waves on the structure. The seismic excitations are Kobe wave and Shanghai wave which are both generated by actual earthquake records. According to the acceleration response of the layers, the first three order modal parameters can be identified by using complex exponential method. Compared the results with theoretical values, and analyzed the accuracy, the method was considered to have an effective application.

Abstract: This paper introduces the modal parameter identification method of a reinforced concrete block foundation under ambient excitation. On this basis, the dynamic characteristics of a stone cutting machine foundation are obtained by modal test under different operating conditions, and test results reveal that the main cause of abnormal vibration lies in lower dynamic stiffness of the whole structure. With the comparison of dynamic response between pre-reinforcement and post-reinforcement, reinforcement effects of high pressure grouting technique and pre-stressed bolt applied to restrain foundation vibration are verified effectively.

Abstract: With the evolution and degradation of mechanical fault, changes of the structural inherent characteristics will directly affect the overall response of system. Spur gear, which worked as the research object, is to be explored on the changes of modal parameters under different damage state. Optimum driving-point mobility and modal parameter identification is achieved by comprehensive utilization of experimental modal analysis and finite element analysis. is used to determine the experiment results is whether accurate or not. Then comparing with the differences of modal parameters, the preliminary judgment of gear damage can be made. According to the experimental data of different gears, theis taken to complete the correlation analysis and to judge the degree of the damage. The results shows that provide an effective basis for the identification of vibration mechanism and vibration characteristic of fault gear.

Abstract: In order to keep gas turbine disk safe and reliable, and to provide reliable data for the dynamic design or modification of a gas turbine disk, dynamic characteristic of the gas turbine disk has to be obtained. In the paper, the method based on the combination of calculation mode and the experiment mode is proposed to analysis the dynamic characteristic of the gas turbine disk. The modal parameters and the mode shapes are calculated through ANSYS program. On the basis of these modal parameters, the faults of the gas turbine disk are shown and its weak points of the design are illustrated. The reason for deformation is analyzed and relevant measures employed to reduce faults are proposed. By these improvements in question, a guarantee of the gas turbine disk working normally has been available.

Abstract: In order to provide high precise data for urban natural gas pipeline network dynamic modification and to diagnose the urban natural gas pipeline network fault, the dynamic characteristic of the flow-meter system, which is the main component of a natural gas pipeline network, has to be obtained precisely. The experimental modal parameters identification method base on the modal theories is proposed to substitute for the finite element method to identify the modal parameters of the flow-meter System. Multiple-point exciting by a hammer and single-point collecting by acceleration sensor can obtain testing data of the flow-meter System. The initial frequency and damping ratio of the flow-meter System can be distinguished out base on the testing impulse respond functions data. According to these modal parameters, the reasons of its faults under a certain working condition can be analyzed specifically. Simultaneously, the accuracy and reliability of this parameter identification method can be inspected on experiment.

Abstract: In this study, the modal identification methods based on time and frequency domain are summarized, and the working condition, identified accuracy and some fundamental idea of these approaches are discussed. By comparing the characteristic of different identification method, the identification technique based on ambient excitation is promising in bridges since it is difficult to measure the excitation information. Some challenge and key issues of modal identification of bridges are pointed out in the last part.

Abstract: The bridge inspection based on dynamical characteristics is the main technique for evaluating and diagnosing the performance of bridges, especially, for the situation that the bridge inspection based on static performance cannot be carried out. This study investigated the application of dynamical inspection to a bridge with accident during the construction. The dynamical performance of the damaged girders and piers were measured and compared with the healthy ones which have the same structural form in order to assess the performance of damaged bridge, and some treatment suggestions were proposed by account for the results obtained by visual inspection and crack observation.

Abstract: To study validity of power spectrum density peak method which be used to identified modal parameter of concrete bridge under ambient excitation, number simulation of one Pre-stressed concrete bridge is carried out.3D model of the bridge is established by FEM software , FEM analysis and time-history analysis of 3D model of PC continuous beam bridge are carried out.During the simulation,practical factors such as acceleration measuring and white noise are taken into account. In the only case of the output signal modal parameter of bridge can be identified. Six-order modal parameters of the structure are identified by the number simulation which the average error is less than 5%. It is revealed that power spectrum density peak method is suitable for bridges monitoring and diagnosis, with important practical engineering application value.