The line modal testing was carried out for analyzing the modal parameters of the body structure of high speed train. The LMS test.lab, a famous noise and vibration test system, was used for data collection and processing. Based on the theory of modal parameter identification and the modal testing method under environmental excitation, the PolyMax modal extraction method was used and the elastic modal parameters and the corresponding vibration modes of the first three orders of the train’s body were obtained. This work may provide a reference for body structure optimization.

In order to overcome the interference of environmental noise and improve the quality of EMD, the wavelet method is used to eliminate the noise signal. The correlation coefficients are applied to remove the pseudo components. And then, the random decrement method and ITD method are used to identify the natural frequency and damping ratio of train’s floor. Compared the identification results with those from LMS commercial software, it is found that the relative error of frequency is less than 5%, the relative error of damping ratio is less than 7%. This shows that the method has high precision of identification.

The structure of High-speed vehicle is complex, though simulation to obtain structural properties on the current computer simulation is still difficult.Modal testing is used to obtain dynamic characteristics of the structure. This paper describes a test method for structural characteristics, and its realization of the basic algorithm. Multi-excitation method is to be used and the measuring point for the minimum non-resonant component of the objective function of the adjustment force method is to establish. Simulation results show this method is simple, less post-processing work,and high reliability.

The welding seam of the upper tensilerods safety hangers of GQ70 light oiltank truck may split easily during the operation. But the safety hangers usually bear small load, and its failure is not a material strength problem. The modal test with hammering method is carried out at some key portions of the safety hangers. Using experimental modal analysis method, the modal frequencies of the hangers are found. Through comparative analysis, the cause of splitting of the hangers is found, and some suggestions for repairing are proposed.