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.