11Automated techniques for analyzing the dynamic behavior of full-scale civil structures are becoming 12 increasingly important for continuous structural health monitoring applications. This paper aims to extract the 13 structural modal parameters of a full-scale cable-stayed bridge from the collected 'output-only' vibration data 14 without the need of any user interactions. The work focuses on the development of an automated and robust 15 operational modal analysis (OMA) algorithm, utilizing a multi-stage clustering approach. The main 16 contribution of the work is to define a novel way of automatically defining the hierarchical clustering threshold 17 to enable the accurate identification of a complete set of modal parameters. The proposed algorithm is 18 demonstrated to work with any parametric system identification algorithm that uses the system order 'n' as the 19 sole parameter. In particular the results from Covariance-driven Stochastic Subspace Identification (SSI-Cov) 20 methods are presented. 21

Drive axle housing is one of the major load-supporting components of trucks. This paper takes a drive axle housing of a light commercial vehicle as the research object. The model of the drive axle housing is established by Pro/E software, on the basis of this model, the finite element analysis is carried by ANSYS to get the results of stress and strain under the defined constraints and loads, to find the weak links in the design. Aiming at achieving the goal of the least weight, the permission stress and displacement are defined and the thickness of the drive axle housing is considered as the design variable to optimize the design. The result of optimization design provides a theoretical guidance for truck driving axle housing designing.

In this paper, a time-frequency analytic system is implemented by using mixed programming of Matlab and Delphi languages based on COM (Component Object Model）module technology. Matlab possesses many signal analytic functions and Delphi has a friendly visual programming environment. These two advantages are fully combined in the mixed programming. This system can be easily upgraded to expand new analytic functions with help of COM module technology. Fault diagnosis of a grinding machine is carried out by using this system. A same vibrational signal sampled from the machine is analyzed in turn by three methods in this system that are Fast Fourier Transform(FFT), Wigner-Ville Distribution(WVD) and Choi-Williams Distribution(CWD). Comparing with the three results, it shows that CWD can get best diagnostic information and validity of the estimation on the instantaneous frequency of a signal. Success of the mixed programming is presented meantime.

The shock absorber plays an important role in the properties of stability and riding comfort of the vehicle. A virtual model of a double cylinder hydraulic vehicle shock absorber is developed for motion simulation and stress analysis by SolidWorks software. The kinematic character of the shock absorber was simulated by using the virtual model. And the stress analysis result showed that the shock absorber had high liability. All the results can also be helpful to design the double cylinder hydraulic vehicle shock absorber.