No abstract

After a short introduction about vehicle wind buffeting noise generation mechanisms, sunroof buffeting characteristics of a production sedan under different wind speeds and operating modes are investigated through full-scale aeroacoustic wind tunnel tests. As sunroof fully open, the severest buffeting effect occurs at wind speed 50kph, with the peak SPL 122dB and the corresponding resonance frequency 18Hz for the test point at the front row. From ca. 60kph it seems that the buffeting effect disappeared. As sunroof tilt, the severest buffeting effect occurs at wind speed equal or less than 30kph, the resonance frequency equal or less than 15Hz. From ca. 40kph the buffeting effect almost disappeared. Whether sunroof fully open or tilt, the resonance frequency increases all along as wind speed goes up till the buffeting effect disappeared (less than 20Hz). Different test positions at the front row or back row show very similar buffeting characteristics.

Cooling stage is a key stage of injection molding. It affects both the quality and efficiency of injection molding of products. Conformal cooling channel, due to its advantages in uniform cooling and rapid cooling, could improve the cooling effect obviously. Therefore, study on methods of machining curved hole are proposed to be used for practice. In this thesis, some methods of machining curved hole and their features in general were introduced.

A new method of optimal sensor placement which is called sensitivity analysis method (SAM) is presented in this paper. It uses structural curvature mode shape changes due to stiffness changes (damages are simulated as stiffness reductions) to analyze the sensitivity. Then, another two traditional methods of optimal sensor placement-the effective independence method (EIM) based on maximizing the data information and the kinetic energy method (KEM) based on maximizing the kinetic energy are discussed briefly, and we compare our new method (SAM) with the two traditional methods under two modal criteria, mean square error (MSE) and modal assurance critical (MAC). The numerical simulation results show that the SAM is the best one of the three.

A new compound method of physical parameters identification of bridge structures under traffic excitation is presented in this paper. Employing the Dynamic Nodal Loading (DNL) approach, which could consider the dynamic response due to the road irregularities and vehicle inertia effect of a vehiclestructure system, the moving vehicle load could be converted into the transient load on each node in time domain. Then, the accelerate response of bridge structures calculated with the Newmark β − method, is used to construct the displacement, velocity and acceleration response in the transform space. At last, the recurrence formula derived based on the principle of least squares, is utilized to obtain the physical parameters of bridge structures in the transform space. The feasibility and effectiveness of the proposed identification technique are demonstrated by a numerical example on the two-span Benchmark structure proposed by the Bridge Health Monitoring (SHM) Community of International Association of Bridge Maintenance and Safety (IABMAS). With the proposed technique, information collected about the traffic such as the arrival time and speed of vehicles will directly contribute to improving the structural property identification. The method should be more accessible to theoretical significance and merit of potentially practical utilization.