Study On Vibro-acoustic Characteristics And Optimization Design Of Loader Cab

The modern engineering machinery is rapidly developing towards the complication, upsizing and high-power direction and the following vibration and noise problems have been stood out. The loader is a kind of widely used high-power construction machinery and the sound field environment of interior cab has drawn people's attention increasingly, therefore the reduction of its interior noise is of great importance to improve the man-machine environment. The dissertation focused on the low-noise technology research of wheel loader cab based on the subject of ?the key low-noise technology study of wheel loader by simulated analysis and measured test methods, and it deeply studied the mechanism of vibration and noise production, vibro-acoustic coupling characteristics, vibration and sound field characteristics of interior cab, the optimization of structures. And it provided the technical routes to design the improved low-noise loader cab, reduced the sound level of interior cab effectively, and made the sound field environment better.The finite element model of cab structure and its acoustic cavity have been built respectively and the vibro-acoustic coupling finite element model also has been built by the node correlation method based on the wheel loader cab. The vibro-acoustic coupling characteristics were analyzed based on the calculated results of the structure mode, the acoustic mode and the vibro-acoustic coupling mode. The interactive influence between the structure and the acoustic cavity was studied based on the related mode participation factor between the coupled and uncoupled modes. The vibro-acoustic coupling model was verified by SIMO mode test and the model foundation was provided for the next analysis.Based on the correct vibro-acoustic coupling model, the excited force signals at the rear of suspension points were measured and input into the acoustic-structural coupling model. The frequency response analysis was conducted by the mode superposition method to study the vibratory characteristic of the cab structure. The response result was regarded as the boundary condition of the acoustic calculation. The sound pressure of the driver's ear was predicted by the acoustic finite element method and the sound characteristic of the cab was analyzed. The acoustic sensitivity analysis was proceeded in order to represent the resonant characteristic between the structures and the acoustic cavity, and also the scale effects of the input energy was represented. It also provided referenced frequency targets for the panel contribution analysis and the optimization of structures. Therefore, the panel contribution analysis was conducted by the acoustic transfer vector method based on the determined frequency targets. The main panels that caused key noise peaks were found out and provided the effective areas for the optimization of structures.The typical conditions were analyzed, the flexibility and some key frequencies were determined based on the acoustic sensitivity analysis and the results of virtual sound pressure prediction. The combination of the compromise programming approach and the average frequency method was applied to the multi-objective topography optimization of cab by merging the static stiffness and several critical dynamic frequencies as Euclidean distance's multi-objective function. The multi-objective topography optimization of cab was conducted, avoiding the frequency of oscillation phenomenon and getting the Pareto solution of the optimal objectives. At the same time, based on the manufacture process and the stamping technology, the specific panels were optimized with the line shape of the rib according to the panel contributions analysis results. The optimized model was revised and input the same boundary condition, the second prediction of the virtual pressure was also proceeded. The results show that the optimization of structures can reduce the interior noise of the cab and improve the sound field environments.