Study On Structural Noise Of Loader Cab Based On Vibro-acoustic Coupling Method

Construction machinery plays an important role in national development and social construction.In order to reduce the adverse effects of noise from construction machinery,many countries formulate laws and regulations to limit the noise.Cab is the communication medium between the driver and the external vibration and noise,the acoustic vibration characteristics of the cab affect the working environment of the driver directly.The dissertation takes the cab of a certain loader as the research object based on the project of loader low-noise design.Lots of analysis and research have been done to studied the vibro-acoustic characteristics and internal sound field.Put forward the structure optimization plan as technical route to lower the noise standard of cab.The main research contents are as follows:The finite element model of cab structure and its acoustic cavity have been built based on the wheel loader geometric model.Vibro-acoustic coupling finite model has been built and simulation calculation of the structure mode,the acoustic mode and the vibro-acoustic coupling mode also have been carried out based on FEM theory and modal analysis theory.The structure stiffness of cab have been analyzed by comparing mode frequency and vibration.The effect of the seat on the acoustic cavity is also considered.Based on the vibro-acoustic coupling theory,the excited force signal of the target working condition was measured and input into the vibro-acoustic coupling finite model.The frequency response analysis of cab internal acoustic field was conducted by mapping nodes of structure model and acoustic model.The frequency response functions of driver ears location were obtained,and the results were compared with the experimental data.It was considered that the calculation method of the vibro-acoustic coupling model had reference value.Based on panel contribution method,the positive contribution of main source panels for peak frequency of sound pressure curve were sought out.Found out the main structure source of acoustic pressure on field node in 20-200Hz.According to the result,cab structure optimization was carried out in order to lower the structure noise in low frequency.Topography optimization,thickness optimization and structure damping were introduced.Considered the reality,topography optimization was applied to the top ceiling.And thickness of six plates was optimized by multi-objective method while took the plate weighted velocity as the objective function.A layer of free damping maternal to the floor was added.As a result,the optimization of structure had lowered the structure noise in low frequency effectively.Above all,the characteristics of the three optimization methods are summarized.It was believed that the effective control of structure noise can be realized by using the three optimization methods reasonably.