Study On Noise Analysis And Control Of Excavator Cab Structure

With the rapid development of engineering machinery, people have more high-level demands for vibration and noise. NVH (Noise, Vibration & Harshness) characteristics of engineering machinery cab not only affect driver’s health and work efficiency, but also influence service life of the components. Therefor, great emphasis have been put by enterprises on NVH characteristics of engineering machinery cab and effective reduction of cab noise has been an important objective in engineering machinery cab designing.One certain model of excavator cab is studied in this thesis. Integrated with analysis of structural performance and internal noise by advanced technologies of numerical analysis of finite element and acoustic CAE, noise and vibration testing technology is applied in actual working conditions. Some corresponding measures have been adopted according to the major influence factors. The main contents of this thesis are as follows:1. Response signals of acceleration and sound pressure at different engine speed of the cab are measured by noise and vibration testing technology. Six mounting vibration acceleration spectrum and sound pressure spectrum at different rotating speed are obtained and the acquired signals are pre-processed. By detailed analysis of test data, primary reason for abnormal sound and vibration is confirmed and it also provides data for following CAE analysis.2. By establishing finite element model of the cab, free modal of the structure is calculated and dynamic characteristics of major parts are analyzed. By building cab acoustic model, acoustic modal of discretized air basin and acoustic-structure coupling modal are analyzed and the effect degree of cab structure to the distribution of sound pressure is also studied. Considering the impact of acoustic-structure coupling, acoustic modal characteristics are obtained by analyzing acoustic properties which can be applied to estimate whether the cab acoustic cavity is reasonable. To verify the efficiency of finite element method, frequency respond analysis in various conditions is done to observe vibration displacement of the cab plates under important frequencies.3. Noise transfer function is established by dynamic response of coupling acoustics and analyzed to predict and study peak frequency band of the cab. Based on finite element method, noise prediction can be made by testing data and accuracy validation of noise prediction can be made by comparing with tested sound pressure curve. By analyzing cab plate acoustic contribution, greater influence factors which cause noise problems under important frequencies can be found.4. Topological optimization and sound package are taken to optimize and reduce noise for key components in the excavator cab aiming at the problems revealed by acoustic vibration test and CAE analysis. Simulation of the optimized cab shows the effectiveness of optimization methods.