Backhoe Loader Cab Internal Acoustic Simulation And Structure Improvement

With the development of economic construction and the improvement of people’s consciousness about the environmental protection, in addition to dynamic property, economical efficiency and emissions, noise, vibration and harshness have become the important indicators to measure the quality of loaders. Started later than foreign enterprises and research institutions, it is not yet mature currently to analyze, forecast and control cab noise of the engineering vehicle applying FEM and other modern design and analysis methods in domestic, especially for the low-frequency noise within the scope of20～200Hz. Aiming at the low frequency cab noise of a certain type of backhoe loader, the performance of the cab structure and noise characteristic in cab is analyzed by using FEM.Firstly, the vibration and noise signal of some model of backhoe loader is collected, frequency spectrum and numerical analysis is carried out with the corresponding test data to learn about its current vibration and noise level, and the preliminary conclusions is acquired to provide effective basis for the subsequent finite element analysis.Next, as the intermediate link to transmit vibration for engine to cab, modal analysis for the frame is conducted to forecast whether it will exacerbate vibration of the cab or not, and the result is presented indicating that the intrinsic frequency of the frame keeps away from the base frequency of the engine and the frame structure will not exacerbate vibration of the cab. Then, the free modal and harmonic response of the cab structure finite element model within the low frequency of20-200Hz is analyzed and the results show that modal frequency is dense in low frequency range, appearing the obvious local vibration.Then, the free modal analysis of the acoustic cavum FEM model with seat and without seat is analyzed and compared, the results of which show that every order of modal frequency with seat is relatively low and the mode of vibration also changes, indicating the importance of seat to the acoustic cavum model and providing more accurate model with seat for subsequent acoustic analysis. With the results of cab structure harmonic response analysis as boundary conditions, the acoustic properties of cab interior is simulated using Virtual.lab Acoustics, the acoustic frequency response curve in driver’s right ear and the contribution of each panel to the noise of driver’s right ear is obtained, then the panel with most significant contribution to concerned frequency is identified.Finally, according to the analysis results of the acoustic contribution, the structural improvements of the panel with highest contribution degree have been proposed by increasing stiffeners, and five different layout schemes have been pertinently presented. By analyzing and comparing the modal of the original structure and the proposed structures, an optimal solution is ultimately determined. The acoustic cavum of the optimal cab interior is simulated and analyzed, and the acoustic frequency response characteristics of the driver’s right ear are obtained and compared with the original cab.