Research On Low Noise Design Of Engine Thin-walled Parts And The Application Of Composite Damping Material

With the development of automotive technology, people require better performance of vibration and noise, which gives the designers a higher challenge. At the same time, with the rapid development of computer technology, the CAE technology, including the finite element method and boundary element method, has been widely used in the design process of engine and its parts. The CAE technology can improve the efficiency and quality of product development, shorten the development cycle; can give the comprehensive evaluation before the structure is done, which greatly saved the cost of design. The studies in this paper are based on a kind of diesel’s NVH performance analysis and improvement projects cooperated with a vehicle factory. During the project, engine thin-walled parts, such as engine oil pan, cylinder head cover and gear housing cover, are all redesigned to meet the low-noise target. In addition, taking the number of the oil pan bolt and flange thickness into account, we also do some research on their optimization. Details are as follows:1) Introduced the research background and status of the engine vibration and noise control technology and the composite damping material both in and outside of the motherland. Also described the application of modern design method in the simulation and optimization of engine performance.2) In explaining the basic theory of finite element method and boundary element method, with an engine oil pan, cylinder head cover, gear cover as research object, carried out modal analysis, frequency response analysis and acoustic simulation calculation. And compared the simulation results with the experimental results to verify. With the verification, strong to ensure the accuracy of the simulation analysis work, provide a good support for the following improvement design work.3) According to the simulation results, find the weak parts of the structure and improve the design. In the design process, take the use of topography optimization method to find a reasonable location and size of the reinforced. The acoustic performance of the improved sump significantly improved, achieved the desired effect.4) Take the number of the oil pan bolt and flange thickness into account to do some research. Make9different models with the different parameters of bolts number and the flange thickness. Through the comparison of sound power level of the nine models, find out the discipline to provide a reference for the manufacturers.5) Proposed the method to replace the sump material to composite damping material. Briefly introduced the damping mechanism, performance parameters, processing performance and modeling methods of the composite damping material. Analyzed the vibration and acoustic performance of the sump using composite damping material, significant noise reduction can be seen after compared.6) Combined the method of using composite damping material and reinforced structure. But after compared, we can find that although this method play a good effect comparing with the original model, it plays little better effect than only using the composite damping material model.