Research On The Vibration And Noise Radiation Of Engine Magnesium Alloy Oil Pan During Its Development And Optimization Design

There is a general uptrend of oil price these days and the energy supply becomes ever-insufficient. Consequently, to light weight vehicles is getting more and more pressing and vital because of its heavy oil consumption. Automobile industry has made great efforts to reduce weight using varies of high-intensity low density materials since last century. However, the CAE analysis and optimizing design as to the new parts with alternative material, which is indispensable, was not carried out timely. The dissertation conducts a particularly comparative research on the NVH performance of magnesium alloy oil pan and aluminum alloy oil pan respectively, utilizing FEM/BEM method. The research mainly focuses on the following aspects:1) Firstly, modal parameter identifying was carried out with oil pan suspended freely.Furthermore, the structure surface vibration was tested, finding that vibration response around 500～3000Hz was comparatively higher, 1000～1700Hz the most intensive.2) Modal frequency of aluminum alloy oil pan was calculated, keeping great consistence with the experiment value. Meanwhile, the modal frequency of magnesium alloy oil pan is somewhat smaller than the aluminum one.3) The frequency response up to 2000Hz of two oil pans was analyzed, the results of aluminum alloy oil pan validated by experiment .The difference of peak value distribution of two oil pans was interpreted based on the principle of mechanical vibration. What impressed us is that magnesium alloy oil pan responses less intensively than aluminum alloy one under the same load due to its significant damping value.4) The BEM method is used to predict noise radiation. The result indicated that the total power level of magnesium alloy oil pan is lower than that of aluminum alloy one.5) Finally, the optimized designed was carried out as to magnesium alloy oil pan basing on the previous analysis results, with the purpose of enhancing the strength further. The sound power level of new magnesium alloy oil pan was reduced by 3 decibels compared to the original aluminum alloy oil pan, while it was still one-fifth lighter.