| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 99 === This study adopted the finite element model and imported the loading input force of each major engine bearings. The authors had MSC. Nastran's solving engine vibrated at medium to high rotation speed (3200 and 4400 rpm) and then imported the vibration speed of the engine surface to the engine’s boundary element model. Acoustic power and acoustic pressure distribution of each rotation speed were obtained from VL Acoustics. Our results suggest that the noise volume of oil pan component is higher, and thus its structure should be stiffened to reduce the noise volume. For the oil pan model, the study adopted strain distribution to determine the placement of ribs for stiffening the oil pan, elevating the natural frequency of the model, and keeping it away from other modes. These measures should be cable of reducing the vibration effectively.
According to the above-mentioned techniques, the authors removed the half-moon and the triangle ribs that are originally located at the bottom of the oil pan. After the modification, the stiffness was improved significantly and the natural frequency was increased to 1368 Hz, i.e., a 148 Hz increase from the original frequency (1220 Hz). The total weight of the newly added ribs was 170 g, which is 110 g heavier than the original half-moon and triangle ribs, yet this increase is only 2.5% of the total weight of the oil pan. In other words, this increase in weight is acceptable.
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