Fabrication process of ultra micro-perforated panels (ultra-MPPs) with perforations of diameter below 100 um based on MEMS technology is expatiated in this paper. As a promising alternative to the conventional porous absorbing materials, MPP absorber is now being widely used in noise control engineering. Theory reveals that the maximum sound absorption bandwidth of a single MPP absorber could be achieved by reducing the perforation diameter to a certain limit and the desirable perforation diameters are less than 100um under many circumstances. However, due to the limitation of traditional manufacturing tools and techniques, MPPs with ultra-micro perforations of diameter less than 100um, namely for ultra micro-perforated panel (ultra-MPPs), have seldom been investigated yet. In this study, micro electro mechanical systems (MEMS) technology was applied to a trial production of ultra-MPPs and the measurement of their normal absorption coefficients were carried out in the impedance tube. Results show that ultra-MPPs could attain high absorption over a broad frequency range, indicating that as a micro machining process, MEMS technology is suitable for fabricating ultra-MPPs in order to ensure the absorption performance.
This paper uses ProCast software to simulate Mg-Gd alloy solidification process, calculates temperature field and solidification field for Mg-9.76Gd at different stages and compares the influence of different heat transfer coefficient on the solidification structure. The results show that the crystallization process which is simulated is consistent with the actual crystallization process; as the heat transfer coefficient increases, the average grain size decreases. With the result, the reasonable casting formation control parameters can guide the practical production, which can reduce human and financial resources.
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