| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 106 === The purpose of this study is to develop a numerical model presenting for a direct energy deposition process. In order to make the thermal and fluidic behaviors more accurate, the additional terms such as surface tension, Marangoni force, Gaussian laser, solidification and melting are considered. In this article, the assumption that the powder source term is a function derived from the empirical equation is applied to three-dimension model. However, due to the enormous computational time in three-dimension model, the equivalent two-dimension model, in which the space axis (z) is converted into time axis (t), is built. It means the laser intensity and powder deposition rate are distributed as Gaussian functions on x-t plane and therefore the three-dimension problem can be solved. The two-dimension model is used to simulate the deposition platform, of which the width and height are not changed with scanning direction in three-dimension model.
The laser tracks cross-section map established by numerous simulation results demonstrates clearly the process parameters, and is capable of predicting the results of actual processing. Furthermore, it is possible to avoid choosing the parameters leading to detached laser tracks and to lower the cost of raw material.
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