| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 100 === This text pursues the causes and phenomena in the course of the collapse of the molten metal layer surrounding a keyhole which is full of vapor and liquid particles during the high energy laser or electron beam drilling process. And the formation mechanism of the pores for the drilling process, to study the collapse phenomenon of the liquid layer is essential.
In the research the collapse of the keyhole is taken as approximated to a transition between the slug and annular two-phase flows in a vertical pipe of varying cross-section. We develop and solve a quasi-steady, one-dimensional model for two phase flow with the assumption that the mixture in the core homogenous, ignoring the friction of the liquid layer, regarding the flow in the keyhole as supersonic, considering the mass transfer of the liquid layer to the keyhole. Two-phase flow can be liquid particle entrainment characteristics, infiltration precipitation, divided into two regions. The collapse of keyhole resulted from the infiltration of the liquid particles is chained to the pore formation. Based on the realization of annular two phase flow, In this text, that the liquid into the holes in the physical properties and caused pores formation.
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