tailieunhanh - Fundamentals of Die Casting Design P2

Tham khảo tài liệu 'fundamentals of die casting design p2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Section . Numerical Simulations when it flows as continuous liquid. Experimental work has demonstrated that the flow for large part of the filling time is atomized Bar-Meirl995a . The pressure in the mold cavity in all the commercial codes are calculated without taking into account the resistance to the air flow out. Thus built-up pressure in the cavity is poorly estimated and therefore the characteristic flow of the liquid metal in the mold cavity is poorly estimated as well. . The flow in all the simulations is assumed to be turbulent flow However time and space are required to achieved a fully turbulent flow. For example if the flow at the entrance to a pipe with the typical conditions in die casting is laminar actually it is a plug flow it will take a runner with a length of about 10 m to achieved fully developed flow. With this in mind clearly some part of the flow is laminar. Additionally the solidification process is faster compared to the dissipation process in the initial stage so it is also a factor in changing the flow from a turbulent in case the flow is turbulent to a laminar flow. The liquid metal velocity at the entrance to the runner is assumed in the numerical simulation and not calculated. In reality this velocity has to be calculated utilizing pQ2 diagram. If turbulence is exist in the flow field what is the model that describes it adequately Clearly model such k e are based on isentropic homogeneous with mild change in the properties cannot describes situations where the flow changes into two-phase flow solid-liquid flow etc. The heat extracted from the die is done by cooling liquid oil or water . In most models all the commercial models the mechanism is assumed to be by regular cooling . In actuality some part of the heat is removed by boiling heat transfer. The governing equations in all the numerical models I am aware of neglecting the dissipation term in during the solidification. The dissipation term is the most import term in that case.