The Simulation And Optimization Of Temperature Field In Laser Engineered Net Shaping Alumina Thin-walled Parts

Al2O3ceramics have been widely used in aerospace, metallurgy and MHD power generation because of its high melting point, high hardness, high strength and high chemical stability characteristics. Especially in some extreme operating conditions, Al2O3ceramics have took the place of traditional metal materials gradually. The conventional sintering process is used to manufacture Al2O3parts, but the density of parts is very low and the shape of parts can’t be too complicated. Using Laser Engineered Net Shaping technology to manufacture Al2O3parts could alleviate these drawbacks, and the parts present high performance, fully dense, complex shape. However, because of the high thermal stress caused by high temperature gradient and the brittleness of ceramic materials, ceramic parts can easily lead to defects such as cracks and warping. So reducing the temperature gradient during shaping process is of great significant. To obtain the temperature field information is the premise to reduce the temperature gradient. Since the molten pool is very small and the temperature is very high during shaping process, it’s very difficult to measure the temperature. Therefore, the numerical simulation method is applied to obtain the temperature field of shaping process. In this paper, a finite element model is established to calculate the temperature and temperature gradient of shaping process. The influence of process parameters on the temperature field is studied to optimize process parameters. The simulation result could provide theoretical guidance for the experiment. Specific studies are as follows:(1) A finite element model for Laser Engineered Net Shaping10layers Al2O3thin-walled parts is established by using ANSYS software. This model takes into account the basic assumptions, materials thermal property, modeling, meshing, heat source, initial conditions, boundary conditions and "birth and death" technology at the same time. The temperature field distribution is obtained by calculating this model. The Laser Engineered Net Shaping experiment and thermocouple experiment are carried out to verify the reliability of the model.(2) Firstly, the temperature variation of shaping process is studied. And the reason for the production of the unstable area is given. By optimizing the scanning path the unstable region has been minimized. Furthermore, the temperature gradient variation of shaping process is studied. And the major temperature gradient direction and position of the maximum temperature gradient have been gotten. Finally, the plasticity point temperature gradient variation of shaping process is studied. And the main cause of cracks has been found out.(3) Changing the laser power, scanning speed, preheating model and preheating temperature to analysis the influence of these factors on the maximum temperature and plasticity point temperature gradient variation of shaping process. Furthermore, optimizing the process parameters of Laser Engineered Net Shaping Al2O3thin-walled parts and getting a set of optimum process parameters which can not only ensure the stability of shaping process, but also decrease the plasticity point temperature gradient sharply.