| Selective laser sintering(SLS) is an important technology of additive manufacturing(AM), and it has been widely used in aerospace, medical, automotive and other fields. There are two kinds of SLS technology, direct SLS and indirect SLS. The indirect SLS can be employed to manufacture ceramic parts with complex shapes. The current research shows that there are some problems in manufacturing ceramic parts by using indirect SLS, such as incomplete process and low strength of parts.The thesis studied the indirect selective laser sintering of alumina/epoxy powder by using finite element simulation and experimental research. The main research contents are as follows:(1) The energy transfer and the interaction between laser and materials during SLS were studied. It was found that the energy absorption rate of alumina/epoxy mixture increases with increase of the laser wavelength. The laser intensity distribution in the laser beam is not uniform, which is showing Gaussian distribution. The mechanism of indirect SLS is determined as the liquid phase sintering. Three important conditions, i.e., wettability, solubility and liquid volume were discussed.(2) A finite element method model is developed during selective laser sintering of alumina/epoxy powder by using the ANSYS software. A moving Gaussian thermal resource was realized by using APDL language. The temperature filed was investigated during the entire SLS process. The stress field was studied by coupling temperature filed indirectly. The stress distribution and deformation of the part caused by non-uniform temperature were discussed and it was found that the largest warping occurs at both ends of the part. The effects of preheat temperature, laser power, scanning speed, scanning space and layer thickness on final parts were analyzed, which provided theoretical direction for the selection of process parameters in the experiment of indirect selective laser sintering.(3) Alumina powder and epoxy resin E-12 powder were mixed by mechanical method. The orthogonal experiments were carried out to investigate the influence of sintering parameters to the quality of the final parts. By analyzing compressive strength, dimensional accuracy and warping deformation of sintered parts, the best set of parameters were obtained with preheat temperature of 333 K, laser power of 20 W, scanning speed of 2000 mm/s, scanning space of 0.2 mm, and layer thickness of 0.17 mm. Also, from the results of experiments, the maximum warping deformation occurs at both ends of final parts, which verified the simulation results. |
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