Influence Of Laser Heating Al₂O₃ Ceramics’ Softened Layer On Cutting Process Parameters

Engineering ceramics materials have excellent mechanical and physical properties, such as high hardness, high resistance to pressure, high resistance to corrosion, high resistance to temperature, oxidation resistance and wear resistance, etc, and have been found more and more widely application in aviation, aerospace, telecommunications, petrochemical engineering, electric power, metallurgy, machinery, modern biomedicine and other industrial fields. However, due to their high hardness and brittleness, the problems such as high temperature, large cutting force, tool wear, poor surface quality and low efficiency, etc, always exist during traditional machining methods. Laser heating assisted machining (LHAM) is one of the effective way to improve the cutting performance and solve the problem existed in the difficult-to-be-machined ceramics materials. To improve processing quality, efficiency and expand the application of ceramic parts, theoretical and experimental research on influence of laser heating Al2O3 ceramics’softened layer on cutting process parameters is carried out in the thesis. The main contents are as the following:(1) Considering the laser beam irradiating curved spot on cylindrical workpiece surface, the heat transfer is analyzed during laser heating assisted machining Al2O3 ceramics. On the basis of heat transfer control equations, combining the laser heat source model and the material’s physical and geometric parameters, the three dimensional heat transfer model is established. Using MATLAB software, the discrete heat transfer differential equations are solved and the temperature field on the workpiece’surface, cross-section and longitudinal section are obtained. And the theoretical basis for process parameters selection based on the material’s softened layer size during laser heating assisted machining Al2O3 ceramics is provides.(2) A experimental platform of laser heating assisted CNC machining Al2O3 ceramics is built. Based on solving results of the temperature field, the softened layer size range of workpiece is obtained under differential parameters of combinations as laser power, spot radius and workpiece speed. According to softened layer grid partitioning and cutting experience, the process parameters including cutting depth, feed are chosen and the experimental parameters table is planned for the performing of laser heating assisted cutting Al2O3 ceramics.(3) The laser heating assisted cutting Al2O3 ceramics is performed, the removal rate is calculated, and the surface roughness, pit, microcrack and other surface morphology of the workpiece are detected and studied. The results indicates that the theoretical removal rate is about 1.9 times of the actual removal rate, which is within the softened layer and the workpiece damage defects can be avoided effectively. The machined surface roughness is 0.83～1.73/μm, averaged 1.23μm, without obvious pit, microcrack and other defects.The research provides a certain theoretical and practical reference for the mechanism revealing and cutting parameters selecting based on softened layer during laser heating assisted machining of ceramics.