Study On The Machinability Of Alumina Ceramics By Laser Assisted Waterjet

In this thesis, the effects of processing parameters on the material removal rate of alumina ceramics by laser assisted waterjet were investigated,and regression model of material removal rate was formulated. The finite element model of temperature field for impacting alumina ceramics by laser assisted waterjet was established, and the distribution of the temperature field was analyzed. The effects of processing parameters on the kerf width, kerf depth and HAZ size (heat affected zone) of alumina ceramic by laser assisted waterjet were studied. With the target of maximum kerf depth, the processing parameters were optimized by regression analysis. It was proved the machinability of hard brittle material such as ceramics by laser assisted waterjet.The effects of processing parameters on material removal rate of alumina ceramic by laser assisted waterjet were experimentally studied. It was shown that the material removal rate of alumina ceramics was firstly increased and then reduced with an increase in the laser pump current and waterjet pressure, was hardly changed with an increase in the focal plane position, and was totally reduced with an increase in the offset distance. And the laser pump current and waterjet pressure had a significant influence on the material removal rate. The regression model of material removal rate for alumina ceramics by laser assisted waterjet were established. It was shown that the verification results of regression analysis was in agreement with the experimental results, and was of a guiding significance for laser assisted waterjet machining technology.A simulation study of temperature field for impacting the workpiece by laser assisted waterjet, and the distributionof the temperature field was revealed. The finite element simulation model of temperature field for impacting the workpiece by laser assisted waterjet was established. The influence of pulse laser power and laser pulse frequency on the simulated temperature field was studied. The results shown that the surface temperature on the workpiece was increased as a shape of the sawtooth with an increase in the acting interval by laser, and the temperature field distribution inside the workpiece was a parabola. And the temperature inside the workpiece was increased with an increase in the pulse laser power and laser pulse frequency.The effects of processing parameters on the kerf width of alumina ceramic by laser assisted waterjet were studied. It was shown that, compared with the conventional laser cutting ceramics, the laser assisted waterjet could achieve a larger kerf width and a better processing quality. The kerf width was increased with an increase in the laser pulse frequency, waterjet impact angle and standoff distance, and was decreased with an increase in the movement speed of cutting head. The effects of processing parameters on the kerf depth of alumina ceramic by laser assisted waterjet were also studiedI It was shown that the kerf depth was decreased with an increase in the movement speed of cutting head and the waterjet impact angle, was increased slightly with an increase in the laser pulse frequency, and was firstly increased and then decreased with an increase in the standoff distance. The effects of processing parameters on the HAZ size of alumina ceramics by laser assisted waterjet were studied. The results shown that the HAZ size was hardly related with the laser pulse frequency, the movement speed of cutting head and waterjet impact angle. It was increased with an increase in the standoff distance, was decreased with an increase in the focal plane position, and was changed with the laser pump current. With the target of maximum kerf depth, the processing parameters were optimized by regression analysis. The focal plane position, the offset distance, the movement speed of cutting head, the laser pump current and the waterjet pressure affect the kerf depth in a descending order. The optimal combination of parameter level is, the focal plane position is -0.2mm, the offset distance is 0.4mm, the movement speed of cutting head is lmm/s, the laser pump current is 42A and the waterjet pressure is 12MPa. The kerf depth model was established. According to their significances of regression coefficient, the focal plane position, the offset distance, the movement speed of cutting head, the laser pump current and the waterjet pressure can be ranked in a descending order, of which the laser focal plane position is of the most significant influence on the kerf depth, and the significance of laser pump current is obviously better than the significance of waterjet pressure.