Research On Surface Quality And Tool Wear In Milling Of SiCp/Al Composites

SiCp/Al composites are widely used in automobile, energy, aerospace and many other engineering fields because of its excellent properties, such as high-specific strength and stiffness. Because of the addition of the reinforcing particles, the wear-resisting property of SiCp/Al composites was improved significantly, also brings some problems such as the machining quality difficult to control and serious tool wear. In this thesis, the properties of SiCp/Al composites were studied, the cutting parameters were optimized, and the evolution rules of tool wear initiation and propagation were explored. The main research contents in this thesis are as follows:(1) Through single factor experiment, the influence of cutting parameters(cutting speed, feed, axial cutting depth and radial cutting depth) on cutting force and surface quality(surface roughness, surface morphology and edge defects) is investigated. The results show that when the high cutting speed, low feed, low axial cutting depth and the radial cutting depth, the cutting force is smaller. The machined surface quality could be improved by using large cutting speed, small feed and the radial cutting depth equal or less than 4mm.The edge defect is mainly affected by cutting speed and feed. In order to improve the edge quality, cutting speed should not be selected in the transition between high and low speed,and the selection of feed should also be appropriate.(2) Based on the results of single factor experiment, the range of machining parameters is further reduced, and the central composite experiment has been carried out. The second order model of surface roughness was established by response surface method, and the machining parameters were optimized under the target of the minimum surface roughness.The results show that the cutting speed has the most significant influence on the surface roughness, followed by the feed and axial cutting depth. The optimized cutting parameters are v=199.22m/min,f=0.01mm/z, ap=0.11mm and ae=4mm.(3) The influence of cutting speed, feed and axial cutting depth on tool wear was investigated. The evolution rules of tool wear initiation and propagation were also explored.The results show that the cutting length is longer under the condition of large feed, but the surface roughness increases sharply. Therefore, considering the cutting quality, large feed is not desirable. In the process of finishing SiCp/Al composites with cemented carbide coating tools, the contact form between knifepoint and workpiece is convex arc contact at first, then turn into concave arc contact, and finally turn into plane contact.