Papers by Author: Ying Fei Ge

Abstract: Polycrystalline diamond (PCD) tools were used in high speed machining of SiCp/2009Al and TiCp/TC4 composites. The results showed that milling forces decreased with the increasing cutting speed, and that the force value of vol.20%SiCp/2009Al was less than that of the matrix. The machined surface roughness Ra is less than 0.8μm for all the milling experiments until cutting time was 180 minutes. The machined surface included some defects such as scratches, craters, micro cracks and so on. Surface finish can be improved through increasing cutting speed. When milling, gradual flank wear and slight edge chipping took place on the PCD tool flank. But no obvious abrasive wear was observed. However, the PCD tool suffered from significant abrasive wear in the flank when turning. A flow type chip was formed either for milling or turning when vol.20%SiCp/2009Al was used. Some voids and micro cracks were found in the chip. For TiCp/TC4 composite, the chip took the form of interrupted saw-toothed due to the dynamic behavior of micro crack. Although PCD tool was very suitable for high speed machining of SiCp/2009Al, its geometry parameters must be rightly chosen for TiCp/TC composite, or else sever edge chipping would take place in a few minutes.

Abstract: Chip formation and surface generation were investigated when ultra-precision turning of SiCp/2009Al and SiCp/ZL101A composites using Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) tools. The results showed that the machined surfaces took on many defects of pits, voids, microcracks, grooves, protuberance, matrix tearing etc. It was noticed that most of these defects had an intimate relationship with the removal process of SiC particle. The surface finish was much better when the SiC particles were removed by cut through or in-situ pressed into mechanisms. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were these main mechanisms of surface generation. Generally, a saw-toothed chip was formed when ultra-precision turning this kind of material and the mechanisms of this type of chip were dynamic microcrack behavior and strain concentration, which induced by the non-uniform deformation of the workpiece material.

Abstract: The wear pattern and its mechanisms of Single Crystal Diamond (SCD) tool has been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced aluminum matrix composite. The results showed that micro wear, chipping, peeling, abrasive wear and chemical wear were the dominating wear patterns of SCD tools. Coupled with XRD analysis on the machined surface and Raman studies on the flank wear land of SCD tool, it was pointed that the combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix have caused the severe graphitization.

Abstract: This paper deals with the milling machinability of gamma titanium aluminide at speeds of 60-240m/min. The results showed that surface roughness was less than Ra0.44μm at all cutting speeds used in the tests even when the tool wear reached VB0.2mm. The milling forces increased slightly with increasing cutting speed but increased rapidly with the elevated flank wear value especially for the Fy component. Compared to those of titanium alloy TA15, the milling forces of γ-TiAl were 190%, 180% and 200% greater for Fx, Fy and Fz respectively under the same machining conditions. Workpiece surface has a maximum microhardness of approximately 600HV0.100, and the depth of maximum hardened layer was confined to 180μm below the surface. When cut with TiAlN coated carbide tool, tool life was 35 min which was only about 1/2 of that for titanium alloy TA15.

Abstract: A series of experiments were carried out on normal and high speed milling of a high strength titanium alloy (TA15). TA15 is a close alpha titanium alloy strengthened by solid solution with Al and other component. It is often used to make large structural parts in airplane and welded parts subject to heavy load. The tool life of several typical types of cutter commonly used in the milling of titanium alloy was studied by the orthogonal experiment design method. After multi-element regression analysis, the empirical equation of the tool life was stablished. The milling force and temperature were measured under different cutting conditions and tool wear status. The knowledge is useful to further understand and analysis of the cutting mechanism, machining quality and tool wear. The study on the machined surface integrity includes the following content: surface roughness, metallographic examination, work hardening and residual stress.