Papers by Author: H. Xu

Abstract: Coating is an effective method to solve the contradiction between the wear resistance and the toughness for tool materials and the coated tool can yield satisfied cutting performances. Now the coated high-speed steel (HSS) drill is widely used in drilling of stainless steel. This paper studied the tool life of the TiN, the TiAlN and the TiCN coated special drills in drilling austenitic stainless steel 1Cr18Ni9Ti through contrastive experiments. The tool life of the TiN coated drill was only 81.5% of TiCN, and 66% of TiAlN because of its low oxidization resistance and hardness. The wearing features of TiAlN and TiCN coating were also studied by experiments and the different wear mechanisms were revealed. Finally the comparison of cutting performance was given between TiAlN and TiCN coated drills and recommendation of coating selection for drilling austenitic stainless steel was also presented. TiCN coating is suitable for HSS cutting tool base, which is often used for drilling austenitic stainless steel at low speed. TiAlN coating is appropriate for tungsten carbide cutting tool base, which is used for drilling austenitic stainless steel at high speed. The special designed drill with optimal geometrical structure plus appropriate coating can yield long tool life and high material removal rate in high-efficient drilling austenitic stainless steel.

Abstract: Austenitic stainless steel is a kind of difficult-to-cut material widely utilized in various industry fields. But cutting tools is the uppermost obstacle in the application of high efficient and precise machining of austenitic stainless steel. Drill is the one of the most complicated universal cutting tools, whose geometry structure influences greatly on drilling performance. So the development of special drills is imperative for high-efficient drilling. This paper presented the optimal geometrical characteristics of the special drills, with138° point angle and 38° helix angle, for high-efficient drilling austenitic stainless steel. The drilling performance has been evaluated completely and comprehensively through the experiments including measuring cutting deformation coefficient, thrust force, torque, cutting temperature near the cutting point, cutting tool life, drill wear mechanism and so on. The special drill indicated appreciated cutting performance during drilling austenitic stainless steel with high efficiency. Compared to the commercial available standard drill with 118° point angle and 32° helix angle, the cutting tool life of the special drill was 1.6 times of the standard drill and the special drill yielded good performance of chip evacuation, good wear resistance and great drilling quality.

Abstract: PCD tools, especially curve edge PCD compound tools are used widely in machining nonferrous and non-metal materials with high efficiency and precision because of their excellent cutting properties. But high quality grinding of PCD tools is the uppermost obstacle in application because there are great difficulties to profile and sharpen edge in grinding, especially for milling cutter and drill with curve edge. This paper studied technology of wire EDG curve edge PCD compound tools by wire electrical discharge grinding machine with five-axis CNC system. The grinding quality was evaluated by scanning electron microscope (SEM) and roughometer. Three steps processing technique (roughing, finishing and fine finishing) and optimal process parameters of wire EDG PCD tools were recommended after considering synthetically the surface quality, precision and machining efficiency. The results met the requirement of high surface quality, precision and efficiency. This paper also applied successfully the optimal technology to grind a PCD milling cutter with outer and inner blade by electrical discharge grinding machine with five-axis CNC system. By the optimal parameters, the process yielded high precision of ±4.3µm and low roughness of 0.30µm. Experiment results have great practical significance to the high precise and efficient wire EDG of PCD tools.

Abstract: In this paper elastic stress field in an elliptic inhomogeneity embedded in orthotropic media due to non-elastic deformation is determined by the complex function method and the principle of minimum strain energy. Two complex parameters are expressed in a general form, which covers all characterizations of the degree of anisotropy for any ideal orthotropic elastic body. The stress acting on the long side of ellipse can be considered as a crack driving force and applied in failure and fatigue analysis of composites. For some special cases, the resulting solutions will reduce to the known results.