Papers by Author: Cheng Yong Wang

Abstract: The cryogenic treatment is an extension of the cold processing technology by which the material properties could be changed. This provides a new method for people to improving the performance of the cutting tools and prolonging the tool life. The micro-structure of two unknown types of carbide reamers after different cryogenic treatment was introduced in this paper. From the metallographic microstructure, SEM microstructure, EDS spectrum analysis and the hardness measurement, the detailed analysis on the microstructure of the reamers (1# and 2#) was provided in this paper. The results show that the matrix materials of the two reamers were the WC-Co cemented carbide, and they were the ultra-fine grain carbide (＜500nm); 2# reamer belonged to the high Co cemented carbide reamer. By the cryogenic treatment, the hardness of two reamers has increased. And the value of the hardness for 1# reamer was higher than that for 2#.

Abstract: X-axis and Y-axis workbenches are important parts of PCB drilling machine. Theirs dynamic properties directly affect the overall performance of drilling machine. Modal analysis method was adopted in this paper. Measurement and analysis on vibration of X-axis and Y-axis workbenches based on LMS Test. Lab was carried out. The modal parameters such as natural frequency, damping ratio and corresponding vibration modes were obtained. The results present that the X-axis and Y-axis workbenches have a high fundamental frequency, which is 564Hz and 1014Hz respectively. And the damping ratio is less than 4.91% and 2.99%, which shows that the stiffness of the X-axis and Y-axis workbenches are higher. The FEM modal analysis shows that it has the similar results with the experiments in modal parameters. The analysis of natural characteristics of workbench provides guidance for optimizing machining parameters of drilling and improving structure of workbench.

Abstract: As one of the excellent decorative materials, ceramic tiles must be ground and polished to present the glossy surface. Diamond cup wheel is one of important tools. Ceramic tiles were ground by diamond cup wheel with a special designed test machine. The materials’ removal process of ceramic tiles had been tested, and surface roughness was measured. The surface micromorphology of the polished ceramic tiles under different depth of grinding and feed speed was examined by Scanning Electron Microscopy (SEM). The results showed that a lot of materials’ removal can be obtained by increasing the depth of grinding and feed speed in rough process of ceramic tile. On the contrary, good surface can be obtained by reducing depth of grinding and feed speed in fine process of ceramic tile.

Abstract: Drilling force and temperature of tibia at the high speed drilling for improving the design of surgical drills are very important. In this paper we describe experiments using pig tibia bones, measuring the drilling force and temperature of a new design of drill bit and compare the results against a twist drill. The result shows that the drilling force and temperature are affected by the feed rate and drilling speed, which vary with the drilling depth into the bone. The new surgical drill with three top cutting edges can achieve lower temperature below 47oC and lower drilling force than with the stainless steel twist drill and carbide twist drill.

Abstract: We compared the characteristics and polishing effect of abrasive suspension slurry jets with and without high polymer added. Results show that adding high polymer to the slurry jet leads to more concentrated jet beam and, consequently, surface roughness in the jet polished region is approximately equal and the interface between polished and unpolished regions is narrowed. We also examined the surface forming process polishing with slurry jet added with high polymer, and then proposed a polishing model of the process.

Abstract: The modeling and simulation of chip formation during high speed milling of hardened mold steel are systematically studied by the Finite Element Analysis (FEA). The modified Johnson-Cook’s constitutive equation for hardened mold steel is introduced. Comparing to the experimental results, the simulated results of cutting force, chip morphology, effective stress and cutting temperature in deformation zones of high speed peripheral milling indicate good consistence and the models established can be used to accurately predict the behavior of hardened mold steel.

Abstract: For defects of low-plastic, brittle damage and micro-crack, brittle-hard materials are often collapsed and ruptured, and processing surface was made by complicated micro grooves after repeated processing. In order to know the complex rules of surface generation, series tests of diamond abrasives scratching glass with different processing paths and depth of cut were done. Cutting force and acoustic emission signal were collected. Crack generation, path interference, dynamic characteristic of glass processing were observed.

Abstract: TiAlSiN coatings with different Al content were prepared by hollow cathode discharge ion plating (HCDIP) and medium frequency magnetron sputtering ion plating (MFMSIP) hybrid physical vapor deposition (PVD) coating system. The composition, microstructure, mechanical properties of these coatings were systematically investigated by means of EDX, XRD, SEM, nanoindentation, scratch and tribological tests. It was found that the coatings had (111) or (200) preferred orientation with addition of Al. Proper content of Al led to increase of microhardness and adhesion. The flank wear of carbide end mill coated with TiAlSiN had the least wear than those coated with TiAlN and TiSiN coatings under the high speed milling of hardened steel experiments.

Abstract: Hardened steel P20 at 50 HRC is milled at high speed by TiN coated and TiAlN coated solid carbide straight end mills, and the cutting forces and tool wear are measured. The result shows that TiAlN coated tool is more suitable for cutting hardened steel at high speed. Then the hardened steel is milled under different cutting parameters. It is indicated that the effect of cutting speed on cutting forces is small, but the effect of cutting speed on machine vibration should be considered. Increase feed per tooth or radial depth of cut will increase the cutting forces.

Abstract: Cutting tools suffer severe abrasive friction and wear in high speed milling of graphite. Cutting forces were measured and analyzed using time-frequency analysis method to reveal the correlation between cutting force variations and tool wear evolution. The static and dynamic force components increased prominently with tool wear. The cutting force Fy was found the most sensitive to the tool wear evolution. The waveform of cutting force became periodic and irregular with the increase of tool wear. Good correlation was found between the first force harmonic and tool wear.