Papers by Author: Wu Yi Chen

Abstract: In this paper, fine-grain WC/Co tools were utilized in dry turning of the Ti-6Al-4V alloy. The wear modes of the cutting tools at different cutting speeds were analyzed. The diffusion behavior between the cutting tool and the workpiece was studied in detail based on the Auger electron spectroscopy (AES) depth profile technology. The diffusion wear mechanism was revealed. The results showed that the diffusion layer formed at the interface between the cutting tool and the adhering material. The diffusion ability of C was the strongest, followed by W, the weakest was Co in all the elements of the cutting tool. The chemical reactions took place close to the adhering material, forming the reaction layer. As a diffusion barrier, it was possible to limit the elements diffusion from the cutting tool to the adhering material, decrease the changes in the cutting tool composition and damages. The diffusion layer, which was weakened by diffusion, was worn off and taken away by the fast flowing chip during the cutting process, causing the diffusion wear characterized by a smooth crater formation on the tool surface.

Abstract: The Kane equations were applied in the dynamic analysis of a 3-DOF parallel mechanism, whose sub-chains consisted of three pairs of parallel legs. According to the characteristic of the parallel mechanism, it was simplified to 3PSS structure. Dynamics equations were derived based on the kinematical analysis. Computing simulation example was presented through MATLAB programming and verified by ADAMS simulation. The results showed that the approach was correct. It provides theoretical reference for the actual experiment and the choice of subsequent control method.

Abstract: A simple approach to multi-objective optimization of machining parameters is presented. Regression analysis of experimental data is carried out to obtain the correlation between cutting parameters and response variables. Finally, Genetic Algorithm (GA) toolbox of MATLAB is used to carry out multi-objective optimization of two objective functions (surface roughness “Ra” & material removal rate “MRR”). Genetic algorithm is found to be a powerful tool for multi-objective optimization of machining parameters in this study.

Abstract: The present investigation was dedicated to elucidate grinding characteristics during surface grinding of titanium alloy(TC6) and high temperature alloy (GH2132) by using silicon carbide(SiC) and sol-gel (SG) wheel respectively. The grinding characteristic of SG wheel on aeronautical alloys was studied on the base of systematical measurement of the grinding force, grinding temperature, surface roughness and grinding ratio. The results indicated that the SG grinding wheel possesses excellent grinding properties and is more suitable for grinding these aeronautical alloys compared with conventional abrasive tools. Finally, the grinding mechanism of new-typed SG wheel was unveiled on the base of the microcrystalline structure analysis of SG grains.

Abstract: An experimental study was carried out to investigate the temperature measurement method and burn mechanism in the surface grinding of a stainless steel 1Cr11Ni2W2MoV with SG abrasive wheels. The temperature response at the wheel-workpiece interface was measured using a pair of thermocouple composed of the workpiece material and a single enameled constantan wire which was implanted in the workpiece. Changes in the ground surface morphology and metallography of the specimens in different grinding conditions were analyzed. Plastically deformed coating layers and micro-cracks were observed on ground surface by SEM (Scanning Electronic Microscopy) when grinding burn occurs. Grinding burn mechanism was unveiled from a metallographic point of view. When the average temperature exceeded phase alteration temperature of 1Cr11Ni2W2MoV, the original gray strip martensite structure was replaced by tempered sorbite structure, which caused a sharp reduction of the workpiece surface hardness. The results provided a theoretical and experimental basis for technical optimization in the grinding of high temperature stainless steel with high efficiency and high quality.

Abstract: It is necessary for cutting simulation to determine the friction model at the tool-chip interface suitable for metal cutting process. Cutting force experiments in orthogonal turning titanium alloy TI6AL4V are carried out with cement carbide tool KW10. The Coulomb frictions at the tool-chip interface are calculated based on measured cutting force, and the friction model is regressed, where cutting speed and feed rate are presented.

Abstract: 2D finite element modeling of the broaching process of Inconel718 was conducted by using the commercial software. Models between cutting forces and cutting parameters were obtained. In addition, a general understanding of the effects of two machining variables rake angle and rising per tooth on chip curling process and gullet-to-chip area ratio, was also obtained.

Abstract: Trying to analysis the influence of the instability of carbide tool materials on cutting temperature measurement by natural thermocouples, a series of experiments calibrating the thermal emf properties of tool inserts were carried out with an improved tool-workpiece thermocouple calibration device. Four chosen types of carbide tools were examined to detect their thermal emf on their different cutting edge areas. By calculating and comparing the thermal emf waving range of them, the thermal emf stability of carbide tools and the temperature measurement error lead by it was evaluated. As the experiments result, the influence was confirmed. The thermal emf variation among the cemented carbide tools was detailed by using certain statistics processing to the experiment data.

Abstract: The study focused on surface burn of titanium alloy (TC4) in the grinding process using a novel segmented cup wheel with internal cooling structure. The threshold burn temperature was found in grinding TC4. Plastically deformed coating layers and micro-cracks were observed on ground surface by SEM (Scanning Electronic Microscopy) and depth of microstructure alterations was more than 180 microns in high temperature. Finally, a novel wheel with internal cooling structure was developed for reducing grinding temperature and suppressing surface burn.

Abstract: The effects of cutting parameters and tool wear on the surface damage generated in hole making of cast GH625 nickel-based alloy were investigated. The machined surfaces were examined by employing a scanning electron microscopy (SEM). The SEM micrographs of the machined surfaces showed that surface damages induced by boring operation comprised surface cavities, smeared material and ridges parallel to feed marks. Surface cavities were associated with the carbide particles contained in workpiece material and the intrinsic defect of cast GH625 alloy. The cutting conditions had little impact on the extent of surface cavities, but they significantly affected the extent of smearing. Severe smearing of workpiece material could occur at higher cutting speed due to the relatively high cutting temperature generated and the relatively rapid tool wear.