Papers by Author: Zhi Tong Chen

Abstract: The wear process of electroplated CBN grinding wheel is difficult to predict and control because of the lack of unified evaluation index of wear degree. This paper investigates the service life cycle of electroplated CBN grinding wheel in grinding of nickel-based superalloy GH4169. The evolution of topography of grinding wheel, diameter of grinding wheel, grinding force and surface roughness are tracked in the wear process. Using the analytic hierarchy process (AHP), the optimal evaluation index of service life of electroplated CBN grinding wheel is proposed.

Abstract: The large complex structure integral components composed of difficult-to-machine material (such as titanium alloy, high temperature alloy) are more and more widely applied in aerospace, weapon equipment and other industries. The material utilization rate and the processing efficiency of the milling process are very low, the cost is high. Micro copper tubes (diameter 2mm, inner diameter 1.6mm) are arranged to electrode with shape to be processed, which could cut these components with a high efficiency and low cost. The fabrication of electrode is simple and convenient, so the cost of electrode could be reduced too. The flow field design is an important problem to be solved. The model of flow field is established, and flow field of different cathodes are simulated．The analysis results show that the rectifying ring is favorable for the electrochemical machining. Finally, the cathode with rectifying ring is used in processing experiment, the edge of cutting zone is orderly, no spark and short circuit occurs. Straight line and circular hole is successfully processed. The feasibility of the scheme is proved.

Abstract: In this paper, we proposed a new ellipse fitting method converting the ellipse fitting into a circle fitting based on projection transformation. Numerical experiments demonstrate that our approach have good stability and strong robustness against noise in addition to excellent precision and accuracy. In our further research, we successfully extend our algorithm to the construction of the elliptic arc-shaped leading edge by using a tangential contact constraint. Keywords: Ellipse fitting; Projection; PSO; Leading edge

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: With the continuous improvement of the calculation speed of computer, tool positioning methods based on numerical calculation in five-axis NC programming will play a greater role. First, this paper introduces three numerical methods for calculating tool position error distribution between a torus cutter and design surface in 5-axis machining of sculptured surfaces, namely a method for discretizing design surface, a method for discretizing the torus central circle, and a longitude method. At the same time, the detailed calculating steps are also given. An example of a cylindrical surface machined with torus tool is then conducted to compare and analyze the calculation accuracy and efficiency of the above methods. Results obtained show that the calculating deviation for computing tool position error distribution using the method for discretizing the torus central circle is minimum, while that using another two methods are larger; the calculation time of the method for discretizing the torus central circle is shortest, while that of the longitude method is longest; within the given programming tolerance, the machining strip widths calculated by the above methods are appropriately same, and the maximum deviation of actual machining strip width is within 2% of the theoretical value.