The inter-electrode gap(IEG) is an essential parameter for the anode shaping process in electrochemical machining(ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of...The inter-electrode gap(IEG) is an essential parameter for the anode shaping process in electrochemical machining(ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of an oval anode workpiece in counter-rotating ECM(CRECM)is investigated. The variation of the minimum IEG is analyzed theoretically, and the results indicate that rather than reaching equilibrium, the minimum IEG in CRECM expands constantly when a constant feed speed is used for the cathode tool. This IEG expansion leads to a poor localization effect and has an adverse influence on the roundness of the machined workpiece. To maintain a small constant IEG in CRECM, a variable feed speed is used for the cathode based on a fitted equation. The theoretical results show that the minimum IEG can be controlled at a small value by using an accelerated feed speed. Experiments have been conducted using a specific experimental apparatus in which the cathode tool is designed as a combined structure of two sectors and a thin sheet. By detecting the machining currents flowing through the minimum IEG, how the latter varies is obtained indirectly. The results indicate that using an accelerated feed speed is effective for controlling the IEG, thereby improving the roundness of the machined workpiece.展开更多
Using sequential DEA methodology, this paper has measured the variations in the technological gaps of China＇s industrial sectors compared with the world frontiers of technology. From a temporal dimension, variations ...Using sequential DEA methodology, this paper has measured the variations in the technological gaps of China＇s industrial sectors compared with the world frontiers of technology. From a temporal dimension, variations in the technological gaps of China＇s industrial sectors can be divided into the following four stages： slight abatement of technological gaps between 1985 and 1992, and between 1999 and 2007; stagnation in the variation of technological gaps between 1994 and 1999; and continuous abatement of technological gaps between 2008 and 2009. From the industry dimension, by 2009, 58.8% of China＇s industrial sectors had gradually reached or approached the world frontiers of technology; 29.4% of industrial sectors had experienced technological improvements but still lagged far behind the world frontiers of technology; 11.8% of industrial sectors significantly lagged behind the world frontiers of technology.展开更多
基金supported by the National Natural Science Foundation of China (51535006, 51805259)Natural Science Foundation of Jiangsu Province of China (BK20180431)+2 种基金Fundamental Research Funds for the Central Universities of China (3082018NP2018406)Young Elite Scientists Sponsorship Program by CAST of ChinaJiangsu Key Laboratory of Precision and Micro-Manufacturing Technology of China
文摘The inter-electrode gap(IEG) is an essential parameter for the anode shaping process in electrochemical machining(ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of an oval anode workpiece in counter-rotating ECM(CRECM)is investigated. The variation of the minimum IEG is analyzed theoretically, and the results indicate that rather than reaching equilibrium, the minimum IEG in CRECM expands constantly when a constant feed speed is used for the cathode tool. This IEG expansion leads to a poor localization effect and has an adverse influence on the roundness of the machined workpiece. To maintain a small constant IEG in CRECM, a variable feed speed is used for the cathode based on a fitted equation. The theoretical results show that the minimum IEG can be controlled at a small value by using an accelerated feed speed. Experiments have been conducted using a specific experimental apparatus in which the cathode tool is designed as a combined structure of two sectors and a thin sheet. By detecting the machining currents flowing through the minimum IEG, how the latter varies is obtained indirectly. The results indicate that using an accelerated feed speed is effective for controlling the IEG, thereby improving the roundness of the machined workpiece.
文摘Using sequential DEA methodology, this paper has measured the variations in the technological gaps of China＇s industrial sectors compared with the world frontiers of technology. From a temporal dimension, variations in the technological gaps of China＇s industrial sectors can be divided into the following four stages： slight abatement of technological gaps between 1985 and 1992, and between 1999 and 2007; stagnation in the variation of technological gaps between 1994 and 1999; and continuous abatement of technological gaps between 2008 and 2009. From the industry dimension, by 2009, 58.8% of China＇s industrial sectors had gradually reached or approached the world frontiers of technology; 29.4% of industrial sectors had experienced technological improvements but still lagged far behind the world frontiers of technology; 11.8% of industrial sectors significantly lagged behind the world frontiers of technology.
