In this paper, turning experiments of machining particle reinforced metal matri x composites(PRMMCs) SiC p/Al with PCD tools have been carried out. The cutting force characteristics in ultrasonic vibration turning com...In this paper, turning experiments of machining particle reinforced metal matri x composites(PRMMCs) SiC p/Al with PCD tools have been carried out. The cutting force characteristics in ultrasonic vibration turning compared with that in com mon turning were studied. Through the single factor experiments and multiple fac tor orthogonal experiments, the influences of three kinds of cutting conditions such as cutting velocity, amount of feed and cutting depth on cutting force were analyzed in detail. Meanwhile, according to the experimental data, the empirica l formula of main cutting force in ultrasonic vibration turning was conclude d. According to the test results, the cutting force is direct proportion to cutt ing depth basically according to the relation between cutting force and other fa ctors, which is similar to that of common cutting, so is the feed rate, but the influence is not so big. The influence of cutting speed is larger than that of f eed rate on cutting force because the efficient cutting time increases in vibrat ion cycle with the increase of cutting speed, which causes cutting force to incr ease. The research results indicate: (1) Ultrasonic vibration turning possesses much lower main cutting force than that in common turning when adopting smaller cutting parameters. If using larger cutting parameters, the difference will inco nspicuous. (2) There are remarkable differences of cutting force-cutting veloci ty characteristics in ultrasonic vibration turning from that in common turning m ainly because built-up edge does not emerge in ultrasonic turning unlike common turning in corresponding velocity range. (3) In ultrasonic vibration cutting, t he influence of cutting velocity on cutting force is most obvious among thre e cutting parameters and the influence of feed is smallest. So adopting lower cu tting velocity and larger cutting depth not only can reduce cutting force effect ively but also can ensure cutting efficiency. (4) The conclusions are useful in precision and super precision manufacturing thin-wall pieces.展开更多
Characteristics of the turn-on and turn-off voltage of avalanche p-n junctions were demonstrated and studied. As opposed to existing reports, the differences between the turn-on and turn-offvoltage cannot be neglected...Characteristics of the turn-on and turn-off voltage of avalanche p-n junctions were demonstrated and studied. As opposed to existing reports, the differences between the turn-on and turn-offvoltage cannot be neglected when the size of the p-n junction is in the order of microns. The difference increases inversely with the area of a junction, exerting significant influences on characterizing some parameters of devices composed of small avalanche junctions. Theoretical analyses show that the mechanism for the difference lies in the increase effect of the threshold multiplication factor at the turn-on voltage of a junction when the area of a junction decreases. Moreover, the ＂breakdown voltage＂ in the formula of the avalanche asymptotic current is, in essence, the avalanche turn-off voltage, and consequently, the traditional expression of the avalanche asymptotic current and the gain of a Geiger mode avalanche photodiode were modified.展开更多
A novel high performance SemiSJ-CSTBT is proposed with the p-pillar under the bottom of the trench gate. The inserted p-pillar with the neighbouring n-drift region forms a lateral P/N junction, which can adjust the el...A novel high performance SemiSJ-CSTBT is proposed with the p-pillar under the bottom of the trench gate. The inserted p-pillar with the neighbouring n-drift region forms a lateral P/N junction, which can adjust the electric distribution in the forward-blocking mode to achieve a higher breakdown voltage compared to the conventional CSTBT. Also, the p-pillar can act as a hole collector at turn-off, which significantly enhances the turn-off speed and obtains a lower turn-off switching loss. Although the turn-off switching loss decreases as the depth of the p-pillar increases, there is no need for a very deep p-pillar. The associated voltage overshoot at turn-off increases dramatically with increasing the depth of p-pillar, which may cause destruction of the devices. Plus, this will add difficulty and cost to the manufacturing process of this new structure. Therefore, the proposed SemiSJ- CSTBT offers considerably better robustness compared to the conventional CSTBT and SJ-CSTBT. The simulation results show that the SemiSJ-CSTBT exhibits an increase in breakdown voltage by 160 V （13%） and a reduction of turn-off switching loss by approximately 15%.展开更多
A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly do...A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly doped n- regions embedded in the p＋-emitter. Compared with the conventional structure of a buffed-gate with a diffused source region （DSR buffed-gate）, besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-offtime decreased from 0.8 to 0.4μs.展开更多
文摘In this paper, turning experiments of machining particle reinforced metal matri x composites(PRMMCs) SiC p/Al with PCD tools have been carried out. The cutting force characteristics in ultrasonic vibration turning compared with that in com mon turning were studied. Through the single factor experiments and multiple fac tor orthogonal experiments, the influences of three kinds of cutting conditions such as cutting velocity, amount of feed and cutting depth on cutting force were analyzed in detail. Meanwhile, according to the experimental data, the empirica l formula of main cutting force in ultrasonic vibration turning was conclude d. According to the test results, the cutting force is direct proportion to cutt ing depth basically according to the relation between cutting force and other fa ctors, which is similar to that of common cutting, so is the feed rate, but the influence is not so big. The influence of cutting speed is larger than that of f eed rate on cutting force because the efficient cutting time increases in vibrat ion cycle with the increase of cutting speed, which causes cutting force to incr ease. The research results indicate: (1) Ultrasonic vibration turning possesses much lower main cutting force than that in common turning when adopting smaller cutting parameters. If using larger cutting parameters, the difference will inco nspicuous. (2) There are remarkable differences of cutting force-cutting veloci ty characteristics in ultrasonic vibration turning from that in common turning m ainly because built-up edge does not emerge in ultrasonic turning unlike common turning in corresponding velocity range. (3) In ultrasonic vibration cutting, t he influence of cutting velocity on cutting force is most obvious among thre e cutting parameters and the influence of feed is smallest. So adopting lower cu tting velocity and larger cutting depth not only can reduce cutting force effect ively but also can ensure cutting efficiency. (4) The conclusions are useful in precision and super precision manufacturing thin-wall pieces.
基金supported by the Doctoral Start-Up Fund of Xi'an Polytechnic University,China(No.BS1126)the Project of Ministry of Education,Shanxi Province(No.12JK0975)
文摘Characteristics of the turn-on and turn-off voltage of avalanche p-n junctions were demonstrated and studied. As opposed to existing reports, the differences between the turn-on and turn-offvoltage cannot be neglected when the size of the p-n junction is in the order of microns. The difference increases inversely with the area of a junction, exerting significant influences on characterizing some parameters of devices composed of small avalanche junctions. Theoretical analyses show that the mechanism for the difference lies in the increase effect of the threshold multiplication factor at the turn-on voltage of a junction when the area of a junction decreases. Moreover, the ＂breakdown voltage＂ in the formula of the avalanche asymptotic current is, in essence, the avalanche turn-off voltage, and consequently, the traditional expression of the avalanche asymptotic current and the gain of a Geiger mode avalanche photodiode were modified.
基金supported by the National Major Science and Technology Special Project of China(No.2013ZX02305005-002)the Major Program of the National Natural Science Foundation of China(No.51490681)
文摘A novel high performance SemiSJ-CSTBT is proposed with the p-pillar under the bottom of the trench gate. The inserted p-pillar with the neighbouring n-drift region forms a lateral P/N junction, which can adjust the electric distribution in the forward-blocking mode to achieve a higher breakdown voltage compared to the conventional CSTBT. Also, the p-pillar can act as a hole collector at turn-off, which significantly enhances the turn-off speed and obtains a lower turn-off switching loss. Although the turn-off switching loss decreases as the depth of the p-pillar increases, there is no need for a very deep p-pillar. The associated voltage overshoot at turn-off increases dramatically with increasing the depth of p-pillar, which may cause destruction of the devices. Plus, this will add difficulty and cost to the manufacturing process of this new structure. Therefore, the proposed SemiSJ- CSTBT offers considerably better robustness compared to the conventional CSTBT and SJ-CSTBT. The simulation results show that the SemiSJ-CSTBT exhibits an increase in breakdown voltage by 160 V （13%） and a reduction of turn-off switching loss by approximately 15%.
基金supported by the Scientific and Technological Development Plan of Lanzhou City of China(No.2009-1-1).
文摘A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly doped n- regions embedded in the p＋-emitter. Compared with the conventional structure of a buffed-gate with a diffused source region （DSR buffed-gate）, besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-offtime decreased from 0.8 to 0.4μs.
