超精密磨削加工技术外文翻译文献
jimmy eat world超精密磨削加工技术外文翻译文献(文档含中英文对照即英文原文和中文翻译)
英语作文出国留学
原文：
refu的名词Precision internal grinding with a metal-bonded diamond
grinding wheel
Jun Qian, Wei Li, Hitoshi Ohmorib
Nanjing University of Aeronautics and Astronautics
Abstract
A metal-bonded grinding wheel, compared with conventional grinding wheels, offers the advantage of high hardness, high holding ability and finer usable abrasive grit mesh sizes. The truing and dressing of a metal-bonded diamond (MBD) wheel, in practice, are very difficult. To grind small-diameter internal cylindrical surface with MBD-wheels, an interval electrolytic in-process dressing (E
LID) method was utilized. Experiments were carried out on an ordinary cylindrical grinding machine with an attached internal grinding t-up, and straight type grinding wheels of different grit sizes were ud. The grinding wheels were trued, using the electrical discharge method, and the effects of electrode shapes, grinding parameters, and grit sizes were evaluated experimentally. Mirror surface grinding of different materials was carried out with a #4000 CIB-D wheel, incorporated with this interval ELID (ELID II) method. The experimental results are reported # 2000 Elvier Science S.A. All rights rerved.
Keywords:Cylindrical grinding; Metal-bonded grinding wheel; Dressing; Electrolytic in-process dressing；Precision grinding
1. Introduction
Along with the technological advancement of ultra-precision grinding, applications and requirements for precision cylindrical surfaces have incread significantly in the recent years [1]. As a principal processing method for an internal surface, cylindrical grinding has been commonly utilized as a final operation in the production of precision components. Since grinding is usually the most costly of all manufacturing process, considerable attempts have been focud on the analysis and optimizatio
n of the grinding process to minimize machining time [2-6], and on various compensatory control strategies to improve workpiece quality[7-10]in the cylindrical grinding. However, few rearches on mirror-surface internal grinding have been reported [5,6,11], probably due to the limitation of abrasive grit size applicable to non-metallic bond grinding wheels [5,7,8,10].
Rearch on high efficiency grinding of advanced materials, by utilizing high-rigidity grinding machines and tough metal-bonded superabrasive wheels, has led to the successful development of cast iron bonded diamond (CIB-D) grinding wheels [12]. The wheels are manufactured by mixing diamond
grits, cast iron powder or fiber, and a small amount of carbonyl iron powder. The wheels are compacted to a desired form under high pressure and then sintered in an atmosphere of ammonia. The wheels are not suitable for continuous grinding for a long period of time for the following reasons: (1) As tougher metal-bonded wheels exhibit poor dressing ability, it is difficult to achieve efficient and stable dressing simultaneously. (2) Higher rate of material removal in the grinding promotes wear of the abrasive grains, therefore, more frequent redressing of the grinding wheel will be required by stopping the grinding process. (3) While machining metals such as steel, wheel loading (embedding of swarf) occurs, making effective dressing of metallic bond wheel difficult in pra
ctice. Although a diamond slab incorporated with an abrasive jet sharpening method is able to dress a bronze-bonded wheel to the same topography as an electroplated wheel [12], complex equipment must be added inevitably which cau working-environment problem. Dressing by electrical discharge is a good method, but it is difficult to conduct on-line dressing, and dressing stripes appear on the wheel periphery when a pair of parallel electrodes is ud [13,14]. Electrolytic in-process dressing (ELID) has so far rved as the most successful dressing method for metal-bonded wheels. It has been devid and applied successfully in precision surface grinding [15-17]. However, its application to internal grinding has not been well investigated; especially when the internal diameter of the workpiece is just slightly larger than that of the grinding wheel, it is very difficult or even impossible to fix a dressing electrode mounted parallel to the wheel surface as in ordinary ELID grinding [15]. A novel method to carry out ELID grinding of internal cylindrical surfaces on an ordinary grinding tool is prented in this paper. The principle and process of this method, namely interval ELID (ELID II) grinding, is also discusd. Applying ELID II grinding to an ordinary grinding machine, some preliminary experiments have been carried out. Two types of dressing electrodes were ud and their dressing effects were investigated. With this technology, four specimens of alumina ceramic, hardened steels SKH51 and SKD11 and bearing steel, were ground to mirror finish. The results of this rearch are prented in the following ctions.
fabricated2. Principle of interval ELID grinding
The interval dressing of an abrasive grinding wheel itlf is not a new technology. In fact, using the common mechanical dressing methods, the wheel is usually dresd at intervals. The grinding process is stopped to dress the wheel after grinding one workpiece or veral work pieces. The tool life limit can be chatter vibration, surface roughness and burning marks, etc. [2]. However, with the ELID II method, the wheel is dresd at intervals and the abrasives remain protruding, enabling the grinding process to go on without any interruption and conquently realizing high efficiency grinding.小学五年级上册英语录音mp3下载
valThe interval ELID system is esntially compod of thefollowing elements: (i) a metal-bonded grinding wheel, (ii)an ELID power source, (iii) electrolytic coolant, and (iv) a pipe dressing electrode.
The most important feature of this process is that no special machine is required, and in fact the experimental system we ud is an auxiliary internal cylindrical grinding attachment on an external cylindrical grinder.
The fundamental principle of interval ELID grinding is same as that of ordinary ELID grinding [15]. Fig. 1 shows a schematic diagram of the interval ELID grinding system. The metal-bonded grinding
wheel, which is electrically conductive, is connected to the positive terminal of a DC-pul power suppl
Fig. 1. Schematic diagram of interval ELID grinding.
-y with a smooth brush contact, and a fixed electrode is made negative. A proper clearance of approximately 0.1 mm is originally t between the positive pole (wheel) and the negative one (dressing electrode). By virtue of electrolysis between two electrodes, the wheel and the dressing electrode, the grinding wheel is dresd and a non-conductive film is formed on the wheel periphery. This occurs upon the supply of current from the power source and the electrically conductive coolant. During the interval ELID grinding process, the protruding grains grind the workpiece and as
a result, the grains and the oxide layer wear down. The wheel's electrical conductivity increas, due to the wear of the non-conductive oxide layer. The current in the circuit increas, thus increasing the electrolysis. The abrasive grains therefore become more protruding and an insulating layer is formed.
3. Experimental procedure
Usually, interval ELID grinding consists of the following steps. (i) Truing: truing is required to reduce the initial eccentricity of the wheel, especially when a new wheel is ud for the first time. It is difficult to apply conventional truing methods, such as brake dresr, to metallic bond wheels due to the high bond strength. In this investigation, the cast iron bonded wheel was trued by the electrical discharge (ED) process. (ii) ELID dressing, also known as pre-dressing by electrolysis, prently performed at a much lower wheel rotation speed and higher electric ttings. (iii) Grinding: interval
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ELID grinding. The conditions of electrolysis, during the last two steps, differ due to change in the wheel state and grinding conditions.
3.1. ED-truing
norman
recruitedTo true a cast iron bonded diamond wheel at high speed and with high precision, an electrical discharge truing (ED-truing) method was ud in this study. Fig. 2 shows the details of this method. A special ED-truing wheel,made of high temperature alloy and insulated from its central shaft, was mount
Fig. 2. View of the ED-truing t-up.
-ed on the three-jaw chuck of the grinding tool. The ED-truing wheel was connected to the negative pole of an ELID power source originating from ordinary ED power supply, whilst the grinding wheel was linked to the positive pole. Both the ED-truing wheel and the grinding wheel, especially the latter, rotated at a fairly low speed and the ED truing wheel reciprocated along with the machine's saddle. Little and sometimes even no coolant was supplied to the working area to prevent electrolysis to the full and to pursue high truing precision.
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3.2. Pre-dressing
Following the ED-truing, pre-dressing was carried out before starting ELID grinding (e Fig. 1). When the pre-dressing began, the surface of the trued wheel showed a good electrical conductivity. Therefore, the current would be very high and the voltage between the wheel and electrode would be low, varying in accordance with the wheel size and dressing ttings. After veral minutes, the cast iron fiber bond material, which is mostly ionized into Fe+2, is dissolved by electrolysis. The ionized Fe+2 will react with nonconductive ferrous hydroxides and oxides to form a layer on the wheel periphery. This insulating oxide layer would grow on the wheel surface, whereby its electrical c
onductivity would be reduced. Conquently, the current would decrea and the working voltage would remain quite high (90 V, in ca that the originally t open voltage is 100 V) after 20 min. The color of the wheel change
