机械类英文文献

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Manufacturing Engineering and Technology(机械类英文文献+翻译)

Manufacturing Engineering and Technology—MachiningSerope kalpakjian；Steven R.Schmid机械工业出版社2004年3月第1版20.9 MACHINABILITYThe machinability of a material usually defined in terms of four factors:1、Surface finish and integrity of the machined part;2、Tool life obtained;3、Force and power requirements;4、Chip control.Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone.Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below.20.9.1 Machinability Of SteelsBecause steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers inresulfurized steels.Phosphorus in steels has two major effects. It strengthens the ferrite, causing increased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with built-up edge formation and poor surface finish. The second effect is that increased hardness causes the formation of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron, copper, and alumin um and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant (Section 32.11) and is smeared over the tool-chip interface du ring cutting. This behavior has been verified by the presence of high concentra tions of lead on the tool-side face of chips when machining leaded steels.When the temperature is sufficiently high-for instance, at high cutting spee ds and feeds (Section 20.6)—the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Le aded steels are identified by the letter L between the second and third numeral s (for example, 10L45). (Note that in stainless steels, similar use of the letter L means “low carbon,”a condition that improves their corrosion resistance.)However, because lead is a well-known toxin and a pollutant, there are se rious environmental concerns about its use in steels (estimated at 4500 tons of lead consumption every year in the production of steels). Consequently, there is a continuing trend toward eliminating the use of lead in steels (lead-free ste els). Bismuth and tin are now being investigated as possible substitutes for lea d in steels.Calcium-Deoxidized Steels. An important development is calcium-deoxidize d steels, in which oxide flakes of calcium silicates (CaSo) are formed. These f lakes, in turn, reduce the strength of the secondary shear zone, decreasing tool-chip interface and wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at high cutting speeds.Stainless Steels. Austenitic (300 series) steels are generally difficult to mac hine. Chatter can be s problem, necessitating machine tools with high stiffness. However, ferritic stainless steels (also 300 series) have good machinability. M artensitic (400 series) steels are abrasive, tend to form a built-up edge, and req uire tool materials with high hot hardness and crater-wear resistance. Precipitati on-hardening stainless steels are strong and abrasive, requiring hard and abrasio n-resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and silicon in steels is always harmful because these elements com bine with oxygen to form aluminum oxide and silicates, which are hard and a brasive. These compounds increase tool wear and reduce machinability. It is es sential to produce and use clean steels.Carbon and manganese have various effects on the machinability of steels, depending on their composition. Plain low-carbon steels (less than 0.15% C) c an produce poor surface finish by forming a built-up edge. Cast steels are mor e abrasive, although their machinability is similar to that of wrought steels. To ol and die steels are very difficult to machine and usually require annealing pr ior to machining. Machinability of most steels is improved by cold working, w hich hardens the material and reduces the tendency for built-up edge formation.Other alloying elements, such as nickel, chromium, molybdenum, and vana dium, which improve the properties of steels, generally reduce machinability. T he effect of boron is negligible. Gaseous elements such as hydrogen and nitrog en can have particularly detrimental effects on the properties of steel. Oxygen has been shown to have a strong effect on the aspect ratio of the manganese sulfide inclusions; the higher the oxygen content, the lower the aspect ratio an d the higher the machinability.In selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strengt h of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels (liquid-metal embrittlement, hot shortness; see Se ction 1.4.3), although at room temperature it has no effect on mechanical prop erties.Sulfur can severely reduce the hot workability of steels, because of the fo rmation of iron sulfide, unless sufficient manganese is present to prevent such formation. At room temperature, the mechanical properties of resulfurized steels depend on the orientation of the deformed manganese sulfide inclusions (aniso tropy). Rephosphorized steels are significantly less ductile, and are produced so lely to improve machinability.20.9.2 Machinability of Various Other MetalsAluminum is generally very easy to machine, although the softer grades te nd to form a built-up edge, resulting in poor surface finish. High cutting speed s, high rake angles, and high relief angles are recommended. Wrought aluminu m alloys with high silicon content and cast aluminum alloys may be abrasive; they require harder tool materials. Dimensional tolerance control may be a pro blem in machining aluminum, since it has a high thermal coefficient of expans ion and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, t hough, it requires machining in a controlled environment.Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating to ols with high toughness. Nodular and malleable irons are machinable with hard tool materials.Cobalt-based alloys are abrasive and highly work-hardening. They require sharp, abrasion-resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge form ation, although cast copper alloys are easy to machine. Brasses are easy to ma chine, especially with the addition pf lead (leaded free-machining brass). Bronz es are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolong ed tool life. However care should be exercised because of its high rate of oxi dation and the danger of fire (the element is pyrophoric).Molybdenum is ductile and work-hardening, so it can produce poor surfac e finish. Sharp tools are necessary.Nickel-based alloys are work-hardening, abrasive, and strong at high tempe ratures. Their machinability is similar to that of stainless steels.Tantalum is very work-hardening, ductile, and soft. It produces a poor surf ace finish; tool wear is high.Titanium and its alloys have poor thermal conductivity (indeed, the lowest of all metals), causing significant temperature rise and built-up edge; they can be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low, although it greatly improves at elevated temperatures.Zirconium has good machinability. It requires a coolant-type cutting fluid, however, because of the explosion and fire.20.9.3 Machinability of Various MaterialsGraphite is abrasive; it requires hard, abrasion-resistant, sharp tools.Thermoplastics generally have low thermal conductivity, low elastic modul us, and low softening temperature. Consequently, machining them requires tools with positive rake angles (to reduce cutting forces), large relief angles, small depths of cut and feed, relatively high speeds, and proper support of the work piece. Tools should be sharp.External cooling of the cutting zone may be necessary to keep the chips f rom becoming “gummy”and sticking to the tools. Cooling can usually be achi eved with a jet of air, vapor mist, or water-soluble oils. Residual stresses may develop during machining. To relieve these stresses, machined parts can be an nealed for a period of time at temperatures ranging from to ( to ), and then cooled slowly and uniformly to room temperature.Thermosetting plastics are brittle and sensitive to thermal gradients during cutting. Their machinability is generally similar to that of thermoplastics.Because of the fibers present, reinforced plastics are very abrasive and are difficult to machine. Fiber tearing, pulling, and edge delamination are significa nt problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires careful rem oval of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics has improved steadily with the development of nanoceramics (Section 8.2.5) and with the selection of appropriate processi ng parameters, such as ductile-regime cutting (Section 22.4.2).Metal-matrix and ceramic-matrix composites can be difficult to machine, d epending on the properties of the individual components, i.e., reinforcing or wh iskers, as well as the matrix material.20.9.4 Thermally Assisted MachiningMetals and alloys that are difficult to machine at room temperature can be machined more easily at elevated temperatures. In thermally assisted machinin g (hot machining), the source of heat—a torch, induction coil, high-energy bea m (such as laser or electron beam), or plasma arc—is forces, (b) increased too l life, (c) use of inexpensive cutting-tool materials, (d) higher material-removal rates, and (e) reduced tendency for vibration and chatter.It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machi ning are in the turning of high-strength metals and alloys, although experiment s are in progress to machine ceramics such as silicon nitride.SUMMARYMachinability is usually defined in terms of surface finish, tool life, force and power requirements, and chip control. Machinability of materials depends n ot only on their intrinsic properties and microstructure, but also on proper sele ction and control of process variables.20.9 可机加工性一种材料的可机加工性通常以四种因素的方式定义：1、分的表面光洁性和表面完整性。

机械设计外文文献【范本模板】

Mechanical DesignJohn ErnstAbstract：A machine is a combination of mechanisms and other components which transforms transmits。

Examples are engines, turbines，vehicles，hoists，printing presses，washing machines，and movie cameras. Many of the principles and methods of design that apply to machines also apply to manufactured articles that are not true machines. The term "mechanical design” is used in a broader sense than "machine design" to include their design. The motion and structural aspects and the provisions for retention and enclosure are considerations in mechanical design. Applications occur in the field of mechanical engineering, and in other engineering fields as well, all of which require mechanical devices, such as switches，cams, valves，vessels, and mixers。

Keywords：Mechanical Design; Mechanisms Design Process;Application1。

机械类外文文献及翻译

机械类外文文献及翻译(文档含中英文对照即英文原文和中文翻译)原文：GEAR AND SHAFT INTRODUCTIONAbstract:The important position of the wheel gear and shaft can't falter in traditional machine and modern machines.The wheel gear and shafts mainly install the direction that delivers the dint at the principal axis box. The passing to process to make them can is divided into many model numbers, using for many situations respectively. So we must be the multilayers to the understanding of the wheel gear and shaft in many ways .Key words: Wheel gear; ShaftIn the force analysis of spur gears, the forces are assumed to act in a single plane. We shall study gears in which the forces have three dimensions. The reason for this, in the case of helical gears, is that the teeth are not parallel to the axis of rotation. And in the case ofbevel gears, the rotational axes are not parallel to each other. There are also other reasons, as we shall learn.Helical gears are used to transmit motion between parallel shafts. The helix angle is the same on each gear, but one gear must have a right-hand helix and the other a left-hand helix. The shape of the tooth is an involute helicoid. If a piece of paper cut in the shape of a parallelogram is wrapped around a cylinder, the angular edge of the paper becomes a helix. If we unwind this paper, each point on the angular edge generates an involute curve. The surface obtained when every point on the edge generates an involute is called an involute helicoid.The initial contact of spur-gear teeth is a line extending all the way across the face of the tooth. The initial contact of helical gear teeth is a point, which changes into a line as the teeth come into more engagement. In spur gears the line of contact is parallel to the axis of the rotation; in helical gears, the line is diagonal across the face of the tooth. It is this gradual of the teeth and the smooth transfer of load from one tooth to another, which give helical gears the ability to transmit heavy loads at high speeds. Helical gears subject the shaft bearings to both radial and thrust loads. When the thrust loads become high or are objectionable for other reasons, it may be desirable to use double helical gears. A double helical gear (herringbone) is equivalent to two helical gears of opposite hand, mounted side by side on the same shaft. They develop opposite thrust reactions and thus cancel out the thrust load. When two or more single helical gears are mounted on the same shaft, the hand of the gears should be selected so as to produce the minimum thrust load.Crossed-helical, or spiral, gears are those in which the shaft centerlines are neither parallel nor intersecting. The teeth of crossed-helical fears have point contact with each other, which changes to line contact as the gears wear in. For this reason they will carry out very small loads and are mainly for instrumental applications, and are definitely not recommended for use in the transmission of power. There is on difference between a crossed heli : cal gear and a helical gear until they are mounted in mesh with each other. They are manufactured in the same way. A pair of meshed crossed helical gears usually have the same hand; that is ,a right-hand driver goes with a right-hand driven. In the design of crossed-helical gears, the minimum sliding velocity is obtained when the helix angle areequal. However, when the helix angle are not equal, the gear with the larger helix angle should be used as the driver if both gears have the same hand.Worm gears are similar to crossed helical gears. The pinion or worm has a small number of teeth, usually one to four, and since they completely wrap around the pitch cylinder they are called threads. Its mating gear is called a worm gear, which is not a true helical gear. A worm and worm gear are used to provide a high angular-velocity reduction between nonintersecting shafts which are usually at right angle. The worm gear is not a helical gear because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point contact. However, a disadvantage of worm gearing is the high sliding velocities across the teeth, the same as with crossed helical gears.Worm gearing are either single or double enveloping. A single-enveloping gearing is onein which the gear wraps around or partially encloses the worm.. A gearing in which each element partially encloses the other is, of course, a double-enveloping worm gearing. The important difference between the two is that area contact exists between the teeth of double-enveloping gears while only line contact between those of single-enveloping gears. The worm and worm gear of a set have the same hand of helix as for crossed helical gears, but the helix angles are usually quite different. The helix angle on the worm is generally quite large, and that on the gear very small. Because of this, it is usual to specify the lead angle on the worm, which is the complement of the worm helix angle, and the helix angle on the gear; the two angles are equal for a 0-deg. Shaft angle.When gears are to be used to transmit motion between intersecting shaft, some of bevel gear is required. Although bevel gear are usually made for a shaft angle of 0 deg. They may be produced for almost any shaft angle. The teeth may be cast, milled, or generated. Only the generated teeth may be classed as accurate. In a typical bevel gear mounting, one of the gear is often mounted outboard of the bearing. This means that shaft deflection can be more pronounced and have a greater effect on the contact of teeth. Another difficulty, which occurs in predicting the stress in bevel-gear teeth, is the fact the teeth are tapered.Straight bevel gears are easy to design and simple to manufacture and give very good results in service if they are mounted accurately and positively. As in the case of squr gears, however, they become noisy at higher values of the pitch-line velocity. In these cases it is often go : od design practice to go to the spiral bevel gear, which is the bevel counterpart of thehelical gear. As in the case of helical gears, spiral bevel gears give a much smoother tooth action than straight bevel gears, and hence are useful where high speed are encountered.It is frequently desirable, as in the case of automotive differential applications, to have gearing similar to bevel gears but with the shaft offset. Such gears are called hypoid gears because their pitch surfaces are hyperboloids of revolution. The tooth action between such gears is a combination of rolling and sliding along a straight line and has much in common with that of worm gears.A shaft is a rotating or stationary member, usually of circular cross section, having mounted upon it such elementsas gears, pulleys, flywheels, cranks, sprockets, and other power-transmission elements. Shaft may be subjected to bending, tension, compression, or torsional loads, acting singly or in combination with one another. When they are combined, one may expect to find both static and fatigue strength to be important design considerations, since a single shaft may be subjected to static stresses, completely reversed, and repeated stresses, all acting at the same time.The word “shaft” covers numerous v ariations, such as axles and spindles. Anaxle is a shaft, wither stationary or rotating, nor subjected to torsion load. A shirt rotating shaft is often called a spindle.When either the lateral or the torsional deflection of a shaft must be held to close limits, the shaft must be sized on the basis of deflection before analyzing the stresses. The reason for this is that, if the shaft is made stiff enough so that the deflection is not too large, it is probable that the resulting stresses will be safe. But by no means should the designer assume that they are safe; it is almost always necessary to calculate them so that he knows they are within acceptable limits. Whenever possible, the power-transmission elements, such as gears or pullets, should be located close to the supporting bearings, This reduces the bending moment, and hence the deflection and bending stress.Although the von Mises-Hencky-Goodman method is difficult to use in design of shaft, it probably comes closest to predicting actual failure. Thus it is a good way of checking a shaft that has already been designed or of discovering why a particular shaft has failed in service. Furthermore, there are a considerable number of shaft-design problems in which the dimension are pretty well limited by other considerations, such as rigidity, and it is only necessary for the designer to discover something about the fillet sizes, heat-treatment,and surface finish and whether or not shot peening is necessary in order to achieve the required life and reliability.Because of the similarity of their functions, clutches and brakes are treated together. In a simplified dynamic representation of a friction clutch, or brake, two in : ertias I and I traveling at the respective angular velocities W and W, one of which may be zero in the case of brake, are to be brought to the same speed by engaging the clutch or brake. Slippage occurs because the two elements are running at different speeds and energy is dissipated during actuation, resulting in a temperature rise. In analyzing the performance of these devices we shall be interested in the actuating force, the torque transmitted, the energy loss and the temperature rise. The torque transmitted is related to the actuating force, the coefficient of friction, and the geometry of the clutch or brake. This is problem in static, which will have to be studied separately for eath geometric configuration. However, temperature rise is related to energy loss and can be studied without regard to the type of brake or clutch because the geometry of interest is the heat-dissipating surfaces. The various types of clutches and brakes may be classified as fllows:. Rim type with internally expanding shoes. Rim type with externally contracting shoes. Band type. Disk or axial type. Cone type. Miscellaneous typeThe analysis of all type of friction clutches and brakes use the same general procedure. The following step are necessary:. Assume or determine the distribution of pressure on the frictional surfaces.. Find a relation between the maximum pressure and the pressure at any point. Apply the condition of statical equilibrium to find (a) the actuating force, (b) the torque, and (c) the support reactions.Miscellaneous clutches include several types, such as the positive-contact clutches, overload-release clutches, overrunning clutches, magnetic fluid clutches, and others.A positive-contact clutch consists of a shift lever and two jaws. The greatest differences between the various types of positive clutches are concerned with the design of the jaws. To provide a longer period of time for shift action during engagement, the jaws may be ratchet-shaped, or gear-tooth-shaped. Sometimes a great many teeth or jaws are used, and they may be cut either circumferentially, so that they engage by cylindrical mating, or on the faces of the mating elements.Although positive clutches are not used to the extent of the frictional-contact type, they do have important applications where synchronous operation is required.Devices such as linear drives or motor-operated screw drivers must run to definite limit and then come to a stop. An overload-release type of clutch is required for these applications. These clutches are usually spring-loaded so as to release at a predetermined toque. The clicking sound which is heard when the overload point is reached is considered to be a desirable signal.An overrunning clutch or coupling permits the driven member of a machine to “freewheel” or “overrun” bec ause the driver is stopped or because another source of power increase the speed of the driven. This : type of clutch usually uses rollers or balls mounted between an outer sleeve and an inner member having flats machined around the periphery. Driving action is obtained by wedging the rollers between the sleeve and the flats. The clutch is therefore equivalent to a pawl and ratchet with an infinite number of teeth.Magnetic fluid clutch or brake is a relatively new development which has two parallel magnetic plates. Between these plates is a lubricated magnetic powder mixture. An electromagnetic coil is inserted somewhere in the magnetic circuit. By varying the excitation to this coil, the shearing strength of the magnetic fluid mixture may be accurately controlled. Thus any condition from a full slip to a frozen lockup may be obtained.齿轮和轴的介绍摘要:在传统机械和现代机械中齿轮和轴的重要地位是不可动摇的。

机械专业英语英文专业文献

Keywords: Rotary tool; Hard turning; Chip morphology; Tool wear
1. Introduction Turning instead of grinding hardened steel is an economical method to generate a high quality machined surface. During the past few years, there has been signiﬁcant industrial interest in using dry machining rather than grinding of hardened steel and other difﬁcult-to-machine materials. As an example, dry hard turning of automotive differential side gears is a successful industrial application of this technology. This technology reduces both the machining time and the speciﬁc cutting energy, and eliminates the health and environmental hazards associated with coolant usage in conventional machining operations. Although a large volume of literature exists on hard turning [1–10], the control of the tool wear and its effect on the machined surface’s physical properties represent a major technical challenge. Understanding the chip formation mechanism is essential to achieve a better insight of the machining process fundamentals. Saw toothed chip formation is observed during hard turning

机械专业英语-英文专业文献1

Int J Adv Manuf TechnolDOI10.1007/s00170-005-0266-8ORIGINAL ARTICLERichard Y.Chiou.Lin Lu.Jim S.J.Chen.Mark T.NorthInvestigation of dry machining with embedded heat pipe cooling by finite element analysis and experimentsReceived:8March2005/Accepted:18May2005 / Published online: 30 March 2006#Springer-Verlag London Limited2006Abstract This paper investigates the performance of a cutting tool embedded with a heat pipe on reducing cutting temperature and wear in machining.The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy,as well as the tool life in machining.A new embedded heat pipe technology has been developed to effectively remove the heat gen-erated at the tool–chip interface in machining,thereby, reducing tool wear and prolonging tool life.In particular, the technique can effectively minimize pollution and con-tamination of the environment caused by cutting fluids,and the health problems of skin exposure and particulate inha-lation in manufacturing.The ANSYS finite element analysis simulations show that the temperature near the cutting edge drops significantly with an embedded heat pipe during machining.Temperature measurements at sev-eral locations on the cutting tool insert agree with the simulation results both with and without the heat pipe. Experiments were carried out to characterize the temper-ature distributions when performing turning experiments using a cutting tool installed with an embedded heat pipe. The performance of the heat pipe on reducing the cutting tool temperature was further supported by the observations of cutting tool material color,chip color,and the chip radius of curvature.Keywords Dry machining.Tool design.Heat pipe. Heat transfer.Wear.Temperature Nomenclaturea Insert lengthαT Tool thermal diffusivityb Insert widthc Insert heightC eff Heat pipe specific heatC S Specific heat of tool holder and shim seatC T Specific heat of tool insertd Depth of cutf Feed rate(mm/rev)h Convective heat transfer coefficientK eff Heat pipe effective thermal conductivityK G Thermal conductivity of thermal greaseK H Thermal conductivity of tool holderK S Thermal conductivity of shim seatK T Thermal conductivity of tool insertρeff Heat pipe densityρS Density of tool holder and shim seatρT Density of tool insertQ Heat generation rate(W)q c Heat flux flowing into the tool insert(W/m2)θAngle of heat zone on tool insert rake faceR Radius of heating zoneT TemperatureT0Initial temperaturet TimeV Cutting speed(m/min)X Coordinatex Position in the X directionY Coordinatey Position in the Y directionZ Coordinatez Position in the Z direction1IntroductionMachining is an important manufacturing operation in industry.The purpose of a machining process is to generate a surface having a specified shape and acceptable surface finish,and to prevent tool wear and thermal damage thatR.Y.Chiou(*).L.LuApplied Engineering Technology,Drexel University, Philadelphia,PA19104,USAe-mail:ryc23@J.S.J.ChenMechanical Engineering Department,Temple University, Philadelphia,PA19122,USAM.T.NorthThermacore,Inc.,Lancaster,PA17601,USA(2007)31:905–914leads to geometric inaccuracy of the finished part.The thermodynamic approach to the activity at the cutting edge attempts to account for the energy consumed[25].Re-search has shown that at least99%of the input energy is converted into heat by deformation of the chip and by friction of the chip and workpiece on the tool[2,23].The interface at which the chip slides over the tool is normally the hottest region during cutting.The actual temperature is strongly affected by workpiece material,cutting speed, feed,depth of cut,tool geometry,coolant,and many other variables[7,12,34,37].Due to the interaction of the chip and tool,which takes place at high pressures and high temperatures,the tool will always wear.The use of fluids inmachining is well known[3,4,13].Among the functions of a cutting fluid,cooling and lubrication are generally regarded as the most important,since they directly relate to heat generation and tool wear.However,significant negative consequences for environmental health and safety are associated with the use of cutting fluids[1,5,10,11, 15,17,28,32].Numerous methods have also been applied to predict temperatures in machining processes[8,18,19,26].Tay et al.[36]used a finite element method and Usui et al.[37] used a finite difference method to determine the proportion in which the cutting energy is distributed among the tool, chip,and workpiece.Radulescu and Kapoor[30]devel-oped an analytical model for the prediction of tool tem-perature fields in continuous or interrupted3-D cutting processes.The analysis predicts time-dependent heat fluxes in the cutting tool,and it only requires the cutting forces as inputs.Stephenson et al.[35]described a method for calculating cutting tool temperatures in contour turning based on Radulescu and Kapoor’s model for temperatures in interrupted cutting.Their model is adapted to account for variations in the dimensions of the heat source with time.In addition,insulated conditions are used on the boundaries exposed to the environment,in order to sim-plify input requirements and reduce computing time.A heat pipe is a passive heat transfer device with a very high thermal conductance.It is used to transport heat from one location to another by means of evaporation and sub-sequent condensation of an appropriate fluid,in which circulation of the fluid is maintained by capillary forces[6, 16,20,21,29,33].Heat pipes are used for cooling pur-poses in a wide range of applications,including electron-ics,die-casting and injection molding,heat recovery, aircraft de-icing,the cooling of batteries,and the control of manufacturing temperatures.The objective of this re-search is to contribute to the fundamental understanding of the new embedded heat pipe technology in metal cutting that can effectively carry away the heat generated at the tool–chip interface in machining,and,thus,reduce tool wear and prolong tool life.In this paper,a finite element model is presented for dry machining.This work departs from previous work in that a more realistic tool design has been adapted for the cutting process with an embedded heat pipe[9].Because the use of the heat pipe cooling system may reduce or eliminate the need for cutting fluid use,the pollution and contamination of the environment by cutting fluids and the health problems of skin exposure and particulate inhalation in manufacturing can be effectively minimized.2Heat generation in machiningIn machining operations,mechanical work is converted to heat through the plastic deformation involved in chip formation and through friction between the tool and the workpiece.Figure1shows the subsequent dissipation of that heat in the chip,tool,and the workpiece.Most of the analytical methods for steady-state temperature prediction in machining were developed based on Merchant’s model [27]for orthogonal cutting,which gives the shear and friction energy in terms of the measured cutting forces, tool–chip contact length,and chip thickness ratio.From Radulescu and Kapoor’s model[30]and Stephenson and Ali’s approach[34],the force model predicts the depen-dence of the forces on the cutting parameters and the workpiece’s geometry.It can predict the actual force magnitudes or their dependence on material types and cutting conditions.The heat generated during the metal cutting process where the work being done on the tool insert transforms itself in the form of heat.Consequently, the heat generation rate,Q(W),is given by Sata and Takeuchi[31]as:Q¼1:68df0:15V0:85(1) where d is the depth of cut(mm),f is the feed rate(mm/ rev),and V is the cutting speed(m/min).Fig.1Zones of heat generation and heat dissipation during the metal cutting processYFig.2Heating of a tool carbide insert9063Finite element simulation of cutting temperatureA finite element model (FEM)3-D model (ANSYS 6.1)was developed for the simulation of temperature based on the estimated machining heat flux over the tool –chip contact area on a tool insert of a cutting tool.Heat is generated at the tool –chip interface in the quarter-circular area (heat source area)of the tool insert rake surface,and a portion of it flows into the tool,as shown in Fig.2.The temperature distribution is obtained from the balance of the heat generated and transient thermal analysis for two cases:without and with heat pipe cooling.The real geometry of the cutting tool is chosen as the computational domain.Figures 3and 4show schematic views of the finite element analysis (FEA)models of the cutting tool for the two cases of without and with heat pipe cooling.To achieve more realistic and accurate simulation results,the model takes into account the real geometry of the cutting tool and the thermal resistance.By using con-stant thermophysical properties,the 3-D transient heat conduction equation becomes:@2T @x 2þ@2T @y 2þ@2T @z 2¼1αT @T@t(2)where αT is the tool thermal diffusivity.The initial condition is:T x ;y ;z ;t ¼0ðÞ¼T 0(3)Fig.3Schematic view of the finite element analysis (FEA)model without a heatpipeFig.4a Schematic illustration of an embedded heat pipe in a cutting tool in machining.b Schematic view of the FEA model with heat pipe cooling907The boundary condition for the present model in the heat source area is as follows:Àk T@T ðx ;y ;z ;t Þ@z j¼q c ;0 ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃx 2þy 2p R ;z ¼0;0 θ 90h ðT ÀT 0Þ;otherwise()(4)where K T is the tool thermal conductivity,q c is the heat fluxflowing into the tool insert,R is the radius of heating zone,h is the convective heat transfer coefficient,and θis the angle of the heat zone on the tool insert rake face.The typical FEM used in this work for cutting sim-ulations consists of 4,228eight-node triangle elements for modeling the tool without a heat pipe and 6,915eight-node triangle elements for modeling with an installed heat pipe.The heat converted from the work of plastic deformation and friction is assumed to be the same for the two cases in the simulations.A typical simulation is based on a constant time step of 40s and a substep of 1s for a cutting time of 400s.To simulate the thermal resistance of the thermal grease,a layer of 0.1mm in height is placed between the heat pipe and the tool insert.The effective thermal conductivity of the heat pipe is obtained from experiments by Chiou et al.[10].The weighted average method was used to evaluate the effective density and specific heat of the heat pipe in the simulations [24].The geometry and material properties of the tool and the heat pipe are listed in Tables 1and 2.To simulate the heat pipe ’s thermal be-havior,the convective heat transfer coefficients for the heat pipe ’s adiabatic section and condense section are set to 5W/m 2°C and 1,200W/m 2°C,respectively.The con-vective heat transfer coefficients for most surfaces on the tool holder are set to 10W/m 2°C,except the one for theTable 2Properties of the installed heat pipe Heat pipe length 152.4mm Heat pipe width 8.38mm Heat pipe thickness2.16mm Condenser length of heat pipe30mmHeat pipe effective thermal conductivity,K eff 11,960W/m·K Heat pipe density,ρeff3,395kg/m 3Heat pipe specific heat,C eff 1,985J/kg·K Initial temperature,T 025°CFig.5Cutting tool temperature distribution without heat pipe cooling (Q =15.7W)Table 1Input values of the FEA model for the cutting tool Insert,shim seat,and thermal grease width,a 9.525mm Insert,shim seat,and thermal grease length,b 9.525mm Insert thickness,c 1.5mm Shim seat thickness4.84mm Thermal grease thickness 0.1mm Tool holder length114.3mm Tool holder width and height19.05mm Thermal conductivity of insert,K T 112.5W/m·K Density of insert,ρT14,900kg/m 3Specific heat of insert,C T208J/kg·K Thermal conductivity of tool holder,K H 42.6W/m·K Thermal conductivity of shim seat,K S 42.6W/m·K Density of tool holder and shim seat,ρS7,850kg/m 3Specific heat of tool holder and shim seat,C S 473J/kg·K Thermal conductivity of thermal grease,K G 9.8W/m·K Initial temperature,T 025°C908back surface,which is set to 5W/m 2°C.Other convective heat transfer coefficients for the cutting tool top surface and the side surface are set to 20W/m 2°C and 15W/m 2°C,respectively,with the one for the shim seat set at 5W/m 2°C.All the case studies were conducted to simulate the heat transfer behavior by varying the input heat flux from 20×106W/m 2to 60×106W/m 2,applied to the top corner of the insert,where the heating zone on the corner was held constant:A=π×1mm 2/4=0.78×10−6m 2.A typical simula-tion for a cutting tool without a heat pipe in Fig.5for heat flow Q =15.7W shows that the maximum temperature near the heat source is 352°C.With the same heat flow as shown in Fig.6,the maximum tool tip temperature is reduced to 293°C with a heat pipe installed in the cutting tool,a reduction of 59°C compared to the no heat pipe case.It may be inferred that the heat-pipe system designed has lower thermal resistance than the non-heat-pipe system.Without a heat pipe,the heat transferred to the tool is resisted and accumulates on the tool –chip interface,and takes time to diffuse into the inner region of the cutting tool.4Experiments with an embedded heat pipe in a cutting toolAn experimental study was undertaken with the use of a heat pipe to remove heat from the tool –chip interface in a carbide insert.A series of cutting experiments were con-ducted on a conventional lathe using a commercially available SPU 422grade VC2with 11°rake angle un-coated carbide insert.The workpiece materials are AISI 1020and 1040carbon steels in the form of a 30-cm-long cylindrical rod with a diameter of 50mm.A standard tool holder manufactured by Valenite was modified for the purpose of the investigation.A VC2carbide insert was cut into the 1.5-mm-thick slot by wire electrical-discharge machining (EDM)to accommodate a flattened 6-mm copper water heat pipe.The heat pipe had a 135°bend to match the cutting rake insert geometry used.Arctic Silver thermal grease was used between the heat pipe,insert,and the tool holder to ensure good thermal contact.The proto-type insert fixture,carbide insert,and heat pipe were securely assembled and are shown in Fig.7a.Two system configurations (without and with heat pipe cooling)were studied and compared in order to determine the effect of the heat pipe on the removal of heat from themachiningFig.6Cutting tool temperature distribution with a heat pipe installed (Q =15.7W)Fig.7a Experimental setup with an embedded heat pipe in a cutting tool.b Locations of two thermocouples on the carbide insert.Temperature readings:(T c1,T c2)without heat pipe cooling;(T f1,T f2)with heat pipe cooling909processes.The flat-plate heat pipes with a 135°angle made by Thermacore Inc.to match the cutting rake insert geometry was studied in this project.Two 0.127-mm-diameter K-type (chromel-alumel)thermocouples (T c1and T c2,without heat pipe;T f1and T f2,with heat pipe)were affixed on the back side of the carbide insert,with a vertical distance (VD)of Z =1.5mm and horizontal distances (HD)of X =1.05mm and 4.22mm each from the cutting edge,as shown in Fig.7b.The depth of cut and the feed rate were fixed at 2mm and 0.1mm/rev,respectively,for all of thetests in machining AISI 1020steel.The thermocouples permitted the measurement of the transient temperature response at the side surface of the insert.Figure 8shows representative temperature variations for the two cases without and with heat pipe cooling at a cutting speed of 29.9m/min in machining AISI 1020steel.While the steady-state temperature T c1reaches 120°C for the cutting experiment without heat pipe cooling on the tool insert at the location of HD=1.05mm,the lower steady-state temperature T f1at the same locationreachesFig.8Temperature variation for the machining experiment without and with heat pipe cooling at a depth of cut of 2mm,a feed rate of 0.1mm/rev,and a cutting speed of 29.9m/minFig.9Temperature variations for the machining experiment without and with heat pipe cooling at a depth of cut of 2mm,a feed rate of 0.1mm/rev,and a cutting speed of 40.94m/min91096°C with heat pipe cooling.It can be seen that the temperature drop associated with the installed heat pipe is 24°C.Similarly,the steady-state temperature readings of T c2=110°C without heat pipe cooling and T f2=97°C with heat pipe cooling at the location of HD=4.22mm show a temperature drop of 23°C due to the embedded heat pipe.Figure 9shows the temperature variations for the same AISI 1020steel machining experiments at a higher cutting speed of 40.94m/min.For the case without heat pipe cooling,the steady-state temperature T c1at the location of HD=1.05mm is increased to 135°C.However,the steady-state temperature T f1with heat pipe cooling reaches about 106°C.The temperature drop in the case associated with the installed heat pipe is 29°C.The result at the location of HD=4.22mm is quite similar to that at the location of HD=1.05mm.The steady-state temperature readings of T c2=123°C without heat pipe cooling and T f2=95°C with heat pipe cooling at the same location show a temperature drop of 28°C.The experiments demonstrate the same results as the simulations indicating that the effect of the heat pipe is to reduce the steady-state temperature dependent upon the generated heat influx in machining.As predicted by the FEM analysis,the data shows that the thermal resistance of the heat pipe system is lower than the non-heat-pipe system.In order to estimate the temperature on the tool –chip interface and its effect on tool hardness and tool wear,a series of experiments in machining harder material AISI 1040steel with a diameter of 50mm were conducted.The same tendency appears in Fig.10for the effect of an installed heat pipe on steady-state temperature drops from the temperature readings at different locations of thermo-couples.In particular,the changes of the tool and chip material properties due to the temperature drop were also observed with the measurement of tool insert hardness and chip properties.It should be noted that similar methodshave been widely used to verify the cutting temperature for high-speed steel and carbide tool materials,since the material hardness is closely correlated to the history of heating [23].Figure 11shows the formation of the chips for the two cases without and with a heat pipe in machining a workpiece AISI 1040steel at a depth of cut of 1mm,a feed rate of 0.1mm/rev,and a cutting speed of 32.57m/min.It can be observed from the image that the formation of chips for the two cases are quite different.The chip radius of curvature for cutting without a heat pipe is longer than that in cutting with heat pipe cooling.Since chip generation is a major concern in machining ductile materials,it has drawn the interest of many researchers.It is well known from a number of papers [14,22]that the chip geometry is heavily dependent upon the temperature at which the material makes the transition from ductile to brittle.As observed from the research,the intense temper-ature rise at the tool –chip interface without a heat pipe tends to generate a higher heat flux in the secondary deformation zone,which makes up a metallurgicalstruc-Fig.10Temperature variation for the machining experiment without and with heat pipe cooling at a depth of cut of 1mm,a feed of 0.1mm/rev,and a cutting speed of 32.57m/minFig.11Formation of the chips.Top Cutting without heat pipe cooling.Bottom Cutting with heat pipe cooling911ture in the chip.Because the chip flow carries away a large portion of the heat generated,the temperature rise of the chip tends to make the chips more ductile,and,thus,increase the chip radius of curvature.It was also observed that the chip color is blue when the cutting is performed without a heat pipe;however,the chip color becomes dark brown when cutting is conducted with an installed heat pipe.The blue discoloration of the oxidized chip as a result of high temperature reveals that the tool –chip interface temperature is higher in cutting without heat pipe cooling.The corresponding wear rates of the tool insert for the cases without and with heat pipe cooling are also quite different.It is interesting to note that the location of maximum crater wear generally coincides with the location of the maximum temperature at some distance from the cutting edge of the rake face.One explanation of this behavior is that the tool –chip contact area combines the heat due to the frictional effect on the tool –chip interface and the heat from the primary deformation zone carried,largely convected with material flow along the interface,isconducted into the tool.Therefore,the temperature distri-bution at some distance away from the primary deforma-tion in the tool insert has a clear difference between the cases without and with a heat pipe.In addition,the shapes of both tool wear zones in the image confirm the assumed quarter-circular heating zone at the tool –chip interface at the tool insert rake surface in Fig.2.As shown in Fig.12,an examination of the test results reveals that there is a direct relation between the crater-wear rate and the tool –chip interface temperature.It can be seen in Fig.12a that there is sharp increase in crater wear after a higher temperature range has been reached for the tool insert without a heat pipe installed.Note the location of the crater-wear pattern and the discoloration of the tool insert (loss of temper)as a result of high temperatures.The discoloration profiles agree with the temperature shown by Kalpakjian and Schmid [23].From the photomicrographs in machining with and without an embedded heat pipe,it can be concluded that the installed embedded heat pipe reduces the temperature of the tool –chip interface.The temperature drop enhances the performance of the tool,reduces the tool wear,and increases the tool life,as shown in Fig.12b.The comparisons between the simulated and actual experimental data at different horizontal locations on the tool insert from the cutting edge are shown in Fig.13.While the two curves at the top of the figure represent the simulated data for the case without heat pipe cooling at the vertical distance (VD)of Z =1.5mm and the horizontal distances (HD)of X =1.5mm and 4.5mm from the tool –chip interface,the lower two temperature curves in the figure are at the locations of 2.1mm and 3.2mm from the cutting edge X =0for the case with heat pipe cooling.The overall trend of the FEA results shows reasonably good agreement with the measured results,except that the figure shows a lower measured value than thecalcu-Fig.12a Carbide insert without heat pipe cooling.b Carbide insert with heat pipe cooling at a depth of cut of 1mm,a feed of 0.1mm/rev,a cutting speed of 32.57m/min depth of cut,and a cutting time of 5min.(Photomicrographs,×50)Fig.13Comparison of simu-lated temperature profiles and actual experimental temperature measurements with the thermo-couples at different locations for two cases without and with heat pipe cooling912lated temperature predicted by the FEA model for the case without a heat pipe.This is because the time of150s for data acquisition of the steady-state temperature readings in the experiment was much lower than that which lasted for400s in the FEA simulation.In general, the installed heat pipe in the cutting tool has an effect of reducing the temperature on the tool–chip interface and other locations on the tool insert.Based on the experimental data at different locations,the extrapolated simulation results,the observed tool wear and chip properties,and the actual tool–chip interface tempera-tures are in good agreement with those predicted by the FEA simulation.5ConclusionsThe finite element model(FEM)analysis of heat transfer behavior and machining experimental results in the present study demonstrate that the heat generated in machining can be effectively removed by the use of a heat pipe installed on a cutting tool insert.The experimental results also agree with the analysis in the sense that the installed heat pipe in a cutting tool has a significant effect on the temperature drop at the tool–chip interface,tool wear reduction,and tool life prolongation in machining.The results based on the comparison between heat pipe and non-heat-pipe dry machining demonstrate the feasibility of the concept of using a heat pipe for reducing the generated heat and the use of cutting fluids in machining.Acknowledgement The authors would like to thank the National Science Foundation(grant nos.DMI-0115620and DMI-0342088) for its financial support of the project.References1.Ay H,Yang W-J(1998)Heat transfer and life of metal cuttingtools in turning.Int J Heat Mass Trans41(3):613–6232.Balaji AK,Sreeram G,Jawahir IS,Lenz E(1999)The effect ofcutting tool thermal conductivity on tool–chip contact length and cyclic chip formation in machining with grooved tools.Annals CIRP48(1):33–383.Beaubien SJ,Cattaneo AG(1964)A study of the role of cuttingfluid in machining operations.Lubr Eng10:74–794.Bishop KE,Lype EF,Raynor S(1950)The role of cutting fluidas a lubricant.Lubr Eng6:70–735.Byrne G,Scholta E(1993)Environmentally clean machiningprocesses—a strategic approach.Annals CIRP42(1):471–474 6.Cao Y,Faghri A(1994)Micro/miniature heat pipes andoperating limitations.J Enhanced Heat Trans1(3):265–274 7.Chao BT,Trigger KJ(1958)Temperature distribution at tool-chip and tool-work interface in metal cutting.Trans ASME 80:311–3208.Chandrasekaran H,Thuvander A(1998)Modeling tool stressesand temperature evaluation in turning using finite element method.Mach Sci Technol2(2):355–3679.Chiou RY,Chen JSJ,Cooper D,Ciuciu C(2000)Environmen-tally conscious investigation of cutting fluid mist behavior via particle image velocimetry in turning.In:Proceedings of the 2000ASME International Mechanical Engineering Congress and Exposition,Orlando,Florida,November2000,vol11,pp 829–83410.Chiou RY,Chen JSJ,Lu L,Cole I(2002)Prediction of heattransfer behavior of carbide inserts with embedded heat pipes for dry machining.In:Proceedings of the2002ASME International Mechanical Engineering Congress&Exposition, New Orleans,Louisiana,November2002,pp17–2211.Chen Z,Wong K,Li Wei,Stephenson DA,Liang SY(1999)Cutting fluid aerosol generation due to spin-off in turning operation:analysis for environmentally conscious machining.In:Proceedings of the ASME International Mechanical Engineering Conference and Exposition,Manufacturing Sci-ence and Engineering,Nashville,Tennessee,November1999, MED-vol10,pp285–29112.Chu TH,Wallbank J(1998)Determination of the temperatureof a machined surface.J Manuf Sci Eng120:259–26313.De Chiffre L(1988)Function of cutting fluids in machining.Lubr Eng44(6):514–51814.Ding Y,Hong SY(1998)Improvement of chip breaking inmachining low carbon steel by cryogenically precooling the workpiece.J Manuf Sci Eng—Trans ASME120:76–8315.Erdel BP(1999)Environmental issues in machining.SMEMachining Technology,vol10,no4,4th quarter16.Faghri A(1995)Heat pipe science and technology.Taylor andFrancis,Washington,DC17.Graham D(2000)Dry machining.Manuf Eng121(1):72–7818.Jen TC,Anagonye AU(2001)An improved transient model oftool temperatures in metal cutting.J Manuf Sci Eng—Trans ASME123(1):30–3719.Jen TC,Gutierrez G,Eapen S,Barber G,Zhao H,Szuba S,Manjunathaiah J,Labataille J(2002)Investigation of heat pipes cooling in drilling applications.Part I:preliminary numerical analysis and verifications.Int J Mach Tools Manuf42:643–652 20.Judd RL,Aftab K,Elbestawi MA(1994)An investigation ofthe use of heat pipes for machine tool spindle bearing cooling.Int J Mach Tools Manuf34(7):1031–104321.Judd 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机械类英文文献+翻译

机械类英文文献+翻译20.9 MACHINABILITYThe machinability of a material usually defined in terms of four factors:1、Surface finish and integrity of the machined part;2、Tool life obtained;3、Force and power requirements;4、Chip control.Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone.Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below.20.9.1 Machinability Of SteelsBecause steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in resulfurized steels.Phosphorus in steels has two major effects. It strengthens the ferrite, causingincreased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with built-up edge formation and poor surface finish. The second effect is that increased hardness causes the formation of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron, copper, and alumin um and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant (Section 32.11) and is smeared over the tool-chip interface du ring cutting. This behavior has been verified by the presence of high concentra tions of lead on the tool-side face of chips when machining leaded steels.When the temperature is sufficiently high-for instance, at high cutting spee ds and feeds (Section 20.6)—the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Le aded steels are identified by the letter L between the second and third numeral s (for example, 10L45). (Note that in stainless steels, similar use of the letter L means 〝low carbon,〞a condition that improves their corrosion resistance.)However, because lead is a well-known toxin and a pollutant, there are se rious environmental concerns about its use in steels (estimated at 4500 tons of lead consumption every year in the production of steels). Consequently, there is a continuing trend toward eliminating the use of lead in steels (lead-free ste els). Bismuth and tin are now being investigated as possible substitutes for lea d in steels.Calcium-Deoxidized Steels. An important development is calcium-deoxidize d steels, in which oxide flakes of calcium silicates (CaSo) are formed. These f lakes, in turn, reduce the strength of the secondary shear zone, decreasing tool-chip interface and wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at high cutting speeds.Stainless Steels. Austenitic (300 series) steels are generally difficult to mac hine. Chatter can be s problem, necessitating machine tools with high stiffness.However, ferritic stainless steels (also 300 series) have good machinability. M artensitic (400 series) steels are abrasive, tend to form a built-up edge, and req uire tool materials with high hot hardness and crater-wear resistance. Precipitati on-hardening stainless steels are strong and abrasive, requiring hard and abrasio n-resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and silicon in steels is always harmful because these elements com bine with oxygen to form aluminum oxide and silicates, which are hard and a brasive. These compounds increase tool wear and reduce machinability. It is es sential to produce and use clean steels.Carbon and manganese have various effects on the machinability of steels, depending on their composition. Plain low-carbon steels (less than 0.15% C) c an produce poor surface finish by forming a built-up edge. Cast steels are mor e abrasive, although their machinability is similar to that of wrought steels. To ol and die steels are very difficult to machine and usually require annealing pr ior to machining. Machinability of most steels is improved by cold working, w hich hardens the material and reduces the tendency for built-up edge formation.Other alloying elements, such as nickel, chromium, molybdenum, and vana dium, which improve the properties of steels, generally reduce machinability. T he effect of boron is negligible. Gaseous elements such as hydrogen and nitrog en can have particularly detrimental effects on the properties of steel. Oxygen has been shown to have a strong effect on the aspect ratio of the manganese sulfide inclusions; the higher the oxygen content, the lower the aspect ratio an d the higher the machinability.In selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strengt h of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels (liquid-metal embrittlement, hot shortness; see Se ction 1.4.3), although at room temperature it has no effect on mechanical prop erties.Sulfur can severely reduce the hot workability of steels, because of the fo rmation of iron sulfide, unless sufficient manganese is present to prevent suchformation. At room temperature, the mechanical properties of resulfurized steels depend on the orientation of the deformed manganese sulfide inclusions (aniso tropy). Rephosphorized steels are significantly less ductile, and are produced so lely to improve machinability.20.9.2 Machinability of Various Other MetalsAluminum is generally very easy to machine, although the softer grades te nd to form a built-up edge, resulting in poor surface finish. High cutting speed s, high rake angles, and high relief angles are recommended. Wrought aluminu m alloys with high silicon content and cast aluminum alloys may be abrasive; they require harder tool materials. Dimensional tolerance control may be a pro blem in machining aluminum, since it has a high thermal coefficient of expans ion and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, t hough, it requires machining in a controlled environment.Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating to ols with high toughness. Nodular and malleable irons are machinable with hard tool materials.Cobalt-based alloys are abrasive and highly work-hardening. They require sharp, abrasion-resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge form ation, although cast copper alloys are easy to machine. Brasses are easy to ma chine, especially with the addition pf lead (leaded free-machining brass). Bronz es are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolong ed tool life. However care should be exercised because of its high rate of oxi dation and the danger of fire (the element is pyrophoric).Molybdenum is ductile and work-hardening, so it can produce poor surfac e finish. Sharp tools are necessary.Nickel-based alloys are work-hardening, abrasive, and strong at high tempe ratures. Their machinability is similar to that of stainless steels.Tantalum is very work-hardening, ductile, and soft. It produces a poor surf ace finish; tool wear is high.Titanium and its alloys have poor thermal conductivity (indeed, the lowest of all metals), causing significant temperature rise and built-up edge; they can be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low, although it greatly improves at elevated temperatures.Zirconium has good machinability. It requires a coolant-type cutting fluid, however, because of the explosion and fire.20.9.3 Machinability of Various MaterialsGraphite is abrasive; it requires hard, abrasion-resistant, sharp tools.Thermoplastics generally have low thermal conductivity, low elastic modul us, and low softening temperature. Consequently, machining them requires tools with positive rake angles (to reduce cutting forces), large relief angles, small depths of cut and feed, relatively high speeds, and proper support of the work piece. Tools should be sharp.External cooling of the cutting zone may be necessary to keep the chips f rom becoming 〝gummy〞and sticking to the tools. Cooling can usually be a chieved with a jet of air, vapor mist, or water-soluble oils. Residual stresses m ay develop during machining. To relieve these stresses, machined parts can be annealed for a period of time at temperatures ranging from to ( to ), and th en cooled slowly and uniformly to room temperature.Thermosetting plastics are brittle and sensitive to thermal gradients during cutting. Their machinability is generally similar to that of thermoplastics.Because of the fibers present, reinforced plastics are very abrasive and are difficult to machine. Fiber tearing, pulling, and edge delamination are significa nt problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires careful rem oval of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics has improved steadily with the development of nanoceramics (Section 8.2.5) and with the selection of appropriate processi ng parameters, such as ductile-regime cutting (Section 22.4.2).Metal-matrix and ceramic-matrix composites can be difficult to machine, d epending on the properties of the individual components, i.e., reinforcing or wh iskers, as well as the matrix material.20.9.4 Thermally Assisted MachiningMetals and alloys that are difficult to machine at room temperature can be machined more easily at elevated temperatures. In thermally assisted machinin g (hot machining), the source of heat—a torch, induction coil, high-energy bea m (such as laser or electron beam), or plasma arc—is forces, (b) increased too l life, (c) use of inexpensive cutting-tool materials, (d) higher material-removal rates, and (e) reduced tendency for vibration and chatter.It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machi ning are in the turning of high-strength metals and alloys, although experiment s are in progress to machine ceramics such as silicon nitride.SUMMARYMachinability is usually defined in terms of surface finish, tool life, force and power requirements, and chip control. Machinability of materials depends n ot only on their intrinsic properties and microstructure, but also on proper sele ction and control of process variables.20.9 可机加工性一种材料的可机加工性通常以四种因素的方式定义：1、分的表面光洁性和表面完整性。

关于机械的英文文献

关于机械的英文文献以下是一篇有关机械的英文文献：Title: The Development and Applications of Mechanical SystemsAbstract:Mechanical systems are used in a wide range of applications from everyday household items to complex industrial machinery. Mechanical systems are composed of various mechanical components that interact with each other to perform mechanical tasks. The development of mechanical systems has been a continuous process, improving over time with the introduction of new technologies and materials.Mechanical systems can be classified into three main categories: power transmission systems, motion control systems, and structural systems. Power transmission systems transmit power from one location to another, either through a series of gears or a belt drive system. Motion control systems control the movement of a mechanical object through the use of servo motors, linear actuators, and other components. Structural systems provide the necessary support and stability for mechanical systems.One of the most important applications of mechanical systems is in the manufacturing industry. Mechanical systems are used in everything from assembly line machinery to robotic systems for welding, painting, and other tasks. Mechanical systems are also commonly used in transportation systems, including automobiles, airplanes, and trains.In recent years, the development of smart mechanical systems has become an area of focus in the research and development of mechanical systems. Smart mechanical systems are designed to be more autonomous and can include features such as sensors, actuators, and advanced control systems. These features allow the mechanical system to operate more efficiently and autonomously.Overall, the development and applications of mechanical systems have played a significant role in the advancement of modern society. As technology continues to evolve, so too will the capabilities of mechanical systems, allowing for new and innovative applications in a wide range of fields.Keywords: mechanical systems, power transmission, motion control, structural systems, manufacturing, smart mechanical systems, sensors,actuators, control systems.。

机械专业外文文献

NC Technology1、Research current situation of NC lathe in our timesResearch and development process to such various kinds of new technologies as numerical control lathe , machining center , FMS , CIMS ,etc. of countries all over the world, linked to with the international economic situation closely. The machine tool industry has international economy to mutually promote and develop, enter 21 alert eras of World Affairs, the function that people's knowledge plays is more outstanding , and the machine tool industry is regarded as the foundation of the manufacturing industry of the machine, its key position and strategic meaning are more obvious. Within 1991-1994 years, the economic recession of the world, expensive FMS, CIMS lowers the temperature, among 1995-2000 years, the international economy increases at a low speed, according to requisition for NC lathe and the world four major international lathes exhibition in order to boost productivity of users of various fields of present world market (EMO , IMTS , JIMTOF , China CIMT of Japan of U.S.A. of Europe), have the analysis of the exhibit, there are the following several points mainly in the technical research of NC lathe in our times.⑴Pay more attention to new technology and innovationWorldwide , are launching the new craft , new material , new structure , new unit , research and development of the new component in a more cost-effective manner, developmental research of for instance new cutter material , the new electric main shaft of main shaft structure , high speed , high-speed straight line electrical machinery ,etc.. Regard innovating in improvement of the processing technology as the foundation, for process ultra and hard difficult to cut material and special composite and complicated part , irregular curved surface ,etc. research and develop new lathe variety constantly.⑵Improve the precision and research of machine toolingIn order to improve the machining accuracy of the machining center , are improving rigidity of the lathe , reduction vibration constantly, dispel hotly and out of shape, reduce the noise , improve the precision of localization of NC lathe , repeat precision , working dependability , stability , precision keeping, world a lot of country carry on lathe hot error , lathe sport and load out of shape software of error compensate technical research, take precision compensate , softwarecompensate measure improve , some may make this kind of error dispel 60% already. And is developing retrofit constantly, nanometer is being processed.⑶Improve the research of the machine tooling productivityWorld NC lathe, machining center and corresponding some development of main shaft , electrical machinery of straight line , measuring system , NC system of high speed, under the prerequisite of boosting productivity.⑷What a lot of countries have already begun to the numerical control system melt intelligently, openly, study networkedlya、elligent research of the numerical control systemMainly showing in the following aspects: It is intelligent in order to pursue the efficiency of processing and process quality, the self-adaptation to the processing course is controlled, the craft parameter produces research automatically; Join the convenient one in order to improve the performance of urging and use intelligently, to the feedback control , adaptive operation , discerning automatically load selects models automatically , since carries on research whole definitely ,etc. of the electrical machinery parameter; There are such research of the respect as intelligent automatic programming , intelligent man-machine interface , intelligence diagnosing , intelligent monitoring ,etc..b、The numerical control system melts and studies openMainly showing in the following aspects: The development of the numerical control system is on unified operation platform, face the lathe producer and support finally, through changing, increasing or cutting out the structure target(numerical control target ), form the seriation, and can use users specially conveniently and the technical know-how is integrated in the control system, realize the open numerical control system of different variety , different grade fast, form leading brand products with distinct distinction. System structure norm of the open numerical control system at present, norm , disposing the norm , operation platform , numerical control systematic function storehouse and numerical control systematic function software developing instrument ,etc. are the core of present research to pass through.c、Meeting the manufacture system of the production line , demand for the information integration of the manufacturing company networkedly greatly of numerical control equipment, it is a basic unit of realizing the new manufacture mode too.2、Classification of the machining center⑴Process according to main shaft space position when it classifies to be as follows, horizontal and vertical machining center.Horizontal machining center, refer to the machining center that the axis level of the main shaft is set up . Horizontal machining center for 3-5 sport coordinate axis, a common one three rectilinear motion coordinate axis and one turn the coordinate axis of sports round (turn the workingbench round), it can one is it is it finish other 4 Taxi processing besides installing surfaces and top surfaces to insert to install in work piece, most suitable for processing the case body work piece . Compared with strength type machining center it, the structure is complicated, the floor space is large, quality is large, the price is high.Vertical machining center, the axis of the main shaft of the vertical machining center, in order to set up vertically, its structure is mostly the regular post type, the workingbench is suitable for processing parts for the slippery one of cross, have 3 rectilinear motion coordinate axis generally , can find a room for one horizontal numerical control revolving stage (the 4th axle ) of axle process the spiral part at workingbench. The vertical machining center is of simple structure, the floor space is small, the price is low, after allocating various kinds of enclosures , can carry on the processing of most work pieces .Large-scale gantry machining center, the main shafts are mostly set up vertically, is especially used in the large-scale or with complicated form work piece , is it spend the many coordinate gantry machining center to need like aviation , aerospace industry , some processing of part of large-scale steam turbine.Five machining centers, this kind of machining center has function of the vertical and horizontal machining center, one is it after inserting , can finish all five Taxi processing besides installing the surface to install in work piece, the processing way can make form of work pieceerror lowest , save 2 times install and insert working, thus improve production efficiency , reduce the process cost.⑵Classify by craft useIs it mill machining center to bore, is it mill for vertical door frame machining center , horizontal door frame mill the machining center and Longmen door frame mill the machining center to divide into. Processing technology its rely mainly on the fact that the door frame is milled, used in case body, shell and various kinds of complicated part special curve and large processes , curved surface of outline process, suitable for many varieties to produce in batches small.Complex machining center, point five times and compound and process mainly, the main shaft head can be turned round automatically, stand, lie and process, after the main shaft is turned round automatically, realize knowing that varies in the horizontal and vertical direction.⑶Classify by special functionSingle workingbench , a pair of workingbench machining center;Single axle , dual axle , three axle can change machining center , main shaft of case;Transfer vertically to the tower machining center and transfer ;One hundred sheets of storehouses adds the main shaft and changes one one hundred sheets of machining centers;One hundred sheets of storehouses connects and writes hands to add the main shaft and change one hundred sheets of machining centers;One hundred sheets of storehouses adds the manipulator and adds one pair of main shafts to transfer to the tower machining center.3、Development trend of the current numerical control latheAt present, the advanced manufacturing technology in the world is rising constantly, such application of technology as ultrafast cutting , ultraprecision processing ,etc., the rapid development of the flexible manufacturing system and integrated system of the computer one isconstant and ripe, have put forward higher demand to the process technology of numerical control. Nowadays the numerical control lathe is being developed in several following directions.The speed and precision at a high speed , high accuracy are two important indexes of the numerical control lathe , it concerns directly that processes efficiency and product quality. At present, numerical control system adopt-figure number, frequency high processor, in order to raise basic operation speed of system. Meanwhile , adopt the super large-scale integrated circuit and many microprocessors structure, in order to improve systematic data processing ability , namely improve and insert the speed and precision of mending operation. Adopt the straight line motor and urge the straight line of the lathe workingbench to be servo to enter to the way directly, it is quite superior that its responds the characteristic at a high speed and dynamically. Adopt feedforward control technology , make it lag behind error reduce greatly , thus improve the machining accuracy cut in corner not to track.For meet ultrafast demand that process, numerical control lathe adopt main shaft motor and lathe structure form that main shaft unite two into one, realize frequency conversion motor and lathe main shaft integrate , bearing , main shaft of electrical machinery adopt magnetism float the bearing , liquid sound pigeonhole such forms as the bearing or the ceramic rolling bearing ,etc.. At present, ceramic cutter and diamond coating cutter have already begun to get application.Multi-functional to is it change all kinds of machining centers of organization (a of capacity of storehouse can up to 100 of the above ) automatically to furnished with, can realize milling paring , boring and pares , bores such many kinds of processes as paring , turning , reaming , reaming , attacking whorl ,etc. to process at the same time on the same lathe , modern numerical control lathe adopt many main shaft , polyhedron cut also , carry on different cutting of way process to one different position of part at the same time. The numerical control system has because adopted many CPU structure and cuts off the control method in grades, can work out part processing and procedure at the same time on a lathe , realize so-called " the front desk processes , the backstage supporter is an editor ". In order to meet the needs of integrating the systematic one in flexible manufacturing system and computer, numerical control system have remote serial interface , can network , realize data communication , numerical control of lathe, can control many numerical control lathes directly too.Intelligent modern numerical control lathe introduce the adaptive control technology, according to cutting the change of the condition, automatic working parameter, make the processing course can keep the best working state , thus get the higher machining accuracy and roughness of smaller surface , can improve the service life of the cutter and production efficiency of the equipment at the same time . Diagnose by oneself , repair the function by oneself, among the whole working state, the system is diagnosed, checked by oneself to CNC system and various kinds of equipment linking to each other with it at any time. While breaking down , adopt the measure of shutting down etc. immediately , carry on the fault alarm, brief on position , reason to break down ,etc.. Can also make trouble module person who take off automatically , put through reserve module , so as to ensure nobody demand of working environment. For realize high trouble diagnose that requires , its development trend adopts the artificial intelligence expert to diagnose the system.Numerical control programming automation with the development of application technology of the computer, CAD/CAM figure interactive automatic programming has already get more application at present, it is a new trend of the technical development of numerical control. It utilize part that CAD draw process pattern , is it calculate the trailing punishing to go on by cutter orbit data of computer and then, thus produce NC part and process the procedure automatically, in order to realize the integration of CAD and CAM. With the development of CIMS technology , the full-automatic programming way in which CAD/CAPP/CAM integrates has appeared again at present, it, and CAD/CAM systematic programming great difference their programming necessary processing technology parameter needn't by artificial to participate in most, get from CAPP database in system directly.The dependability of the dependability maximization numerical control lathe has been the major indicator that users cared about most all the time . The numerical control system will adopt the circuit chip of higher integrated level , will utilize the extensive or super large-scale special-purpose and composite integrated circuit, in order to reduce the quantity of the components and parts , to improve dependability . Through the function software of the hardware, in order to meet various kinds of demands for controlling the function, adopt the module , standardization , universalization and seriation of the structure lathe noumenonn of the hardware at the same time , make not only improve the production lot of the hardware but also easy to is itproduce to organize and quality check on.. Still through operating and starting many kinds of diagnostic programs of diagnosing , diagnosing , diagnosing off-line online etc. automatically, realize that diagnoses and reports to the police the trouble to hardware , software and various kinds of outside equipment in the system. Utilize the warning suggestion, fix a breakdown in time; Utilize fault-tolerant technology, adopt and design the important part " redundantly ", in order to realize the trouble resumes by oneself; Utilize various kinds of test , control technology , exceed Cheng , one one hundred sheets of damages , interfering , cutting out ,etc. at the time of various kinds of accidents as production, carry on corresponding protection automatically.Control system miniaturization systematic miniaturization of numerical control benefit and combine the machine 、electric device for an organic whole. Adopt the super large-scale integrated component , multi-layer printed circuit board mainly at present, adopt the three-dimensional installation method , make the electronic devices and components must use the high density to install, narrow systematic occupying the space on a larger scale. And utilize the new-type slim display of colored liquid crystal to substitute the traditional cathode ray tube, will make the operating system of numerical control miniaturize further. So can install it on the machine tool conveniently, benefit the operation of the numerical control lathe correctly even more.数控技术1、当前世界NC机床的研究现状世界各国对数控机床、加工中心以至FMS、CIMS等各种新技术的研究与发展进程，是与世界经济形势紧密相连的。

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Available online at Physica A334(2004)243–254/locate/physaStability and transition inmultiple production linesTakashi Nagatani∗Department of Mechanical Engineering,Shizuoka University,Hamamatsu432-8561,JapanReceived28October2003AbstractWe present the dynamical model of the multiple production lines composed of M parallel and u series machines.We extend the single-series production line model to the multiple production lines.We study the e ect of the multiple lines on the dynamical behavior of the production process.We apply the linear stability analysis to the production process in the multiple lines. The linear stability criterion is derived for the production system with the multiple lines.It is shown that the production process in the multiple lines is more unstable than that in the single line.The phase diagram(region map)is given for the multiple production lines.The nonlinear instability and dynamical transition are investigated by using computer simulation.It is shown that the dynamical transitions occur between the stable and oscillatory productions.c 2003Elsevier B.V.All rights reserved.PACS:05.90.+m;89.90.+m;89.40.+kKeywords:Production process;Instability;Dynamical transition;Transportation;Multiple lines1.IntroductionConcepts from statistical physics and nonlinear dynamics have been very successful in discovering and explaining dynamical phenomena in transportation systems[1–5]. Many of these phenomena are based on mechanisms such as delayed adaptation to changing conditions and competition for limited resources.The delayed adaptation is relevant for production systems as well[6–10].Mathematicians,physicists,tra c sci-entists,and economists have suggested that tra c dynamics has also implications for the dynamical behavior of production process.∗Fax:+81-53-478-1048.E-mail address:tmtnaga@ipc.shizuoka.ac.jp(T.Nagatani).0378-4371/$-see front matter c 2003Elsevier B.V.All rights reserved.doi:10.1016/j.physa.2003.11.002244T.Nagatani/Physica A334(2004)243–254The recently proposed supply-chain model[6]is closely related to the tra c model. The stability of a linear supply chain has been investigated by using the linear stability method and computer simulation,which have been developed in the tra c dynamics [1,11].It has been found that the dynamical transition occurs between the stable and oscillatory productions by varying the adaptation time.The strength of the oscillation increases with the adaptation time.The dynamical transition is very similar to the jamming transition in tra c ow.When the consumption rate is subject to perturbations,the perturbations may cause variations in the production of upstream producers.This is due to delays in their adaptation of the production speed.Under certain conditions,the oscillations in the production and in the resulting inventories(stock levels)of the generated products grow from one producer to the next upstream one.This is called the bullwhip e ect and known,for example,from the“beer distribution game”.Until now,the production process composed of a series line of machines has been proposed and investigated by means of linear stability analysis and computer simula-tions[6,11].A control strategy of the production process has been developed to manage the process of bringing an unstable system into the stable regime.However,there are various production systems in real factories.Products are made through the production processes composed of complex networks.As a result,the products depend highly on the network structure of the production process.In this paper,we consider the dynamical behavior of products produced through the multiple production lines.We present an extended dynamical model of the multiple supply chains to take into account the network structure of M parallel and u series production lines.We study the e ect of multiple lines on the production process.We show that the multiple production lines induce the instability of the production process easier than that of the single production line,and perturbations of consumption grow to higher oscillations of the products.We analyze the stability of multiple production lines using the linear stability analysis method.We show the stability,dynamical transition, and phase diagram(region map).2.ModelWe present the dynamical model of the multiple production lines to take into account the network structure of M parallel and u series machines.The model consists of M parallel chains in which each chain is composed of a series of u production units j, which receive products from the next upstream producer j−1and generate products for the next downstream producer j+1.First,we describe the supply-chain model for late convenience.Recently,Helbing [6]has suggested the following model for the dynamics of supply chains:d N j d t =ub=1(f j b−n j b) b(t)min1;C0b N0(t)c0b;V k b N k(t)c k b−Y j u+1(t);(1)where N j denotes the inventory(stock level)of product j, b is the desired production speed of production unit(machine)b,f j b the number of products generated in eachT.Nagatani/Physica A334(2004)243–254245 production step,n j b the number of products(educts)needed,V k b a limitation of transport capacity in the delivery of the required educts,and Y j u+1the consumption rate of product j.Moreover,there is usually a considerable delay in the adaptation of the (desired)production speeds b,which may be modeled byd b d t =1T[W({N k(t)};{d N k(t)=d t})− b(t)]:(2)Herein,W(···)denotes a control function re ecting the decisions of the production management as a function of the inventories N k(t),their temporal changes d N k=d t,and T is the delay or adaptation time.If we focus on a linear supply chain with f k b= bk and n j b= b;j+1,where b;j represents the Kronecker delta function,the above equations simplify considerably.For j∈{0;1;:::;u}they readd N jd t= j(t)− j+1(t)(3) withd j d t =1T[W({N k(t)};{d N k(t)=d t})− j(t)];(4)where we assume the boundary condition Y j u+1(t)= u+1(t) j;u.In the previous paper [11],we have investigated the stability of the linear supply chain assuming control function of the formW(N)=1−[tanh(N−N c)+tanh(N c)]=2:(5) We have presented the criterion of the strategies to manage to bring into the stable production process.We extend the single linear supply-chain model to the multiple production lines. Fig.1shows the schematic illustration of the multiple production lines.The production system is composed of M parallel and u series machines.Fig.1shows the special case of M=3and u=4for illustration.At each production step,a bu er is set and all the products produced by all machines(i=1;2;:::;M,j)at step j are stocked,transiently,j+1j-1(i-1, j)(i+1, j)Supply DemandFig.1.Schematic illustration of the production process.The system is composed of M(=3)parallel and u(=4)series machines.At each production step,a bu er is set and all the products produced by the machines at step j are stocked,transiently,into bu er j.Then,the products are supplied to the next machines at step j+1.The original materials are supplied on the left boundary.Theÿnal products are consumed on the right boundary.246T.Nagatani/Physica A334(2004)243–254into bu er j.Then,the products are supplied to the next machines(i=1;2;:::;M, j+1).The product N j(t)at bu er j and production rate i;j(t)of machine(i;j)are described by the following equations:d N j d t =Mi=1i;j(t)−Mi=1i;j+1;(6)d i;j d t =1T[W i;j(N j(t))− i;j(t)]:(7)Here,we assume that the control function W i;j(t)of machine(i;j)at time t depends only on the product N j(t)at bu er j and time t.The control function is given by W i;j(N j(t))=1− tanh(N j(t)−N c;i;j)+tanh(N c;i;j) =2;(8) where N c;i;j is the turning point at machine(i;j).We assume that the control function on line i is the same for any machine on the same line:W i;j(N j(t))=W i(N j(t)).In the following sections,we study the dynamical behavior for the production sys-tem described by Eqs.(6)–(8),by using the linear stability analysis and computer simulation.3.Linear stability analysisLet us study the instability of the steady solution for Eqs.(6)–(8).The steady solutions are given by the uniform distribution.The steady solutions are set as N0and i;0,where i;0satisÿes i;0=W i(N0).Let N i(t)and i;j(t)be small deviations from the steady solutions N0and i;0:N j(t)=N0+ N j(t);(9) i;j(t)=W i(N0)+ i;j(t):(10) Then,the linearized equations are obtained from Eqs.(6)and(7)d N j d t =Mi=1i;j(t)−Mi=1i;j+1(t);(11)d i;j d t =1T[W i(N0) N j(t)− i;j(t)];(12)where W i(N0)is the derivative of control function on line i and at N=N0.By expanding N j(t)=X exp(Ikj+zt)and i;j(t)=Y i exp(Ikj+zt),one obtainszX=(1−e Ik)Mi=1Y i;(13) zTY i=W i(N0)X−Y i;(14) where I is the imaginary unit.T.Nagatani/Physica A334(2004)243–254247 By inserting Eq.(13)into Eq.(14),one obtainsY i=W i(N0)(1+zT)X:(15)By solving Eq.(15)with z,oneÿnds that the leading term of z is order of Ik.When Ik→0,z→0.Let us derive the long wave expansion of z,which is determined order by order around Ik≈0.By expanding z=z1(Ik)+z2(Ik)2+···,theÿrst-and second-order terms of Ik are obtained:z1=−Mi=1W i(N0);(16)z2=−Tz21−12Mi=1W i(N0):(17)If z2is a negative value,the steady state becomes unstable for long wavelength modes. When z2is a positive value,the steady state is stable.Therefore,the linear stability condition is given byT¡−12(Mi=1W i(N0)):(18)When the adaptation time(delay)of the production lines satisÿes the above rela-tion(18),the uctuation of consumption decays accordingly as going to the upstream machines.Otherwise,the production lines become unstable and the perturbation of consumption grows with time and accordingly as going to the upstream.The unstable production system results in the oscillating inventories.The neutral stability curve is given byT=−12(Mi=1W i(N0)):(19)The threshold between the stable and oscillating productions is given by the neutral stability curve.We study the e ect of the multiple lines on the neutral stability curve.We compare the neutral stability curve of double production lines with that of the single production line.Fig.2shows the plot of the delay’s threshold T against inventory(product)N where M=2,u=200,N c;1=3,and N c;2=6.In the production system of double lines, the production rate on theÿrst line is one until about N c;1=3and decreases to zero when the inventory is higher than about N c;1=3.While the production rate on the second line is one until about N c;2=6and decreases to zero when the inventory is higher than about N c;2=6.For comparison,we show the two neutral stability curves of the production systems of single and double lines.The solid line on the left-hand side indicates the neutral stability curve of the single production line.The region1 above the solid line represents the unstable state.The solid line on the right-hand side indicates the neutral stability curve of the double production lines.The regions1and 2above the solid line represents the unstable state.The neutral stability curve of the single line has a single valley.While the neutral stability curve of the double lines has two valleys and a mountain.Below each curve,the production system is stable and248T.Nagatani/Physica A334(2004)243–254Fig.2.Neutral stability curve and region map(phase diagram)of the production process with double series (M=2),where N c;1=3and N c;2=6.For comparison,the neutral stability curve of the single series(M=1) is also shown where N c;1=3.Region1above the neutral stability curve shows the unstable state for the single series.Regions1and2above the neutral stability curve show the unstable state for the double series. The stable region exits below each curve.robust for the uctuating consumption.The production system of double lines is more unstable than that of the single line.We study the e ect of the line’s number M on the neutral stability curve.We restrict ourselves to the multiple production lines with the same characteristics.Fig.3shows the plots of the delay’s threshold T against inventory N for M=1–4,where u=200 and N c;1=N c;2=N c;3=N c;4=3.Each curve has a single valley.The minimum value at the valley C1presents a critical threshold.The critical threshold decreases accordingly as the number M of production lines increases.The unstable region above the neutral curve extends with increasing M.Therefore,the production system of multiple lines becomes more unstable according as the line’s number M increases.We study the e ect of the di erence between the two production lines on the in-stability of the production system.We consider the production system of double lines with di erent value of N c;i in the control function.Fig.4shows the neutral stability curves for N c;2=4,6,7where N c;1=3and M=2.Point C1on each curve indicates the ÿrst minimum value of the delay’s threshold.Point C2indicates the maximum value. Point C3indicates the second minimum value.With increasing N c;2,point C3shifts to the right and the second minimum value does not change.While point C2shifts to the right and the maximum value increases with N c;2.Thus,the unstable region extends to higher values of inventory,but the stable region also extends below point C2.Therefore,the stable production process changes highly by varying N c;2in the control function.T.Nagatani/Physica A334(2004)243–254249Fig.3.Neutral stability curves for the line’s number M=1–4,where N c;1=N c;2=N c;3=N c;4=3.Fig.4.Dependence of the neutral stability curve on N c;2for the double series(M=2),where N c;1=3. Three neutral stability curves are shown for N c;2=4,6,7.We study the stability of the triple production lines.Fig.5shows the neutral stability curve in(N;T)parameter space for N c;1=3,N c;2=6,and N c;3=9.The solid line indicates the neutral stability curve of the triple series.The dotted line indicates the neutral stability curve of the double series with N c;1=3and N c;2=6.Points C1,C3, and C5indicate theÿrst,second,and third minimum values,respectively.These points present the same value for the delay time,but the value of the corresponding inventory250T.Nagatani/Physica A334(2004)243–254Fig.5.Neutral stability curve of triple series(M=3)for N c;1=3,N c;2=6,and N c;3=9.Three local minimum values are indicated by points C1,C3,and C5.Two local maximum values are indicated by points C2and C4.increases.Points C2and C4indicate theÿrst and second maximum values.The neutral stability curve of triple series is consistent with that of double series until about N=7. When the inventory is higher than about N=7,the neutral stability curve of triple series deviates from that of double series.The unstable region of triple series extends to the higher values of inventory.Thus,the stability of production systems changes highly with number M of production line.The neutral stability criterion presents the transition line(boundary)between the unstable and stable regions.However,by the linear stability analysis,it is unknown how the production process develops after the production system becomes unstable. In the following section,we carry out computer simulation.We study the dynamical behavior of the production system after the system becomes unstable.4.SimulationWe have carried out computer simulations of Eqs.(6)–(8),using Euler integration with a time discretization of t=0:01,u=200production units,and N c;1=3.The boundary condition has been chosen as follows:N u+1(t)=N0+ (t);(20) where (t)is a white noise with mean value (t) =0and time correlation (t) (t ) = tt =4.We study the dynamical behavior of inventory N j(t)by varying the initial value N0. Fig.6shows the time evolution of the inventory distribution N j(t)of the double series (M=2)for adaptation time(delay)T=1:5at some values(a)N0=3,(b)N0=4,T.Nagatani/Physica A334(2004)243–254251Fig.6.Time evolution of the inventory distribution N j(t)of the double series(M=2)for adaptation time (delay)T=1:5at some values(a)N0=3,(b)N0=4,and(c)N0=6of initial inventory N0for t= 1800–2000,where u=200,N c;1=3and N c;2=6.and(c)N0=6of initial inventory N0for t=1800–2000,where u=200,N c;1=3 and N c;2=6.For(a)initial value N0=3,when the production process starts from the initial uniform distribution,the process becomes unstable,the uctuating consumption propagates upstream,grows accordingly as going to the upstream,and the inventories oscillate highly in time.The oscillation has a constant period.For(b)initial value N0=4,when the production process starts from the initial uniform distribution,the process is stable,the uctuating consumption does not propagates upstream,decays accordingly as going to the upstream,and the inventory distribution remains to be the initial form.For(c)initial value N0=6,starting from the initial uniform distribution, the process becomes unstable,the perturbations of consumption propagate upstream, grow accordingly as going to the upstream,and the inventories oscillate periodically. The space–time pattern of(c)N0=6is consistent with that of(a)N0=3.This is due to the symmetry at N=4:5in the neutral stability curve of Fig.2.At two minimum points,the dynamical behavior of the double series is consistent with one another.The stable uniform distribution occurs below the neutral stability curve in Fig.2.We study the dynamical behavior of oscillating inventories by varying the adaptation time for the production system of double series(M=2).Fig.7shows the plots of the inventory N j(2000)against bu er’s number j at initial value N0=3and t= 2000for adaptation times(a)T=2:5,(b)T=2:25,(c)T=1:75,and(d)T=1:5, where u=200,N c;1=3and N c;2=6.For(a)T=2:5,the inventory oscillates higher accordingly as going to the upstream.With high values of adaptation time T,the width of oscillation is large.Fig.8(a)shows the plot of the maximum and minimum values252T.Nagatani/Physica A334(2004)243–254Fig.7.Plots of the inventory N j(2000)against bu er’s number j at initial value N0=3and t=2000for adaptation times(a)T=2:5,(b)T=2:25,(c)T=1:75,and(d)T=1:5,where u=200,N c;1=3and N c;2=6.(N max and N min)of oscillating inventories against adaptation time T for initial value N0=3where u=200,N c;1=3and N c;2=6.When the inventory distribution exhibits the uniform distribution,the maximum value agrees with the minimum value.The di erence between the maximum and minimum values is consistent with the maximum width of oscillating inventories.At T c;1=1:0,theÿrst dynamical transition occurs. The stable production process changes to the oscillating production process at theÿrst transition point.Furthermore,the second transition occurs at T c;2=2:0.At the second transition point,the oscillation width increases discontinuously and abruptly.Thus,we ÿnd that there are the two transition points in the production process of double lines. Theÿrst transition point is consistent with the neutral stability point,but the second transition point cannot be predicted by the linear stability theory.Fig.8(b)shows the plot of the maximum and minimum values(N max and N min)of oscillating inventories against adaptation time T for initial value N0=2:5,where u=200, N c;1=3and N c;2=6.At T c;1=1:5,theÿrst dynamical transition occurs.The stable production process changes to the oscillating production process at theÿrst transition point.Furthermore,the second transition occurs at T c;2=2:12.At the second transitionT.Nagatani/Physica A334(2004)243–254253Fig.8.Plots of the maximum and minimum values(N max and N min)of oscillating inventories against adaptation time T,where u=200,N c;1=3and N c;2=6.(a)Initial value N0=3.(b)Initial value N0=2:5.(c)Initial value N0=6.point,the oscillation width increases discontinuously and abruptly.The transition points are deÿnitely di erent from those in Fig.8(a).Theÿrst transition point agrees nearly with the neutral stability point.Fig.8(c)shows the plot of the maximum and minimum values(N max and N min)of oscillating inventories against adaptation time T for initial value N0=6,where u=200, N c;1=3and N c;2=6.At T c;1=1:0,theÿrst dynamical transition occurs.The stable production process changes to the oscillating production process at theÿrst transition point.Furthermore,the second transition occurs at T c;2=2:0.At the second transition point,the oscillation width increases discontinuously and abruptly.The transition points agree with those in Fig.8(a).The curve re ected graph(c)at horizontal line N=6 is consistent with that re ected graph(a)at horizontal line N=3.This is due to the symmetry at N=4:5in the neutral stability curve of Fig.2.At two minimum points of the neutral stability curve,the dynamical behavior of the double series is consistent with one another.The stable uniform distribution appears below the neutral stability curve in Fig.2.Thus,weÿnd that theÿrst dynamical transition point is determined by the linear stability theory.However,the second transition point cannot be estimated by the linear stability theory.Also,we are not able to determine the oscillation width analytically,254T.Nagatani/Physica A334(2004)243–254but can calculate the nonlinear dynamical behavior numerically.The production system of multiple series exhibits more complex behavior than that of the single series.It has richer physical context.5.SummaryWe have investigated the dynamical behavior of products in the production process of multiple series analytically and numerically.We have presented the extended dynamical model to take into account the production network composed of M parallel and u series machines.We have clariÿed the e ect of multiple lines on the dynamical characteristics of the production process.We have shown that the dynamical transition occurs between the stable and oscillating production states.We have found that the production process in the multiple series of machines becomes more unstable than that in the single series. We have presented the neutral stability criterion by using the linear stability analysis. We have shown that the neutral stability curve agrees with the dynamical transition line.AcknowledgementsWe would like to thank Professor Dirk Helbing for useful discussions. References[1]T.Nagatani,Rep.Prog.Phys.65(2002)1331.[2]D.Helbing,Rev.Mod.Phys.73(2001)1067.[3]D.Chowdhury,L.Santen,A.Schadschneider,Phys.Rep.329(2000)199.[4]B.S.Kerner,Netw.Spatial Econ.1(2001)35.[5]L.A.Safonov,E.Tomer,V.V.Strygin,Y.Ashhkenazy,S.Havlin,Chaos12(2002)1006.[6]D.Helbing,New J.Phys.5(2003)901.[7]C.Daganzo,A Theory of Supply Chains,Springer,New York,2002.[8]J.D.Sterman,Business Dynamics,McGraw-Hill,Boston,2000.[9]J.A.Buzacott,J.G.Shanthikumar,Stochastic Models of Manufacturing Systems,Prentice-Hall,Englewood Cli s,NJ,1993.[10]D.Helbing,preprint,/abs/cond-mat/0301204,2003.[11]T.Nagatani,D.Helbing,preprint,/abs/cond-mat/0304476,2003.。