完整版毕业设计机械外文翻译.docx

1、完整版毕业设计机械外文翻译附录1：外文原文The machinability of materialThe 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

2、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 diff

3、icult 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 ava

4、ilable in the example below.1. Machinability Of SteelsBecause steels are among the most important engineering materials , their machinability studied extensively. The machinability of steels mainly improved by adding lead and sulfur to obtain so-called free-machining steels.Resulfurized and Rephosph

5、orized 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 in

6、clusions 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 better chip formation and surface finish. Note that soft steels can be difficult to machine, wi

7、th built-up edge formation and poor surface finish. The second effect is that increased of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes th

8、e form of dispersed fine particles. Lead is insoluble in iron, copper, and aluminum and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant and is smeared over the tool-chip interface during cutting. This behavior verified by the presence of the tool-side face

9、of chips when machining leaded steels.When the temperature is sufficiently 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, suc

10、h as 10xx, 11xx, 12xx, 41xx, etc. Leaded steels are identified by the letter L between the second and third numerals (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

11、well-known toxin and a pollutant, there are serious 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 steels). Bismuth a

12、nd tin are now being investigated as possible substitutes for lead in steels.Calcium-Deoxidized Steels. An important development is calcium-deoxidized steels, in which oxide flakes of calcium silicates (CaSo) are formed. These flakes, in turn, reduce the strength of the secondary shear zone, decreas

13、ing tool-chip interface and wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at be s problem, necessitating machine tools with -resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and

14、 silicon in steels is always to form aluminum oxide and silicates, which are steels.Carbon and manganese the machinability of steels, depending on their composition. Plain low-carbon steels (less than 0.15% C) can produce poor surface finish by forming a built-up edge. Cast steels are more abrasive,

15、 although their machinability is similar to that of wrought steels. Tool and die steels are very difficult to machine and usually require annealing prior to machining. Machinability of most steels is improved by cold working, which .Other alloying elements, such as nickel, chromium, molybdenum, and

16、vanadium, which improve the properties of steels, generally reduce machinability. The effect of boron is negligible. Gaseous elements such as and nitrogen can the properties of steel. Oxygen shown to the aspect ratio of the manganese sulfide inclusions; the content, the lower the aspect ratio and th

17、e selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strength of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels (liquid-metal embrittlement, mechani

18、cal properties.Sulfur can severely reduce the 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 (anisotropy). Rephosphorized s

19、teels are significantly less ductile, and are produced solely to improve machinability.2. Machinability of Various Other Metals Aluminum is generally very easy to machine, although the softer grades tend to form a built-up edge, resulting in poor surface finish. High cutting speeds, content and cast

20、 aluminum alloys may be abrasive; they require machining aluminum, since it and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, though, it requires machining in a controlled environment.Cast gray irons are generally machinable but are. Free

21、 carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating tools with -resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge formation, although cast copper alloys are easy to machine. Brasses ar

22、e easy to machine, especially with the addition pf lead (leaded free-machining brass). Bronzes are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolonged tool life. However care should be exercised because of its and the danger of fire (the ele

23、ment is pyrophoric).Molybdenum is ductile and work- produce poor surface finish. Sharp tools are necessary.Nickel-based alloys are work- be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low, although it greatly improves at elevated temperatures.Zirconiu

24、m and fire.3. Machinability of Various MaterialsGraphite is abrasive; it requires -resistant, sharp tools.Thermoplastics generally usually be achieved with a jet of air, vapor mist, or water-soluble oils. Residual stresses may develop during machining. To relieve these stresses, machined parts can b

25、e annealed 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 fiber

26、s present, reinforced plastics are very abrasive and are difficult to machine. Fiber tearing, pulling, and edge delamination are significant problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires careful removal

27、of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics of appropriate processing parameters, such as ductile-regime cutting .Metal-matrix and ceramic-matrix composites can be difficult to machine, depending on the properties of the individual components, i

28、.e., reinforcing or whiskers, as well as the matrix material.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 machining ( coil, beam), or plasma arcis forces, (b) increased t

29、ool life, (c) use of inexpensive cutting-tool materials, (d) and chatter.It may be difficult to a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of the turning of progress

30、 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 not only on their intrinsic properties and microstructure, but also on proper selection and

31、control of process variables.附录2：外文中文翻译 材料的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。（2）、刀具的寿命。（3）、切削力和功率的需求。（4）、切屑控制。以这种方式，好的可机加工性指的是好的表面光洁性和完整性，长的刀具寿命，低的切削力和功率需求。关于切屑控制，细长的卷曲切屑，如果没有被切割成小片，以在切屑区变的混乱，缠在一起的方式能够严重的介入剪切工序。因为剪切工序的复杂属性，所以很难建立定量地释义材料的可机加工性的关系。在制造厂里，刀具寿命和表面粗糙度通常被认为是可机加工性中最重要的因素。尽管已不再大量

32、的被使用，近乎准确的机加工率在以下的例子中能够被看到。1.钢的可机加工性因为钢是最重要的工程材料之一，所以他们的可机加工性已经被广泛地研究过。通过宗教铅和硫磺，钢的可机加工性已经大大地提高了。从而得到了所谓的易切削钢。二次硫化钢和二次磷化钢 硫在钢中形成硫化锰夹杂物（第二相粒子），这些夹杂物在第一剪切区引起应力。其结果是使切屑容易断开而变小，从而改善了可加工性。这些夹杂物的大小、形状、分布和集中程度显著的影响可加工性。化学元素如碲和硒，其化学性质与硫类似，在二次硫化钢中起夹杂物改性作用。钢中的磷有两个主要的影响。它加强铁素体，增加硬度。越硬的钢，形成更好的切屑形成和表面光洁性。需要注意的是软钢不适合用于有积屑瘤形成和很差的表面光洁性的机器。第二个影响是增加的硬度引起短切屑而不是不断的细长的切屑的形成，因此提高可加工性。含铅的钢 钢中高含量的铅在硫化锰夹杂物尖端析出。在非二次硫化钢中，铅呈细小而分散的颗粒。铅在铁、铜、铝和它们的合金中是不能溶解的。因为它的低抗剪强度。因此，铅充当固体润滑剂并且在切削时，被涂在刀具和切屑的接口处。这一特性已经被在机加工铅钢时，在切屑的刀具面表面有高浓度的铅的存在所证实。当温度足够高时例如，在高的切削速度和进刀速度下铅在刀具前直接熔化，并且充当液体润滑剂。除了这个作用，铅降低第一剪切区中的剪应力，减小切削力和