毕业设计英文翻译 This process is ideal for cylindrical products such as pipes and tanks. The process is the same as its counterpart in metal casting (Section 11.3.5). Chopped fibers combined with liquid resin are poured into a fast-rotating cylindrical mold. Centrifugal force presses the ingredients against the mold wall, where curing takes place. The resulting inner surfaces are quite smooth. Part shrinkage or use of split molds permits part removal. 此过程是理想的圆筒状的产品，如管道和坦克。其对应的金属铸造（第11.3.5节）的过程是相同的。切碎的纤维结合液态树脂倒入一个快速旋转的圆筒形模具。激振力压力机对模具壁，在固化的成分的地方。产生的内表面相当光滑。剖分式模具零件的收缩或使用允许部分切除。FRP tubes can be fabricated from prepreg sheets by a rolling technique 7l,shown in Figure 15.13. Such tubes are used in bicycle frames and space trusses. In the process,a precut prepreg sheet is wrapped around a cylindrical mandrel several times to obtain a tube wall of multiple sheet thicknesses. The rolled sheets are then encased in a heat-shrinking sleeve and oven cured. As the sleeve contracts, entrapped gases are squeezed out the ends of the tube. When curing is complete, the mandrel is removed to yield a rolled FRP tube. The operation is simple, and tooling cost is low. There are variations in the process, such as usingdifferent wrapping methods or using a steel mold to enclose the rolled prepreg tube for better dimensional control. 由轧制技术7升的FRP管可以由预浸料坯片材制造，图15.13中所示。使用这种管在自行车车架和空间桁架。在这个过程中，预切割的预浸料坯片缠绕在一个圆柱形心轴几次以获得的管多个工作表壁的厚度。然后，热轧板是装在热收缩套筒和烘烤处理。作为套筒合约，截留的气体被挤压的端部管。固化完成时，心轴被除去，得到的轧制的FRP管。 操作很简单，模具成本低。有变化的过程中，如使用不同的包装方法，或使用steel mold，附上更好的热轧预浸料管尺寸控制。Chapter 16 Powder Metallurgy 345 production technology. Considerations that make powder metallurgy an important commercial technology include: PM parts can be mass produced to net shape or near net shape, eliminating or reducing the need for subsequent processing. The PM process itself involves very little waste of material; about 97% of the starting powders are converted to product. This compares favorably with casting processes in which sprues, runners. and risers are wasted material in the production cycle. Owing to the nature of the starting material in PM, parts having a specified level of porosity can be made. This feature lends itself to the production of porous metal parts such as filters and oil-impregnated bearings and gears. Certain metals that are difficult to fabricate by other methods can be shaped by powder metallurgy. Tungsten is an example; tungsten filaments used in incandescent lamp bulbs are made using PM technology.毕业设计论文代做平台 580毕业设计网 是专业代做团队 也有大量毕业设计成品提供参考 www.bysj580.com QQ3449649974 Certain metal alloy combinations and cermets can be for rued by PM that cannot be produced by other methods. PM compares favorably with most casting processes in terms of dimensional control of the product. Tolerances of +0.13 mm (1-0.005 in) are held routinely. PM production methods can be automated for economical production.Powder Metallurgy.This clip contains two segments: powder metal parts production and PM overview.There are limitations and disadvantages associated with PM processing. These include the following: tooling and equipment costs are high, metallic powders are expensive, and there are difficulties with storing and handling metal powders (such as degradation of the metal over time, and fire hazards with particular metals). Also, there are limitations on part geometry because metal powders do not readily flow laterally in the die during pressing, and allowances must be provided for ejection of the part from the die after pressing. In addition, variations in material density throughout the part may be a problem in PM, especially for complex part geometries. Although parts as large as 22 kg (50 lb) can be produced, most PM components are less than 2.2 kg (5 lb). A collection of typical PM parts is shown in Figure 16.1. The largest tonnage of metals for PM are alloys of iron. steel, and aluminum. Other PM metals include copper, nickel, and refractory metals such as molybdenum and tungsten. Metallic carbides such as tungsten carbide are often included within the scope of powdermetallurgy: however. because these materials are ceramics. we defer their consideration until the next chapter. The development of the modern field of powder metallurgy dates back to the 1800s(Historical Note 16.1). The scope of the modern technology includes not only parts production, but also preparation of the starting powders.Success in powder metallurgy depends to a large degree on the characteristics of the starting powders; we discuss this topic in Section 16.1. Later sections describe powder production, pressing, and sintering. There is a close correlation between PM technology and aspects of ceramics processing (Chapter 17) .In ceramics (except glass), the starting material is also powder, so the methods for characterizing the powders are