外文翻譯--材料選擇與熱處理-展示頁
2024-11-15 02:07本頁面
【正文】 lativity, appearance, serviceability, and so on. Although it is expected that such testing might show that some changes may have to be made in materials before the product is advanced to the production design stage, this should not be taken as an excuse for not doing a though job of ma terial selections . Appearance, cost and reliability faction should be considered in detail, together with the functional factors. There is much merit to the practice of one very successful pany which requires that all prototypes be built with the same materials that will be used in production and, insofar as possible, with 2 the same manufacturing techniques. It is of little value to have a perfectly functioning prototype that cannot be manufactured economically in the expected sales volume, or one that is substantially different from what the production units will be in regard to quality and reliability. Also, it is much better for design engineers to do a plete job of material analysis, selection, and specification at the development stage of design rather than to leave it to the productiondesign stage, where changes may be made by other, possibly less knowledgeable about all of the functional aspects of the product. At the productiondesign stage, the primary corner relative to materials should be that they are specified fully, that they are patible with, and can be processed economically by, existing equipment, and that they are readily available in the needed quantities. As manufacturing progresses, it is inevitable that situations will arise that may require modifications of the materials being used. Experience may reveal that substitution of cheaper materials can be made. In most cases, however, changes are much more costly to make after ma nufacturing is in progress than before it starts. Good selection during the productiondesign phase will eliminate the necessity for most of this type of change. The more mon type of change the occurs after manufacturing starts is the result of the availability of new materials. These, of course, present possibilities for cost reduction and improved performance. However, new materials must be evaluated very carefully to make sure that all their characteristics are well established. One should always remember that it is indeed rare that as much is known about the properties and reliability of a new material as about those of an existing one. A large proportion of product failure and productliability cases have resulted from new materials being substituted before their longterm properties were really known. Product liability actions have made it imperative that designers and panies employ the very best procedures in selecting materials. The five most mon faults in material selection have been: (a) failure to know and use the latest and best information available about the materials utilized。 1 Material Selection and Heat Treatment of Metal During recent years the selection of engineering materials has assumed great importance. Moreover, the process should be one of may be a decreasing availability of them. Concerns regarding environmental pollution, recycling and worker health and safety often impose new constraints. The desire for might reduction or energy savings foreign pellation, increased serviceability requirements, and customer liability actions, oft
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