外文翻译----机械设计理论-机械设计(编辑修改稿)

外文翻译----机械设计理论-机械设计(编辑修改稿)内容摘要：

duct the first step of work all is designs. Designs usually may divide into several explicit stages: (a) preliminary design。 (b) functional design。 (c) production design. In the preliminary design stage, the designer emphatically considered the product should have function. Usually must conceive and consider several plans, then decided this kind of thought is whether feasible。 If is feasible, then should makes the further improvement to or several plans. In this stage, the question which only must consider about the choice of material is: Whether has the performance to conform to the request material to be possible to supply the choice。 If no, whether has a bigger assurance all permits in the cost and the time in the limit develops one kind of new material. In the functional design and the engineering design stage, needs to make a practical feasible design. Must draw up the quite plete blueprint in this stage, chooses and determines each kind of ponents the material. Usually must make the prototype or the working model, and carries on the experiment to it, the appraisal product function, the reliability, the outward appearance and the service maintenance and so on. Although this kind of experiment possibly can indicate, enters in the product to the production base in front of, should replace certain materials, but, absolutely cannot this point take not earnestly chooses the material the excuse. Should unify the product the function, earnestly carefully considers the product the outward appearance, the cost and the reliability. Has the achievement very much the pany when manufacture all prototypes, selects the material should the material which uses with its production in be same, and uses the similar manufacture technology as far as possible. Like this has the advantage very much to the pany. The function plete prototype if cannot act according to the anticipated sales volume economically to make, or is prototypical and the official production installment has in the quality and the reliable aspect is very greatly different, then this kind of prototype does not have the great value. Project engineer is best can pletely plete the material in this stage the analysis, the choice and the determination work, but is not remains it to the production design stage does. Because, is carries on in the production design stage material replacement by other people, these people are inferior to project engineer to the product all functions understanding. In the production design stage, is should pletely determine with the material related main question the material, causes them to adapt with the existing equipment, can use the existing equipment economically to carry on the processing, moreover the material quantity can quite be easy to guarantee the supply. In the manufacture process, inevitably can appear to uses the material to make some changes the situation. The experience indicated that, may use certain cheap materials to take the substitute. However, in the majority situation, in。