机电技术专业英语 教学课件 作者 徐起贺 张庆良pata b lesson Eight.pptVIP

* 机电技术专业英语 Lesson Eight Text Fasteners are devises which permit one part to be joined to1 a second part and, hence, they are involved in almost all designs. The acceptability of any product depends not only on the selected components, but also on the means by which they are fastened together. The principal purposes of fasteners are to provide the following design features. (1) Disassembly for inspection and repair. (2) Modular design where a product consists of a number of subassemblies. Modular design aids manufacturing as well as transportation. There are three main classifications of fasteners, which are described as follows. Fasteners and springs Lesson Eight (1) Removable. This type permits the parts to be readily disconnected without damaging the fasteners. An example is the ordinary nutandbolt fasteners. (2) Semipermanent. For this type, the parts can be disconnected, but some damage usually occurs to the fastener. One such example is a cotter pin. (3) Permanent. When this type of fastener is used, it is intended that the parts will never be disassembled. Examples are riveted and welded joints. The following factors should be taken into account when selecting fasteners for a given application: (1) Primary function. (2) Appearance. (3) A large number of small size fasteners versus a small number of large size fasteners (an example is bolts). Lesson Eight (4) Operating conditions such as vibration, loads and temperature. (5) Frequency of disassembly. (6) Adjustability in the location of parts. (7) Types of materials to be joined. (8) Consequences of failure or loosening of fastener. Lesson Eight New Words and Expressions Lesson Eight Lesson Eight Lesson Eight Notes 1. join to 意为“把两件东西连接到一起”。 2. be proportional to 意为“与…成比例”。 3. automotive suspension system springs and bumper springs 意为：“汽车悬挂系统弹簧和缓冲弹簧”。 4. parking meter 意为“停车计时器”。 5. harddrawn o