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16.03.2020 00:28

Английский язык

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Metal Adhesives Properties and advantages .
Although metal adhesives have only existed for some years, they have already justified their existence by the contribution which they have made to the more outstanding products of the aircraft industry. Other industries are now utilizing the advantages conferred by using adhesives, notably the electrical industry, which for the first time is able to join together similar or dissimilar materials with a high-strength adhesive which is also an insulating film. The conventional methods for joining metals are bolting, riveting, soldering, and welding, all of which are well-tried processes with which every engineer is familiar. There are, however, many applications, where none of these really meet the demands of the situation and in such cases adhesives with their rather different properties may be more suitable. The properties and advantages of adhesives usage may be summarized as follows: 1) Simplification of design. 2) Possible reduction of production time and consequently production cost. 3) Ability to join together dissimilar materials. 4) Increased strength over comparable riveted or sport - welded joints. 5) The ability to join together high-strength aluminium alloys without lowering the physical properties of the alloy. 6) Absence of distortion in a bonded structure, due to the avoidance of local heating and the lower temperatures used when compared with welding or brazing. 7) Even stress distribution over the whole of the bonded area and consequent avoidance of areas of high stress concentration, such as occur around rivet holes, spot welds or bolt holes. 8) Increased fatigue strength. 9) Adhesives do not cause corrosion. In spite of these advantages, however, there are certain limitations controlling the use of adhesives, and one of these is the thickness of the parts being bonded. It is not the case that adhesives cannot be used for joining together materials greater than a certain thickness but rather that as the thickness of the material increases, so that advantages become fewer. It is therefore with sheet and strip materials that the greatest field for the application of adhesives is found.

Exercise 1.
Specify a question to which you will not find the answer in the text.
a) What conventional methods for joining metals are given in the text? b) How is soldering done? c) What properties and advantages of adhesive usage are summarized in the text? d) Who suggested first to use metal adhesives? e) What does the quality of metal adhesives depend on? f) What types of adhesives do you know?

Eexrcise 2.
1. Where we can use adhesives?
2. What are the main properties of adhesives?
3. What are the conventional methods for joining metals?
4. What are the limitations controlling the use of adhesives?
5. What is the greatest field for the application of adhesives ?