G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

JOKES, LAUGHS, SMILES

Prof.: “Wake up that fellow next to you.”

Stud.: “You do it professor, you put him to sleep.”

UNIT XI
Invention breeds invention

Emerson, Ralph, Waldo

ULTRASONIC

Ultra-sonic is believed to have given modern industry one of the most versatile and most powerful tools invented by man. It throws molecules of matter against each other to shake, break, weld, boil, cut, grind and clean. It is known to detect minute flaws or measure the thickness of an ultra-thin sheet of steel with the greatest accuracy. It combines solids and liquids nature has never intended as mixtures, controls television sets, etc. all this being achieved with but one tool, ultra-sonic waves.

Only a few applications of ultrasonic have been touched upon, the future is sure to bring many others.

What are ultra-sonic waves? They are waves like sound waves, but they are beyond the range of sound , beyond the normal range of human hearing. Any sound-like wave above 20.000 cycles is known as ultrasonic including vibrations up to a frequency of 25.000,000,000 cycles per second in solid materials and liquids.

Experiments with ultrasonic have been carried out for a long time. The versatile and fantastic genius of man invented one of the first useful tools for ultra-sonic experiments, a whistle producing sound waves beyond human hearing that a dog could distinguish. Of course, nature has preceded us as usual and provided bats with ultra-sonic “radar” system so accurate that they can fly in the dark between thin wires only a few inches apart without ever touching them.

How is this tool to be used in industry? Let us first look into why it is such a powerful tool. The molecules of even the hardest steels are separated by enormous distances compared to the size of the molecules. And in this space the molecules are in constant motion. Heating a substance increases this motion and the hotter it becomes, the more rapidly the molecules move. If we succeeded in somehow pushing some of these molecules around, they would in turn push on other molecules, and it is this push that allows a sound wave to travel through a substance. The distance between molecules being shorter for solids than for air, the chance of the molecules colliding with each other is much greater. This explains why sound travels faster through solids than liquids and faster through liquids than through gases. The wild shaking of molecules which arise in passing an ultrasonic wave through a body can be used in a great many ways for cold welding, cleaning, grinding, cutting, etc. to be carried out.

What are the advantages of ultrasonic over other methods? In cleaning the answer is obvious. Only very thorough and repeated mechanical cleaning plus special solvents could do a good job. Flaw detection by ultrasonic allows an accuracy to be reached unheard of by other methods except X-rays, and is much safer and much more economical to use. In machining ultrasonic can do things that can not be done in any other way. It can handle materials no other machining methods can touch. For example, ultrasonic equipment can machine glass, ceramics and hard materials. It can drill holes through materials which will withstand any other attempts at penetration. In medicine ultrasonic waves can reach inaccessible places and be focused on tiny spots in the brain or other parts of the human body to perform operations.