Famous people of science

Dmitry Ivanovich Mendeleyev

Dmitry Ivanovich Mendeleyev is a famous Russian chemist. He is best known for his development of the periodic table of the properties of the chemical elements. This table displays that elements' properties are changed periodically when they are arranged according to atomic weight.

Mendeleyev was born in 1834 in Tobolsk, Siberia. He studied chemistry at the University of St. Petersburg, and in 1859 he was sent to study at the University of Heidelberg. Mendeleyev returned to St. Petersburg and became Professor of Chemistry at the Technical Insti­tute in 1863. He became Professor of General Chemistry at the University of St. Petersburg in 1866. Mendeleyev was a well-known teacher, and, because there was no good textbook in chemistry at that time, he wrote the two-vol­ume «Principles of Chemistry» which became a classic textbook in chemistry.

In this book Mendeleyev tried to classify the elements according to their chemical properties. In 1869 he pub­lished his first version of his periodic table of elements. In 1871 he published an improved version of the peri­odic table, in which he left gaps for elements that were not known at that time. His table and theories were proved later when three predicted elements: gallium, germanium, and scandium were discovered.

Mendeleyev investigated the chemical theory of solu­tion. He found that the best proportion of alcohol and water in vodka is 40%. He also investigated the thermal expansion of liquids and the nature of petroleum.

In 1893 he became director of the Bureau of Weights and Measures in St. Petersburg and held this position until his death in 1907.

Unit 2

Metalworking

I. Text A: Metalworking processes: Rolling. Extrusion,

Text B: Drawing. Forging. Sheet metal forming,

Text C: Metalworking and Metal Properties.

II. Famous scientists. Mikhail Vasilyevich Lomonosov.

Text a: «metalworking processes»

Metals are important in industry because they can be easily deformed into useful shapes. A lot of metalworking processes have been developed for certain applica­tions. They can be divided into five broad groups:

1. rolling,

2. extrusion,

3. drawing,

4. forging,

5. sheet-metal forming.

During the first four processes metal is subjected to large amounts of strain (deformation). But if deformation goes at a high temperature, the metal will recrystallize — that is, new strain-free grains will grow instead of deformed grains. For this reason metals are usually rolled, ex­truded, drawn, or forged above their recrystallization temperature. This is called hot working. Under these conditions there is no limit to the compressive plastic strain to which the metal can be subjected.

Other processes are performed below the recrystalli­zation temperature. These are called cold working. Cold working hardens metal and makes the part stronger. However, there is a limit to the strain before a cold part cracks.

Rolling

Rolling is the most common metalworking process. More than 90 percent of the aluminum, steel and copper produced is rolled at least once in the course of produc­tion. The most common rolled product is sheet. Rolling can be done either hot or cold. If the rolling is finished cold, the surface will be smoother and the product stronger.

Extrusion

Extrusion is pushing the billet to flow through the orifice of a die. Products may have either a simple or a complex cross section. Aluminum window frames are the examples of complex extrusions.

Tubes or other hollow parts can also be extruded. The initial piece is a thick-walled tube, and the extruded part is shaped between a die on the outside of the tube and a mandrel held on the inside.

In impact extrusion (also called back-extrusion) (штамповка выдавливанием), the workpiece is placed in the bottom of a hole and a loosely fitting ram is pushed against it. The ram forces the metal to flow back around it, with the gap between the ram and the die determin­ing the wall thickness. The example of this process is the manufacturing of aluminum beer cans.

Vocabulary:

useful — полезный

shape — форма, формировать

rolling — прокатка

extrusion — экструзия, выдавливание

drawing — волочение

forging — ковка

sheet — лист

to subject — подвергать

amount — количество

condition — состояние, условие

perform — выполнять, проводить

to harden — делаться твердым, упрочняться

at least — по крайней мере

common — общий

billet — заготовка, болванка

orifice — отверстие

die — штамп, пуансон, матрица, фильера, во­лочильная доска

cross section — поперечное сечение

window frame — рама окна

tube — труба

hollow — полый

initial — первоначальный, начальный

thick-walled — толстостенный

mandrel — оправка, сердечник

impact — удар

loosely — свободно, с зазором

fitting — зд. посадка

ram — пуансон, плунжер

force — сила

gap — промежуток, зазор

to determine — устанавливать, опреде­лять