Work in pairs. Listen to your partner reading out some trivia about materials and translate into Russian.

Uranium

· Uranium is a chemical element, its symbol is U and its atomic number is 92.

· Refined uranium is a silvery-white weakly radioactive metal.

· Uranium is hard, malleable, ductile, and a poor electrical conductor. The metal has a very high density, around 70% denser than lead, yet less dense than gold.

· There are three naturally occurring uranium isotopes. Uranium-238 is the most stable of these and makes up over 99%, uranium-235 makes up 0.72% of natural uranium and uranium-234 just 0.005%.

· German chemist Martin Heinrich Klaproth is credited with discovering uranium in 1789. He named the new element after the recently discovered planet Uranus.

· In 1841, Eugène-Melchior Péligot became the first person to isolate uranium and in 1896 Henri Becquerel discovered it had radioactive properties.

· Uranium has a melting point of 2,075 °F (1,135 °C) and a boiling point of 7,468 °F (4,131 °C).

· Uranium has been in use as far back as ancient Rome and during the Middle Ages when its orange-red to lemon-yellow shades were used as coloring agents in ceramic glazes and glass.

· Fissile isotopes of uranium have the ability to cause a nuclear chain reaction making the metal important for generating heat in nuclear power reactors and producing fissile material for nuclear weapons.

· Uranium-235 is the most important uranium isotope for the creation of nuclear reactors and weapons because it is the only naturally occurring isotope that is fissile (meaning it can be split into 2 or 3 fission fragments by thermal neutrons).

· One kilogram of 235U can theoretically produce 20 terajoules of energy, equivalent to the energy produced from 1500 tonnes of coal.

· The first atomic bomb used in World War II, dropped on Hiroshima, Japan, in 1945, contained a uranium core. Today nuclear bombs are usually made from other materials such as plutonium.

· The military uses uranium when making special ammunition. It helps make bullets and larger projectiles hard and dense enough to punch through armor.

· Over 33% of the world's uranium is mined in Kazakhstan. Other uranium mining countries include Canada, Australia, Namibia, Niger, and Russia.

· Marie Curie's discovery of radium in uranium ore meant uranium mining increased so radium could be extracted to make glow-in-the-dark paints. It takes 3 tonnes of uranium to get 1 gram of radium, leaving massive amounts of uranium waste material which was sent for use in the glazing and tiling industry.

Translation

Metal Stamping

Powered presses apply force to sheetmetal through hard tooling, producing a variety of parts. Sheet or sheetmetal blanks can be fed manually or automatically into a press or series of presses to produce the parts. Often, automation such as robots or transfer mechanisms are used to transfer material from press to press or from die to die for various part-forming operations.

Progressive dies, making use of a single die where multiple operations are performed in consecutive stations, allow all main forming processes to take place in a single press. In-die capability for tapping, coining, bending, deep drawing and other processes makes stamping an even more capable process.

Competitive processes: CNC fabrication, bending, casting, waterjet cutting and slideforming.

Parts produced: Stamping produces a multitude of parts and panels for home appliances, home electronics, furniture, fixtures and residential construction. Automotive applications include body panels, structural members, fasteners and metal trim. Other parts typically produced via stamping include computer cases and interior parts, electrical boxes, switches, connectors, control panels, fasteners, machine panels and parts, and material-handling parts as well as a multitude of airplane and space parts and panels.

Benefits: Some parts are produced in rapid fashion, as presses can move at speeds above 2000 strokes/min. At such speeds, high-volume runs are accomplished quickly, with various control and measurement checks built-in to ensure parts meet specifications. Presses run at much lower speeds for deep-drawn parts or parts requiring in-die work or longer forming time. Simple two-dimensional parts are created with ease in the stamping process, while the addition of in-press tooling allows for creation of complex curved and shaped parts. Generally, hard tooling used in stamping provides superior dimensional precision and uniformity throughout a production run, and in successive production runs.

Capacities: Stamping presses provide low, medium and high runs, ranging from a few hundred to millions of parts. Due to tooling costs, stamping is not recommended for one-off parts, short-run prototypes or low-volume one-time production.

Materials: All forms of sheetmetal.

Should I use it? Dedicated hard tooling can be costly to design and build, and requires tool-construction and part-production lead times from a few days to months. The specifier should weigh the minimal tooling cost of fabrication, and short lead times and relatively low production rates, against the higher tooling cost, greater precision, longer lead times and higher operating efficiencies of dedicated tooling. Also, consider part size and dimensional-precision needs. Some parts may be too large for all but the most specialized tooling and press equipment, and some parts may require dimensional precision beyond the capabilities of fabrication processes.

Unit VII

Date: 2016-04-22; view: 1148