時間：2011-03-11 23:11來源：藍天飛行翻譯 作者：admin 點擊：次
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chemical etching (metal processing). A process in which a chemical is used to microscopically roughen the surface of a metal. Chemical etching is used to prepare a metal so primer will form a tight bond to its surface. chemical fire extinguisher. Any of three types of fire extinguishers: vaporizing liquid, carbon dioxide, or dry powder. All three types of fire extinguishers expel the extinguishing agent and blanket the fire with an inert gas to keep oxygen away from it. When a fire can no longer get oxygen, it will go out. chemical milling. A method of machining large sheets of metal by chemically etching away part of the surface. The inside of the skins of some high-performance aircraft are etched to remove metal not needed for strength. Removing this metal by chemical milling reduces the weight of the aircraft. Chemical milling produces a lightweight skin with all the needed strength and rigidity far more economically than can be done with conventional machining or by building up a skin with riveted-on stiffeners. chemical oxygen candle system. An oxygen system used for emergency or backup use. Solid blocks of a material that releases oxygen when burned are carried in special fireproof fixtures. When oxygen is needed, the candles are ignited with a built in igniter, and oxygen flows into the tubing leading to the masks. chemical reaction. A change in the chemical nature (the chemical characteristics) of elements when they unite to form a chemical compound. Hydrogen is a lighter-than-air gas, and oxygen is also a gas. But when two atoms of hydrogen unite with one atom of oxygen, one molecule of water (H2O), a liquid, is formed. The compound water has different chemical characteristics from those of either of the elements oxygen or hydrogen. When hydrogen and oxygen combine to form water, a chemical reaction takes place. chemical salt. A product that forms when an acid combines with a metal. For example, when hydrochloric acid reacts with zinc, zinc chloride, a salt, forms. Most chemical salts are porous and powdery and have no strength. chemistry. The branch of science that deals with the composition, properties, and structure of matter. Chemistry is primarily concerned with the materials of which matter is made, and with the energy absorbed or released during changes in the characteristics of these materials. cherry picker (maintenance equipment). A long, hydraulically operated boom with a man-carrying bucket on its end. A person can be lifted in the bucket of the cherry picker so he can work at a high location. They are used in aircraft maintenance for working on large airplanes. Cherry pickers are usually mounted on a truck so that they can be moved from place to place where they are needed. Cherry rivet. A patented blind rivet manufactured by the Cherry Rivet Division of Townsend, Inc. The shank of the rivet is inserted through a hole in the metals to be joined and is upset by pulling a tapered stem through the hollow shank. After the shank is upset, further pulling on the stem breaks it off. |
