时间：2011-03-11 23:11来源：蓝天飞行翻译 作者：admin 点击：次
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below minimums (air traffic control). Weather conditions below the minimums prescribed by regulations for the particular action involved. These are conditions such as landing minimums, takeoff minimums. belt frame (aircraft structural component). A frame that goes around the inside of the fuselage of an aircraft. Belt frames are normally made in the form of a channel or hat section. bench check. A functional test of a piece of equipment in which the equipment is set up on a test bench and operated to find out whether or not it functions as it should. A bench check can tell whether or not a piece of equipment is working satisfactorily by itself, but it tells little about the way it will perform when it is interconnected with other equipment. bench plate. A flat cast-iron plate built into a bench used for working sheet metal. Holes in the bench plate support stakes used to form sheet metal. bend allowance (sheet metal layout). The amount of material actually needed to make a bend in a piece of sheet metal. When a flat layout of a piece of sheet metal is being made, an allowance must be made for the bend. The amount of material in the bend is determined by both the radius of the bend and the number of degrees the metal is bent. The amount of material in the bend is usually found by using a bend allowance chart. bend radius (sheet metal layout). The radius of the inside of a bend in a piece of sheet metal, tubing, or wire bundle. bend tangent line (sheet metal layout). A line made in a sheet metal layout that indicates the point at which the bend is started. The material on one side of the bend tangent line is the flat surface, and the material on the other side is the bend allowance. bending strength. The resistance a piece of material offers to bending stresses. bending stress. The type of stress that tries to pull up or push down on one end of a beam while the other end is held stationary. When a beam is bent down, the top is under a tensile stress, and the bottom is under a compressive stress. benzene. A colorless, volatile, flammable, aromatic hydrocarbon liquid which has the chemical formula C6H6. Benzene, sometimes called benzoil, is used as a solvent, as a cleaning fluid, and as a fuel for some special types of reciprocating engines. berkelium. A synthetic, radioactive chemical element in the actinide series. Berkelium’s properties resemble those of cerium. Berkelium’s symbol is Bk, and its atomic number is 97. Bernoulli’s principle. A fundamental principle of physics that explains the relation between kinetic and potential energy in a fluid in motion. When the total energy in a column of moving fluid remains constant, any increase in the kinetic energy of the fluid (its velocity) results in a corresponding decrease in its potential energy (its pressure). beryllium. A high-melting-point, lightweight, corrosion-resistant, steel-gray metallic chemical element. Beryllium’s symbol is Be, its atomic number is 4, and its atomic weight is 9.0122. Beryllium’s main importance is in its use as an alloying agent for copper. |
