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机电工程专业英语 1 The rotor (rotating member) in an electric motor has rotational inertia, and a torque is required to bring it up to speed when the motor is started. If the motor shaft is rigidly connected to a load with a large rotational inertia, and the motor is started suddenly by closing a switch, the motor may not have sufficient torque capacity to bring the motor shaft up to speed before the windings in the motor are burned out by the excessive current demands . A clutch between the motor and the load shafts will restrict the starting torque on the motor to that required to accelerate the rotor and parts of the clutch only. 电机的转子(转动元件之一)是有惯性的。当电机启动时， 需要一个力矩使转子提升速度。如果电机轴与负荷是刚性连 接，就会有更大的惯性。这样启动，电机在还没有足够的力 1 矩使转子提升到一定速度，可能就被过电流烧毁了线圈。在 电机和负荷之间的离合器，会限制启动转矩来保证有足够的 力矩只加速转子和离合器。有些机床，可以非常方便的在电 机连续运转时，通过操作离合器来启动或停止机器的。 2 To keep the parts separated, it is necessary that the pressure within the lubrication film balance the load on the sliding surfaces. If the lubricating film’s pressure is supplied by an external source, the system is said to be lubricated hydro-statically. If the pressure between the surfaces is generated as a result of the shape and motion of the surfaces themselves, however, the system is hydro-dynamically lubricated. This second type of lubrication depends upon the viscous properties of the lubricant. 为了把零件隔离开，润滑膜中的压力必须和作用在滑动面上 的负载(荷)保持平衡。如果润滑膜的压力是由外部来源提 供，该系统被认为是流体静压润滑。如果润滑表面之间的压 力是由于滑动面本身的形状和运动所共同产生的，这种系统 就称为流体动压润滑。第二种润滑与润滑剂的粘性密切相 2 关。 3 The material must resist deformation and fracture. Hardness must be balanced against elasticity. The frame must withstand impact, yet yield under load without cracking or permanently deforming. The frame material must eliminate or block vibration transmission to reduce oscillations that degrade accuracy and tool life. It must withstand the hostile shop-floor environment, including the newer coolants and lubricants. Material expansion must be understood (in order) to minimize forces needed to move slides. The material must not build up too much heat, must retain its shape for its lifetime, and must be dense enough to distribute forces throughout the machine. 材料必须能够抵抗变形和断裂。硬度必须与其弹性相平衡。 机身必须能承受冲击且在载荷作用下不能裂缝和永久性变 形。机身材料具有消除或阻止振动传递的性能。以减轻降低 精度和刀具寿命的振荡。它必须面对不利的车间环境，包括 冷却液和润滑剂。材料的膨胀不能妨碍滑动部件的运动。在 3 正常工作期间材料不能产 生太多的热量，应能保护其形状，且具有足够大的密度以支 承机床的其它部件。 4 A threaded fastener is a device that can effectively exert and maintain a large force in one direction (axially) through the application of a small force in another direction (tangentially). All are based on the single threaded screw, a simple machine that yields a large mechanical advantage in minimal space and theoretically is self locking. Effective use however, requires the aid of two other simple machines: the lever and the wheel-and-axel machine. The wrench is basically a lever, the screwdriver is a wheel-and-axle machine. 螺纹紧固件是一种装置，可以有效地发挥和保持一个方向的 大的力(轴向)通过在另一个方向上的一个小的力(切向) 的应用。所有这些都是基于单头螺纹螺钉的，它是一个简单 机械，可以在最小的空间内产生很大的机械效益，而且在理 论上是自锁的。然而使用时需要两个简单机械辅助:杠杆和 4 轴机。扳手是一个杠杆，螺丝刀是一个轴机。 5 A group of materials which appears promising for ultra-high temperature bearing operation is high performance ceramics .At temperatures above 1100c these ceramic materials have a higher hardness than normal bearing steels. For the past decade one ceramic material has been developed to the virtual exclusion of all others for high speed, high temperature rolling bearings: hot pressed or hot isostatically pressed silicon nitride (Si3N4).Silicon nitride is desirable because it has good temperature strength and hardness, an advantageous strength relationship and excellent resistance to rolling contact fatigue when there is adequate lubrication. 有希望用于高温轴承的材料是高性能的陶瓷系列。在温度高 于1100?时陶瓷材料比一般轴承钢有更高的硬度。在过去的 十几年里出现了一种代替其他轴承材料的高速高温陶瓷材 料:热压瓷和匀压硅。氮化硅是合乎要求的，因为它具有良 好的高温强度和硬度，理想的强度/重量关系，并且当润滑充 5 分时，它具有优异的滚动接触疲劳强度。 6 Three-dimensional geometric modeling involves wireframe,surface,and solid models. A wireframe model shows a series of nodes connected by lines to form an object. A surface model completely defines a series of areas connected to form the boundary of an object. The solid model is a total definition of an object which includes knowledge of all boundary and internal points. From a solid model, a complete analysis of performance of the object can be performed on the computer with appropriate software. 三维几何建模包括线框，表面，和实体模型。线框模型显示 一系列线连接形成的目标节点。表面模型完全定义了一系列 的连接形成一个对象的边界。实体模型是一个包括边界和内 部点的参数的对象。可以在计算机上应用适当的软件进行实 体模型性能的一个完整分析。 7 Engineering design is a systematic progress by which 6 solutions to the needs of humankind are obtained. The progress is applied to problems (needs) of varying complexity. For example, mechanical engineers will use the design process to find an effective, efficient method to convert reciprocating motion to circular motion for the drive train in an internal combustion engine; electrical engineers will use the process to design electrical generating systems using falling water as the power source; and materials engineers use the process to design ablative materials which enable astronauts to safety reenter the earth's atmosphere. 工程设计是一个系统的过程，通过它可以解决人类需要解决 的问题。这一过程被用于解决许多变化的复杂性的问题。例 如，机械工程师应用这一设计过程去找到一种有效的高效的 方法，把用于动力传送系统的内燃机中的往复运动转化为旋 转 百度搜索“就爱阅读”,专业、生活学习,尽在就爱阅读网 92to.com,您的在线图书馆! 7