机械设计英文翻译.doc

Design, Invention, CreativityThese are all familiar terms but may mean different things to different people. These terms can encompass a wide range of activities from styling the newest look in clothing, to creating impressive architecture, to engineering a machine for the manufacture of facial tissues. Engineering design, which we are concerned with here, embodies all three of these activities as well as many others. The word design is derived from the Latin designate, which means “to designate, or mark out.” Webster's gives several definitions, the most applicable being “to outline, plot, or plan, as action or work., to conceive, invent - contrive.” Engineering design has been defined as “. the process of applying the various techniques and scientific principles for the purpose of defining a device, a process or a system in sufficient detail to permit its realization. Design may be simple or enormously complex, easy or difficult, mathematical or nonmathematical; it may involve a trivial problem or one of great importance.” Design is a universal constituent of engineering practice. But the complexity of engineering subjects usually requires that the student be served with a collection of structured, set-piece problems designed to elucidate a particular concept or concepts related to the particular topic. These textbook problems typically take the form of “given A, B, C, and D find E.” Unfortunately, real-life engineering problems are almost never so structured. Real design problems more often take the form of "What we need is a frame to stuff this widget into that hole within the time allocated to the transfer of this other gizmo.” The new engineering graduate will search in vain among his or her textbooks for much guidance to solve such a problem. This unstructured problem statement usually leads to what is commonly called “blank paper syndrome.” Engineers often find themselves staring at a blank sheet of paper pondering how to begin solving such an ill-defined problem.Much of engineering education deals with topics of analysis, which means to decompose, to take apart, to resolve into its constituent parts. This is quite necessary. The engineer must know how to analyze systems of various types, mechanical, electrical, thermal, or fluid. Analysis requires a thorough understanding of both the appropriate mathematical techniques and the fundamental physics of the system's function. But, before any system can be analyzed, it must exist, and a blank sheet of paper provides little substance for analysis. Thus the first step in any engineering design exercise is that of synthesis, which mean putting together.The design engineer, in practice, regardless of discipline, continuously faces the challenge of structuring the unstructured problem. Inevitably, the problem as posed to the engineer is ill-defined and incomplete. Before any attempt can be made to analyze the situation he or she must first carefully define the problem, using an engineering approach, to ensure that any proposed solution will solve the right problem. Many examples exist of excellent engineering solutions which were ultimately rejected because they solved the wrong problem, i.e., a different one than the client really had.Much research has been devoted to the definition of various “design processes” in tended to provide means to structure the unstructured problem and lead to a viable solution. Some of these processes present dozens of steps, others only a few. The one presented in Table 1-1 contains 10 steps and has, in the author's experience, proven successful in over 30 years of practice in engineering design.Table 1-1 A design process1Identification of need2Background research3Goal statement4Performance specifications5Ideation and invention6Analysis.7Selection8Detailed design9Prototyping and testing10ProductionITERATION Before discussing each of these steps in detail it is necessary to point out that this is not a process in which one proceeds from step one through ten in a linear fashion. Rather it is, by its nature, an iterative process in which progress is made haltingly, two steps forward and one step back. It is inherently circular. To iterate means to repeat, to return to a previous state. If, for example, your apparently great idea, upon analysis, turns out to violate the second law of thermodynamics, you can return to the ideation step and get a better idea! Or, if necessary, you can return to an earlier step in the process, perhaps the background research, and learn more about the problem.Mechanical System1) AxleThe structure appearance of the axle depends on the axle erection site and form on the case body mainly, axle part decorate and fix way , receive strength situation and processing technology ,etc. Structure designing requirement of the axle : The part should have accurate , firm job positions on the axle and axle; The part is installed and dismantled, adjusted conveniently on the axle; The axle should have good manufacturing engineering ,etc. . Try one's best to prevent the stress from being centralized2) Worm transmission The sport transmission interlocking among the axles for the implementation space, generally interlock in the angle. Characteristic its structure compactness, than heavy, transmission steady, apt lock since transmission. The shortcoming rubs and is worn and torn largely, the caloric value is big, is low, suitable for the transmission of the power of centre. 3) Rolling bearingBecause rolling bearing is the rolling friction, it is small to rub obstruction, the caloric value is small , with high efficiency, start sensitively, safeguard it conveniently, and already standardization, easy to select for use and change, it is very extensive so use. The invalid form of the rolling bearing and calculation criterion: Main invalid form: (1) Lose a bit more tiredly -Installation lubricates and safeguards the normal invalid form under the good situation -Basis of calculating in main invalid form and life-span of bearing (2)Plasticity is out of shape -The rotational speed is very low and doing the main invalid form when the intermittence is swung -Cause the vibration , noise , rub the moment to increase, operate the precision to reduce (3) Wearing and tearing -Under lubricating badly and sealing the situation not tight, or the main invalid form of bearing working under many dust condition. Wear and tear the consequence: The bearing swims in the crack and strengthens, the precision of movement is reduced, vibration and noise increase. Calculate criterion : The general bearing carry on fatigue life and calculate (to clicking losing ); The quiet intensity is checked. Low-speed bearing: Only go on (quiet intensity is checked) . High-speed bearing: Calculate fatigue life ; Rotational speed of check-up limit.