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1、2023年机械专业英文翻译 Design of machine and machine elements Machine design Machine design is the art of planning or devising new or improved machines to accomplish specific purposes.In general, a machine will consist of a combination of several different mechanical elements properly designed and arranged t
2、o work together, as a whole.During the initial planning of a machine, fundamental decisions must be made concerning loading, type of kinematic elements to be used, and correct utilization of the properties of engineering materials.Economic considerations are usually of prime importance when the desi
3、gn of new machinery is undertaken.In general, the lowest over-all costs are designed.Consideration should be given not only to the cost of design, manufacture the neceary safety features and be of pleasing external appearance. The objective is to produce a machine which is not only sufficiently rugg
4、ed to function properly for a reasonable life, but is at the same time cheap enough to be economically feasible. The engineer in charge of the design of a machine should not only have adequate technical training, but must be a man of sound judgment and wide experience, qualities which are usually ac
5、quired only after considerable time has been spent in actual profeional work.Design of machine elements The principles of design are, of course, universal.The same theory or equations may be applied to a very small part, as in an instrument, or, to a larger but similar part used in a piece of heavy
6、equipment.In no ease, however, should mathematical calculations be looked upon as absolute and final.They are all subject to the accuracy of the various aumptions, which must necearily be made in engineering work.Sometimes only a portion of the total number of parts in a machine are designed on the
7、basis of analytic calculations.The form and size of the remaining parts are designed on the basis of analytic calculations.On the other hand, if the machine is very expensive, or if weight is a factor, as in airplanes, design computations may then be made for almost all the parts. The purpose of the
8、 design calculations is, of course, to attempt to predict the stre or deformation in the part in order that it may sagely carry the loads, which will be imposed on it, and that it may last for the expected life of the machine.All calculations are, of course, dependent on the physical properties of t
9、he construction materials as determined by laboratory tests.A rational method of design attempts to take the results of relatively simple and fundamental tests such as tension, compreion, torsion, and fatigue and apply them to all the complicated and involved situations encountered in present-day ma
10、chinery. In addition, it has been amply proved that such details as surface condition, fillets, notches, manufacturing tolerances, and heat treatment have a market effect on the strength and useful life of a machine part.The design and drafting departments must specify completely all such particular
11、s, must specify completely all such particulars, and thus exercise the neceary close control over the finished product. As mentioned above, machine design is a vast field of engineering technology.As such, it begins with the conception of an idea and follows through the various phases of design anal
12、ysis, manufacturing, marketing and consumerism.The following is a list of the major areas of consideration in the general field of machine design: Initial design conception; Strength analysis; Materials selection; Appearance; Manufacturing; Safety; Environment effects; Reliability and life; Strength
13、 is a measure of the ability to resist, without fails, forces which cause strees and strains.The forces may be; Gradually applied; Suddenly applied; 2 Applied under impact; Applied with continuous direction reversals; Applied at low or elevated temperatures. If a critical part of a machine fails, th
14、e whole machine must be shut down until a repair is made.Thus, when designing a new machine, it is extremely important that critical parts be made strong enough to prevent failure.The designer should determine as precisely as poible the nature, magnitude, direction and point of application of all fo
15、rces.Machine design is mot, however, an exact science and it is, therefore, rarely poible to determine exactly all the applied forces.In addition, different samples of a specified material will exhibit somewhat different abilities to resist loads, temperatures and other environment conditions.In spi
16、te of this, design calculations based on appropriate aumptions are invaluable in the proper design of machine. Moreover, it is absolutely eential that a design engineer knows how and why parts fail so that reliable machines which require minimum maintenance can be designed.Sometimes, a failure can be serious, such as when a tire blows out on an automobile traveling at high speeds.On the oth
