【正文】 Consideration should be given not only to the cost of design, manufacture the necessary safety features and be of pleasing external appearance. The objective is to produce a machine which is not only sufficiently rugged to function properly for a reasonable life, but is at the same time cheap enough to be economically feasible.機器設(shè)計為了特定的目的而發(fā)明或改進機器的一種藝術(shù)。一般來講，機器時有多種不同的合理設(shè)計并有序裝配在一起的部件構(gòu)成的，在最初的機器設(shè)計階段，必須基本明確負載、元件的運動情況、工程材料的合理使用性能。負責新機器的設(shè)計最初的最重要的是經(jīng)濟性考慮。一般來說，選擇總成本最低的設(shè)計方案，不僅要考慮設(shè)計、制造、銷售、安裝的成本。還要考慮服務的費用，機械要保證必要的安全性能和美觀的外形。制造機器的目標不僅要追求保證只用功能的合理壽命，還要保證足夠便宜以同時保證其經(jīng)濟的可行性。 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 acquired only after considerable time has been spent in actual professional work.負責設(shè)計機器的工程師，不僅要經(jīng)過專業(yè)的培訓，而且必須是一個準確判斷而又有豐富經(jīng)驗的人，具有一種有足夠時間從事專門的實際工作的素質(zhì)。Design of machine elements機器零件的設(shè)計 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 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 assumptions, which must necessarily be made in engineering work. Sometimes only a portion of the total number of parts in a machine are designed on the 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 putations may then be made for almost all the parts.相同的理論或方程可應用在一個一起的非常小的零件上，也可用在一個復雜的設(shè)備的大型相似件上，既然如此，毫無疑問，數(shù)學計算是絕對的和最終的。他們都符合不同的設(shè)想，這必須由工程量決定。有時，一臺機器的零件全部計算僅僅是設(shè)計的一部分。零件的結(jié)構(gòu)和尺寸通常根據(jù)實際考慮。另一方面，如果機器和昂貴，或者質(zhì)量很重要，例如飛機，那麼每一個零件都要設(shè)計計算。 The purpose of the design calculations is, of course, to attempt to predict the stress 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 the 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, pression, torsion, and fatigue and apply them to all the plicated and involved situations encountered in presentday machinery. 當然，設(shè)計計算的目的是試圖預測零件的應力和變形，以保證其安全的帶動負載，這是必要的，并且其也許影響到機器的最終壽命。當然，所有的計算依賴于這些結(jié)構(gòu)材料通過試驗測定的物理性能。國際上的設(shè)計方法試圖通過從一些相對簡單的而基本的實驗中得到一些結(jié)果，這些試驗，例如結(jié)構(gòu)復雜的及現(xiàn)代機械設(shè)計到的電壓、轉(zhuǎn)矩和疲勞強度。 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 pletely all such particulars, must specify pletely all such particulars, and thus exercise the necessary close control over the finished product.另外，可以充分證明，一些細節(jié)，如表面粗糙度、圓角、開槽、制造公差和熱處理都對機械零件的強度及使用壽命有影響。設(shè)計和構(gòu)建布局要完全詳細地說明每一個細節(jié)，并且對最終產(chǎn)品進行必要的測試。 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 analysis, manufacturing, marketing and consumerism. The following is a list of the major areas of consideration in the general field of machine design:綜上所述，機械設(shè)計是一個非常寬的工程技術(shù)領(lǐng)域。例如，從設(shè)計理念到設(shè)計分析的每一個階段，制造，市場，銷售。以下是機械設(shè)計的一般領(lǐng)域應考慮的主要方面的清單： ① Initial design conception。 最初的設(shè)計理念 ② Strength analysis。受力分析 ③ Materials selection。材料的選擇 ④ Appearance。 外形 ⑤ Manufacturing。制造 ⑥ Safety。安全性 ⑦ Environment effects。環(huán)境影響 ⑧Reliability and life。 可靠性及壽命 Strength is a measure of the ability to resist, without fails, forces which cause stresses and strains. The forces may be。在沒有破壞的情況下，強度是抵抗引起應力和應變的一種量度。這些力可能是： ① Gradually applied。漸變力 ② Suddenly applied。瞬時力 ③ Applied under impact。沖擊力 ④ Applied with continuous direction reversals。不斷變化的力 ⑤ Applied at low or elevated If a critical part of a machine fails, the 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 possible the nature, magnitude, direction and point of application of all forces. Machine design is mot, however, an exact science and it is, therefore, rarely possible 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 spite of this, design calculations based on appropriate assumptions are invaluable in the proper design of machine.如果一個機器的關(guān)鍵件損壞，整個機器必須關(guān)閉，直到修理好為止。設(shè)計一臺新機器時，關(guān)鍵件具有足夠的抵抗破壞的能力是非常重要的。設(shè)計者應盡可能準確地確定所有的性質(zhì)、大小、方向及作用點。機器設(shè)計不是這樣，但精確的科學是這樣，因此很難準確地確定所有力。另外，一種特殊材料的不同樣本會顯現(xiàn)出不同的性能，像抗負載、溫度和其他外部條件。盡管如此，在機械設(shè)計中給予合理綜合的設(shè)計計算是非常有用的。 Moreover, it is absolutely essential 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 other hand, a failure may be no more than a nuisance. An example is the loosening of the radiator hose in the automobile cooling system. The consequence of this latter failure is usually the loss of some radiator coolant, a condition which is readily detected and corrected. 此外，顯而易見的是一個知道零件是如何和為什麼破壞的設(shè)計師可以設(shè)計出需要很少維修的可靠機器。有時，一次失敗是嚴重的，例如高速行駛的汽車的輪胎爆裂。另一方面，失敗未必是麻煩。例如，汽車的冷卻系統(tǒng)的散熱器皮帶管松開。這種破壞的后果通常是損失一些散熱片，可以探測并改正過來。 The type of load a part absorbs is just as significant as the magnitude. Generally speaking, dynamic loads with direction reversals cause greater difficulties than static l