【正文】 give a much smoother tooth action than straight bevel gears, and hence are useful where high speed are It is frequently desirable, as in the case of automotive differential applications, to have gearing similar to bevel gears but with the shaft gears are called hypoid gears because their pitch surfaces are hyperboloids of tooth action between such gears is a bination of rolling and sliding along a straight line and has much in mon with that of worm shaft is a rotating or stationary member, usually of circular cross section, having mounted upon it such elementsas gears, pulleys, flywheels, cranks, sprockets, and other powertransmission may be subjected to bending, tension, pression, or torsional loads, acting singly or in bination with one they are bined, one may expect to find both static and fatigue strength to be important design considerations, since asingle shaft may be subjected to static stresses, pletely reversed, and repeated stresses, all acting at the same word “shaft” covers numerous variations, such as axles and is a shaft, wither stationary or rotating, nor subjected to torsion shirt rotating shaft is often called a either the lateral or the torsional deflection of a shaft must be held to close limits, the shaft must be sized on the basis of deflection before analyzing the reason for this is that, if the shaft is made stiff enough so that the deflection is not too large, it is probable that the resulting stresses will be by no means should the designer assume that they are safe。it is almost always necessary to calculate them so that he knows they are within acceptable possible, the powertransmission elements, such as gears or pullets, should be located close to the supporting bearings, This reduces the bending moment, and hence the deflection and bending the von MisesHenckyGoodman method is difficult to use in design of shaft, it probably es closest to predicting actual it is a good way of checking a shaft that has already been designed or of discoveringwhy a particular shaft has failed in , there are a considerable number of shaftdesign problems in which the dimension are pretty well limited by other considerations, such as rigidity, and it is only necessary for the designer to discover something about the fillet sizes, heattreatment, and surface finish and whether or not shot peening is necessary in order to achieve the required life and of the similarity of their functions, clutches and brakes are treated a simplified dynamic representation of a friction clutch, or brake, two inertias I1 and I2 traveling at the respective angular velocities W1 and W2, one of which may be zero in the case of brake, are to be brought to the same speed by engaging the clutch or occurs because the two elements are running at different speeds and energy is dissipated during actuation, resulting in a temperature analyzing the performance of these devices we shall be interested in the actuating force, the torque transmitted, the energy loss and the temperature torque transmitted is related to the actuating force, the coefficient of friction, and the geometry of the clutch or is problem in static, which will have to be studied separately for eath geometric , temperature rise is related to energy loss and can be studied without regard to the type of brake or clutch because the geometry of interest is the heatdissipating various types of clutches and brakes may be classified as fllows: type with internally expanding shoes type with externally contracting shoes type or axial type type type The analysis of all type of friction clutches and brakes use the same general following step are necessary: or determine the distribution of pressure on the frictional a relation between the maximum pressure and the pressure at any point the condition of statical equilibrium to find(a)the actuating force,(b)the torque, and(c)the support clutches include several types, such as thepositivecontact clutches, overloadrelease clutches, overrunning clutches, magnetic fluid clutches, and positivecontact clutch consists of a shift lever and two greatest differences between the various types of positive clutches are concerned with the design of the provide a longer period of time for shift action during engagement, the jaws may be ratchetshaped, or a great many teeth or jaws are used, and they may be cut either circumferentially, so that they engage by cylindrical mating, or on the faces ofthe mating positive clutches are not used to the extent of the frictionalcontact type, they do have important applications wheresynchronous operation is such as linear drives or motoroperated screw drivers must run to definite limit and then e to a overloadrelease type of clutch is required for these clutches are usually springloaded so as to release at a predetermined clicking sound which is heard when the overload point is reached is considered to be a desirable overrunning clutch or coupling permits the driven member of a machine to “freewheel” or “overrun” because the driver is stopped or because another source of power increase the speed of the type of clutch usually uses rollers or balls mounted between an outer sleeve and an inner member having flats machined around the action is obtained by wedging the rollers between the sleeve and the clutch istherefore equivalent to a pawl and ratchet with an infinite number of fluid clutch or brake is a relatively new development which has two parallel magnetic these plates is a lubricated magnetic powder electromagnetic coil is inserted somewhere in the magnetic varying the excitation to this coil, the shearing strength of the magnetic fluid mixture may be accurately any condition from a full slip to a frozen lockup may be 第五篇：畢業(yè)論文外文翻譯外文翻譯：安全評估和風險管理方法建設張軍，張明元，袁勇波，周靜（中國土木與水利工程大學，大連理工，大連116085）摘要： 改進后的LEC法是用于處理與期貨大廈項目的安全評估的。經(jīng)修訂的評估項目L的危險方法隱藏的工作條件，存在由實驗結果確定了不同價值體系之間的能源和人工能源，表明該方法的科學性和實用性，并能提高安全成本的經(jīng)濟效率。關鍵詞：建設危害，安全評價，安全管