机械毕业设计英文外文翻译607自卸车举升系统设计浅谈

附录Lifting machine main structure identificationThis topic is the main content of design is based on small scissors type elevator machine structure design, scissors, type elevator machine market are more mature, type very rich also. According to the size of the scissors into large scissor lifting machine (and JiaoZi mother type), and small cut (single cut) lift; According to the driving type can be divided into mechanical, electrical and hydraulic, gas to liquid driving type; According to installation forms can be divided into hiding again to install, ground installation. Because the design of lifting weight to passenger vehicles for 2t below, so adopt double hinged scissor hydraulic lift is fully comply with design concept. In order to suit the size, the foundation maintenance enterprises without excessive requirements, the flat panel installation can be put on the ground directly.Judging from the overall structure, double scissor lift hinged by lifting arm, slide device, fluctuation platform, electronically controlled hydraulic system four major part. Lifting height in reach, because of hydraulic system of choice of piston rod is greater than the actual lifting travel to travel, so must needed to block block to slide place to limit its lifting height. Because of this design uses slope type FangDeng to make cars rise to lifting position, the application of galvanism use safety higher hydraulic system to control, so avoid plus hydraulic cylinder with self-locking device, namely cost savings have safe operation. Double articulated lift two groups of identical lifting arm agencies on both sides, respectively, between a pulley about put in. By lifting machine electric control system, by hydraulic system output hydraulic oil as driving, driving the piston rod telescopic lifting arm while both sides rise and fall, the lock. Lift side for the lower welding beam and floor in the fixed hinge bearing, by lifting arm in hinge pin connections on fixed bearings. Another side to the lower Angle, within the slide block lifting arm through the axes and pulley connection. The hydraulic cylinder by lifting transverse axis to lift the whole platform, lifting arm to fixed hinge on one side for the fulcrum, pulley bearings inside or outside to slide, make lift up and down, when reaching an appropriate position, use the lifting control platform and block block the lock. Scissors type elevator machine operation isconvenient, simple structure and easy maintenance, cover an area of an area small, suitable for most cars maintenance, and safe and reliable.译文举升系统主要结构的设计本课题设计的内容主要是基于小型剪刀式举升机的结构设计，剪刀式举升机的市场较成熟，类型也很丰富。

本科毕业论文（设计）外文翻译学院：机电工程学院__________专业：机械工程及自动化姓名：高峰指导教师：李延胜2011年05月10日教育部办公厅Failure An alysi§ Dime nsional Determ in ati on And An alysis Applicati ons Of Cams INTRODUCTIONIt is absolutely essential that a design engineer know how and why parts fail so that reliable mach ines that require minimum maintenance can be desig nedbmetimes a failure can be serious such as when a tire blows out on an automobile traveling at high speOn the other hand a failure may be no more than a nuisanceAn example is the loosening of the radiator hose in an automobile cooling systemThe consequence of this latter failure is usually the loss of some radiator coo la^a con diti on that is readily detected and correctedThe type of load a part absorbs is just as sig nifica nt as the magn itude Gen erally speak ing dyn amic loads with directi on reversals cause greater difficulty tha n static loads and therefore, fatigue strength must be considered Another concern is whether the material is ductile or brittleFor example brittle materials are considered to be unacceptable where fatigue is invo IvedMany people mistak in gly in terpret the word failure to mean the actual breakage of a part. However, a design engineer must consider a broader understanding of what appreciable deformation occur s A ductile material, however will deform a large amount prior to rupture . Excessive deformation without fracture, may cause a machine to fail becausethe deformed part interferes with a moving second part. Therefore, a part fails(eve n if it has not physically broke n) whe never it no Ion ger fulfills its required function. Sometimesfailure may be due to abnormal friction or vibration between two mating parts Failure also may be due to a phenomenon called creepwhich is the plastic flow of a material under load at elevated temperaturesIn addition, the actual shape of a part may be responsiblefor failure. For example stressconcentrationsdue to sudden cha nges in con tour must be take n into acco unt Evaluatio n of stress con siderati on sis especially importa nt whe n there are dyn amic loads with directi on reversals and the material is not very ductileIn general, the design engineer must consider alpossible modes of failure, which in clude the followi ng.StressDeformati on---- Wear---- Corrosi on---- Vibrati on---- En viro nmen tal damage---- Loose ning of faste ning devicesThe part sizes and shapesselectedalso must take into acco unt many dime nsional factors that produce external load effects, such as geometric discontinuities residual stresses due to formi ng of desired con toqrsa nd the applicati on of in terfere nee fit joi ntsCams are among the most versatile mechanisms available A cam is a simple two-member device The in put member is the cam itsejfwhile the output member is called the follower. Through the use of cams a simple in put motio n can be modified in to almost any con ceivable output moti on that is desired Some of the com mon applicati ons of cams are---- Camshaft and distributor shaft of automotive engine---- Productio n mach ine toolsAutomatic record playersPrinting machines---- Automatic washi ng mach ines---- Automatic dishwashersThe con tour of high-speed cams (cam speed in excess of 1000 rpm) must be determined mathematicall y However, the vast majority of cams operate at low speeds(less than 500 rpm) or medium-speedcams can be determined graphicallyusing a large-scale layout. In gen era, the greater the cam speed and output load the greater must be the precisi on with which the cam con tour is machi nedDESIGN PROPERTIES OF MATERIALSThe following design properties of materials are defined as they relate to the tensile test.Figure 2.7Static Strength The strength of a part is the maximum stressthat the part can sustain without losing its ability to perform its required function. Thus the static strength may be con sidered to be approximately equal to the proporti on al lirps ince no plastic deformatio n takes place and no damage theoretically is done to the materialStiff ness Stiff ness is the deformati on-resisti ng property of a materiaThe slope of the modulus line and, hence the modulus of elasticity are measuresof the stiffness of amateria lResilienee Resilienee is the property of a material that permits it to absorb energy withoutpermanent deformation The amount of energy absorbed is represented by the area undern eath the stress-strain diagram within the elastic regi onToughness Resilienee and toughness are similar propertiesHowever, toughness is the ability to absorb energy without rupture. Thus toughness is represented by the total area undern eath the stress-stra in diagramas depicted in Figure 28b. Obviously, the tough ness and resilienee of brittle materials are very low and are approximately equalBrittleness A brittle material is one that ruptures before any appreeiableplastie deformatio n takes plaee Brittle materials are gen erally eon sidered un desirable for maeh ine eomp onents beeause they are un able to yield loeally at loeati ons of high stress beeause of geometrie stress raisers sueh as shouldeholes, notehes, or keywaysDuetility . A duetility material exhibits a large amount of plastie deformatio n priorto rupture . Duetility is measured by the pereent of area and pereent elongation of a part loaded to rupture A 5%elongation at rupture is eonsidered to be the dividing line between duetile and brittle materialsMalleability. Malleability is essentiallya measure of the eompressiveduetility of a material and, as sueh is an important eharaeteristie of metals that are to be rolled into sheetsHardness The hardness of a material is its ability to resist indentation or scratchi ng Gen erally speak ing the harder a material the more brittle it is and hence the less resilient Also, the ultimate strength of a material is roughly proportional to its hard nessMach in ability. Mach in ability is a measure of the relative ease with which a material canbe machi ned In gen era] the harder the material the more difficult it is to mach ineFigure 2.8COMPRESSION AND SHEAR STATIC STRENGTHIn addition to the tensile tests there are other types of static load testing that provide valuable in formatio nCompressi on Test ing Most ductile materialshave approximatelythe same properties in compression as in tension The ultimate strength, however, can not be evaluated for compression As a ductile specimen flows plastically in compressionthe material bulges out, but there is no physical rupture as is the case in tensionherefore, a ductile material fails in compressi on as a result of deformatio nnot stressShear Testi ng Shafts bolts, rivets, and welds are located i n such a way that shear stresses are produced plot of the tensile test The ultimate shearing strength is defined as the stress at which failure occursThe ultimate strength in shearhowever, does not equal the ultimate strength in tension. For example in the caseof stee, the ultimate shear stre ngth is approximately 75% of the ultimate stre ngth in ten sionThis differe nee must be take n into aeeo unt whe n shear stresses are encoun tered in maehi ne compo s e ntsDYNAMIC LOADSAn applied force that does not vary in any manner is called a static or steady」oads alsocom mon practice to con sider applied forces that seldom vary to be static loadsThe force that is gradually applied duri ng a ten sile test is therefore a static .loadOn the other hand, forces that vary freque ntly in magn itude and direct ion are called dynamic loads Dynamic loads can be subdivided to the following three categoriesVarying Load. With vary ing loads, the magn itude cha nges but the directi on doesnot. For example the load may produce high and low tensile stresses but no compressive stressesRevers ing Load I n this case both the magn itude and direct ion cha nge These load reversalsproduce alternatelyvaryi ng ten sile and compressivestressesthat are com mon ly referred to as stress reversalsShock Load This type of load is due to impact One example is an elevator dropping on a nest of springs at the bottom of a chute The resulting maximum spring force can be many times greater tha n the weight of the elevatorThe same type of shock load occurs in automobile spri ngs whe n a tire hits a bump or hole in the roadFATIGUE FAILURE-THE ENDURANCE LIMIT DIAGRAMThe test specimen in Figure 2.10a , after a given number of stress reversalswill experie nee a crack at the outer surface where the stress is greateThe in itial crack starts where the stress exceeds the strength of the grain on which it actsThis is usually where there is a small surface defectsuch as a material flaw or a tiny scratchAs the number of cycles in creases the initial crack begi ns to propagate into a con ti nu ous series of cracks all around the periphery of the shaft. The conception of the initial crack is itself a stress concentration that acceleratesthe crack propagation phenomenon. Once the entire periphery becomes crackedhe cracks start to move toward the cen ter of the shaFti nally, whe n the remai ning solid inner area becomes small en oug h e stress exceeds the ultimate strength and the shaft suddenly breaks Inspection of the break reveals a very interesting patter n,as show n in Figure 2.13The outer annu lar area is relatively smooth because mati ng cracked surfaces had rubbed against each otheHowever, the center portion is rough indicating a sudden rupture similar to that experieneed with the fracture of brittle materialsThis brings out an interesting fact When actual machine parts fail as a result of static loads, they normally deform appreciably because of the ductility of the materialFigure 2.13Thus many static failures can be avoided by making freque nt visual observati ons and replacing all deformed partsHowever, fatigue failures give to warning Fatigue fail mated that over 90% of broke n automobile parts have failed through fatigueThe fatigue strength of a material is its ability to resist the propagation of cracks under stress reversals En dura nee limit is a parameter used to measure the fatigue stre ngth of a materia l By definition, the enduraneelimit is the stressvalue below which an infinite nu mber of cycles will not cause failureLet us return our attention to the fatigue testing machine in Figure 2.9The test is run as follows： A small weight is inserted and the motor is turned on. At failure of the test specimenthe coun ter registers the nu mber of cycles, Na nd the corresp onding maximum bending stress is calculated from Equation 2.The broken specimen is then replaced by an iden tical one and an additi onal weight is in serted to in crease the loAdnew value of stress is calculated and the procedure is repeated until failure requires only one complete cycle plot is then made of stress versus number of cycles to failurFigure 2.14a shows the plot which is called the endurance limit or S-N curv.e Since it would take forever to achieve an infinite number of cycles 1 million cycles is used as a referencHence the endurance limit can be found from Figure 2.14a by noting that it is the stress level below which the material can susta in 1 milli on cycles without failure The relati on ship depicted in Figure 2.14 is typical for steebecause the curve becomes horiz on tal as N approaches a very large nu mbeThus the en dura nce limit equals the stress level where the curve approaches a horiz on tal tan geOtw ing to the large nu mber of cycles invoIved, N is usually plotted on a logarithmic scajeas shown in Figure 2.14.bWhen this is done,the endurance limit value can be readily detected by the horizontal straight Foe stee, the endurance limit equals approximately 50% of the ultimate strengtHowever, if the surface finish is not of polished equality the value of the enduraneelimit will be lower. For example for steel parts with a machined surface finish of 63 microinches ( 卩助，.the percentage drops to about 40%For rough surfaces (300 or greater).the perce ntage may be as low as 25%The most com mon type of fatigue is that due to bending The n ext most freque nt is torsi on failure, whereas fatigue due to axial loads occurs very seldoSpri ng materials are usually tested by appl ying variable shearstressesthat alternatefrom zero to a maximum value,simulating the actual stress patternsIn the caseof some non ferrous metals the fatigue curve does not level off as the nu mber of cycles becomes very largeThis continuing toward zero stress means that a large number of stress reversalswill causefailure regardlessof how small the value of stress is. Such a material is said to have no en dura nee linFior most non ferrous metals hav ing an en dura nee limit the value is about 25% of the ultimate stre ngthEFFECTS OF TEMPERATURE ON YIELD STRENGTH AND MODULUS OF ELASTICITY Gen erally speak ing, when stat ing that a material possessesspecified values of properties such as modulus of elasticity and yield stre ngth it is implied that these values exist at room temperatureAt low or elevated temperaturesthe properties of materials may be drastically different For example many metals are more brittle at low temperature" addition, the modulus of elasticity and yield strength deteriorate as the temperature in creases Figure 2.23 shows that the yield stre ngth for mild steel is reduced by about 70%in going from room temperature to 100°F.Figure 2.24 shows the reduct ion in the modulus of elasticity E for mild steel as the temperature in creases As can be see n from the graph, a 30% reduct ion in modulus of elasticity occurs in going from room temperature to 10°F). In this figure, we also can see that a part loaded below the proportional limit at room temperaturecan be permanently deformed un der the same load at elevated temperaturesFigure 2.24CREEP: A PLASTIC PHENOMENONTemperature effects bring us to a phenomenon called creep which is the increasing plastic deformation of a part under constant load as a function of timCreep also occurs at room temperature but the process is so slow that it rarely becomes significant during the expected life of the temperature is raised to 300o C or more, the increasing plastic deformation can become significant within a relatively short period of time. The creep stre ngth of a material is its ability to resist creea nd creep stre ngth data can be obta ined by con duct ing Ion g-time creep tests simulati ng actual part operat ing con diti ons During the test, the plastic strain is monitored for given material at specified temperaturesSince creep is a plastic deformation phenomenon, the dimensions of a part experiencing creep are permanently altereThus, if a part operates with tight clearances the desig n engin eer must accurately predict the amount of creep that will occur duri ng the life of the machine Otherwise, problems such binding or interferenee can occurCreep also can be a problem in the case where bolts are used to clamp tow parts together at elevated temperaturesThe bolts, under tension, will creep as a function of time. Since the deformation is plastic loss of clamping force will result in an undesirable loosening of the bolted joint The extent of this particular phenomenon called relaxation can be determ ined by running appropriate creep stre ngth testsFigure 2.25 shows typical creep curves for three samples of a mild steel part un der a consta nt ten sile loadNotice that for the high-temperature case the creep tends to accelerate until the part fails . The time line in the graph (the x-axis) may represent a periodof 10 years the anticipated life of the productFigure 2.25SUMMARYThe machine designer must understand the purpose of the static tensile strength test. This test determ in esa nu mber of mecha ni calproperties of metalsthat are used in desig n equati ons Such terms as modulus of elasticjtyproporti on al limit, yield stre ngth, ultimate strength, resilienee and ductility define properties that can be determined from the ten sile test Dyn amic loads are those which vary in magn itude and direct ion and may require an investigation of the machine part ' s resisSmeestoeveurals may require thatthe allowable desig n stress be based on the en dura nee limit of the material rather tha n on the yield strength or ultimate strengthStress concen trati on occurs at locati ons where a mach ine part cha nges,sizech as a hole in a flat plate or a sudden change in width of a flat plate or a groove or fillet on a circular shaf t Note that for the case of a hole in a flat or ba, the value of the maximum stress becomes much larger in relation to the averagestress as the size of the hole decreases Methods of reducing the effect of stress concentration usually invoIve making the shape cha nge more gradual Mach ine parts are desig ned to operate at some allowable stress below the yield stre ngthor ultimate strength This approach is used to take care of such unknown factors as material property variati ons and residual stresses produced duri ng manu facture and the fact that the equati ons used may be approximate rather that exadthe factor of safety is applied to the yield stre ngth or the ultimate stre ngth to determ ine the allowable stressTemperature can affect the mecha ni cal properties of metals ncreases in temperature may cause a metal to expand and creep and may reduce its yield strength and its modulus of elasticity. If most metals are not allowed to expa nd or con tract with a cha nge in temperature then stresses are set up that may be added to the stresses from the lTais phe nomenon is useful in assembli ng parts by means of in terfere nce.fiA hub or ring has an in side diameter slightly smaller tha n the mati ng shaft or p.osithe hub is the n heated so that it expa nds eno ugh to slip over the shaW/he n it cools, it exerts a pressure on the shaft result ing in a strong frict ional force that preve nts loose ningTYPES OF CAM CONFIGURATIONSPlate Cams This type of cam is the most popular type becauseit is easy to design and manufacture Figure 6. 1 shows a plate camNotice that the follower moves perpendicular to the axis of rotation of the camshaf t All cams operate on the principle that no two objects can occupy the same space at the same .tiTheis, as the cam rotates ( in this case coun terclockwise ) the follower must either move upward or bind in side the guidWe will focus our attention on the prevention of binding and attainment of the desired output follower moti on. The spri ng is required to mai ntain con tact betwee n the roller of the follower and the cam con tour whe n the follower is movi ng dow nwardThe roller is used to reduce frict ion and hence wear at the contact surfacFor each revolutio n of the cam the follower moves through two strokes-bottom dead cen ter to top dead cen ter (BDC to TDC) and TDC to BDC .Figure 6.2 illustrates a plate cam with a poin ted follower . Complex motio ns can be produced with this type of follower becausethe point can follow precisely any sudden cha nges in cam con tour However, this desig n is limited to applicati ons in which the loads are very light; otherwise the con tact point of both members will wear prematurely with subseque nt failure Two additional variations of the plate cam are the pivoted follower and the offset sliding follower, which are illustrated in Figure 6.3A pivoted follower is used when rotary output motion is desired Referring to the offset follower; note that the amount of offset used depe nds on such parameters as pressure an gle and cam profile flatnwhich will be covered later A follower that has no offset is called an in-line followerFigure 6..3Translation Cams Figure 6.4 depicts a translation canThe follower slides up and down as the cam translates motion in the horizontal direction Note that a pivoted follower can be used as well as a sliding-type follower. This type of action is used in certain production machines in which the pattern of the product is used as the cam variation on this design would be athree-dimensional cam that rotates as well as translates For example a hand-constructed rifle stock is placed in a special lathe This stock is the pattern, and it performs the function of a cam As it rotates and translatesthe follower controls a tool bit that mach ines the product ion stock from a block of woodFigure 6.4Positive-Moti on Cams In the forego ing cam design,the con tact betwee n the cam and the follower is en sured by the action of the spri ng forces duri ng the retur n strokedowever, in high-speed cams the spri ng force required to maintain con tact may become excessive whe n added to the dyn amic forces gen erated as a result of accelerationsis situati on can result in un acceptablylarge stress at the con tact surface which in turn can result in premature wear Positive-motion cams require no spring because the follower is forced to con tact the cam in two directi ons There are four basic types of positive-moti on cams: the cylindrical cam thegrooved-plate cam ( also called a face cam Xhe matched-plate cam and the scotch yoke cam Cylindrical Cam The cylindrical cam shown in Figure 6.5 produces reciprocating follower motion, whereas the one shown in Figure 6.6 illustrates the application of a pivoted follower. The cam groove can be designedsuch that several camshaft revolutions are required to produce one complete follower cycleGrooved-plate Cam In Figure 6.8 we see a matched-plate cam with a pivoted follow e r although the design also can be used with a translation follower. Cams E and F rotate together about the camshaft B Cam E is always in con tact with roller C , while cam F mai ntai ns con tact with roller D Rollers C and D are moun ted on a bell-cra nk levewhich is the follower oscillating about point A Cam E is designed to provide the desired motion of roller C, while cam F provides the desired motion of roller DScotch Yoke Cam This type of cam, which is depicted in Figure 6.,consists of a circular cam moun ted ecce ntrically on its camshafThe stroke of the follower equals two times the ecce ntricity e of the cam . This cam produces simple harm on ic motio n with no dwell times. Refer to Secti on 6.8 for further discussi onCAM TERMINOLOGYBefore we become invoIved with the design of cams it is desirable to know the various terms used to identify important cam design parameters The following terms refer to Figure 6.11. The descriptions will be more understandableif you visualize the cam as stati onary and the followeras movi ng around the camTrace Point. The end point of a knife-edge follower or the center of the roller of a roller-type follower.Cam Con tour. The actual shape of the camBase Circle The smallest circle that can be draw n tangent to the cam con to us cen ter is also the center of the camshaft The smallest radial size of the cam stars at the base circlePitch Curve. The path of the trace point assuming the cam is stationary and the follower rotates about the camPrime Circle The smallest circle that can be drawn tangent to the pitch curves center is also the cen ter of the camshaftPressure An gle The an gle betwee n the direct ion of moti on of the follower and the normal to the pitch curve at the point where the center of the roller liesCam Profile. Same as cam con tourBDC . Bottom Dead Center, the position of the follower at its closest point to the cam hub .Stroke. The displaceme nt of the follower in its travel betwee n BDC and TDCRise. The displacement of the follower as it travels from BDC to TDCReturn. The displacement of the follower as it travels from TDC or BDCEwell. The actio n of the follower whe n it remai ns at a con sta nt dista nce from the cam hub while the cam turnsA clearer understandingof the significance of the pressureangle can be gained by referring to Figure 6.12 Here F T is the total force acting on the rollerIt must be normal to the surfaces at the con tact point Its directi on is obviously not parallel to the directi on of motio n of the follower. In stead, it is in dicated by the an gle the pressure a glemeasured from the line represe nting the directi on of motio n of the follower Therefore, the force F T has a horizontal component Fand a vertical component F. The vertical component is the one that drives the follower upward and therefore, neglecting guide friction equals the follower F load. The horizontal component has no useful purpose but it is unavoidabJeIn fact, it attempts to bend the follower about its guiderhis can damage the follower or cause it to bind in side its guide. Obviously, we want the pressurea ngle to be as possible to mini mize the side thrust F. A practical rule of thumb is to desig n the cam con tour so that the pressure angle does not exceed 30 The pressure angle in general depends on the followi ng four parameters:---- Size of base circleAmount of offset of followerSize of roller---- Flat nessof cam con tour ( which depe ndson follower stroke and type of follower motio n used )Some of the preceding parameters cannot be changed without altering the cam requireme nts such as space limitationsAfter we have lear ned how to desig n a cawe will discuss the various methods available to reduce the pressure an gle故障的分析、尺寸的决定以及凸轮的分析和应用前言介绍：作为一名设计工程师有必要知道零件如何发生和为什么会发生故障，以便通过进行最低限度的维修以保证机器的可靠性。

附录附录ALifting sytem failure analysis Below a certain brand can explain a type of lift accident .Because lifting machine structure is more complicated ,e to maintenance enterprise use it frequently in work under high load ,We have to consider its damaged condition. actual use, as repeated wear and tear of fatigue damage ,So anytime possible lifting system failure .If the downturn is likely to cause maintenance personnel injured and vehicles damaged .After the failure of the lift inspection, analysis, found its existence defects in design.This product for the mechanical lifting machine, uses the pin shaft transmission, driven by shaft lifting arm motion realization Auto lift. Unless the power cut off the motor car, driven shaft lifting stop failure analysis personnel of nantong product quality supervision, inspection ZouLei can observed. To effectively guarantee the safety, auto lift should lock up the device. In order to effectively To protect the security, automotive lift Should stop the browser and the backstop. From The Brand Lift of the occurrence of several Lapsed since the incident, the principal, Vice-nut at the sametime lead to wear and tear due to strong Decreases occurred in the thread root cut Letter, which of course, and materials selection, Manufacturing quality, the use of maintenance due to Su-relevant, but imagine if Is an independent work of the backstop , And even in the absence of Vice-nut, so that The possibility of a thing you Moment of downtime in order to achieve things, it does not work independently of the stop device and the backstop , And only made use of the role of self-locking screw to prevent the decline in our care arm Know that the conditions for self-locking thread is the thread friction angle or Chaetoceros. It's an But to protect the whole body is fitted with a nut in the bottom of the main vice of the so-called Nut, through institutions linked synchronous rotation with the main nut. There is no denying that when the Lord, Vice-nut There is a certain gap between the, if nut the main event of an accident, child care Vice-nut will be on the arm and not the accidents. However, the main, the Deputy nut As the gap between the main nut and gradually reduce the wear and tear, when reduced to a Certain extent, it must be replaced with new ones of the main nut, otherwise, continue to use When the owners go, the gap between the Deputy nut completely disappear, the Lord, is Vice-nut Quality has become one, and act as security devices has been gradually Vice nut Until all the nuts to replace the main workload. At this point if an accident such as Thread occur due to wear and cut theroot, see the attached map, security protection devices can play It should be the role to be sure, if the timely replacement of the main nut, can be avoided Some accidents, but not all users have the professional knowledge and Lord, the gap between the Vice-nut is not clear at a glance from the outside can, it is necessary to disassemble Therefore, the use of cars to check whether the lift should be independent Work backstop safety protection device, if not, be sure to strengthen the Inspection and timely replacement of drive nut to avoid accidents. If not, then, be sure to strengthening inspection and change in time transmission nut, lest produce an accident. The manufacturers character, also Should improve design.Hope so as to remind each manufacturer .附录BLifting machine main structure identificationThis topic is the main content of design is based on small scissors type elevator machine structure design, scissors, type elevator machine market are more mature, type very rich also. According to the size of the scissors into large scissor lifting machine (and JiaoZi mother type), and small cut (single cut) lift; According to the driving type can be divided into mechanical, electrical and hydraulic, gas to liquid driving type; According to installation forms can be divided into hiding again to install, ground installation. Because the design of lifting weight to passenger vehicles for 2t below, so adopt double hinged scissor hydraulic lift is fully comply with design concept. In order to suit the size, the foundation maintenance enterprises without excessive requirements, the flat panel installation can be put on the ground directly.Judging from the overall structure, double scissor lift hinged by lifting arm, slide device, fluctuation platform, electronically controlled hydraulic system four major part. Lifting height in reach, because of hydraulic system of choice of piston rod is greater than the actual lifting travel to travel, so must needed to block block to slide place tolimit its lifting height. Because of this design uses slope type FangDeng to make cars rise to lifting position, the application of galvanism use safety higher hydraulic system to control, so avoid plus hydraulic cylinder with self-locking device, namely cost savings have safe operation. Double articulated lift two groups of identical lifting arm agencies on both sides, respectively, between a pulley about put in. By lifting machine electric control system, by hydraulic system output hydraulic oil as driving, driving the piston rod telescopic lifting arm while both sides rise and fall, the lock. Lift side for the lower welding beam and floor in the fixed hinge bearing, by lifting arm in hinge pin connections on fixed bearings. Another side to the lower Angle, within the slide block lifting arm through the axes and pulley connection. The hydraulic cylinder by lifting transverse axis to lift the whole platform, lifting arm to fixed hinge on one side for the fulcrum, pulley bearings inside or outside to slide, make lift up and down, when reaching an appropriate position, use the lifting control platform and block block the lock. Scissors type elevator machine operation is convenient, simple structure and easy maintenance, cover an area of an area small, suitable for most cars maintenance, and safe and reliable.附录C举升系统失效分析下面是某个品牌的一次事故分析,因为起重机械结构比较复杂,维护企业使用它经常在工作在高负载时,我们必须考虑其受损的情况.实际使用中因为重复的磨损及疲劳损伤,所以随时可能发生举升系统的损坏事故。

Mechanical EngineeringIntroduction to Mechanical EngineeringMechanical engineering is the branch of engineering that deals with machines and the production of power. It is particularly concerned with forces and motion.History of Mechanical EngineeringThe invention of the steam engine in the latter part of the 18th century, providing a key source of power for the Industrial Revolution, gave an enormous impetus to the development of machinery of all types. As a result a new major classification of engineering, separate from civil engineering and dealing with tools and machines, developed, receiving formal recognition in 1847 in the founding of the Institution of Mechanical Engineers in Birmingham, England.Mechanical engineering has evolved from the practice by the mechanic of an art based largely on trial and error to the application by the professional engineer of the scientific method in research, design, and production.The demand for increased efficiency, in the widest sense, is continually raising the quality of work expected from a mechanical engineer and requiring of him a higher degree of education and training. Not only must machines run more economically but capital Costs also must be minimized.Fields of Mechanical EngineeringDevelopment of machines for the production of goods the high material standard of living in the developed countries owes much to the machinery made possible by mechanical engineering. The mechanical engineer continually invents machines to produce goods and develops machine tools of increasing accuracy and complexity to build the machines.The principal lines of development of machinery have been an increase in the speed of operation to obtain high rates of production, improvement in accuracy to obtain quality and economy in the product, and minimization of operating costs. These three requirements have led to the evolution of complex control systems.The most successful production machinery is that in which the mechanical design of the machine is closely integrated with the control system, whether the latter is mechanical orelectrical in nature. A modern transfer line (conveyor) for the manufacture of automobile engines is a good example of the mechanization of a complex series of manufacturing processes. Developments are in hand to automate production machinery further, using computers to store and process the vast amount of data required for manufacturing a variety of components with a small number of versatile machine tools. One aim is a completely automated machine shop for batch production, operating on a three shift basis but attended by a staff for only one shift per day.Development of machines for the production of power Production machinery presuppose an ample supply of power. The steam engine provided the first practical means of generating power from heat to augment the old sources of power from muscle, wind, and water One of the first challenges to the new profession of mechanical engineering was to increase thermal efficiencies and power; this was done principally by the development of the steam turbine and associated large steam boilers. The 20th century has witnessed a continued rapid growth in the power output of turbines for driving electric generators, together with a steady increase in thermal efficiency and reduction in capital cost per kilowatt of large power stations. Finally, mechanical engineers acquired the resource of nuclear energy, whose application has demanded an exceptional standard of reliability and safety involving the solution of entirely new problems- The control systems of large power plank and complete nuclear power stations have become highly sophisticated networks of electronic, fluidic. Electric, hydraulic, and mechanical components, ail of these involving me province of the mechanical engineer.The mechanical engineer is also responsible for the much smaller internal combustion engines, both reciprocating (gasoline and diesel) and rotary (gas-turbine and Wankel) engines, with their widespread transport applications- In the transportation field generally, in air and space as well as on land and sea. the mechanical engineer has created the equipment and the power plant, collaborating increasingly with the electrical engineer, especially in the development of suitable control systems.Development of military weapons The skills applied to war by the mechanical engineer are similar to those required in civilian applications, though the purpose is to enhance destructive power rather than to raise creative efficiency. The demands of war have channeled huge resources into technical fields, however, and led to developments that have profound benefits in peace. Jet aircraft and nuclear reactors are notable examples.Biaengineering Bioengineering is a relatively new and distinct field of mechanical engineering that includes the provision of machines to replace or augment the functions of the human body and of equipment for use in medical treatment. Artificial limbs have been developed incorporating such lifelike functions as powered motion and touch feedback. Development is rapid in the direction of artificial spare-part surgery. Sophisticated heart-lung machines and similar equipment permit operations of increasing complexity and permit the vital functions in seriously injured or diseased patients to be maintained.Environmental control Some of the earliest efforts of mechanical engineers were aimed at controlling man's environment by pumping water to drain or irrigate land and by ventilating mines. The ubiquitous refrigerating and air-conditioning plants of the modem age are based on a reversed heat engine, where the supply of power "pumps" heat from the cold region to the warmer exterior.Many of the products of mechanical engineering, together with technological developments in other fields, have side effects on the environment and give rise to noise, the pollution of water and air, and the dereliction of land and scenery. The rate of production, both of goods and power, is rising so rapidly that regeneration by natural forces can no longer keep pace. A rapidly growing field for mechanical engineers and others is environmental control, comprising the development of machines and processes that will produce fewer pollutants and of new equipment and techniques that can reduce or remove the pollution already generated.Functions of Mechanical EngineeringFour functions of the mechanical engineering, common to all the fields mentioned, are cited. The first is the understanding of and dealing with the bases of mechanical science. These include dynamics, concerning the relation between forces and motion, such as in vibration; automatic control; thermodynamics, dealing with the relations among the various forms of heat, energy, and power; fluid flow; heat transfer; lubrication; and properties of materials.Second is the sequence of research, design, and development. This function attempts to bring about the changes necessary to meet present and future needs. Such work requires not only a dear understanding of mechanical science and an ability to analyze a complex system into its basic factors, but also the originality to synthesize and invent.Third is production of products and power, which embraces planning, operation, and maintenance. The goal is to produce the maximum value with the minimum investment and cost while maintaining or enhancing longer term viability and reputation of the enterprise or the institution.Fourth is the coordinating functioning of the mechanical engineering, including management, consulting, and, in some cases, marketing.In all of these functions there is a long continuing trend toward the use of scientific instead of traditional or intuitive methods, an aspect of the ever-growing professionalism of mechanical engineering. Operations research, value engineering, and PABLA (problem analysis by logical approach) are typical titles of such new rationalized approaches. Creativity, however, cannot be rationalized. The ability to take the important and unexpected step that opens up new solutions remains in mechanical engineering, as elsewhere, largely a personal and spontaneous characteristic.The Future of Mechanical EngineeringThe number of mechanical engineers continues to grow as rapidly as ever, while the duration and quality of their training increases. There is a growing: awareness, however, among engineers and in the community at large that the exponential increase in populationand living standards is raising formidable problems in pollution of the environment andthe exhaustion of natural resources; this clearly heightens the need for all of the technical professions to consider the long-term social effects of discoveries and developments. -There will be an increasing demand for mechanical engineering skills to provide for man's needs while reducing to a minimum the consumption of scarce raw materials and maintaining a satisfactory environment.Introduction to DesignThe Meaning of DesignTo design is to formulate a plan for the satisfaction of a human need. The particular need to be satisfied may be quite well defined from the beginning. Here are two examples in which needs are well defined:1. How can we obtain large quantities of power cleanly, safely, and economical/ without using fossil fuels and without damaging the surface of the earth?2. This gear shaft is giving trouble; there have been eight failures in the last six weeks. Do something about it.On the other hand, the statement of a particular need to be satisfied may be so nebulous and ill defined that a considerable amount of thought and effort is necessary in ( order to state it dearly as a problem requiring a solution. Here are two examples.-1. Lots of people are killed in airplane accidents.2. In big cities there are too many automobiles on the streets and highways.This second type of design situation is characterized by the fact that neither the need nor the problem to be solved has been identified. Note, too, that the situation may contain not one problem but many.We can classify design, too. For instance, we speak of:1. Clothing design 7. Bridge design2. Interior design 8. Computer-aided design3. Highway design 9. Heating system design.4. Landscape design 10. Machine design5. Building design 11. Engineering design6. Ship design 12. Process designIn fact, there are an endless number, since we can classify design according to the particular article or product or according to the professional field,In contrast to scientific or mathematical problems, design problems have no unique answers; it is absurd, for example, to request the "correct answer" to a design problem, because there is none. In fact, a "good" answer today may well turn out to be a "poor" answer tomorrow, if there is a growth of knowledge during the period or if there are other structural or societal changes.Almost everyone is Involved with design in one way or another, even in dally living, because problems are posed and situations arise which must be solved. A design problem is not a hypothetical problem at all. Design has an authentic purpose—the creation of an end result by taking definite action, or the creation of something having physical reality. In engineering, the word design conveys different meanings to different persons. Some think of a designer as one who employs the drawing board to draft the details of a gear, clutch, or other machine member. Others think of design as the creation of a complex system, such as a communications network. In some areas of engineering the word design has been replaced by other terms such as systems engineering or applied decision theory. But no matter what words are used to describe the design function, in engineering it is still the process in which scientific principles and the tools of engineering—mathematics, computers, graphics, and English—are used to produce a plan which, when carried out, will satisfy a human need.Mechanical Engineering DesignMechanical design means die design of things and systems of a mechanical nature machines, products, structures, devices, and instruments. For the most part, mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences.Mechanical engineering design includes all mechanical design, but it is a broader study, because it includes all the disciplines of mechanical engineering, such as the thermal and fluids sciences, too. Aside from the fundamental sciences that are required, the first studies in mechanical engineering design are in mechanical design.The Phases of DesignThe complete process, from start to finish. The process W begins with a recognition of a need and a decision to do something about it. After much iteration, the process ends with the presentation of the plans for satisfying the need.Design ConsiderationsSometimes the strength required of an element in a system is an important factor in the determination of the geometry and the dimensions of the element. In such a situation we say that strength is an important design consideration. When we use the expression design consideration, we are referring to some characteristic which influences the design of the element or, perhaps, the entire system. Usually quite a number of such characteristics must be considered in a given design situation. Many of the important ones are as follows:1. Strength2. Reliability3. Thermal properties4. Corrosion5. Wear6. Friction7. Processing8. Utility9. Cost10. Safety11. Weight12. Life13. Noise14. Styling15. Shape16. Size17. Flexibility18. Control19. Stiffness20. Surface finish21. Lubrication22. Maintenance23. Volume24. LiabilitySome of these have to do directly with the dimensions, the material, the processing, and the joining of the elements of the system. Other considerations affect the configuration of the total system.To keep the correct perspective, however, it should be observed that in many design situations the important design considerations are such that no calculations or experiments are necessary in order to define an element or system. Students, especially, are often confounded when they run into situations in which it is virtually impossible to make a single calculation and yet an important design decision must be made. These are not extraordinary occurrences at all; they happen every day. Suppose that it is desirable from a sales standpoint—for example, in medical laboratory machinery—to create an impression of great strength and durability. Thicker parts assembled with larger-than-usual oversize bolts can be used to create a rugged-looking machine. Sometimes machines and their parts are designed purely from the standpoint of styling and nothing else. These points are made here so that you will not be misled into believing that there is a rational mathematical approach to every design decision.ManufacturingManufacturing is that enterprise concerned with converting raw material into finished products. There are three distinct phases in manufacturing. These phases are as follows: input, processing, and output.The first phase includes all of the elements necessary to create a marketable product. First, there must be a demand or need for the product. The necessary materials must be (available. Also needed are such resources as energy, time, human knowledge, and human skills. Finally, it takes capital to obtain all of the other resources.Input resources are channeled through the various processes in Phase Two. These are the processes used to convert raw materials into finished products. A design is developed. Based on the design, various types of planning are accomplished. Plans are put into action through various production processes. The various resources and processes are managed to ensure efficiency and productivity. For example, capital resources must be carefully managed to ensure they are used prudently. Finally, the product in question is marketed.The final phase is the output or finished product. Once the finished product has been purchased it must be transported to users. Depending on the nature of the product, installation and ongoing field support may be required. In addition, with some products, particularly those of a highly complex nature, training is necessary.Materials and Processes in ManufacturingEngineering materials covered herein are divided into two broad categories: metals and nonmetals. Metals are subdivided into ferrous metals, nonferrous metals, high-performance alloys, and powdered metals. Nonmetals are subdivided into plastics, elastomers, composites, and ceramics. Production processes covered herein are divided into several broad categories including forming, forging,casting/molding, .heat treatment^ .fastening joining metrology/quality control, and material removal. Each of these is subdivided into several other processes.Stages in the Development of ManufacturingOver the years, manufacturing processes have- gone through four distinct,-although overlapping, stages of development. These stages are as follows: Stage 1 ManualStage 2 MechanizedStage 3 AutomatedStage 4 IntegratedWhen people first began converting raw materials into finished products, they used manual processes. Everything was accomplished using human hands and manually operated tools. This was a very rudimentary form of fully integrated manufacturing. A person identified the need, collected materials, designed a product to meet the need, produced the product, and used it. Everything from start to finish was integrated within the mind of the person who did all the work.Then during the industrial revolution mechanized processes were introduced and humans began using machines to accomplish work previously accomplished manually. This led to work specialization which, in turn, eliminated the integrated aspect of manufacturing. In this stage of development, manufacturing workers might see only that part of an overall manufacturing operation represented by that specific piece on which they worked. There was no way to tell how their efforts fit into the larger picture or their workpiece into the finished product.The next stage in the development of manufacturing processes involved the automation of selected processes. This amounted to computer control of machines and processes. During this phase, islands of automation began to spring up on the shop floor. Each island represented a distinct process or group of processes used in the production of a product. Although these islands of automation did tend to enhance the productivity of the individual processes within the islands, overall productivity often was unchanged. This was because the islands were sandwiched in among other processes that were not automated and were not synchronized with them.The net result was that workpieces would move quickly and efficiently through the automated processes only to back up at manual stations and create bottlenecks. To understand this problem, think of yourself driving from stoplight to stoplight in rush hour traffic Occasionally you find an opening and an: able to rush ahead of the other cars that are creeping along, only to find yourself backed up at the next light. The net effect of your brief moment of speeding ahead is canceled out by the bottleneck at the next stoplight. Better progress would be made if you and the other drivers could synchronize your speed to the changing of the stoplights. Then all cars would move steadily and consistently along and everyone would make better progress in the long run.This need for steady, consistent flow on the shop floor led to the development of integrated manufacturing, a process that is still emerging. In fully integrated settings, machines and processes are computer controlled and integration is accomplished through computers. In the analogy used in the previous paragraph, computers would synchronize the rate of movement of all cars with the changing of the stoplights so that everyone moved steadily and consistently along.The Science of MechanicsThat branch of scientific analysis which deals with motions, time, and forces is called mechanics and is made up of two parts, static’s and dynamics. Static’s deals with the analysis of stationary systems, i. e., those in which time is not a factor, and dynamics deals with systems which change with time.Dynamics is also made up. of tyro major disciplines, first recognized as separate entities by Euler in 1775.The investigation of the motion of a rigid body may be conveniently separated into two parts, the one geometrical, the other mechanical. In the first part, the transference of the body from a given position to any other position must be investigated without respect to the cause of the motion, and must be represented by analytical formulae, which will define the position of each point of the body. This investigation will therefore be referable solely to geometry, or rather to stereotomy.It is clear that by the separation of this part of the question from the other, which belongs properly to Mechanics, the determination of the motion from dynamical principles will be made much easier than if the two parts were undertaken conjointly.These two aspects of dynamics were later recognized as the distinct sciences of kinematics and kinetics, and deal with motion and the forces producing it respectively.The initial problem in the design of a mechanical system therefore understands its kinematics. Kinematics is the study of motion, quite apart from the forces whichproduce that motion. More particularly, kinematics is the study of position, displacement rotation, speed, velocity, and acceleration. The study, say of planetary or orbital motion is also a problem in kinematics.It should be carefully noted in the above quotation that Euler based his separation of dynamics into kinematics and kinetics on the assumption that they should deal with rigid bodies. It is this very important assumption that allows the two to be treated separately. For flexible bodies, the shapes of the bodies themselves, and therefore their motions, depend on the forces exerted on them. In this situation, the study of force and motion must take place simultaneously, thus significantly increasing the complexity of the analysis.Fortunately, although all real machine parts are flexible to some degree, machines are usually designed from relatively rigid materials, keeping part deflections to a minimum. Therefore, it is common practice to assume that deflections are negligible and parts are rigid when analyzing a machine's kinematics performance, and then, after the dynamic analysis when loads are known, to design the parts so that this assumption is justified.。

中国地质大学长城学院本科毕业设计外文资料翻译系别：工程技术系专业：机械设计制造及其自动化姓名：王宁宁学号： 05211607 2015 年 4 月 1 日外文翻译原文Scissor lifeIn today's society rapid development, some companies in the process of work to help, you need to use lifting machine. Lifters began using the invention of the United States in 1925, development has been through a lot of changes and improvements, types and development to a lot of kinds, generally has the pillar type and scissors, the drive mode with mechanical drive, hydraulic transmission, pneumatic transmission, etc. This design is from the generation and development of lifting machine, and introduces the manufacturing process improvement, etc.The direction of the lifting machine design choiceNow we can see most of the lifting machine most fixed installation. Portable lifting machine but we also have several successful design, such as traction type lifting machine, shear fork lift machine, etc. The prominent nature of this type of lifting machine advantage is good flexibility, can open at any time to repair the field service, easy to use, which make full use of its advantages. Because now lifting machine more fixed, so we consider the development and use of portable lifting machine, this scissor lift machine is designed.Until now we have the potential of the lifting machine for the development and utilization of the many ways, but there is still a developing widely and use efficiency is not high enough. Lifting machine, however, is when is now one of the essential equipment of many industries, is also one of the indispensable accessories on many large machinery in the future, thus promote our better to study about the structure of it, to improve, so as to extend the service life of the equipment and improve the performance of equipment. So far, our country's lifting machine manufacturing technology over, there have been some quality technology is more mature, yu shu to lifting device has also been widely used in various fields, for our country's economic and social development has made irreplaceable contributions.The history of lifting machineLifting machine in the world already had 70 years of history. Production in the United States in 1925 the first car lifting machine, it is a kind of controlled by pneumatic lifting machine, single column due to the use of air pressure is low, and block; Using leather to seal at the same time, thus when compressed air driven bounce and serious instability. Until ten years later, in 1935 the single-column lifting machine is adopted in other parts of the outside of the United States.In 1966, a German company produced the first double column lifting machine, this is another breakthrough in the design of the lifting machine, but it was not until 1977 the lifting machine in other countries outside Germany. Now double column lifting machine in the market to occupy astrong position, its sales still continues to grow. It compared with the four pillars of elevator, has both advantages and disadvantages as well as, the following will make a brief description.We see the vast majority of the lifting machine adopt fixed installation. Before lifting the car must be on the lifting machine. In terms of portable lifting machine also has several successful design, such as scissors lifting machine, diamond frame lifting machine, etc. But this kind of lifting machine there are still two major issues, close to the car bottom is difficult; In the workshop mobile lifting machine difficult to overcome the obstacles on the ground. Mobility is, of course, this kind of the prominent advantages of lifting machine. Now fixed installation of single column and double column, four-column lifting machine has already been widely adopted in service field, and the portable lifting machine is relatively far less.Lifting machine design requirementsDesign before you determine the basic situation of product design, to develop basic scheme according to the design requirement. The following is a list of the design - the scissors hydraulic lifting platform of some basic requirements:1) overview of the host: it is mainly used for the repair and maintenance of the crane is of workshop maintenance personnel;2) main lifting and falling of lifting movement, speed is slow, small hydraulic impact;3) the maximum load of 0.3 tons, with double hydraulic cylinder control connection combination fork lever mechanism. Maximum lifting height 15 meters;4) movement stability and security needs better;5) artificial control operation, button start control lift;6) working environment requirement: should not be in the sand on the ground floor, plank brick plate and so on more than a solid ground, not in the ground of the slope or potholes, should not be operated in excessive cold outside;7) reliable performance, low cost, easy to move, without other auxiliary function and special function;Lifting machine safeguardsUse the maintenance of safety assurance measures involving range is very wide, including lifting machine have the preparing work before use, for example, the bracket, the closing of the door, and seat belt is lie. Despite the lifting machine has a history of 70 years of development, but its design principle and little change; If neglecting safety requirements, the overload use, still can cause serious accident, even casualties accident. So security problem must has drawn great attention of using unit and operators. Here is only use lifting machine maintenance items that should be paid attention.(1) the lifting machine lift platform lifting operations, working mesa should guarantee thehorizontal and vertical strut fork group keep vertical state.(2) when working outside, wind more than 5 is strictly prohibited. Platform in the process of lifting, all personnel are strictly prohibited to climb.(3) leg brace, ascending and descending homework; Platform after rising, before back to the original height, mobile is prohibited.(4) use is strictly prohibited in the process of super high platform, overload operation; Platform in the process of the cargo lift, goods cannot be moved; Platform manned in the process of the rise and fall, not moving and shaking.(5) the hydraulic oil should be kept clean, shall not be mixed with water and other impurities.(6) when the platform malfunction cannot work normally, should be promptly cut off the power supply.(7) equipment are in need of repair, the platform should be rising prison rear can run.With the characteristics of the hydraulic system1) in order to prevent the bedplate load weight down, the system adopts sealing good hydraulic controlled check valve self-locking;2) in order to make weight down smoothly, USES the one-way speed regulating valve control of motor speed, less noise;3) the system doesn't gesture, unloading directly, saving energy consumption;4) to make the lifting platform structure is more compact, the ease of installation and maintenance of superimposed components, hydraulic system, a unified arrangement within hydraulic station; 5) in order to prevent accident in work safety accidents, the system USES a pipeline rupture protection valve installed on the cylinder inferior vena inlet connection, once a line or other part of the pipeline suddenly burst, loose connection, pressure or the abnormal out-of-control speeding down counter, it can according to the differential pressure automatically cut off oil, prevent falling accidents, protect the equipment and personal safety;6) in addition, on the electrical control, at the edge of lift platform setting limit switch, bedplate rise, once rose to the limit of maximum height, limit switch signal, unloading to ensure that the compulsory system bedplate rise to the right height.Hydraulic pressure source selectionThe working medium of hydraulic system completely provided by the hydraulic source, hydraulic source is the core of hydraulic pump. Without other auxiliary oil source, under the condition of the hydraulic pump oil should be greater than the need of system of oil, excess oil through the overflow valve back to tank, develop and stable oil source pressure relief valve at the same time. V olumetric speed control system mostly with variable pump, oil pressure relief valve caps on system. To save energy and improve efficiency, hydraulic pump oil to try to match the requiredflow system. In the stage of the work cycle of each system under the condition of the oil quantity is large, have more oil supply or variable pump oil. For this design, due to the short work cycle, cycle times, less oil can be reduced to save energy, using single pump oil can, need not be stored energy accumulator. For the purification of oil: oil purification device in the hydraulic source is indispensable. Are generally equipped with crude oil filter, the entrance of the pump into oil according to the requirement of the protected components in the system, through the corresponding fine oil filter filter again. To prevent impurities in the system flow back to the fuel tank, can be set up on the back to oil magnetic filter or other forms of oil filter. According to the hydraulic equipment environment and the requirement of temperature rise, but also heating, cooling and other measures.Lifting machine bedplateCounter located in the upper lifting platform, is part of the support member. However, in order to secure our installed in the bedplate security fence, ensure staff is in a relatively safe environment. The counter here is not a simple steel plate, but in the following ways, because the lifting platform fork lever arm on the pulley, the track's role is to make the pulley sliding back and forth within the ramp, the lifting platform lifting and falling movement. Under the floor. These parameters according to the height of lifting weight and lift, to determine the length of the bedplate is 2800 mm, width 1500 mm, material adopt three thick checkered plate. Fork lever is one of the main lifting platform lifting parts, are the main force. For the success of its design relates to the success or failure of the whole design work, material selection of 45 # steel, 160 * 80 seamless steel tube.The three kinds of structure of lifting machinesVertical fixed shear fork structure, hydraulic cylinder stroke is equal to the lifting platform stroke, the overall structure of large size, and the spherical hinge processing load, less in actual application.Level fixed fork scissors mechanism, through the analysis and calculation, the platform lifting stroke is greater than the hydraulic cylinder stroke, can achieve rapid control in the process of application the purpose of the elevator, but the shortcoming is the role of the piston rod under transverse force, affect the service life of seals. And the piston rod on the load force platform of load force is larger than it actually is. So practical and rarely used.Two hinged shear fork structure to avoid the above shortcomings. Structure is reasonable, the platform of movements itinerary can achieve hydraulic cylinder stroke more than two times. Therefore, gradually has been widely used in engineering practice. This design is the key of double hinged shear fork structure analysis, in this paper.外文翻译译文剪式小型举升机当今社会高速发展，一些企业在工作过程中都需要使用举升机来帮助，。

装载机发展概况AbstractThis paper have discussed s.s. ZL-50 type fork-lift truck mainly overall fictitious prototype design as well as some kinds of typical schoolwork operating modes imitate and emulate , include equipment and the overall parts needed build mould. In this design course, have applied ADAMS software and the software of PRO/ENGINEER. ADAMS software is used in the emulation of some kinds of schoolwork operating modes, and the software of PRO/ENGINEER is used to build mould mainly. Through the simulated emulation for some kinds of overall schoolwork operating modes, can see relatively distinctly the overall possible condition in actual schoolwork course that met , can in time modify , have reduced actual design time , have raised production efficiency.The innovation of this design Zhi is in in, imitate and have emulated fork-lift truck the 3 kinds of typical schoolwork operating mode in actual schoolwork, is effect again have imitated in actual schoolwork the hydraulic impact of use, so when being helpful to solve actual loading, the actual problem of meeting the stock that is hard to uninstall can so raise production efficiency.Key words: Fork-lift truck 、 fictitious prototype , build mould,emulation, optimization、 production efficiencyLoader DevelopmentChina's modern 20 wheel loaders began in the mid-1960s of the Z435. The aircraft as a whole rack, rear axle steering. After years of hard work, the attraction was the world's most advanced technology wheel loader on the basis of the successful development of the power of 162 KW of shovel-fit wheel loaders, stereotypes for Z450 (later ZL50), and in 1971 December 18, formally appraised by experts. Thus the birth of China's first articulated wheel loader, thus creating our industry loader formation and development history.Z450-type loader with hydraulic mechanical transmission, power shift, Shuangqiaoshan drive, hydraulic manipulation, articulated power steering, gas oil Afterburner brake wheel loaders, and other modern, the basic structure of the world's advanced level for the time . Basically represent the first generation of wheeled loading the basic structure. The aircraft in the overall performance of dynamic, and insertion force a rise of power and flexibility, manipulation of light, the higheroperating efficiency of a series of advantages.1978, Heavenly Creations by the Department in accordance with the requirements of machinery, worked out to LIUGONG Z450-based type of wheel loaders series of standards. The development of standards, with reservations Z representatives loaders, L replaced by "4" on behalf of wheel, for ZL50 to Z450, it is so developed a LIUGONG ZL50-based China ZL-wheel loaders series of standards, this is Wong loader on the development of China's a major turning point. The standard was worked out by the industry after the division of labor, LIUGONG Xiamen ZL40 the manufacture of the large and medium wheel loaders, as workers, to the following small and medium-sized manufacturing ZL30 wheel loaders, and gradually formed a LIUGONG Xiamen workers, and 10% for workers at the loader to four backbone enterprises. To the late 1970s, early 1980s loader manufacturing enterprises inChina has increased to more than 20, China has initially formed the loader industry. So far, China has developed wheel loader to the third generation, but the basic structure is still the Z450 (ZL50) evolved from. Change is not a very large second generation, third generation of some larger changes. 2001 China loader industry-wide total sales have exceeded 30,000 Taiwan, the world loader in the forefront of the market. Therefore, at present, China has become the world's loader marketing power.Prospect of small loaderFor a long time, small loader always been neglected in the status of a government department, not to regulate the management of the industry, well-known businesses loader products is dismissive. However, these did not affect small loader (hereinafter referred to small equipment) rapid development, and now with a small market despite its huge market demand has attracted such as the Long renowned engineering machinery enterprises to participate in the competition, the main battlefield in the rural areas with the small size of the market, sales have already reached 4 ~ 5 million, more than 200 brands to participate in market competition. But small market can be said to be installed speed expansion disorderly competition coexist. How to achieve industrial upgrading is placed in front of the small equipment industry must resolve a problem.Lack industry attributionCompared with large and medium-sized industries loaders, small with the development of the industry can use "plan" to describe, not only government departments related to the absence of industrial policies or development plans, and to date, industry has not completely clear attribution, the reality of the small equipment industries across engineering machinery, agricultural machinery and construction machinery, the three industries of grey areas. Despite the small market with a flourishing, but all small equipment manufacturers and dealers can dodge exists in the industry before the many obstacles to development.Small installed mainly refers to the rated load between 0.3 ~ 0.9 T products, also known as micro-loader. As industry ownership is not clear, with small products has been no unified national technology and quality standards, the overwhelming majority of products are installed in the small-wheeled tractor developed on the basis of the. In addition small installed the product is currently used by the main component parts from tractors and light truck, not by the needs of small equipment for low-speed heavy-duty bridge, special bins key component parts, including even small projects with special tires. As a low technical content, resulting in a very low threshold of industry and become the de facto "open" industry, any person, business can be very easily installed into small industries.Small enterprises have installed a number of "fans", according to Construction Machinery Association Scraper Branch Secretary-General Chen Kai Yun, a conservative estimate at more than 200. More concentrated in Shandong Laizhou, Taian, Weifang, in Luoyang, Henan Province, Quanzhou, Fujian Province, and other places, annual sales of more than 2,000 Taiwanenterprises with a small handful, the majority of small businesses with annual sales in 3200 by the following, with the production of small enterprises , the same easy to set up and close down.It is precisely because the strength of small enterprises with very limited products without high technology content, in the vast majority of enterprises to participate in market competition are in the process of basically a single means to price competition to sell products for the purpose, without taking into account future market things. In the common with the credit industry, services, brand competition means small industry basically not installed, in addition to differences in the strength of enterprises and product differentiation, marketing and management philosophy that is the deep-seated causes.Because users of the products of small equipment to mainly rural users, and users can only cover rural farm machinery sales networks, construction machinery and construction machinery sales are only part of the network coverage in rural areas. And the sale of equipment similar, with small products also requires agents or distributors can take the initiative to sell products to users and to users with standard and thoughtful service, and farm machinery dealers more customary sit shop operator, has no sales force, There is no specialized service teams, more difficult to expect the market planning, customer management. Construction machinery dealers and farm machinery dealers also have a lot of similarities, and engineering machinery dealers not accustomed to deal with rural users. Therefore, the small market is not mature with the sales network, to a large extent affected the market maturation process can not be achieved on the one hand, the user guide, on the other hand, can not be achieved on the manufacturers facilitating role. Operating environment and the use of the different habits, resulting in a lack of support for non-small pieces of installed products can hardly meet the actual needs of users, increasing the cost of services at the same time, improve customer satisfaction become almost impossible task.Increased market differentiationUnlike the preceding two years, with no small on the future of the market is basically no doubts. However, when the small rural installed by the new face of the building the vast potential market demand, whether it is the product itself, or the level of industrial development is clearly not satisfied., And because of the double impact of external factors, with small market differentiation is an inexorable trend.Relying solely on price competition means does not make the small favorably with industry development. In fact, it is due to excessive price competition, leading to small enterprises with low profitability, sales, and the prosperity of the entire industry can not hide the crisis of survival. Anticipate with a few small companies have started the "innovation" in the product upgrades at the same time, learn from the equipment industry and other related industries experience, to establish their own marketing team and distribution network and market competition tends to differentiation.In the high-end users with the needs of small change, directly contributing to small enterprises with the differentiation, with the concept of progress and consumer financial strength of the expansion, some of the rural users (particularly in the industrialized operation of agriculture users) product performance and after-sales service and put forward higher requirements. Liaoning Anshan Haihong such as production of high-end products not only with small to have their own patented technology (use of mechanical devices greatly enhance the performance of its products, avoid using electric control, hydraulic devices, such as product performance after upgrading to the use of rural users increased maintenance costs ), and introduced the "non-controversial" services.Especially in big enterprises with increased involvement of small enterprises with pressure, the end of 2006, the Dragon Holdings acquired Henan Baiyun electrical and mechanical equipment involved in the production of small fields.Small with a huge potential market demand, but only to meet user needs, and guide the user needs, small equipment will have lasting vitality. Existing small enterprises with well-known loaders already facing small enterprises involved with the production sectors and small users to buy equipment or equipment, such as small excavators alternative products twin crises, with the production of small enterprises can take the initiative to upgrade their win more more time and greater market space.Any industries are indispensable for the development of market competition and government regulations two factors. With the status quo on small industries, market competition and excessive government regulation missing, the entire industry in a very low level of operation development, and a lack of development of the industry often staying power will gradually shrink, or even disappear.First to be addressed is the issue of trade with small, small equipment products really have their own products "definition", a specialproduct standards. Although at this stage with small user groups mainly concentrated in the rural market, but the market coverage of the future is certainly both urban and rural areas, this is because small equipment can be widely used for municipal maintenance, landscape construction, building and construction, underground loading and unloading areas.Second, improve industry access threshold is a feasible solution. Small equipment industry can learn from the industry's largest equipment manufacturers licensing system, in terms of production quality suitable restrictions and improve the industry's manufacturing standards.In recent years loader well-known enterprises in recent years have involved with the production of small areas, such as the Dragon, XCMG, and the mountains, but not really most of the production of one ton of small equipment products, the main reason is hindering their high-end products in the market inadequate capacity. However, this also means that for the small enterprises with not too much time, if not in the relatively short period of time upgrading of enterprises and products, from business philosophy, product marketing idea to the concept of all-roundself-improvement, self-transformed into a long-term development objectives and market competition-conscious modern manufacturing enterprises, and a larger-scale sales, in the future and well-known enterprises loader win in the competition may be very small.Mechanical Engineering Society of China was founded in 1936, China was set up earlier, the largest one of the Institute of Engineering. The existing 33 professional chapters, 180,000 members, of whom there are more than 3,000 senior members, more than 500 members of Hong Kong, Macao and overseas, there are more than 4,000 corporate members.Academic exchange is the Institute's basic functions, the Institute is held annually hundreds, and colorful academic conferences. Special is an annual Chinese Mechanical Engineering Society annual meeting, the topic is the integration activities of the various large-scale comprehensive meeting. , The main thrust of the report will include the General Assembly, the topic of academic, scientific and technological progress releases, forums, lectures, display, a number of activities such as presentation, rich in content, as well as inside and outside the country in the industry has had a tremendous impact.Editing, publishing and academic meetings and academic exchanges wings. Over the years, the organization has prepared a "China Materials Engineering ceremony," and "machine repair manual," such as hundreds of large-scale tool, science and technology books and related materials. Academic journals published by the "Journal of mechanical engineering", "Chinese Mechanical Engineering", more than 60 species, and for promoting the development of academic disciplines has played an important role.Member Society is the mainstay of the Institute and the basis for the existence of the necessary conditions for achieving democracy Office will learn organizational guarantee. Member services is the Institute for the work of the main tasks of Institute staff is a sacred duty. Has been the establishment of a wide range of multi-level structure and membership of the service system, and conducting appropriate Member activities, and actively explore characteristics of the times with the Member services. Institute of years of development experience has shown that membership is a source of vitality Institute.Continuing education and professional certification is the Institute's an effective way to serve the community. Over the years, have carried out fruitful work. 1983 founded the mechanical engineer degree (nowBeijing mechanical engineer OLI), is the first in China to establish a "mechatronics" and the "Industrial Engineering" two professional, and entrusted Quanguokaowei for higher education self-study examination. To welding and nondestructive testing for the representatives of accredited professionals work focused on quality, service-oriented economy, and widely alleged members and the industry peer Road. In recent years, actively promote the international mutual recognition of qualifications engineers.Chinese Mechanical Engineering Society of China's machinery industry is a very important external communication channels, to the industry and the large number of government departments entrusted task of the international exchange and cooperation. Chinese Mechanical Engineering Society of China's accession to the representatives of 11 international organizations, 23 countries and 38 first-class academic institutions and professional organizations has signed bilateral cooperation agreements with more than 60 countries and regions, including more than 1,000 scientific research, teaching, design, manufacturing, consulting, intermediary and social welfare institutions established a good working relationship.I will stick to science and technology and economic integration as the key link, and always bring the Institute for Scientific and Technological Advice as to promote economic development and work closely with the main battlefield, active structures for economic development platform. I will rely on his close "in Beijing Teng-day certification Advisory Center," galaxy of talent and give full play to the advantages of network, enterprises actively carry out technical advice, enterprise certification advisory and development strategy consulting. Not only to learn activities closer to the corporate and service industries, and effectively speed up the Institute's own capabilities and the enhancement of overall strength.International Exhibition is I will carry out international exchanges and cooperation forms an important one. The exhibition platform, organizations Chinese and foreign entrepreneurs, technology sector between the exchanges and cooperation and promote economic and trade development and industrialization of technological progress. As Chinese Mechanical Engineering Society masterpiece in the field of exhibitions, Beijing Essen Welding and Cutting Fair has become first inAsia and second in the world in the welding professional exhibitions.I will set up a "Chinese Mechanical Engineering Society Science and Technology Award", and China Machinery Industry Federation and jointly set up the "China Machinery Industry, Science and Technology Award." Over the years, the China Association for Science and Technology, Chinese Academy of Sciences, Chinese Academy of Engineering, recommending talents, and actively promote respect for independent innovation, and abide by scientific ethics, and the pursuit of harmony and progress of scientific thought, effectively mobilize the broad masses of scientific and technological workers initiative and creativity.I will also attach great importance to their work, procedures, scientific management and democratic management, and in 2004 took the lead in the national Institute adopted the ISO9001: 2000 quality management system certification. It is not only that I will work more scientific and standardized At the same time, the community has also been the recognition and praise.翻译:本文主要论述了ZL-50轮式装载机整机虚拟样机设计以及几种典型作业工况的模拟和仿真，包括工作装置和整机所需要部件的建模。

自卸汽车货箱举升机构设计摘要设计一款公路型轻型自卸汽车，本文先通过对国内和国外自卸汽车发展现状进行分析，呈现了未来自卸汽车在国际上占汽车行业比重会更多。

然后选取适合的底盘，进行对车厢和相关车体参数的选择，在对举升机构进行选型和相关零部件的校核，接下来是对自卸车液压进行原理分析和选择适合本设计液压系统，最后使用相应的三维和二维软件对主要零部件进行绘图。

关键词：自卸汽车；车厢；举升机构；液压系统Design of lifting mechanism of dump truckAbstractDesign a highway type light dump truck, this paper first analyzes the development status of domestic and foreign dump trucks, and shows that the proportion of dump trucks in the international automobile industry will be more in the future. Then select the suitable chassis to select the parameters of the carriage and the relevant body, select the lifting mechanism and check the relevant parts, then analyze the principle of the dump truck hydraulic system and select the hydraulic system suitable for this design, and finally use the corresponding 3d and 2d software to draw the main parts.Key words: Dump truck; Carriage; Lifting mechanism; Hydraulic system目录1 绪论 (3)1.1 背景 (3)1.2 国内外专用车辆的发展状况 (3)1.2.1 国外专用汽车的发展现状 (3)1.2.2 国内专用汽车的发展现状 (4)1.3 自卸汽车的性质和类型 (4)1.3.1 自卸汽车的性质 (4)1.3.2 自卸汽车的类型 (4)2 自卸汽车的总体设计 (5)2.1 二类底盘的选择 (5)2.2 整车尺寸参数的确定 (5)2.3 质量参数的确定 (6)2.4 自卸汽车车厢结构的选型和确定 (6)2.4.1 自卸车车厢结构的选型 (6)2.4.2 车厢尺寸的确定 (8)2.4.3 车厢内部尺寸及其质量的确定 (9)2.4.4 车厢举升时间与下降时间 (10)车箱举升时间/s (10)3 自卸汽车自卸举升机构的类型与选择 (10)3.1 举升机构的类型 (10)3.2 自卸汽车举升机构的性能对比 (11)3.3 举升机构的最大举升角 (12)4 液压系统设计 (13)4.1 液压系统的用途 (13)4.2 液压传动系统的组成 (13)4.3 自卸汽车液压系统的设计 (13)4.3.1 液压举升机构的工作原理 (13)5 液压缸的参数与确定 (14)5.1 液压缸的设计参数 (14)5.2 液压缸的受力分析与确定 (15)D (17)5.3 液压缸内径D和外径15.4 液压缸行程的确定 (19)5.5 液压缸基本参数的校核 (19)5.6 液压缸的确定 (20)6 液压元件选择 (21)6.1 液压泵的选择 (21)6.2 阀类元件的选择与确定 (23)6.2.1 选择阀类元件的标准 (23)6.3 油箱的选择 (24)6.4 滤油器的选择 (25)6.5 管路的选择 (25)6.6液压元件型号的确定 (26)7 设计小结 (26)参考文献 (26)谢辞 .......................................................... 错误!未定义书签。

本科毕业论文(设计)外文翻译学院：机电工程学院专业：机械工程及自动化姓名：高峰指导教师：李延胜2011年 05 月 10日教育部办公厅Failure Analysis，Dimensional Determination And Analysis，Applications OfCamsINTRODUCTIONIt is absolutely essential that a design engineer know how and why parts fail so that reliable machines that require minimum maintenance can be designed．Sometimes a failure can be serious，such as when a tire blows outon an automobile traveling at high speed．On the other hand，a failure may be no more than a nuisance．An example is the loosening of the radiator hose in an automobile cooling system．The consequence of this latter failure is usually the loss of some radiator coolant，a condition that is readily detected and corrected．The type of load a part absorbs is just as significant as the magnitude．Generally speaking，dynamic loads with direction reversals cause greater difficulty than static loads，and therefore，fatigue strength must be considered．Another concern is whether the material is ductile or brittle．For example，brittle materials are considered to be unacceptable where fatigue is involved．Many people mistakingly interpret the word failure to mean the actual breakage of a part．However，a design engineer must consider a broader understanding of what appreciable deformation occurs．A ductile material，however will deform a large amount prior to rupture．Excessive deformation，without fracture，may cause a machine to fail because the deformed part interferes with a moving second part．Therefore，a part fails(even if it has not physically broken)whenever it no longer fulfills its required function．Sometimes failure may be due to abnormal friction or vibration between two mating parts．Failure also may be due to a phenomenon called creep，which is the plastic flow of a material under load at elevated temperatures．In addition，the actual shape of a part may be responsiblefor failure．For example，stress concentrations due to sudden changes in contour must be taken into account．Evaluation of stress considerations is especially important when there are dynamic loads with direction reversals and the material is not very ductile．In general，the design engineer must consider all possible modes of failure，which include the following．——Stress——Deformation——Wear——Corrosion——Vibration——Environmental damage——Loosening of fastening devicesThe part sizes and shapes selected also must take into account many dimensional factors that produce external load effects，such as geometricdiscontinuities，residual stresses due to forming of desired contours，and the application of interference fit joints．Cams are among the most versatile mechanisms available．A cam is a simple two-member device．The input member is the cam itself，while the output member is called the follower．Through the use of cams，a simple input motion can be modified into almost any conceivable output motion that is desired．Some of the common applications of cams are——Camshaft and distributor shaft of automotive engine——Production machine tools——Automatic record players——Printing machines——Automatic washing machines——Automatic dishwashersThe contour of high-speed cams (cam speed in excess of 1000 rpm) must be determined mathematically．However，the vast majority of cams operate at low speeds(less than 500 rpm) or medium-speed cams can be determinedgraphically using a large-scale layout．In general，the greater the cam speed and output load，the greater must be the precision with which the cam contour is machined．DESIGN PROPERTIES OF MATERIALSThe following design properties of materials are defined as they relate to the tensile test．Figure 2.7Static Strength．The strength of a part is the maximum stress that the part can sustain without losing its ability to perform its required function．Thus the static strength may be considered to be approximately equal to the proportional limit，since no plastic deformation takes place and no damage theoretically is done to the material．Stiffness．Stiffness is the deformation-resisting property of a material．The slope of the modulus line and，hence，the modulus of elasticity are measures of the stiffness of a material．Resilience．Resilience is the property of a material that permits it to absorb energy without permanent deformation．The amount of energy absorbed is represented by the area underneath the stress-strain diagram within theelastic region．Toughness．Resilience and toughness are similar properties．However，toughness is the ability to absorb energy without rupture．Thus toughness is represented by the total area underneath the stress-strain diagram， as depicted in Figure 2．8b．Obviously，the toughness and resilience of brittle materials are very low and are approximately equal．Brittleness． A brittle material is one that ruptures before any appreciable plastic deformation takes place．Brittle materials are generally considered undesirable for machine components because they are unable to yield locally at locations of high stress because of geometric stress raisers such as shoulders，holes，notches，or keyways．Ductility． A ductility material exhibits a large amount of plastic deformation prior to rupture．Ductility is measured by the percent of area and percent elongation of a part loaded to rupture．A 5%elongation at rupture is considered to be the dividing line between ductile and brittle materials．Malleability．M alleability is essentially a measure of the compressive ductility of a material and，as such，is an important characteristic of metals that are to be rolled into sheets．Hardness．The hardness of a material is its ability to resistindentation or scratching．Generally speaking，the harder a material，the more brittle it is and，hence，the less resilient．Also，the ultimate strength of a material is roughly proportional to its hardness．Machinability．Machinability is a measure of the relative ease with which a material can be machined．In general，the harder the material，the more difficult it is to machine．Figure 2.8COMPRESSION AND SHEAR STATIC STRENGTHIn addition to the tensile tests，there are other types of static load testing that provide valuable information．Compression Testing．M ost ductile materials have approximately the same properties in compression as in tension．The ultimate strength，however，can not be evaluated for compression．As a ductile specimen flows plastically in compression，the material bulges out，but there is no physical rupture as is the case in tension．Therefore，a ductile material fails in compression as a result of deformation，not stress．Shear Testing．Shafts，bolts，rivets，and welds are located in such a way that shear stresses are produced．A plot of the tensile test．The ultimateshearing strength is defined as the stress at which failure occurs．The ultimate strength in shear，however，does not equal the ultimate strength in tension．For example，in the case of steel，the ultimate shear strength is approximately 75% of the ultimate strength in tension．This difference must be taken into account when shear stresses are encountered in machine components．DYNAMIC LOADSAn applied force that does not vary in any manner is called a static or steady load．It is also common practice to consider applied forces that seldom vary to be static loads．The force that is gradually applied during a tensile test is therefore a static load．On the other hand，forces that vary frequently in magnitude and direction are called dynamic loads．Dynamic loads can be subdivided to the following three categories．Varying Load．W ith varying loads，the magnitude changes，but the direction does not．For example，the load may produce high and low tensile stresses but no compressive stresses．Reversing Load．In this case，both the magnitude and direction change．These load reversals produce alternately varying tensile andcompressive stresses that are commonly referred to as stress reversals．Shock Load．This type of load is due to impact．One example is an elevator dropping on a nest of springs at the bottom of a chute．The resulting maximum spring force can be many times greater than the weight of the elevator，The same type of shock load occurs in automobile springs when a tire hits a bump or hole in the road．FATIGUE FAILURE-THE ENDURANCE LIMIT DIAGRAMThe test specimen in Figure 2.10a．，after a given number of stress reversals will experience a crack at the outer surface where the stress is greatest．The initial crack starts where the stress exceeds the strength of the grain on which it acts．This is usually where there is a small surface defect，such as a material flaw or a tiny scratch．As the number of cycles increases，the initial crack begins to propagate into a continuous series of cracks all around the periphery of the shaft．The conception of the initial crack is itself a stress concentration that accelerates the crack propagation phenomenon．Once the entire periphery becomes cracked，the cracks start to move toward the center of the shaft．Finally，when the remaining solid inner area becomes small enough，the stress exceeds the ultimate strength and the shaft suddenly breaks．Inspection of the break reveals a very interesting pattern，as shown in Figure 2.13．The outer annular area is relatively smooth because mating cracked surfaces had rubbed againsteach other．However，the center portion is rough，indicating a sudden rupture similar to that experienced with the fracture of brittle materials．This brings out an interesting fact．When actual machine parts fail as a result of static loads，they normally deform appreciably because of the ductility of the material．Figure 2.13Thus many static failures can be avoided by making frequent visual observations and replacing all deformed parts．However，fatigue failures give to warning．Fatigue fail mated that over 90% of broken automobile parts have failed through fatigue．The fatigue strength of a material is its ability to resist the propagation of cracks under stress reversals．Endurance limit is a parameter used to measure the fatigue strength of a material．By definition，the endurance limit is the stress value below which an infinite number of cycles will not cause failure．Let us return our attention to the fatigue testing machine in Figure 2.9．The test is run as follows：A small weight is inserted and the motor is turned on．At failure of the test specimen，the counter registers the number of cycles N，and the corresponding maximum bending stress iscalculated from Equation 2.5．The broken specimen is then replaced by an identical one，and an additional weight is inserted to increase the load．A new value of stress is calculated，and the procedure is repeated until failure requires only one complete cycle．A plot is then made of stress versus number of cycles to failure．Figure 2.14a shows the plot，which is called the endurance limit or S-N curve．Since it would take forever to achieve an infinite number of cycles，1 million cycles is used as a reference．Hence the endurance limit can be found from Figure 2.14a by noting that it is the stress level below which the material can sustain 1 million cycles without failure．The relationship depicted in Figure 2.14 is typical for steel，because the curve becomes horizontal as N approaches a very large number．Thus the endurance limit equals the stress level where the curve approaches a horizontal tangent．Owing to the large number of cycles involved，N is usually plotted on a logarithmic scale，as shown in Figure 2.14b．When this is done，the endurance limit value can be readily detected by the horizontal straight line．For steel，the endurance limit equals approximately 50% of the ultimate strength．However，if the surface finish is not of polished equality，the value of the endurance limit will be lower．For example，for steel parts with a machined surface finish of 63 micr oinches ( μin．)，the percentage drops to about 40%．For rough surfaces (300μin．or greater)，the percentage may be as low as 25%．The most common type of fatigue is that due to bending．The next most frequent is torsion failure，whereas fatigue due to axial loads occurs very seldom．Spring materials are usually tested by applying variable shear stresses that alternate from zero to a maximum value，simulating the actual stress patterns．In the case of some nonferrous metals，the fatigue curve does not level off as the number of cycles becomes very large．This continuing toward zero stress means that a large number of stress reversals will cause failure regardless of how small the value of stress is．Such a material is said to have no endurance limit．For most nonferrous metals having an endurance limit，the value is about 25% of the ultimate strength．EFFECTS OF TEMPERATURE ON YIELD STRENGTH AND MODULUS OF ELASTICITYGenerally speaking，when stating that a material possesses specified values of properties such as modulus of elasticity and yield strength，it is implied that these values exist at room temperature．At low or elevated temperatures，the properties of materials may be drastically different．For example，many metals are more brittle at low temperatures．In addition，the modulus of elasticity and yield strength deteriorate as the temperature increases．Figure 2.23 shows that the yield strength for mild steel is reduced by about 70% in going from room temperature to 1000o F．Figure 2.24 shows the reduction in the modulus of elasticity E for mild steel as the temperature increases．As can be seen from the graph，a 30% reduction in modulus of elasticity occurs in going from room temperature to 1000o F．In this figure，we also can see that a part loaded below the proportional limit at room temperature can be permanently deformed under the same load at elevated temperatures．Figure 2.24CREEP: A PLASTIC PHENOMENONTemperature effects bring us to a phenomenon called creep，which is the increasing plastic deformation of a part under constant load as a function of time．Creep also occurs at room temperature，but the process is so slow that it rarely becomes significant during the expected life of the temperature is raised to 300o C or more，the increasing plastic deformation can become significant within a relatively short period of time．The creep strength of a material is its ability to resist creep，and creep strength data can be obtained by conducting long-time creep tests simulating actual part operating conditions．During the test，the plastic strain is monitored for given material at specified temperatures．Since creep is a plastic deformation phenomenon，the dimensions of a part experiencing creep are permanently altered．Thus，if a part operateswith tight clearances，the design engineer must accurately predict the amount of creep that will occur during the life of the machine．Otherwise，problems such binding or interference can occur．Creep also can be a problem in the case where bolts are used to clamp tow parts together at elevated temperatures．The bolts，under tension，will creep as a function of time．Since the deformation is plastic，loss of clamping force will result in an undesirable loosening of the bolted joint．The extent of this particular phenomenon，called relaxation，can be determined by running appropriate creep strength tests．Figure 2.25 shows typical creep curves for three samples of a mild steel part under a constant tensile load．Notice that for the high-temperature case the creep tends to accelerate until the part fails．The time line in the graph (the x-axis) may represent a period of 10 years，the anticipated life of the product．Figure 2.25SUMMARYThe machine designer must understand the purpose of the static tensile strength test．This test determines a number of mechanical properties of metals that are used in design equations．Such terms as modulus ofelasticity，proportional limit，yield strength，ultimate strength，resilience，and ductility define properties that can be determined from the tensile test．Dynamic loads are those which vary in magnitude and direction and may require an investigation of the machine part’s resistance to failure．Stress reversals may require that the allowable design stress be based on the endurance limit of the material rather than on the yield strength or ultimate strength．Stress concentration occurs at locations where a machine part changes size，such as a hole in a flat plate or a sudden change in width of a flat plate or a groove or fillet on a circular shaft．Note that for the case of a hole in a flat or bar，the value of the maximum stress becomes much larger in relation to the average stress as the size of the hole decreases．Methods of reducing the effect of stress concentration usually involve making the shape change more gradual．Machine parts are designed to operate at some allowable stress below the yield strength or ultimate strength．This approach is used to take care of such unknown factors as material property variations and residual stresses produced during manufacture and the fact that the equations used may be approximate rather that exact．The factor of safety is applied to the yield strength or the ultimate strength to determine the allowablestress．Temperature can affect the mechanical properties of metals．Increases in temperature may cause a metal to expand and creep and may reduce its yield strength and its modulus of elasticity．If most metals are not allowed to expand or contract with a change in temperature，then stresses are set up that may be added to the stresses from the load．This phenomenon is useful in assembling parts by means of interference fits．A hub or ring has an inside diameter slightly smaller than the mating shaft or post．The hub is then heated so that it expands enough to slip over the shaft．When it cools，it exerts a pressure on the shaft resulting in a strong frictional force that prevents loosening．TYPES OF CAM CONFIGURATIONSPlate Cams．This type of cam is the most popular type because it is easy to design and manufacture．Figure 6．1 shows a plate cam．Notice that the follower moves perpendicular to the axis of rotation of the camshaft．All cams operate on the principle that no two objects can occupy the same space at the same time．Thus，as the cam rotates ( in this case，counterclockwise )，the follower must either move upward or bind inside the guide．We will focus our attention on the prevention of binding and attainment of the desired output follower motion．The spring is required to maintain contact between the roller of the follower and the cam contour when the follower is movingdownward．The roller is used to reduce friction and hence wear at the contact surface．For each revolution of the cam，the follower moves through two strokes-bottom dead center to top dead center (BDC to TDC) and TDC to BDC．Figure 6.2 illustrates a plate cam with a pointed follower．Complex motions can be produced with this type of follower because the point can follow precisely any sudden changes in cam contour．However，this design is limited to applications in which the loads are very light；otherwise the contact point of both members will wear prematurely，with subsequent failure．Two additional variations of the plate cam are the pivoted follower and the offset sliding follower，which are illustrated in Figure 6.3．A pivoted follower is used when rotary output motion is desired．Referring to the offset follower，note that the amount of offset used depends on such parameters as pressure angle and cam profile flatness，which will be covered later．A follower that has no offset is called an in-line follower．Figure 6..3Translation Cams．Figure 6.4 depicts a translation cam．The follower slides up and down as the cam translates motion in the horizontal direction．Note that a pivoted follower can be used as well as a sliding-type follower．This type of action is used in certain production machines in which the pattern of the product is used as the cam．A variation on this design would be a three-dimensional cam that rotates as well as translates．For example，a hand-constructed rifle stock is placed in a special lathe．This stock is the pattern，and it performs the function of a cam．As it rotates and translates，the follower controls a tool bit that machines the production stock from a block of wood．Figure 6.4Positive-Motion Cams．In the foregoing cam designs，the contact between the cam and the follower is ensured by the action of the spring forces during the return stroke．However，in high-speed cams，the spring force required to maintain contact may become excessive when added to the dynamic forces generated as a result of accelerations．This situation can result in unacceptably large stress at the contact surface，which in turn can result in premature wear．Positive-motion cams require no spring because the follower is forced to contact the cam in two directions．There are four basic types of positive-motion cams: the cylindrical cam，the grooved-plate cam ( also called a face cam ) ，the matched-plate cam，and the scotch yoke cam．Cylindrical Cam．The cylindrical cam shown in Figure 6.5 produces reciprocating follower motion，whereas the one shown in Figure 6.6 illustrates the application of a pivoted follower．The cam groove can be designed such that several camshaft revolutions are required to produce one complete follower cycle．Grooved-plate Cam．In Figure 6.8 we see a matched-plate cam with a pivoted follower，although the design also can be used with a translation follower．Cams E and F rotate together about the camshaft B．Cam E is always in contact with roller C，while cam F maintains contact with roller D．Rollers C and D are mounted on a bell-crank lever，which is the follower oscillating about point A．Cam E is designed to provide the desired motion of roller C，while cam F provides the desired motion of roller D．Scotch Yoke Cam．This type of cam，which is depicted in Figure 6.9，consists of a circular cam mounted eccentrically on its camshaft．The stroke of the follower equals two times the eccentricity e of the cam．This cam produces simple harmonic motion with no dwell times．Refer to Section 6.8 for further discussion．CAM TERMINOLOGYBefore we become involved with the design of cams，it is desirable to know the various terms used to identify important cam design parameters．Thefollowing terms refer to Figure 6.11．The descriptions will be more understandable if you visualize the cam as stationary and the follower as moving around the cam．Trace Point．The end point of a knife-edge follower or the center of the roller of a roller-type follower．Cam Contour．The actual shape of the cam．Base Circle．The smallest circle that can be drawn tangent to the cam contour．Its center is also the center of the camshaft．The smallest radial size of the cam stars at the base circle．Pitch Curve．The path of the trace point，assuming the cam is stationary and the follower rotates about the cam．Prime Circle．The smallest circle that can be drawn tangent to the pitch curve．Its center is also the center of the camshaft．Pressure Angle．The angle between the direction of motion of the follower and the normal to the pitch curve at the point where the center of the roller lies．Cam Profile．Same as cam contour．BDC．Bottom Dead Center，the position of the follower at its closest point to the cam hub．Stroke．The displacement of the follower in its travel between BDC and TDC．Rise．The displacement of the follower as it travels from BDC to TDC．Return．The displacement of the follower as it travels from TDC or BDC．Ewell．The action of the follower when it remains at a constant distance from the cam hub while the cam turns．A clearer understanding of the significance of the pressure angle canbe gained by referring to Figure 6.12．Here FTis the total force acting on the roller．It must be normal to the surfaces at the contact point．Its direction is obviously not parallel to the direction of motion of the follower．Instead，it is indicated by the angle α，the pressure angle，measured from the line representing the direction of motion of thefollower．Therefore，the force FT has a horizontal component FHand a verticalcomponent FV．The vertical component is the one that drives the followerupward and，therefore，neglecting guide friction，equals the follower Fload．The horizontal component has no useful purpose but it is unavoidable．In fact，it attempts to bend the follower about its guide．This can damage the follower or cause it to bind inside its guide．Obviously，we want the pressure angleto be as possible to minimize the side thrust F．A practical rule of thumbHis to design the cam contour so that the pressure angle does not exceed 30o．The pressure angle，in general，depends on the following four parameters: ——Size of base circle——Amount of offset of follower——Size of roller——Flatness of cam contour ( which depends on follower stroke and type of follower motion used )Some of the preceding parameters cannot be changed without altering the cam requirements，such as space limitations．After we have learned how to design a cam，we will discuss the various methods available to reduce the pressure angle．故障的分析、尺寸的决定以及凸轮的分析和应用前言介绍：作为一名设计工程师有必要知道零件如何发生和为什么会发生故障，以便通过进行最低限度的维修以保证机器的可靠性。

Original AbstractHydraulic lifting platform is a versatile crane lifting equipment, widely used in factories, docks, construction, transportation, sports, equipment maintenance and other high-altitude operations and maintenance. Existing hydraulic lifting platform there are many, can be roughly divided into: four-wheel mobile lifting platform, push-type lift platform, car load lifting platform, fixed platform lift, scissor lift platform, four-post lift The two column lift and so on.In recent years, with the rapid increase in the use of cars, China's booming auto industry, especially the car industry. This makes the auto repair industry has grown, demand for automotive maintenance equipment rapid expansion, but also the maintenance requirements in the automotive tools and equipment requirements on the increasingly high lift vehicle repair workshop is essential and most important maintenance machinery and equipment. The role of auto lift car is in need of repair, a smooth upgrade to the appropriate height, so that maintenance workers at the bottom of the car chassis maintenance and inspection. Generally divided into high column car lift and scissors. Either way, are required to meet the synchronous lifting the car, cornering can not happen, and asked for the empty chassis bottom for easy maintenance workers for maintenance work which requires lifting platform synchronous lifting, running smoothly. Therefore, maintenance of the car lifting platform equipment is generally driven by hydraulic system.With the expanding service sector, as well as the further development of automation, the maintenance staff to reduce labor intensity, making the easy maintenance, and can better improve the efficiency of vehicle maintenance, and car maintenance service quality, so the hydraulic lift Platform automation requirements are also rising. Vehicle maintenance is currently required to meet the synchronization control, lifting the platform lift system depends mainly on the hydraulic system and electrical control and drive systems, but the lift platform is currently owned by the widespread leakage, internal leakage, short life, the operation not flexible, synchronous operation and low defects. To avoid these disadvantages, require more precise synchronization to ensure that the hydraulic lifting platform lift precision, and now most of the hydraulic lifting platform simultaneously phasing out all traditional hydraulic valves, the use of more precise control of the new electro-hydraulic servo valve, electro-hydraulic proportional digital electro-hydraulic valve and valve to control the hydraulic system, to achieve synchronization and high precision. As a form of electro-hydraulic proportional valve type of diverse, easy to use composition of a variety of electrical and computer-controlled hydraulic system, control of high precision, installation flexibility and strong anti-pollution and many other advantages.Currently used in the automotive repair Hydraulic synchronous lift platform vehicle maintenance plays an important role in synchronous lifting platform on a variety of hydraulic valves, hydraulic cylinders, hydraulic pump station innovation and improvement, making a hydraulic lifting platform synchronization smoothrunning, low noise, fast response, high precision synchronization of the repair and maintenance in the car played a crucial role.With the hydraulic lift platform in the automotive repair industry, application and further improvement and innovation in the maintenance of hydraulic lifting platform has the car can achieve more complex functions, the structure of the platform, drive on, and a variety of control systems, has been greatly improved. The current lift platform lift system is mainly driven by the hydraulic system, of course, do not rely on hydraulic pressure, as well as dual-use diesel electric rotary lift platform, now appeared battery driven lift platform, continuously variable transmission can be achieved with safer, more convenient and low noise advantages. Lifting platform is currently widespread leakage, internal leakage, short life, the operation is not flexible, synchronous operation and low defects. To avoid these disadvantages, require more precise synchronization to ensure that the hydraulic lifting platform lift precision, and now most of the hydraulic lifting platform simultaneously phasing out all traditional hydraulic valves, the use of more precise control of the new electro-hydraulic servo valve, electro-hydraulic proportional digital electro-hydraulic valve and valve to control the hydraulic system, to achieve synchronization and high precision. As a form of electro-hydraulic proportional valve type of diverse, easy to use composition of a variety of electrical and computer-controlled hydraulic system, control of high precision, installation flexibility and strong anti-pollution and many other advantages, applications become increasingly broadened.In China, although synchronous hydraulic lifting platform for such development, production started late, but with China's rapid economic development, in order to adapt to China in various fields used by the synchronous hydraulic lifting platform development needs and take the large-scale, standardized , intensive, product support services, achieving mechanical, electrical, fluid integration platform in the application of synchronous movements. The use of synchronous hydraulic lifting platform surface, the service has been expanding, is now in rapid development stage, and now hydraulic lifting platform reliability, security, easy operation and simple directness, and other aspects greatly improved, and with the the popularity and development of computer and mechanical, electrical, fluid integration progress of the study, major domestic and foreign companies have to compete with the computer (electronic) control system to improve overall performance and reduce the use of hydraulic components, machine, reducing the whole size and weight, improve the sensitivity of control and synchronization accuracy. In particular, the manufacturers actively introducing and digesting foreign advanced technology, development of new varieties, improving product technology and quality level, has been part of the hydraulic lifting platform synchronized at or close to the international level of similar products.Currently used in the automotive repair Hydraulic synchronous lift platform vehicle maintenance plays an important role in synchronous lifting platform on a variety of hydraulic valves, hydraulic cylinders, hydraulic pump station innovation and improvement, making a hydraulic lifting platform synchronization Smooth running, low noise, fast response, high precision synchronization, for the repair and maintenance of the car plays an irreplaceable role in a wide range prospects.Therefore, the lifting platform for further research and improvement, optimize system performance and structure to further improve to make up for the shortcomings of existing technology has important significance.The subject of the design of the hydraulic lifting platform main use of theoretical research and design, through the understanding and study of the hydraulic system, as well as existing control technologies and more in-depth research and development, in the hydraulic system components and further understanding and learning , Combined with the modernization of hydraulic components and automation and control components within the hydraulic control through traditional high-tech components and control elements of existing comparative and comprehensive application of the traditional hydraulic system, based on the research and design more innovative set of machines , Electricity, liquid in one of the hydraulic control system, makes the system more stable and faster to achieve the advantages.Hydraulic lift platform system, requires the ability to achieve four-wheeled vehicles in a controlled synchronous lifting height lifting range, to achieve safe and reliable control of the two front, two rear, two revolvers, two rounds of synchronous lifting the right and to ensure synchronous movements accuracy. The hydraulic lift system also must have a fast response speed, hydraulic power units, small size, compact structure, large power weight ratio, ease of manipulation and control, labor-saving convenience and easy to implement automated, with overload protection for high reliability requirements system, excellent technical performance, while ensuring synchronous hydraulic lifting platform can be anywhere in the vertical direction on a longer time (60 min or longer) within a reliable locking, the system can work continuously and reliably, the system energy efficient, easy to maintain low cost. Hydraulic lift platform to meet system design requirements, synchronous movements smooth, and the design to achieve the functional requirements, develop the system closed-loop control of hydraulic systems, hydraulic systems used to satisfy the synchronization requirements of precision and control to achieve the four-wheeled vehicles in a controlled synchronous lifting height lifting range, to achieve safe and reliable control of the two front, two rear, two revolvers, two rounds of synchronous lifting the right and to ensure the accuracy of synchronous movements.To meet the synchronous lifting hydraulic system, the system needs to have synchronization control device to achieve synchronization. Synchronization of hydraulic system is currently running multiple control methods, mainly mechanical synchronization method, pump or motor parallel method, double rod cylinder in series, control valve, synchronizer, synchronization control valve circuit, servo and so on.According to the design of machinery and equipment requirements for the realization of a better two-car front-wheel, two rear, two revolvers, two synchronous lifting the right wheel, respectively, the flexible control, the design of the four hydraulic cylinders used for its intended to achieve their respective parts of the wheel lift and flexible control. Synchronization to achieve higher accuracy and more flexible control, the design does not use the traditional control valves to control, but intends to adopt more new electro-hydraulic proportional control valve to control. Electro-hydraulic proportional control valve is between the ordinary hydraulic valveand servo valve between a fluid control valves, servo valves with similar functions, but also has its specific advantages. Proportional solenoid valve is replaced by the proportion of ordinary hydraulic valve adjustment and control devices and form, it can be given input voltage or current signal proportional continuous, remote control of the direction of flow, pressure and flow. Reasonable use of electro-hydraulic proportional control valve can improve the automation and accuracy, and simplify the system. Commonly used proportional valve can be divided into: proportional pressure valve, proportional flow valves and proportional directional valve three.The design uses electro-hydraulic proportional control system, closed-loop feedback control system, the detection by the sensor and fed back through the electro-hydraulic proportional plc valve, electro-hydraulic proportional control valve opening size corresponding to the achievement of the hydraulic cylinder to achieve synchronous lifting control accuracy. To ensure the hydraulic cylinder to achieve at work to ensure self-locking, hydraulic system should be in each cylinder fuel supply system with check valve to achieve self-lock function to ensure the safety of hydraulic lifting platform. Overload protection to ensure the realization of the hydraulic system, hydraulic system relief valve in the hydraulic pump that needs to be installed to ensure the safety of the system to provide a certain pressure. Oil to the system to meet the system requirements to run and quality of hydraulic oil, hydraulic system should be in the inlet and outlet port to install filters. In order to meet the hydraulic system can be fully automated, the system of hydraulic directional control valve solenoid valve are used. In order to better respond to energy problems, you can, where necessary, instead of using the accumulator motor-driven pump provides the pressure accumulator to provide the direct use of the hydraulic cylinder pressure to meet the relevant sport.In order to achieve self-locking hydraulic cylinder to the function of the hydraulic system in the bottom of each cylinder are equipped with check valve, check valve can achieve one-way self-locking, two-way communication function of the oil. In order to provide security to meet the hydraulic system pressure, not suddenly as high pressure hydraulic system of the adverse effects or even damage some of the hydraulic components, so as a safety valve with pressure relief valve to prevent hydraulic overload protection. In order to achieve automation of the hydraulic system to meet the simultaneous operation of the system is more accurate, and the realization of the system's high efficiency, rapid response requirements, the use of electro-hydraulic proportional directional control valve to high precision, fast response to the synchronization control. Most of the traditional manual control valve, which controlled comparison machinery, it is difficult to achieve automation. Electromagnetic valve, use the pull solenoid valve to control the direction of control of the commutation circuit to achieve better automated results. Shunt valve assembly, also known as synchronous valve, is a hydraulic diversion valve, valve functions in one set of the independent hydraulic device. Shunt valve synchronization is the set speed sync, that is, when two or more cylinders cylinder under different loads, respectively, the shunt valve set pressure and flow through the sensitive internal components automatically adjust the fuel tank of exercise to maintain synchronization.Shunt valve assembly is mainly used in multi-cylinder hydraulic cylinder and the synchronization control system. Split set by the synchronous control flow valve hydraulic system has a simple structure, low cost, design, sets, debugging and ease of use, reliability and many other advantages, which shunt valve assembly in the hydraulic system has been widely used, so there will also be a reasonable set of flow diversion valve used to achieve simultaneous control of two hydraulic cylinders. In the hydraulic system, the oil cleanliness of the normal operation of the hydraulic system has a vital role, so the oil pump and fuel tank return port port filters have been installed in order to ensure that the cleaning fluid degrees, which is an indispensable circuit hydraulic system attachment.In this system, due to the beneficial effects of gravity, the decline in the course of lifting platform, you can completely rely on gravity to provide power, where only one-way valve on the hydraulic control valve port for remote control of the pressure to provide, in under the action of gravity to allow check valve can be decreased to achieve oil return channel, as the pressure is not big, so no need to re-use of oil pump drive motors to achieve the check valve through the oil pressure can be used directly to provide the pressure accumulator, so the treatment, not only simplifies the system control, and can better save energy and avoid frequent start the motor, can effectively extend the life of the motor and pump, and to improve the efficient use of the hydraulic system, which can be said that the biggest advantage of the system design.Hydraulic platform of exercise is to achieve the various hydraulic cylinders rise and fall, but the rise and fall during the lifting phase will be a period in the acceleration of movement, until the required speed to the speed, the platform will achieve a uniform motion and then decelerate to stop. Throughout the campaign process, the hydraulic lifting platform mainly by the external load platform of the car's own weight of gravity and composition. Therefore, the size of the external load is relatively stable and unchanging, and only in the acceleration phase of operation of the entire platform will have a maximum load.Hydraulic lifting platform synchronized variety of mechanical structure, a four-wheel mobile lifting platform, elevating platform vehicle-mounted, fixed landing platform, sets of cylinder-type lift platform, four-column lifting platform, the two-column lifting platform, scissor Lifting platform, and other mechanical structure, and mechanical structure of different ways to achieve different movements to meet the different, specific ways of working and working environment.The design of synchronous hydraulic lifting platform is designed to meet the car repair industry in the use of lifting platform. Maintenance workers to consider maintenance when the car convenient and comfortable, you need to lift the car a certain height, but such use conditions, most of the requirements of hydraulic lifting platform is fixed, so the fixed hydraulic lift platform. While the four cylinder design can be fixed in the foundation, and to consider their own characteristics and the hydraulic cylinder the height, you can dig a pit in the maintenance shop type of foundation, the four cylinder bolts to fully firmly fixed to the ground by on. In order to be able to check and repair chassis, hydraulic lifting platform not designed for the whole plate fixed on the hydraulic cylinder in the bottom four shelves, is thoughtful, Idesigned the mechanical structure to meet the four-wheel placed in the middle hollow of the platform structure, so that not only meet the maintenance requirements, but also save a portion of material, making the structure more simple and beautiful. Taking into account the car body as a whole if there is a need to use floating platform from the condition, for example, remove the wheels need repair or need to dress up tires, etc., are required to meet all hold up the whole body, this, this design in each set of two plates of another set of lifting devices, lifting devices to facilitate use of the vehicle chassis will hold up, to achieve overall body vacant. To consider the overall open on the car platform, hold up the car fixed and plate lifting devices, and can be used scissor lift to reach the level of a structure. The biggest advantage of using this structure is not hold up in the chassis to the plate when retracted within this structure, so that the overall structure is beautiful and practical. To meet the car on the platform do not slip and stable place on the platform, placed on the plate anti-slip skid plate.Programmable Logic Controller (PLC) is an industrial control computer, is the succession of computer, automatic control technology and communication technology as one of the new automatic device. It has strong anti-interference ability, low price, reliability, programming is simple, easy to use and so on, in the industrial field operators by the likes of engineering, so PLC in all areas of industrial control is widely used.The design is based on the ratio of the hydraulic cylinder piston rod valve position control system, namely the use of PLC control signal generated by electro-hydraulic proportional valve driver to control the exact location of the hydraulic cylinder. Hydraulic cylinder piston rod displacement sensor displacement feedback signal output by the A / D converted into digital signals into the computer, the PLC signals within a given comparison, and the control algorithm according to the set after the output control signal, after D / A converted to analog voltage or current signal proportional electro-hydraulic control valve spool position to control the flow of the hydraulic cylinder transmission, drive hydraulic cylinder, to achieve the position of the piston with a load control system as a whole constitute a closed-loop control for precise positioning .原文摘要液压升降平台是一种多功能起重升降设备，广泛应用于工厂、码头、建筑、交通、体育馆、设备检修等高空作业及维修。

分类号编号烟台大学毕业论文（设计）T式自卸汽车举升机构设计The design of T- type column hydraulic car lift申请学位：工学学士学位院系：机电汽车工程学院专业：机械设计制造及其自动化姓名：学号：指导老师：2014年6月1日烟台大学.T式自卸汽车举升机构设计姓名：指导教师：2014年6月1日烟台大学摘要随着国民经济的增长，我国专用汽车市场进入了快速成长期。

2005 年专用汽车生产企业已经有 628 家，专用汽车品种已经达到 4900 多个，2005 年专用汽车产量达70 万辆，占载货汽车总产量的 40%。

作为专用汽车中一个分支的自卸汽车，陆续出现了多种多样的型式，其中最常见的是后倾式自卸汽车。

本文首先对自卸汽车国内外发展现状及设计内容作了相关的概述。

接着，按照自卸车举升机构的设计过程，完成了对机构的选型、机构的受力分析也计算、液压回路系统的设计与运动仿真分析。

关键字：专用汽车，自卸汽车，举升机构，运动仿真AbstractWith the national economic growth, China's auto market has entered a special rapid gro wth. 2005 Special Purpose Vehicle manufacturers have been 628, Special PurposeVehicle has reached more than 4900 varieties,2005 special vehicle production reached 700,000, Accounting f or 40% of total truck. As a Special Purpose Vehicle in a branch ofthe dump truck, has been found in a wide variety of types , of which the most common isBack ward curved dump truck.In this paper, firstly, I made a general about the auto unload vehicle design and itsdevelopment domestic and abroad. Then, according to the process of the design of lifting mechanism of dump truck, completed the analysis of mechanism selection, mechanism of stress analysis are also calculated, h ydraulic system design and motion simulation.Key words: Special Purpose Vehicle, Dump Truck, Lifting mechanism, motion simulation目录第一章绪论 (1)1.1引言 (1)1.2 国内外专用车辆的发展概况 (1)1.2.1 国外专用车辆发展概况 (1)1.2.2 我国专用汽车的发展状况 (2)1.3自卸车概述 (2)第二章自卸车举升机构选型 (4)2.1自卸车载重与车厢举升角的确定 (4)2.1.1自卸车载重 (4)2.1.2车厢举升角的确定 (4)2.2举升机构结构选型 (4)第三章自卸汽车举升机构的结构与设计 (7)3.1T 式举升机构运动与受力的解析计算 (7)第四章液压系统设计 (12)4.1确定系统方案 (12)4.1.1液压回路系统的设计 (12)4.2液压系统主要元件的性能参数计算与选型 (13)4.2.1举升油缸的性能参数计算与选型 (13)4.2.2液压油泵性能参数计算与选型 (14)4.2.3管路选择 (15)4.2.4油箱容积设计 (15)第五章T式自卸汽车举升机构的动力学仿真 (16)5.1 T式自卸汽车举升机构系统实体模型的建立 (16)5.2举升机构的动力学仿真 (18)5.2.1 模型导入 (18)5.2.2编辑模型构件 (19)5.2.3运动副建立 (19)5.3对三维模型进行运动仿真分析 (20)5.3.1设置运动仿真解算方案 (20)5.3.2仿真曲线输出。