故障的分析、尺寸的决定以及凸轮的分析和应用、国内外轿车覆盖件模具设计概况.docx

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1、外文翻译故障的分析、尺寸的决定以及凸轮的分析和应用Failure Analysis, Dimensional Determination And Analysis,Applications Of CamsAbstract： It is absolutely essential that a design engineer know how and why parts fail so thatreliable machines that require minimum maintenance can be designed； Cams are among themost versatile me

2、chanisms available. A cam is a simple two-member device. The inputmember is the cam itself, while the output member is called the follower. Through the use ofcams, a simple input motion can be modified into almost any conceivable output motion thatis desired.Key words: failure high-speed cams design

3、 propertiesINTRODUCTIONIt is absolutely essential that a design engineer know how and why parts fail so thatreliable machines that require minimum maintenance can be designed. Sometimes a failurecan be serious, such as when a tire blows out on an automobile traveling at high speed. On theother hand,

4、 a failure may be no more than a nuisance- An example is the loosening of theradiator hose in an automobile cooling system. The consequence of this latter failure isusually the loss of some radiator coolant, a condition that is readily detected and corrected.The type of load a part absorbs is just a

5、s significant as the magnitude. Generallyspeaking, dynamic loads with direction reversals cause greater difficulty than static loads, andtherefore, fatigue strength must be considered. Another concern is whether the material isductile or brittle. For example, brittle materials are considered to be u

6、nacceptable wherefatigue is involved.Many people mistakingly interpret the word failure to mean the actual breakage of apart. However, a design engineer must consider a broader understanding of what appreciabledeformation occurs. A ductile material, however will deform a large amount prior torupture

7、. Excessive deformation, without fracture, may cause a machine to fail because thedeformed part interferes with a moving second part. Therefore. a part fails(even if it has notphysically broken)whenever it no longer fulfills its required function. Sometimes failure maybe due to abnormal friction or

8、vibration between two mating parts. Failure also may be due toa phenomenon called creep, which is the plastic flow of a material under load at elevatedtemperatures. In addition, the actual shape of a part may be responsible for failure. Forexample, stress concentrations due to sudden changes in cont

9、our must be taken intoaccount. Evaluation of stress considerations is especially important when there are dynamicloads with direction reversals and the material is not very ductile-In general, the design engineer must consider all possible modes of failure, whichinclude the following.StressDeformati

10、onWearCorrosionVibrationEnvironmental damageLoosening of fastening devicesThe part sizes and shapes selected also must take into account many dimensional factorsthat produce external load effects, such as geometric discontinuities, residual stresses due toforming of desired contours, and the applica

11、tion of interference fit joints.Cams are among the most versatile mechanisms available. A cam is a simpletwo-member device. The input member is the cam itsel while the output member is calledthe follower. Through the use of cams, a simple input motion can be modified into almost anyconceivable outpu

12、t motion that is desired. Some of the common applications of cams areCamshaft and distributor shaft of automotive engineProduction machine toolsAutomatic record playersPrinting machinesAutomatic washing machinesAutomatic dishwashersThe contour of high-speed cams (cam speed in excess of 1000 rpm) mus

13、t be determinedmathematically. However, the vast majority of cams operate at low speeds(less than 500 rpm)or medium-speed cams can be determined graphically using a large-scale layout- In general.the greater the cam speed and output load, the greater must be the precision with which thecam contour i

14、s machined.DESIGN PROPERTIES OF MATERIALSThe following design properties of materials are defined as they relate to the tensile test.Static Strength The strength of a part is the maximum stress that the part can sustainwithout losing its ability to perform its required function. Thus the static stre

15、ngth may beconsidered to be approximately equal to the proportional limit, since no plastic deformationtakes place and no damage theoretically is done to the material.Stiffness Stiffness is the deformation-resisting property of a material. The slope of themodulus line and, hence, the modulus of elas

16、ticity are measures of the stiffness of a material.Resiliencee Resilience is the property of a material that permits it to absorb energywithout permanent deformation. The amount of energy absorbed is represented by the areaunderneath the stress-strain diagram within the elastic region.Toughness Resilience and toughness are similar pro