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Question: sis a bad means of axially locating the shaft elements...

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sis a bad means of axially locating the shaft elements and to hrust loads 25. The S-N diagram is usually obtained by completely reversed stress cycles, in which the stress level altenates between unequal magnitudes of tension and compression 26. For extremely long shafts carrying several load-bearing components, it may be necessary to provide more than two bearing supports. In this case, particular care must be given to the alignment of the bearings 27. If the specimen is loaded beyond this point, the deformation is said to be plastic and the material will take on a permanent set when the load is removed. This point is called the fracture limit 28. The rotating shaft specimen used in the laboratory to determine endurance limits is prepared very carefully and tested under closely controlled conditions. It is unrealistic to expect the endurance limit of a mechanical or structural member to match the values obtained in the laboratory. Some differences include material, manufacturing 29. Cold drawn steel is usually used for diameters over than 75 mm. The nominal diameter of the bar can be left unmachined in areas that do not require fitting of components. Hot rolled steel should be machined all over Life of 14 N < 10 Cycles is generally classified as low cycle fatigue, whereas high- 30. cycle fatigue is considered to be N 10 cycles It is not recommended to have only one bearing to carry the axial load in order to allow greater tolerances on shaft length dimensions, and to prevent binding if the shaft 31. due to 32. In general, it is best to support cantilevered outboard of the bearings. Pulleys and sprockets often need to be mounted outboard for ease of installation of the belt or chain. The length of the cantilever should be kept short to minimize the deflection For steel and iron, the S-N diagram becomes horizontal at some point. The strength at this point is called the yield limit and occurs somewhere between 10 Shafts usually dont need to be surface hardened unless they serve as the actual journal somewhere between 10 and 10 cycles 34 a bearing surface Since most shaft problems incorporate gears or pulleys that introduce forces in two planes, the shear and bending moment diagrams will generally be needed in two planes Resultant moments are obtained by summing moments as absolute values at points of interest along the shaft Stress is something that occurs in a part, usually as a result of its being assembled into a machine and loaded Youngs modulus or the modulus of elasticity is a measure of the strengh of a materal For a stationary load applied on a rotating shaft, a steady bending moment will produce a completely reversed moment as a specific stress element will atternate from compression to tension in every revolution of the shaft. Youngs modulus or the modulus of elasticity has units of strain of a material 35 36. 37. or tapered roller bearings will almost always be negligibly small compared to the bending moment stress 40. Axial stresses on shafts due to the axial components transmitted through helical gears
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