影响耐久性强度的因素外文翻译(编辑修改稿)

影响耐久性强度的因素外文翻译(编辑修改稿)内容摘要：

y slow of endurance strength of 50% or more can be achieved with nitriding. Wrought versus Cast Materials Metal alloys having similar chemical positions can be either wrought or cast to produce the final materials are usually rolled or materials usually have a higher endurance strength than cast materials of similar position in regions where no significant stress concentration ,in the vicinity of notches and other discontinuities,the endurance strength of wrought and cast materials is more nearly possible explanation of this phenomenon is that the cast material is likely to have more isotropic material properties than the wrought material and is less affected by the presence of the stress concentration. To use the more conservative approach,it is remended that a factor of be applied to the basic endurance strength if a cast steel is cast iron,a factor of is remended. Type of Stress Endurance strength data are obtained from the rotating beam test that produces pletely reversed and repeated normal maximum stress is 本科生毕业论文（设计） 第 8 页 共 17 页 producted at the surface of the specimen,and the stress vanes linearly to zero at the center of the circular cross the actual loading is different from bending,a factor for the type of loading should be applied to the endurance strength. Axial Tension Under pure tension, all of the materialnot just the surface— is subjected to the maximum stress. A factor of is suggested to be the bending endurance strength to reflect this different behavior. Effect of Stress Ratio on Endurance Strength Figure 510 shows the general variation of endurancestrength data for a given material when the stress ratio R varies from to +,covering the range of cases including the following: ■ Repeated,reversed stress(Figure 53)。 R= ■ Partially reversed fluctuating stress with a tensile mean stress【 Figure 54(b)】。 R 0 本科生毕业论文（设计） 第 9 页 共 17 页 ■ Repeated,onedirection tensile stress(Figure 56)。 R=0 ■ Fluctuating tensile stress【 Figure 54(a)】。 0 R ■ Static stress(Figure 51)。 R=1 Note that Figure 510 is only an example,and it should not be used to determine actual data such data are desired for a particular material,specific data for that material must be found either experimentally or published literature. The most damaging kind of stress among those listed is the repeated,reversed stress with R=1.(See Reference 27.)Recall that the rotating shaft in bending as shown in Figure 52 is an example of a loadcarrying member subjected to a stress ratio R=1. Fluctuating stresses with a pressive mean stress as shown in Parts(c) and (d) of Figure 54 do not significantly affect the endurance strength of the material 本科生毕业论文（设计） 第 10 页 共 17 页 because fatigue failures tend to originate in regions of tensile stress. Note that the curves。