8-2. Determine the material's fatigue properties for the given data. Shown the plots to obtain the properties. Smooth Specimen-Cyclic Data Total Strain Amplitude. Ac/2 Stress Amplitude. Plastic Strain Reversals to As, Ao o', Ao/2 (ksi) Amplitude. Ae,/2* Failure, 2N, Basquin Equation %3D %3D 2 2E E 0.0393 0.0393 0.02925 0.01975 0.0196 0.01375 162.5 162 155 143.5 143.5 136.5 0.0336 0.0336 0.0238 0.0147 0.0145 50 68 Aɛ, 22ן Coffin-Manson Eguation %3D 256 350 0.00894 488 0.00980 130.5 0.00521 1,364 0.00980 0.00655 0.00630 0.00460 0.00360 0.00295 1.386 3,540 3.590 0.00534 0.00229 0.00211 0.00059 0.00000 0.00000 126.5 121 119 114 106 84.5 Δε 9.100 35.200 (2N E %3D %3D 2E 140.000 All information is giyen
Design Against Fluctuating Loads
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate. The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value. For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions. However, most of the machine elements are subjected to variable or fluctuating stresses, due to the nature of load that fluctuates from high magnitude to low magnitude. Also, the nature of the loads is repetitive. For instance, shafts, bearings, cams and followers, and so on.
Design Against Fluctuating Load
Stress is defined as force per unit area. When there is localization of huge stresses in mechanical components, due to irregularities present in components and sudden changes in cross-section is known as stress concentration. For example, groves, keyways, screw threads, oil holes, splines etc. are irregularities.
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