The same shaft with a keyway, as in the previous question, is considered here again. The diameter of the shaft is d-30mm and the keyway fillet radius is r-3mm. Suppose that the static stress concentration factor is k-2.02 and the shaft is made of wrought steel with UTS-570 MPa. Using the table shown below, find the fatigue stress concentration correction factor (C). (Hint: round-off your answer to 4 decimal places). C₂ = 1/K d/4 d r Material Wrought Steel Cast steel d/8 K, 1+q(K-1) Notch Alleviation factors Flake S.G. 100/ 0.2 0.6 √a(mm) q=1/(1 +√(a/r) 170/0 Lesser of 0.25 or (250/) Gues in MN, Cast iron Aluminium alloys Magnesium alloys 0 Titanium alloys 0 Reinforced plastic composites Very large q-notch sensitivity factor a-notch alleviation factor r-radius of stress raiser K= Fatigue stress concentration factor K = Static stress concentration fac Corrected material properties S=C₂CC.C.S. S=CC.C.C.S. Quin MN, Ques in MN K. =K, K = K K-1
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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