Analyses to be performed at the various locations of the shaft to determine the minimum shaft diameters

Analyses to be performed at the various locations of the shaft to determine the minimum shaft diameters

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Step # 1 - Select Materials for the Shafts

Assume the basic shaft diameters and make a first trial material selection for each shaft

Hint: For strength based designs, shafts having diameters less than 3.5" are usually made from a cold drawn steel in order to resist fatigue

Hence,

For D Ł 3.5" Cold Drawn (CD) Material - better surface finish and easily machinable

For D ł 3.5" Hot Rolled (HR) or preferably Quenched & Treated (Q&T) - generally rough surface but low cost

Step # 2 - Perform Static & Fatigues Analyses

Static Analyses/Assumptions	Fatigue Analyses - eqn. (18-39)
d₃ - using eqn. (18-12) d₂ - using eqn. (18-12) d₁ = 0.8 ´ d₂ d₄ = 0.8 ´ d₃	d₂ - Fillet Location (Sharp) d₃ - Keyseat Location d₄ - Fillet Location (Sharp)

Do NOT use K_f in the numerator of eqn. (18-39)

S_e = k_a.k_b.k_c.k_d.k_e.S_e'

K_t is 2.5 for keyseats