hw6.Fall.2010x

hw6.Fall.2010x - factor of safety for the shear stress in...

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ME 452 Machine Design II Homework Set 6 The steel arm shown below is keyed to a 2.0” diameter shaft which does not rotate. The load applied to the end of the arm, P, varies with time as shown. For the square key, which connects the arm to the shaft, the following is known: Length = 3.0 inches (into the page) S e = 25,000 psi (fully corrected endurance limit) S ut = 70,000 psi (ultimate strength) S y = 45,000 psi (yield strength) a. Calculate the midrange and alternating nominal shear stresses in the key, in terms of the unknown dimension, h (inches). b. Calculate the dimension, h, inches, for the key such that the infinite-life fatigue
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Unformatted text preview: factor of safety for the shear stress in the key using the Goodman failure criteria is 2.0. c. Calculate the infinite-life fatigue factor of safety for the normal stress on the side of the key (crush) using the Goodman failure criteria for the value of h calculated above. d. Calculate the yield factor of safety for both shear and crush for the value of h calculated above. 12 P = 400 + 800sin(10t) (t = time in seconds) Fixed shaft (2.0 dia) does not rotate Arm Key fixes arm to shaft h h 3.0...
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