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MECH 325 Final Exam Practice Set
Problem 1. Estimate the endurance strength of a 1.5-in-diameter rod of AISI 1040 steel having a machined finish and heat-treated to a tensile strength of 110 kpsi, loaded in rotating bending.
Problem 2. The shaft shown in the figure is machined from AISI 1040 CD steel.
The shaft rotates at 1600 rpm and is supported in rolling bearings at A and B. The applied forces are F1 = 2500 lbf and F2 = 1000 lbf. Determine the minimum fatigue factor of safety based on achieving infinite life. If infinite life is not predicted, estimate the number of cycles to failure. Also check for yielding.
Problem 3. The figure shows a fluid-pressure linear actuator (hydraulic cylinder) in which D = 4 in, t=⅜ in, L = 12 in, and w=¾ in. Both brackets as well as the cylinder are of steel. The actuator has been designed for a working pressure of 2000 psi. Six ⅜ in SAE grade 5 coarse-thread bolts are used, tightened to 75 percent of proof load. Assume the bolts are unthreaded within the grip.
a) Find the stiffnesses of the bolts and members, assuming that the entire cylinder is compressed uniformly and that the end brackets are perfectly rigid.
b) Find the factor of safety guarding against the fatigue failure.
c) What pressure would be required to cause total joint separation?
Problem 4. A non-rotating stationary 1-in diameter shaft is loaded with forces at A and B as shown below, with ground reaction forces at O and C. The shaft also transmits a torque of 1500 lbf · in throughout the length of the shaft. The shaft has a tensile yield strength of 50 kpsi. Determine the minimum static factor of safety using the maximum-shear-stress failure theory.
