For a bolted assembly with six bolts, the stiffness of each boltis kb = 4 Mlbf/in and the stiffness of the members is km = 16Mlbf/in per bolt. A fluctuating external load applied to the entirejoint cycles between 20,000 lbf and 40,000 lbf. Assume the load isequally distributed to all the bolts. It has been determined to use3/8 in - 16 UNC grade 8 bolts with rolled threads. Assume the boltsare preloaded to 75% of the proof load.
(a) Determine the alternating stress and mean stress carried by abolt.
(b) Determine the fatigue factor of safety for infinite life, usingthe Goodman criterion and a load line that assumes the preload iscarefully applied and will not vary during operation.
