Question

4) [30 pts] Dynamic bolt factor of safety For a bolted assembly with N = 6 bolts, the stiffness of each bolt is ko = 2 Mibflin and the stiffness of the members is km = 13 Mlbf/in per bolt. A repeated external load of W = 76 kips is applied to the entire joint. Assume the load is equally distributed to all the bolts. It has been determined to use / in-13 UNC grade 8 bolts with rolled threads. Assume the bolts are preloaded to 75 percent of the proof load and the external load is a repeated load. Number of Bolts, N Bolt Grade, G Bolt Diameter, d 6 SAE 8 1/2 in The fatigue factor of safety for the bolts using the Goodman failure criterion is

Answer 1

Km 213 Helfrin number of buffy N=6, a=76 kips Kb = 2 Milloffin £ in-13 UNC grade-s bolto bolts are pclouded 75 to of the proof bad. & load sharing by everybolt F = 76 12.67 kips Bolts are prebaded, Beload for 0.75 ASP A = 0.14 lg in2 > Spa & 2 120kpsi Sut = 150kosi - Fi - 001419x T- 17.03 Kf810 2 Kytkin 2+13 1- 0.133 A maximum lored on bolt mara Fot CF 17.03+0:133712167 Frax. 18.72 Kei minimum on bolt fore Inon cfi 0.133X 12.67 Timor 1169 ksi midrange stores experienced by bolt (&max tfman/ 18.7 2+ 1.65/ om - O. 1419

| me a g2 Ерж alternating stress (Imax-Fron/2 ба. (2Х 1 р. 2- / 6s / 0 14 9 во ов - 12 s/ Ar

by Goodman egin factor of safety Se (Sut - 5 Tal Sut of Se) Se = 18.6 kpoi, st 18.6( 150 - 120) 6o(Isot 1806) n 0.055 bros. noch So, the confonent will fail