7. 55 4. The last situation involves the possibility that the material between bolt holes might fail in tension. If Wis defined as the bolt spacing, center to center, then the area subject to failure is (w-d)t. The tension stress is then given by: 1.2P (w-d) t If it is now assumed that the bolts are made of the same material as the hull plate, the relevant mechanical properties are given as follows : Tensile Yield Stress + ot 1. 034xl0 9 N/m 2 (150,000 psi) Bearing Stress l. 034xl0 9 N/m 2 (150,000 psi) = a + a t br Shear Stress = l 5.17x10 8 N/m 2 (75,000 psi) rt + OS The above four equations may now be rewritten: l. p max 2. p max 3 . p max 4. p max 5.17x10 8 (1Td 2 ) 3 . 38xlo 8 d 2 N 4 (1. 2) 1. 034xl0 9 (td) 8 . 62xl 0 8 td N 1. 2 5 . 17xl0 8 (2 t x) 8.62xl0 8 xt N l. 2 l.034xl09(w-d)t = 8.62xl08 (w-d)t N 1.2 Each of these equations is a constraint on Pmax relating to a specific failure type. Or, if given Pmax' these equations define the relationships existing between d,t,x, and w. It should be noted that Pmax is related to the maximum hull stress, 0 6 , through the following relation: max Given 0 6 , then, the number and configuration of fasteners needed max may be determined. An assumption implicit in the above discussion
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