A hex bolt is needed for an application that will undergo tensile impact. After experimentation, it is found that a redesign of the bolt is needed due to it fracturing by the nut on the other end during the application. A figure is shown below of the original bolt design and one of the redesign.
A. State your assumptions.
B. For the redesign, the fillet is increased below the bolt head causing the K value near it to change. Briefly (1-2 sentences) explain why this is done.
C. For the redesign, an axial hole is drilled into the unthreaded section of the bolt. Calculate the optimum diameter of this hole.
D. Once the hole size is calculated, by what factor is this bolt's absorbing energy increased by once it is drilled in.
Hole dia., d
K = 2.5
K = 1.5
d = 200 mm
dia. = 50 mm
(Fracture location)
A = 1000 mm^2
K = 4
3 mm (negligible)
Original design
Modified design
(a)
(b)