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## Homework Statement

jan 2012 q3.jpg

I've solved everything up to part d). I generally struggle with questions on bolts and I'm really not sure how to tackle this problem.

## Homework Equations

τ = Tr/J, τ = 200MPa, T=1kNm

## The Attempt at a Solution

I worked out the separation of the bolts (I think).

Circumference around the inside: 2π(25mm) = 0.157m ∴ Separation: 0.157/2 = 0.0785m

Not sure where to go next, if I'm honest. I tried this:

T = 1kNm ⇒ F = 1kNm/0.0785m = 12.7kN

so σ = F/2A as double shear so A = F/2σ = 12.7kN/2(200MPa) = 3.19x10

^{-5}m

^{2}

so πr

^{2}= 3.19

^{-5}⇒ r = 3.18mm ⇒ d = 6.37mm

so I went wrong somewhere as the answer is 11.28mm

any help appreciated. Thanks

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