Any Engineers Here?


Nova

Is that a Caanoo in your pocket or are you just ha
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Heya

I have to make a presentation, on stresses on everyday items. The item I have chosen to look at is this:

31pcw1sBVjL._SS500_.jpg
a pair of border shears.

I need to work out the shear stress on the pin in the middle of the blades. I know the length of the handles and the blades, but I have no idea of the formula. Could anyone help?

Thanks :)
 
If I recall correctily: t = F/A
where F is the force being applied perpendicular to the object in question, and A is the area.
The area is easy enough: approximate the radius of the bolt as r, and sub into pi*r^2
The force I forget exactly how to find. All I remember is it's some kind of proportional equation, something like (L/l)*F', where L is the length of the handle, l is the length of the blade, and F' is the force you're applying to the end of the handle. Except that isn't it at all, I'm just remembering that it kind of looks a little like that. F' will be the minimum amount of force needed to cut through a branch.
You can probably look up what the minimum shear force to cut through a branch is, and flip the t = F/A equation around to find F'. Bonus points now, because you've worked out the shear force on the bolt, and also on the branch ;)
I just forget how to do that. Sorry.
 
You really oughta do your own homework. Start with a free body diagram (of course). Then analyze the cases where the shears are at the limits of motions (fully closed, fully open). Your forces are going to be applied to the handles probably near the ends. Shear stresses will be generated when closing the shears around an object (i.e. a child's neck). Assume a point object lying somewhere along the blade. This is where the opposing force will be generated.

@Pickle: Not dynamics! Kinematics. Dynamics often ends up in the same form as RLC circuit analysis (if you stay linear) so being an EE is no excuse :P
 
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