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Unread 08-03-2012, 09:21
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Re: Aluminum Strengths?

Quote:
Originally Posted by BJT View Post
When mounting our bridge pusher downer, we were wondering if our pneumatic cylinder would bend the piece of 1 inch, .063 square tubing it was mounted to. we performed a very scientific test with a couple 2x4s 13 inches apart which we placed a piece of the tubing on. The cylinder has about 100 pounds of push so we had a 150 pound student stand on it, it passed. It also passed the 200 pound mentor test and the 280 pound mentor test. The 280 pound mentor stomp test resulted in a slight bend, that stuff is tougher than I thought
And then you can show the students the engineering behind it (or better yet, show them first, then test it):

1 inch, .063 inch thick square
Moment of inertial (I) = (1^4-.875^4)/12 = .0345 in^4
Distance to center axis (c) = .5 in
Length of span (L) = 13 in
Force (at 1g) = 280#
Moment (simply supported beam) = F*L/4 = 910 in-#
Stress = M*c/I = 13,200 psi

A "stomp" is probably 2-3 g's, so the stress could have exceed 36 ksi, which is the yield strength of the material.
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