Mechanical Engineering

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Showing content with the highest reputation on 12/19/2019 in all areas

1. It can always be calculated by looking at the section modulus. maximum stress = My/I where M is the Moment at the point being calculated y is half (assuming round) the diameter I is the section modulus (sometimes "Z")...I used to use Z, now almost always use I for some reason...(?!?)...same variable though! for round bar/tube the section modulus (I) is pi(D^4 - d^4)/64 Pi = 3.1415926....etc D = outer diameter d = inner diameter (if present or = 0 if not) As you can see from the formula...for the same weight there would have to be a relatively large increase in diameter...ultimately, the larger the diameter the lower the stress whether it be solid or hollow. If it is hollow, the diameter increases significantly for a much lower ultimate stress in bending...the "^4" has a huge effect! The rigidity is directly proportional to the stress for any given material...the larger the I/Z, the lower the realised stress. Hope this helps
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