Saturday, November 17, 2012

MECHANICAL ENGINEERING: Design of Machine Elements - Rod with a circular cross-section


FS = S/Sa


Sa = F/A


A = pi/4 * d^2

A = 0.785 * d^2

A = pi * r^2

A = 3.14 * r^2


where:

FS = factor of safety

S = strength of the material

Sa = allowable stress

F = Force applied

A = cross-sectional area of material

r = radius of circular rod

d = diameter of circular rod


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1. Problem: Circular Rod

Determine the safe size of a circular rod to be loaded with an axial force of 3000 lbs considering a factor of safety of 4 and the material strength of the rod 30,000 psi.


find:

d = diameter of circular rod

given:

F = axial force = 3000 lbs

S = material strength = 30,000 psi

FS = factor of safety = 4


solution:

Sa = F/A

Sa = 3000/0.785 d^2 

Sa = 3821.66 d^2  ---> equation1


FS = S/Sa

4 = 30,000/Sa

Sa = 30,000/4

Sa = 7500  ---> equation2


equation2 in equation1

Sa = 3821.66 d^2

7500 = 3821.66 d^2

d^2 = 1.96

d = 1.4 in ---> use 1.5 in

1 comment:

  1. I was wondering if anyone could help me find some cad software that would be ideal for structural engineering type of things where u plug in numbers and it will tell u the measurements of the metal and etc.,,. i have googled it a zillion times and there are so many types of cad software i really don't know what to pic...........thanks its for an aerospace contract i believe. also by aerospace contract i just mean that i have to build parts, and etc.

    Solidworks

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