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June 28th, 2012, 02:38 AM   #1
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A solid steel shaft is subjected to a torque of 45 KN/m.

A solid steel shaft is subjected to a torque of 45 KN/m. If the angle of twist is 0.5 degree per meter length of the shaft and the shear stress is not exceed 90 MN/m^2
(I) find the suitable diameter of the shaft . Take C = 80 GN/m^2
(II) Maximum shear strain


we can solve the question by torsion equation
T/Ip = e/R = CQ/l

T maximum twisting torque in Nm
Ip polar moment of inertia = pid^4/32 in m^4
e shear stress in N/m^2
R radius of the shaft
Q the angle of the shaft in rad
l length if the shaft in m

[color=#FF0000]my question know why in solving fined two diameter ? [/color]
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June 28th, 2012, 10:29 AM   #2
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Re: A solid steel shaft is subjected to a torque of 45 KN/m.

Do you mean why do you need to find the value of twice the radius?

What is the relationship between the radius and the diameter of a circle?
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June 29th, 2012, 07:45 AM   #3
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Re: A solid steel shaft is subjected to a torque of 45 KN/m.

yes why ?

and here I have the solution

the fist answer is
Diameter on the basic of twist
= 0.16 m

and then diameter on the basis of shear stress :
D = 0.1365 m

Now my question why in answer give us two diameter ?

and which one is correct ?
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June 29th, 2012, 08:44 AM   #4
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Re: A solid steel shaft is subjected to a torque of 45 KN/m.

and my other question why in question written the unit of torque kN/m not KNm
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June 29th, 2012, 09:28 AM   #5
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Re: A solid steel shaft is subjected to a torque of 45 KN/m.

see here the solution may will help

http://store2.up-00.com/June12/yq190516.jpg
http://store2.up-00.com/June12/zj390516.jpg
http://store2.up-00.com/June12/dUP90516.jpg
http://store2.up-00.com/June12/K5m90516.jpg

My questions!

1 - Why in the solution there is two diameter
2 - I second diameter how they got the answer 0.13 m when I do the calculation I got 0.14 not 0.13 m
3 - In last from where he got the formula of maximum shear strain = RQ/l ?
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