5. (10) Calculate the minimum allowable bar diameter to ensure that fatigue failure will not occur for a
cylindrical 1045 steel bar subjected to repeated tension-compression stress cycling along its axis and
an applied load (amplitude) of 41,000 N.
500
400
475 MPa
80
F = 41,000 N
70 $\sigma$ = 475$\times10^3$ Pa
60
$\sigma = \frac{F}{A}$
$A = .0863 m^2$
$A = \pi r^2 = \frac{\pi d^2}{4}$
50
1045 steel
40
300
2014-T6 aluminum alloy
30
$\sqrt{\frac{A}{\pi}} = r$
200
20
100
10
Red brass
0
0
$10^3$
$10^4$
$10^5$
$10^6$
$10^7$
$10^8$
$10^9$
$10^{10}$
Cycles to failure, N
$2r = d$
$\frac{\sqrt{.0863}}{\pi} = .1657 m \times 2 = .3315 m$
$d = .3315$
-9
Farn nort that fractures after being impacted which of the following are likely?
