Problem $3$

A steel rotating$-$beam test specimen $($Moore$\text{'}$s specimen$)$ has $S_{ut}=180k.$

$($a$)$ Detemine the fatigue life of the specimen if the test is conducted at a fully$-$reversed stress amplitude of $120$ kpsi $.$

$($b$)$ Determine the fatigue strength corresponding to a life of $150,000$ cycles of fully reversed stress.

$($ANSWER: a$)$ N$=11396$ cycles b$)$ Sf $=101\mathrm{.}68$ kpsi$)$