$8\mathrm{.}23$ Plot on log$-$log coordinates estimated $S-N$ curves for $($a$)$ bending, $($b$)$ axial, anel $($c$)$ torsional loading of a $1-$in$.-$diameter steel bar having $S_u=110$ksi,$S_y=77k$ and machined surfaces. For each of the three types of loading, what is the fatig strength corresponding to $(1){10}^6$ or more cycles, and $(2)6{10}^4$ cycles?

$[$Partial ans.: For bending $36\mathrm{.}6$ ksi, $55$ ksi$]$

Instead of log$-$log plot, you can do a logarithmic interpolation.

$8\mathrm{.}25$ Repeat the determination of the six fatigue strengths in Problem $8\mathrm{.}23$ for the case zero$-$to$-$maximum $($rather than completely reversed$)$ load fluctuation.

$[$Partial ans.: For bending, $0$ to $56$ksi,$0$ to $74$ ksi $]$

$8\mathrm{.}25$ ONLY