Estimate the rotating beam test endurance limit $S_e^{\text{'}}$ for the following materials:

$[$Answers: $220$ MPa or $32$ksi,$379$MPa or $55$ksi,$138$MPa or $20$ksi,$335$MPa or $31\mathrm{.}5$ ksi $]$

a$.$ AISI $1018$ CD Steel $($Table A$-20)$

b$.$ AISI $1040$ Q&T $800F($Table A$-21)$

c$.2024-$T$3$ Aluminum $($Table A$-24)$

d$.$ AISI $4130$ Normalized $($Table A$-21)$