Design a shaft subjected to fluctuating bending and steady torsion using Soderberg criterion.

For fluctuating loads, separate mean (Mm, Tm) and alternating (Ma, Ta) components. Apply Soderberg: 1/FoS = (32/pi.d^3) x [sqrt((Kf.Ma/Se)^2 + (3/4)(Kt.Ta/Syt)^2) + sqrt((Mm/Syt)^2 + (3/4)(Tm/Syt)^2)]. Kf is fatigue notch factor, Se is corrected endurance limit (Se = Se' x ka x kb x kc x kd x ke). Account for surface finish (ka), size (kb), reliability (kc), temperature (kd), and miscellaneous effects (ke). For keyway, Kf approximately equals 2.0. Iterate diameter until FoS requirement is met.