고체역학 (Gere) — Stresses in Beams (Basic Topics): Problem 5.6-14

5.6-14 A cantilever beam $AB$ with a circular cross section and length $L = 750 \text{ mm}$ supports a load $P = 800 \text{ N}$ acting at the free end (see figure). The beam is made of steel with an allowable bending stress of $120 \text{ MPa}$. (a) Determine the required diameter $d_{\min}$ (figure part a) of the beam, considering the effect of the beam's own weight. (b) Repeat part (a) if the beam is hollow with wall thickness $t = d/8$ (figure part b); compare the cross-sectional areas of the two designs.