고체역학 (Beer) — Pure Bending: Problem 4.55

4.55 and 4.56 Five metal strips, each $0.5 \times 1.5$-in. cross section, are bonded together to form the composite beam shown. The modulus of elasticity is $30 \times 10^6$ psi for the steel, $15 \times 10^6$ psi for the brass, and $10 \times 10^6$ psi for the aluminum. Knowing that the beam is bent about a horizontal axis by a couple of moment 12 kip·in., determine (a) the maximum stress in each of the three metals, (b) the radius of curvature of the composite beam.