고체역학 (Beer) — Pure Bending: Problem 4.166

4.166 For the curved bar and loading shown, determine the percent error introduced in the computation of the maximum stress by assuming that the bar is straight. Consider the case when (a) \(r_1 = 20 \text{ mm}\), (b) \(r_1 = 200 \text{ mm}\), (c) \(r_1 = 2 \text{ m}\). (Referencing Fig. P4.165 and P4.166: Rectangular cross-section with width \(b = 40 \text{ mm}\) and height \(h = 60 \text{ mm}\). Applied bending moment \(M = 120 \text{ N}\cdot\text{m}\).)