고체역학 (Beer) — Pure Bending: Problem 4.62

4.62 Knowing that the allowable stress for the beam shown is 90 MPa, determine the allowable bending moment \(M\) when the radius \(r\) of the fillets is (a) 8 mm, (b) 12 mm. (Note: Problem 4.62 refers to the geometry shown in Figure P4.61 and P4.62. From the figure: \(D = 80\text{ mm}\), \(d = 40\text{ mm}\), and the thickness \(b = 8\text{ mm}\).)