Space limitations in the design of an aircraft limit the wall thickness of an aluminum tor...

Space limitations in the design of an aircraft limit the wall thickness of an aluminum torsion member to 2.0 mm for the top half of the cross section. For simplicity, a constant-thickness tube with mean diameter D = 40 mm is proposed (Figure P6.41a). In an attempt to increase the design torque and torsional stiffness by 30% each, the design is modified such that the bottom half of the circumference has a wall thickness of 4.0 mm (Figure P6.41b). The maximum allowable shear stress is 60 MPa.

a. Compare the allowable torques and the stiffnesses for the two designs.

---

b. Compare the shear stress in the 2-mm and 4-mm sections for the design in Figure P6.41b.

---

c. Which cross section would you recommend? Why?

FIGURE P6.41a

FIGURE P6.41b