고체역학 (Gere) — Applications of Plane Stress: Problem 8.2-13

8.2-13 A hollow, pressurized sphere having a radius \( r = 150 \text{ mm} \) and wall thickness \( t = 13 \text{ mm} \) is lowered into a lake (see figure). The compressed air in the tank is at a pressure of \( 140 \text{ kPa} \) (gage pressure when the tank is out of the water). At what depth \( D_0 \) will the wall of the tank be subjected to a compressive stress of \( 700 \text{ kPa} \)?