Apipe with closed ends has a wall thickness of 10 mm and an inner diameter of 0.60 m. it filled with a gas at 20 mpa pressure and subjected to a torque about its long axis of 1200 kn·m. a. determine the three principal normal stresses and the maximum shear stress. recall from basic mechanics that: = t 2 b. if the pipe is constructed of oil-quenched and tempered 4340 steel with a yield strength of 1620 mpa, what is the safety factor against yielding using the tresca maximum shear stress criterion? c. prior to loading, an inside crack is discovered through 25% of the thickness of the sample. with this crack, what is the safety factor against fracture if the plane strain fracture toughness is 87.4 mpa√m?