Problem #3 : a spherical pressure tank is made of 1050 cold-drawn steel (sy = 84 ksi, su = 100 ksi). the tank has a 40″ inner diameter, has a ½” wall thickness, and is pressurized cyclically between 200 psi and 1000 psi. using the goodman fatigue criterion for infinite life, find the overall safety factor against fatigue failure.
