A 6-in-diameter cast-iron (E = 14.5x106 psi; ? = 0.211) wheel, 2 in wide, rolls on a flat steel (E = 30.0x106 psi; ? = 0.292) surface carrying 800 lb load. Plot the Hertzian contact stresses ?x, ?y , ?z and the shear stress in the cast iron wheel as a function of 'normalized' depth (z/a) from the contact. What is the maximum value of the shear stress, and the corresponding depth?