An aluminum alloy cylindrical roller with diameter 1.25 in and length 2 in rolls on the inside of a cast-iron ring having an inside radius of 6 in, which is 2 in thick. Find the maximum contact force F that can be used if the shear stress is not to exceed 4000 psi. a) What force is required to reach 4000 psi shear in the cast iron? (express in lbf) b) What force is required to reach 4000 psi shear in the aluminum? (express in lbf) Use this information to help you find the answers: Tmax=0.300 Pmax and occurs at =/b=0.786 For homework problem 3-153, for the aluminum roller use: max=0.300 Pmax For the cast iron ring use v=0.211 and: Tmax=0.322 Pmax at approximately =/b=0.33 Then use: K = 2F Pmax = bl b=KF 2(1-1)/E+(1-v)/E) l (1/d+1/d)